Plant Micronutrients: Deficiency and Toxicity Management [1st ed.] 9783030498559, 9783030498566

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Tariq Aftab Khalid Rehman Hakeem  Editors

Plant Micronutrients Deficiency and Toxicity Management

Plant Micronutrients

Tariq Aftab  •  Khalid Rehman Hakeem Editors

Plant Micronutrients Deficiency and Toxicity Management

Editors Tariq Aftab Department of Botany Aligarh Muslim University Aligarh, India

Khalid Rehman Hakeem Department of Biological Sciences Faculty of Science King Abdulaziz University Jeddah, Kingdom of Saudi Arabia

ISBN 978-3-030-49855-9    ISBN 978-3-030-49856-6 (eBook) https://doi.org/10.1007/978-3-030-49856-6 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

This book is dedicated to Sir Syed Ahmad Khan (October 17, 1817–March 27, 1898) Sir Syed Ahmad Khan, one of the architects of modern India, was born on October 17, 1817, in Delhi and started his career as a civil servant. The 1857 revolt was one of the turning points in Syed Ahmed’s life. He clearly foresaw the imperative need for the Muslims to acquire proficiency in English language and modern sciences, if the community were to maintain its social and political clout, particularly in Northern India.

He was one of those early pioneers who recognized the critical role of education in the empowerment of the poor and backward Muslim community. In more than one way, Sir Syed was one of the greatest social reformers and a great national builder of modern India. He began to prepare the road map for the formation of a Muslim university by starting various schools. He instituted Scientific Society in 1863 to instill a scientific temperament into Muslims and to make the Western knowledge available to Indians in their own language. The Aligarh Institute Gazette, an organ of the Scientific Society, was launched in March 1866 and succeeded in agitating the minds in the traditional Muslim society. Anyone with a poor level of commitment would have backed off in the face of strong opposition, but Sir Syed responded by bringing out another journal, Tehzeeb-ul-Ikhlaq, which was rightly named in English as “Mohammedan Social Reformer.” In 1875, Sir Syed founded the Madrasatul Uloom in Aligarh and patterned the MAO College after Oxford and Cambridge universities that he went on a trip to London. His objective was to build a college in line with the British education system but without compromising its Islamic values. He wanted this college to act as a bridge between the old and the new, the East and the West. While he fully appreciated the need and urgency of imparting instruction based on Western learning, he was not oblivious to the value of oriental learning and wanted to preserve and transmit to posterity the rich legacy of the past. Dr. Sir Mohammad Iqbal observes:

“The real greatness of Sir Syed consists in the fact that he was the first Indian Muslim who felt the need of a fresh orientation of Islam and worked for it—his sensitive nature was the first to react to modern age.” The aim of Sir Syed was not merely restricted to establishing a college at Aligarh but at spreading a network of Muslimmanaged educational institutions throughout the length and breadth of the country; keeping in view this end, he instituted All India Muslim Educational Conference that revived the spirit of Muslims at national level. The Aligarh Movement motivated the Muslims to help open a number of educational institutions. It was the first of its kind of such Muslim NGO in India, which awakened the Muslims from their deep slumber and infused social and political sensibility into them. Sir Syed contributed many essential elements to the development of the modern society of the subcontinent. During Sir Syed’s own lifetime, “The Englishman,” a renowned British magazine of the nineteenth century remarked in a commentary on November 17, 1885: “Sir Syed’s life strikingly illustrated one of the best phases of modern history.” He died on March 27, 1898, and lies buried next to the main mosque at Aligarh Muslim University.

Preface

Plants require essential nutrients (macronutrients and micronutrients) for normal functioning and growth. A plant’s sufficiency range is the range of nutrient amount necessary to meet the plant’s nutritional needs and maximize growth. This range depends on individual plant species and the particular nutrient. Nutrient levels outside of a plant’s sufficiency range cause overall crop growth and health to decline due to either a deficiency or a toxicity. In addition to the macronutrients (N, P, K, H, Mg, Ca, and S), micronutrients (B, Cl, Mn, Fe, Zn, Cu, and Mo) are required for optimal plant growth. Micronutrients are required by plants in small amounts but are no less essential than macronutrients. Plant micronutrient concentrations are an integration of the dynamic processes of nutrient uptake, transport, and dry matter accumulation, but levels are ultimately dependent on sufficient available soil concentrations. Total soil micronutrients may exceed the demand of a single crop by more than a thousandfold, but the available fraction may be insufficient, resulting in crop nutrient deficiencies. Available micronutrients are dependent on soil chemical and physical properties such as pH, soil organic matter content, and clay minerals. This book covers a wide range of topics, discussing the management approaches of plant micronutrient deficiency as well as toxicity in plants. Moreover, this will be the first reference book on the topic discussing the management of deficiency and toxicity with latest biotechnological and omics approaches. In this volume, we highlight the working solutions as well as open problems and future challenges in plant micronutrient deficiency and toxicity research. We believe that this book will initiate and introduce readers to state-of-the-art developments and trends in this field of study. The book comprises 20 chapters, most of them being review articles written by experts from around the globe, highlighting wide range of topics, and discussing the management approaches of plant micronutrient deficiency as well as toxicity in plants. We are hopeful that this volume would furnish the need of all researchers who are working or have interest in this particular field. Undoubtedly, this book will be helpful for general use of research students, teachers, and those who have interest in plant micronutrients.

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We are highly grateful to all our contributors for accepting our invitation for not only sharing their knowledge and research, but also venerably integrating their expertise in dispersed information from diverse fields in composing the chapters and enduring editorial suggestions to finally produce this venture. We also thank Springer-Nature team for their generous cooperation at every stage of the book production. Lastly, thanks to well-wishers, research students, and authors’ family members for their moral support, blessings, and inspiration in the compilation of this book. Aligarh, India  Tariq Aftab Jeddah, Kingdom of Saudi Arabia   Khalid Rehman Hakeem

Contents

1 An Overview of Micronutrients: Prospects and Implication in Crop Production����������������������������������������������������������������������������������    1 Hanuman Singh Jatav, L. Devarishi Sharma, Rahul Sadhukhan, Satish Kumar Singh, Surendra Singh, Vishnu D. Rajput, Manoj Parihar, Surendra Singh Jatav, Dinesh Jinger, Sunil Kumar, and Sukirtee 2 Effects of Micronutrient Fertilization on the Overall Quality of Crops��������������������������������������������������������������   31 Majid Abdoli 3 The Role of Micronutrients in Growth and Development: Transport and Signalling Pathways from Crosstalk Perspective��������   73 Sadaf Choudhary, Andleeb Zehra, Kaiser Iqbal Wani, M. Naeem, Khalid Rehman Hakeem, and Tariq Aftab 4 A Critical Review on Iron Toxicity and Tolerance in Plants: Role of Exogenous Phytoprotectants������������������������������������������������������   83 Abbu Zaid, Bilal Ahmad, Hasan Jaleel, Shabir H. Wani, and Mirza Hasanuzzaman 5 Plant Responses to Environmental Nickel Toxicity������������������������������  101 Aditya Banerjee and Aryadeep Roychoudhury 6 Accumulation of Heavy Metals in Medicinal and Aromatic Plants��������������������������������������������������������������������������������  113 Fayaz Ahmad Dar, Tanveer Bilal Pirzadah, and Bisma Malik 7 Micronutrient Movement and Signalling in Plants from a Biofortification Perspective��������������������������������������������������������  129 Shadma Afzal, Preeti Sirohi, Deepa Sharma, and Nand K. Singh

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8 Genetic-Based Biofortification of Staple Food Crops to Meet Zinc and Iron Deficiency-Related Challenges ������������������������  173 Nikwan Shariatipour and Bahram Heidari 9 Biofortification Technologies Used in Agriculture in Relation to Micronutrients�����������������������������������������������������������������  225 Umair Riaz, Humera Aziz, Wajiha Anum, Shahzada Munawar Mehdi, Ghulam Murtaza, and Moazzam Jamil 10 Micro- and Macronutrient Signalling in Plant Cells: A Proteomic Standpoint Under Stress Conditions��������������������������������  241 Jameel R. Al-Obaidi 11 Proteomic Studies of Micronutrient Deficiency and Toxicity��������������  257 Aarif Ali, Basharat Ahmad Bhat, Gulzar Ahmed Rather, Bashir Ahmad Malla, and Showkat Ahmad Ganie 12 Abiotic and Biotic Stress-Induced Alterations in the Micronutrient Status of Plants����������������������������������������������������  285 Amrina Shafi and Insha Zahoor 13 Role of Micronutrients in Secondary Metabolism of Plants����������������  311 Basharat Ahmad Bhat, Sheikh Tajamul Islam, Aarif Ali, Bashir Ahmad Sheikh, Lubna Tariq, Shahid Ul Islam, and Tanvir Ul Hassan Dar 14 A Review of Nutrient Stress Modifications in Plants, Alleviation Strategies, and Monitoring through Remote Sensing��������������������������������������������������������������������������  331 Shabana Gulzar, Afrozah Hassan, and Irshad A. Nawchoo 15 Hyperaccumulation of Potentially Toxic Micronutrients by Plants������������������������������������������������������������������������  345 Razieh Khalilzadeh and Alireza Pirzad 16 Nanocarriers: An Emerging Tool for Micronutrient Delivery in Plants ������������������������������������������������������������������������������������  373 Irsad, Neetu Talreja, Divya Chauhan, Carlos A. Rodríguez, Adriana C. Mera, and Mohammad Ashfaq 17 Genetic and Environmental Influence on Macro- and Microelement Accumulation in Plants of Artemisia Species����������������������������������������������������������������������������������  389 Nadezhda Golubkina, Lidia Logvinenko, Anna Molchanova, and Gianluca Caruso

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18 Wastewater Irrigation-Sourced Plant Nutrition: Concerns and Prospects��������������������������������������������������������������������������  417 Hamaad Raza Ahmad, Muhammad Sabir, Muhammad Zia ur Rehman, Tariq Aziz, Muhammad Aamer Maqsood, Muhammad Ashar Ayub, and Ahsan Shahzad 19 Role of Boron in Growth and Development of Plant: Deficiency and Toxicity Perspective�������������������������������������������������������  435 Sibel Day and Muhammad Aasim 20 The Role of Zinc in Grain Cadmium Accumulation in Cereals����������  455 Ayta Umar and Shahid Hussain

About the Editors

Tariq Aftab  received his Ph.D. in the Department of Botany at Aligarh Muslim University, India, and is ­currently an Assistant Professor there. He is the recipient of a prestigious Leibniz-DAAD fellowship from Germany, Raman Fellowship from the Government of India, and Young Scientist Awards from the State Government of Uttar Pradesh (India) and Government of India. After completing his doctorate, he has worked as Research Fellow at National Bureau of Plant Genetic Resources, New Delhi, and as Postdoctorate Fellow at Jamia Hamdard, New Delhi, India. Dr. Aftab has also worked as Visiting Scientist at Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany, and in the Department of Plant Biology, Michigan State University, USA.  He is a member of various scientific associations in India and abroad. He has edited four books with international publishers, including Elsevier Inc., Springer Nature, and CRC Press (Taylor & Francis Group); co-authored several book chapters; and published over 50 research papers in peer-reviewed international journals. His research interests include physiological, proteomic, and molecular studies on medicinal and aromatic plants.

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About the Editors

Khalid  Rehman  Hakeem, Ph.D.  is a Professor at King Abdulaziz University, Jeddah, Saudi Arabia. After completing his doctorate (botany, specialization in plant ecophysiology and molecular biology) from Jamia Hamdard, New Delhi, India, in 2011, he worked as a lecturer at the University of Kashmir, Srinagar, for a short period. Later, he joined Universiti Putra Malaysia, Selangor, Malaysia, and worked there as Postdoctorate Fellow in 2012 and Fellow Researcher (Associate Prof.) from 2013 to 2016. Dr. Hakeem has more than 10 years of teaching and research experience in plant ecophysiology, biotechnology, molecular biology, medicinal plant research, plant-microbe-soil interactions, as well as environmental studies. He is the recipient of several fellowships at both national and international levels; also, he has served as the visiting scientist at Jinan University, Guangzhou, China. Currently, he is involved with a number of international research projects with different government organizations. So far, Dr. Hakeem has authored and edited more than 50 books with international publishers, including Springer Nature, Academic Press (Elsevier), and CRC Press. He also has to his credit more than 110 research publications in peer-reviewed international journals and 60 book chapters in edited volumes with international publishers. At present, Dr. Hakeem serves as an editorial board member and reviewer of several high-impact international scientific journals from Elsevier, Springer Nature, Taylor & Francis, Cambridge, and John Wiley Publishers. He is included in the advisory board of Cambridge Scholars Publishing, UK. He is also a fellow of Plantae group of the American Society of Plant Biologists; member of the World Academy of Sciences; member of the International Society for Development and Sustainability, Japan; and member of Asian Federation of Biotechnology, Korea. Dr. Hakeem has been listed in Marquis Who’s Who in the World, since 2014–2020. Currently, Dr. Hakeem is engaged in studying the plant processes at ecophysiological as well as molecular levels.

Contributors

Muhammad  Aasim  Department of Plant Protection, Faculty of Agricultural Sciences and Technologies, Sivas University of Science and Technology, Sivas, Turkey Majid Abdoli  Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, Maragheh, Iran Tariq Aftab  Department of Botany, Aligarh Muslim University, Aligarh, India Shadma Afzal  Department of Biotechnology, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, India Bilal Ahmad  Plant Physiology and Biochemistry Section, Department of Botany, Aligarh Muslim University, Aligarh, India Hamaad Raza Ahmad  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Aarif Ali  Department of Clinical Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India Department of Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India Jameel R. Al-Obaidi  Department of Biology, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjong Malim, Perak, Malaysia Wajiha Anum  Department of Agronomy, Regional Agricultural Research Institute, Bahawalpur, Pakistan Mohammad  Ashfaq  Multidisciplinary Research Institute for Science and Technology, IIMCT, University of La Serena, La Serena, Chile School of Life Science, BS Abdur Rahaman Institute of Science and Technology, Chennai, India

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Contributors

Muhammad Ashar Ayub  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Humera  Aziz  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Department of Environmental Sciences, Government College University, Faisalabad, Pakistan Tariq Aziz  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Aditya  Banerjee  Post Graduate Department of Biotechnology, St. Xavier’s College (Autonomous), Kolkata, West Bengal, India Basharat  Ahmad  Bhat  Department of Bioresources, University of Kashmir, Srinagar, Jammu and Kashmir, India Gianluca  Caruso  Department of Agricultural Sciences, University of Naples Federico II, Italy Divya Chauhan  Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, USA Sadaf  Choudhary  Department of Botany, Aligarh Muslim University, Aligarh, India Fayaz Ahmad Dar  Department of Bioresources, University of Kashmir, Srinagar, Jammu and Kashmir, India Sibel Day  Department of Field Crops, Faculty of Agriculture, Ankara University, Ankara, Turkey Showkat  Ahmad  Ganie  Department of Clinical Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India Department of Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India Nadezhda  Golubkina  Laboratory Analytical Department, Federal Scientific Center of Vegetable Production, Moscow Region, Russia Shabana  Gulzar  Department of Botany, Govt. College for Women, Srinagar, Jammu and Kashmir, India Khalid Rehman Hakeem  Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia Mirza Hasanuzzaman  Department of Agronomy, Faculty of Agriculture, Sher-e-­ Bangla Agricultural University, Dhaka, Bangladesh Afrozah  Hassan  Genetic Diversity and Phytochemistry Research Laboratory, Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir, India

Contributors

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Tanvir Ul Hassan Dar  Department of Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, India Bahram  Heidari  Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, Iran Shahid Hussain  Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan Irsad  Department of Plant Protection, Faculty of Agricultural Sciences, A.M.U, Aligarh, India Shahid  Ul  Islam  Department of Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, India Sheikh  Tajamul  Islam  Department of Bioresources, University of Kashmir, Srinagar, Jammu and Kashmir, India Hasan Jaleel  Plant Physiology and Biochemistry Section, Department of Botany, Aligarh Muslim University, Aligarh, India Moazzam Jamil  Department of Soil Science, Islamia University of Bahawalpur, Bahawalpur, Pakistan Hanuman Singh Jatav  College of Agriculture Baseri-Dholpur, S.K.N. Agriculture University-Jobner, Jaipur, Rajasthan, India Surendra  Singh  Jatav  Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India Dinesh Jinger  ICAR-Indian Institute of Soil and Water Conservation, Dehradun, Uttarakhand, India Razieh  Khalilzadeh  Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, Urmia University, Urmia, Iran Lubna  Tariq  Department of Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, India Sunil  Kumar  Department of Agronomy, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India Lidia  Logvinenko  Nikita Botanic Gardens, National Scientific Center of RAS, Yalta, Russia Bisma  Malik  University Centre for Research and Development (UCRD), Chandigarh University, Mohali, Punjab, India Bashir  Ahmad  Malla  Department of Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India Muhammad  Aamer  Maqsood  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan

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Contributors

Shahzada Munawar Mehdi  Rapid Soil Fertility, Survey and Soil Testing Institute, Lahore, Punjab, Pakistan Adriana C. Mera  Multidisciplinary Research Institute for Science and Technology, IIMCT, University of La Serena, La Serena, Chile Anna Molchanova  Laboratory Analytical Department, Federal Scientific Center of Vegetable Production, Moscow Region, Russia Ghulam  Murtaza  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan M. Naeem  Department of Botany, Aligarh Muslim University, Aligarh, India Irshad A. Nawchoo  Genetic Diversity and Phytochemistry Research Laboratory, Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir, India Manoj  Parihar  ICAR-Vivekananda Parvatiya Krishi Anusandhan Sansthan, Almora, India Tanveer  Bilal  Pirzadah  University Centre for Research and Development (UCRD), Chandigarh University, Mohali, Punjab, India Alireza  Pirzad  Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, Urmia University, Urmia, Iran Vishnu  D.  Rajput  Academy of Biology and Biotechnology, Southern Federal University, Rostov-on-Don, Russia Gulzar  Ahmed  Rather  Department of Biomedical Engineering, Sathyabama Institue of Science and technology, Chennai, India Umair Riaz  Soil and Water Testing Laboratory for Research, Bahawalpur, Pakistan Carlos  A.  Rodríguez  Multidisciplinary Research Institute for Science and Technology, IIMCT, University of La Serena, La Serena, Chile Aryadeep  Roychoudhury  Post Graduate Department of St. Xavier’s College (Autonomous), Kolkata, West Bengal, India

Biotechnology,

Muhammad  Sabir  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Rahul  Sadhukhan  Multi Technology Testing Centre & Vocational Training Centre, Selesih, Mizoram, India Amrina  Shafi  Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, Jammu and Kashmir, India Ahsan  Shahzad  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan Nikwan  Shariatipour  Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, Iran

Contributors

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Deepa Sharma  Department of Biotechnology, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, India L.  Devarishi  Sharma  Multi Technology Testing Centre & Vocational Training Centre, Selesih, Mizoram, India Bashir  Ahmad  Sheikh  Department of Bioresources, University of Kashmir, Srinagar, Jammu and Kashmir, India Nand K. Singh  Department of Biotechnology, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, India Satish  Kumar  Singh  Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India Surendra Singh  Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India Preeti  Sirohi  Department of Biotechnology, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, India Sukirtee  Department of Soil Science & Agricultural Chemistry, Chaudhary Charan Singh Haryana Agricultural University, Hisar, India Neetu  Talreja  Multidisciplinary Research Institute for Science and Technology, IIMCT, University of La Serena, La Serena, Chile Ayta  Umar  Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan Kaiser  Iqbal  Wani  Department of Botany, Aligarh Muslim University, Aligarh, India Shabir H. Wani  Mountain Research Centre for Field Crops, Khudwani, Anantnag, India Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar, Jammu and Kashmir, India Insha  Zahoor  Drug Therapeutics & Neurobiology Lab, Department of Biotechnology & Bioinformatics Centre, University of Kashmir, Srinagar, Jammu and Kashmir, India Department of Neurology, Henry Ford Hospital, Detroit, MI, USA Abbu  Zaid  Plant Physiology and Biochemistry Section, Department of Botany, Aligarh Muslim University, Aligarh, India Andleeb Zehra  Department of Botany, Aligarh Muslim University, Aligarh, India Muhammad  Zia  ur  Rehman  Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan

Chapter 1

An Overview of Micronutrients: Prospects and Implication in Crop Production Hanuman Singh Jatav, L. Devarishi Sharma, Rahul Sadhukhan, Satish Kumar Singh, Surendra Singh, Vishnu D. Rajput, Manoj Parihar, Surendra Singh Jatav, Dinesh Jinger, Sunil Kumar, and Sukirtee

Abstract  Micronutrients are important for plant growth and they significantly play an important role in balanced crop nutrition. They are vital for appropriate growth and development of plants in their entire life span. A deficiency of any one of the micronutrients in the soil can limit the growth of plants, even when all other nutrients are available in adequate amounts. The deficiency of micronutrients is widespread in many areas due to the nature of soils, high pH, low organic matter, salt stress, continuous drought, high bicarbonate content in irrigation water and imbalanced application of fertilisers. In India, the most deficient micronutrient in the soil is Zn, followed by B. In recent years, the deficiency of micronutrient has risen to a great extent. Zn and B deficiencies are focussed mainly for their adverse impacts on H. S. Jatav (*) College of Agriculture Baseri-Dholpur, S.K.N. Agriculture University-Jobner, Jaipur, Rajasthan, India L. D. Sharma · R. Sadhukhan Multi Technology Testing Centre & Vocational Training Centre, Selesih, Mizoram, India S. K. Singh · S. Singh · S. S. Jatav Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India V. D. Rajput Academy of Biology and Biotechnology, Southern Federal University, Rostov-on-Don, Russia M. Parihar ICAR-Vivekananda Parvatiya Krishi Anusandhan Sansthan, Almora, India D. Jinger ICAR-Indian Institute of Soil and Water Conservation, Dehradun, Uttarakhand, India S. Kumar Department of Agronomy, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India Sukirtee Department of Soil Science & Agricultural Chemistry, Chaudhary Charan Singh Haryana Agricultural University, Hisar, India © Springer Nature Switzerland AG 2020 T. Aftab, K. R. Hakeem (eds.), Plant Micronutrients, https://doi.org/10.1007/978-3-030-49856-6_1

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human health and food production. This chapter attempts to examine the defects of Zn, Fe, Mn, Cu, B and Mo deficiency in the soil and crops as well as the management of micronutrient deficiencies by way of fertilisation, development of ­agronomic strategies and creation of awareness of micronutrient dose. Deficiencies of Zn and B cause some severe complications in crop production in India. In view of the problems, we discuss the importance of micronutrients in agriculture and their roles and ways to improve crop productivity. Keywords  Micronutrients · Soil fertility · Crop nutrient management · Balanced nutrition

Introduction Micronutrients in small quantity are applied for healthy growth and development of plants. Micronutrients and macronutrients play an important role in completing the life cycle of plants. The role of micronutrients as balanced plant nutrition is well established. Micronutrients are essential for the maintenance of soil health as well as for the enhancement of productivity of crops (Rattan et al. 2009). Zinc, copper, manganese, iron and boron are essential micronutrients for speedy growth of plants. Micronutrients play an indispensable role in the biosynthesis of proteins, nucleic acids, gene expression, growth substances, metabolism of carbohydrates and lipids, stress tolerance, chlorophyll and secondary metabolites, etc. through their association with other physiologically active molecules and various enzymes (Singh 2004; Rengel 2007; Gao et al. 2008). Therefore, the availability of micronutrients is very much essential for proper crop nutrition and development. Geological substrate and pedogenic systems of management determine the quantity of micronutrients in soils. However, plants are unable to indicate the deficiency because the availability of micronutrients depends on organic matter content, soil pH, adsorptive surfaces and other biological, chemical and physical conditions in the environment. Soil plays a significant role in defining the agro-system of sustainable productivity. Sustainable fertility depends on the ability of the soil to supply essential nutrients to the growing plants. Micronutrient deficiency imposes a severe constraint on productivity, stability and sustainability of soils (Bell and Dell 2008). Lack of micronutrients may be due to their low contents, or soil factors reduce plant growth. Inappropriate management of nutrients leads to multi-nutrient deficiencies in Indian soils (Sharma 2008). Moreover, continuous negligence of micronutrient application and avoidance of organic manures are the significant causes of scarcity of micronutrients (Srivastava et al. 2017). The deficiency of the nutrient in plant

1  An Overview of Micronutrients: Prospects and Implication in Crop Production

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Fig. 1.1  Possible steps to identify the nutrient deficiency

and soil can be identified by several steps. Some of the so far established strategies are suggested in Fig. 1.1. Availability of micronutrients to plants is influenced by the distribution within the soil profile (Singh and Dhankar 1989). Land-use pattern, besides soil characterisation, plays a vital role in governing the nutrient dynamics and fertility of soils (Venkatesh et al. 2003). Continuous cultivation following a particular land-use system affects physico-chemical properties of soils resulting in the modification of DTPA-extractable micronutrient content to make available to plants for their growth. It is quite impossible to get the maximum benefit from crop production without the availability of adequate micronutrients. Knowledge of the pedogenic distribution of micronutrients is crucial because the roots of many plants penetrate subsurface layers of the soil to draw required nutrients. Role of micronutrients as a balanced nutrient of crops is well established. Micronutrients are indispensable for the growth and development of plants. The origin of micronutrient management research in India draws back to a publication by Iyer and associates in 1934. Real impetus on micronutrient research came with a report of Khaira disease in mid-1960s (Nene 1966). Keeping in view of the report, All India Coordinated Research Scheme of Micronutrients in Soil and Plants was established in India. The need for inclusion of micronutrients in the crop nutrition programme has become more of an essential nature in the present day (Tables 1.1 and 1.2).

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Table 1.1  Micronutrient elements discovered so far Micronutrient elements Iron Manganese Zinc Copper Molybdenum Boron Chlorine Nickel

Essentiality established by E. Gris J. S. McHargue A L. Sommer and C. B. Lipman A L. Sommer, C. P. Lipman, and C. McKinny D. L. Arnon and P. R. Stout K. Warington Broyer, Carlton, and others P. H. Brown, R. M. Welch, and E. E. Cary

Year of discovery 1843 1922 1926 1931

Plant uptake form Fe2+ Mn2+ Zn2+ Cu2+

1939 1923

MoO42− H3BO3, H2BO3−, HBO32−, BO33− Cl− Ni2+

1954 1982

Table 1.2  The concentration of micronutrients in leaf tissue of various plants Micronutrient B (mg/kg) Mo (mg/kg) Cl (mg/kg) Fe (mg/kg) Mn (mg/kg) Zn (mg/kg) Cu (mg/kg) Ni (mg/kg)

Deficient 5–30 0.03–0.15  Zn > Cu. Kumar et al. (2011) studied arid soils of Chura district of Western Rajasthan and observed that Fe, Mn and Cu had a significant and positive correlation with organic carbon. It showed how organic matter played an important role in promoting the availability of this micronutrient in the soils since organic matter acts as a chelating agent; the availability of this ion (Fe, Mn and Cu) increases with an increase in the organic matter.

 orrelation Between Micronutrients (Fe, Zn, Mn and Cu) C and Physical Properties of Soils Iron Sahu et al. (1990) conducted a study on the distribution of clay content and observed that clay content had a significant and positive correlation with Fe, but the relationship of pH with DTPA-extractable micronutrients was negative. Bhogal et al. (1993) reported that available Fe, Zn, Cu, Mn and B correlated significantly and negatively with pH and correlated positively with organic carbon. Vadivelu and Bandyopadhyay (1995) studied the DTPA-Fe and found that DTPA-Fe correlated positively with organic carbon (r = 0.522) and correlated negatively with CaCO3 (r = −0.549) and

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pH (r = −0.657). Vijay Kumar et al. (1996) revealed that available Fe, Zn, Cu and Mn correlated negatively and significantly with soil pH.  Chattopadhyaya et  al. (1996) studied the available Fe and Mn in the soil and reported that Fe and Mn correlated significantly and negatively with pH, EC and CaCO3. Cu correlated significantly and negatively with pH. Parman et al. (1999) concluded for their investigation that Fe and Mn had a significant and negative correlation with soil pH and also had a significant and positive correlation with organic carbon. Zinc had shown a significant and negative relationship with soil pH. Sarkar et  al. (2000) concluded from their investigation that available Zn and Fe correlated significantly and negatively with pH.  DTPA-extractable Fe, Mn, Cu and Zn correlated positively and significantly with organic carbon. Singh et al. (2006a, b) reported that DTPA-Mn had a negative correlation with available P content but correlated positively with pH. They also said that Fe correlated negatively with pH but correlated significantly and positively with organic carbon, CEC available N and Zn.

Zinc Sharma et al. (1996) investigated the positive correlation of all elements with silt and clay contents as well as a negative correlation with sand content. Silt-size feldspar had a positive relationship with Cu, Zn and Mg, but other size had a negative association with Zn, Fe, Mg and Mn. Singh et al. (1997) revealed that DTPA-Cu and -Zn had a positive correlation with pH and clay. However, DTPA-Zn, -Cu and -Mn were influenced negatively and significantly by organic carbon. Sharma et al. (1999) studied the linear correlation coefficients and revealed that the total content of micronutrients increased with increase in clay content, whereas DTPA-extractable micronutrient content increased with increase in organic carbon and decreased with increase in pH. Sharma et al. (2002) reported that the total micronutrients increased with increase in clay content and CEC, whereas DTPA-extractable micronutrient increased with increase in organic carbon content and CEC and decreased with increase in pH and sand content and decrease in subsurface. Gupta et al. (2003) also confirmed that DTPA-extractable micronutrient cations (Zn, Cu, Fe and Mn) showed a positive correlation with organic carbon but had an inverse relationship with soil pH and CaCO3 content. Venkatesh et al. (2003) reported that available Zn and Cu positively correlated with organic carbon. Sharma et al. (2003) studied molybdenum and found that the molybdenum correlated negatively with silt-added clay and organic carbon but correlated positively with pH and CaCO3 content. They found that available Zn correlated positively and significantly with clay, CEC and OC.  Vijayakumar et  al. (2011) studied Fe and found that Fe had a positive correlation with OC but a negative correlation with pH. Zn had a positive relationship with EC and pH but a negative relationship with OC.

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Manganese Datta and Ram (1993) reported that available Mn had a negative association with clay content in upland and lowland soils of Tripura. Available Cu and Fe correlated positively with organic carbon, whereas available Zn correlated negatively with organic carbon in both upland and lowland soils. The clay content correlated positively with available Zn, Cu and Fe in upland soil. Tripathi et al. studied soils of Himachal Pradesh and observed that organic carbon correlated significantly with Zn, Cu and Fe. However, Cu failed to show any significant relationship with other soil properties. Kher et al. (2004) studied the organic carbon and found that organic carbon correlated significantly and positively with all micronutrient cations. According to the report of Satyavathi and Reddy (2004), DTPA-extractable micronutrient content increased with an upsurge in organic carbon and decreased with increase in pH. Minakshi et al. (2005) observed that all the micronutrient cations correlated significantly and positively with soil organic matter. They found a significant and positive correlation of Fe, Mn and Cu with clay content. However, DTPA-Fe correlated negatively with pH. Sharma et al. (2005a, b) observed that the soils of the area where the study was conducted were adequate in DTPA-extractable micronutrient cations and correlated significantly and negatively with pH.  Sharma et  al. (2006) reported that Cu and Mn correlated positively with organic carbon in the soils of Leh district of Ladakh.

Copper Pradeep Kumar et al. (1996) revealed that among the soil properties, only CEC was related positively with total and available Cu. Nayak et al. (2000) studied the alluvial soils of Arunachal Pradesh and found that available Cu correlated significantly and positively with pH, but it correlated negatively and non-significantly with sand and clay. Available Zn correlated negatively with soil pH but correlated positively with organic carbon, clay and CEC. Fe correlated negatively and significantly with pH and sand. They observed that Mn correlated positively and significantly with organic carbon. Mn and organic carbon, silt and CEC had a significant and positive relationship, but they had shown a negative correlation with pH and sand. Meena et al. (2006) conducted a study on the soils of Tonk district of Rajasthan and reported that soil pH correlated significantly and negatively with available Cu. However, available Cu correlated positively with organic carbon and clay content. Balpande et  al. (2007) conducted a study on the grape-growing soils in Nasik district of Maharashtra and reported that copper had a significant and positive relationship with zinc. They said that extractable Fe did not affect DTPA-Zn whereas zinc had negative correlations with Mn. Similarly, pH influenced DTPA-extractable micronutrients negatively. Verma et al. (2007) investigated the micronutrient cations in alkaline soils of north-east Punjab and concluded that silt had a significant and

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p­ ositive correlation with DTPA-Cu, -Fe and -Mn. A significant and positive relationship between organic carbon and DTPA-extractable micronutrients indicated that organic matter generates complexing agents. However, it was found that the organic carbon had a maximum positive on DTPA-Cu. Vijayakumar et al. (2011) studied the tsunami-­affected areas of Sirkali Taluk of Tamil Nadu and reported that Cu had a positive correlation with organic carbon but negative correlation with pH and EC and Zn.

Harmful Complications of Micronutrients Usage of soluble salts may cause adverse effects as these salts get transformed into an insoluble compound and may get concentrated in the rhizosphere. Harmful effects of one element may cause other deficient, for instance, iron and manganese or calcium and boron. Determination of nutrients after leaf analysis seems to be of infinite importance. Harmful effects created by micronutrients and non-essential elements can be categorised into two categories: (1) facts that are same with ­iron-­deficiency symptoms and can be attributed to the low availability or reduced utilisation of iron and (2) effects which are particular to the elements provided in excess. The most commonly occurring symptom of toxicity of metal is chlorosis of the young leaves, except for chromium.

Zinc In Indian soils, the available Zn ranges between 0.01 and 52.9 mg kg−1. It constitutes less than 1% of the total Zn content. At present 36.5% of soil samples across the country are deficient in available Zn; about 8%, 29% and 15% area of the country is suffering from acute deficiency, deficiency and latent deficiency of Zn, respectively. Coarse-textured (loamy sand/sandy, alkali or sodic soils) and calcareous soils, and soil organic carbon with 7.5 pH. Under drought- or moisture-stress conditions availability of Fe gets poorer owing to the transformation of Fe2+ into less accessible Fe3+. From time to time, iron availability to the crop plants is also hindered by high concentrations of organic matter contents, phosphorus and nitrate N. The acute deficiency, deficiency and latent deficiency of Fe are about 4%, 9% and 6% area of the country, respectively. About 10%, 11% and 60% area is characterised by adequate, high and very high levels of available Fe, respectively. A very high level of available Fe is also associated with strong acid and waterlogged soils. As a result of Fe toxicity in submerged (paddy) rice soils, rice yields get harshly reduced. The problem of iron toxicity in rice paddies is common in the soils of north-east region Odisha and Kerala. Generally, iron chlorosis in plants, also called lime-induced chlorosis, is observed in upland crops primarily aerobic rice, sorghum, groundnut, sugarcane, chickpea grown in Fe-deficient highly calcareous soils, compact soil with limited aeration, and soils with low active Fe and high P and bicarbonate content. By and large, foliar application of 10–12 kg FeSO4 ha−1 or soil application of 50–150 kg ha−1 FeSO4 has been fruitful in easing deficiency of Fe in most of the crops (Takkar et  al. 1989; Singh and Dayal 1992). On average, crop responses to soil and foliar application of Fe range from 0.45 to 0.89 t ha−1 in cereals, 0.3 to 0.68 t ha−1 in millets, 0.34 to 0.58 t ha−1 in pulses, 0.16 to 0.55 t ha−1 in oilseed crops, 0.20 to 1.53 t ha−1 in vegetables and 0.39 to 9.68 t ha−1 in cash and other plants (Takkar et al. 1989, Singh 2008; Shukla et al. 2012). The rates of soil application of Fe are unusually high, because of the rapid pace of oxidation of Fe2+ to Fe3+, and henceforth are uneconomical. Correspondingly, the farmers are discouraged from using Fe chelates due to its high cost. Foliar spray of FeSO4 is recommended for

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horticultural crops. For correcting Fe chlorosis in tomato, chilli, groundnut and sugarcane foliar sprays of FeSO4 are more effective and efficient than soil application.

Copper In Indian soils, copper deficiency is almost negligible. In Indian soils, available Cu varies between 0.01 and 136.4 mg kg−1 with an average of 2.05 mg Cu kg−1 (Shukla and Tiwari 2016). The country has about 2% severe deficiency, 2% deficiency and 3% latent deficiency of Cu, respectively. On the other hand, the area with an adequate level is about 11%, 14% high and 68% very high level of available Cu. pH, SOC, CaCO3 and clay content are the main factors that influence copper availability in soils. A rise in organic matter and clay content increases copper availability, while an increase in pH and CaCO3 content of the soil decreases its availability (Katyal and Agarwala 1982; Rattan et al. 1999). Soils that have copper deficiency are sandy, calcareous, eluviated and organic matter-rich soils. The CaCO3-bound Cu fraction in the soil releases with the addition of organic matter and organic fraction it rebinds. Thus it enhances the availability of Cu in calcareous and sandy loam soils. The Cu availability in the hill (Alfisols), Histosols (organic peat soils) of Kerala and Mollisols (submontane soils) of the Himalayan Tarai zone of Uttarakhand and Himachal Pradesh is reduced by the presence of excess organic matter (Singh 2008; Patel et al. 2009; Behera et al. 2012). Reduced yields and poor crop quality are the results of the crops grown on severe Cu-deficient soils. Cu deficiency in citrus results in low juice content, abnormally shaped fruits with a rough exterior, and weak flavour and in apples small fruits of poor quality are found. In cereals, it includes reduced viability of seeds and shrivelled grains. In sugar beet, higher concentrations of nitrogenous compounds give compressed juice purity. Chlorotic leaves, lesser size, discolouration of edible portions and apparent wilt in gin vegetables lead to fewer commercial opportunities. A typical instance of severe Cu deficiency in the wheat crop grown on organic fertile calcareous soils (a rendzina soil) of north western France exhibited characteristic symptoms; that is, plants were shorter with dark pigmentation (melanism) in the ear and had an inferior density of ears per unit area. For instance, in north western France, wheat grown on severe Cu-deficient rendzina soil (organic fertile calcareous soils) showed specific symptoms, like shorter height with dark pigmentation (melanism) in the ear and decreased density of ears (spikes) per unit area. Generally, crop responses to Cu application in cereals, millets, oilseeds, onion and sugarcane ranged from trace to 1.78 t ha−1, 0.20 to 0.30 t ha−1, trace to 0.80 t ha−1, 4.43 to 6.18  t  ha−1 and 0.30 to 0.50  t  ha−1, respectively (Takkar et  al. 1989). In Typic Ustipsamments, foliar and soil application of Cu in soybean wheat cropping system proves to be useful in correcting its deficiency and use of 5.0 kg Cu ha−1 in the soil gave a significant response of 0.2 t ha−1 to the first crop. An increase of soybean grain yield from 2.18 to 2.35 t ha−1 was found with the foliar spray of 0.2% CuSO4 solution.

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Manganese In Indian soils, available Mn content ranges between 0.01 and 445.0 mg kg−1, with a mean of 21.8 mg kg−1 (Shukla et al. 2014). The country suffers from about 1% acute deficiency, 6% deficiency and 10% latent deficiency of Mn. Avery high level of available Mn has been found in 60% of the region. Mn deficiency increased from 3.0% in 1967–1987 to 7.1% in 2011–2017. Rice-wheat-growing areas of Punjab, Haryana and western Uttar Pradesh witnessed an emerging Mn deficiency due to its increase. The occurrence of Mn-deficiency problems is common in heavily weathered tropical and sandy soils (low total contents of Mn), limed acid soils or calcareous soils, mineral soils with pH values of 6.5 or above, organic-rich soils with a pH above 6 and peaty soils. In India, an increase of Mn deficiency has grown very fast mainly in sandy or loamy sand soils of Punjab and Haryana under rice-wheat cropping systems. Like Fe, crops grown at shallow moisture content have a high risk of incidence and severity of Mn deficiency. The mobility of Mn is more in waterlogged soil, and rice grown under such soil conditions often manifests Mn toxicity. The appearance of greenish-grey specks at the lower base of younger leaves in monocots, which finally become yellowish to yellow-orange, is due to the deficiency of Mn. It often results in the development of marsh spots (necrotic areas) on the cotyledon of legumes. In sugarcane, pahala blight is the name given to Mn deficiency. There was a marked response in crops on Mn-deficient soils with the application of soil and foliar of Mn; responses ranged from traces to 3.78 t ha−1 for wheat, trails to 1.78 t ha−1 for rice, 0.03 to 1.02 t ha−1 for soybean, 0.40 to 0.70 t ha−1 for sunflower, 3.63 to 4.30 t ha−1 for onion and 0.30 to 0.80 t ha−1 for tomato (Takkar and Nayyar 1981). Owing to oxidation of soil-applied Mn, it is challenging to manage severe Mn deficiency with soil application, especially in high-pH soil. An instant effective measure to combat Mn deficiency in wheat and berseem is the foliar application of MnSO4.H2O. In comparison to its soil application with B:C ratio of 2.1, the economic benefit of foliar application of Mn to wheat was twofold with B:C ratio of 4.5.

Boron In India, B deficiency is next to Zn deficiency, and the total B ranges from 2.6 to 630 mg kg−1 (Takkar 2011), and available (hot water soluble, HWS) B ranges from 0.04 to 250 mg B kg−1, with an average of 21.9 mg kg−1 soil (Shukla and Tiwari 2016). In the country, about 4%, 19% and 21% of the area faces acute deficiency, deficiency and latent deficiency of B, respectively. The areas that has adequate, high and very high available B status are about 12%, 11% and 32%, respectively. Soil pH, CaCO3 and organic matter contents govern the availability of B in plants. Besides total B content in the soil, the other factors that have a substantial impact on B availability are its interactions with other nutrients, variety or plant type and ­environmental factors. In some regions of Indian soils, boron deficiency is a harsh

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problem in agricultural productivity. Generally, in sandy leached soils, highly ­calcareous soils, limed acid soils or lateritic or reclaimed yellow soils B deficiency adversely influences crop productivity. In the eastern region of the country, the extent of B deficiency is more significant due to its excessive leaching in sandy loam soils because of high precipitation (Takkar 1996; Shukla and Behera 2012; Shukla and Tiwari 2016). The growing tips and younger leaves with stunted plant growth are the first symptoms of boron ­deficiency. The production of hollow heart in peanut, black heart in beet, distorted and lumpy fruit in papaya and hollow pith in cabbage and cauliflower are its outcomes. To sustain the high productivity of cereals, pulses, oilseeds and cash crops in B-deficient soils of Assam, Bihar, Orissa, Punjab and West Bengal soil application of 0.5–2.5 kg B ha−1 gave a response ranging from 108 to 684 kg grain kg−1 of B or 10 to 44% over NPK (Takkar et  al. 1989; Sakal and Singh 1995; Shukla et al. 2012).

Molybdenum In India, the least studied micronutrient is molybdenum. In Indian soils total Mo ranges from 0.1 to 12 mg kg−1 and ammonium oxalate (pH 3.3)-extracted available Mo varies from traces to 2.8 mg kg−1 (Behera et al. 2011, 2014). Soil colloids and minerals (at pH 80% of soil total Zn is present in the non-labile fraction even in slightly polluted soils. In ionic forms, both Cd and Zn may precipitate with phosphates, carbonates and sulphur. In anoxic conditions, such as in paddy rice fields, these undergo precipitation that decreases their availability to plants (Das et al. 2012). Owning to similar chemistry, soluble fractions of Zn and Cd compete for sorption sites onto soil solids. In alkaline soils, this competition occurs when competing metal is present at high concentration while, in acidic soil, this effect is significant even at low concentration of the competing metal. High Zn concentration in soil solution desorbed other exchangeable cations, including Cd (Diatta et  al. 2004; Lambert et al. 2007). In a soil spiked with Cd and Zn, most of the exchange sites were occupied by Zn (de Livera et al. 2011). Due to this competitive behaviour, both metals showed non-linear partitioning between the solid phase and solution phase (Ming et al. 2016). However, Zn shows more affinity for sorption in alkaline soils than Cd. In acidic soils, Cd showed no partitioning to soil solid phase in the presence of Zn, and therefore it is highly mobile in soil solution phase. This is one of the reasons for a severe ecotoxicological danger of Cd in acidic soils.

Mobility in Rhizosphere In soils, the rhizosphere is the surrounding area that shows physical, chemical and biological changes mediated by plant roots. Various changes in rhizosphere soil, such as high organic matter, enhanced microbial activity and low pH, determine metal distribution in chemical pools and solubility of solid labile fractions (Khoshgoftarmanesh et al. 2018). Root exudates (including low-molecular-weight organic compounds) may solubilise inorganic element fractions, mobilise organic fractions, enhance desorption from exchange sites, chelate soluble cations, enhance mobility in soil solution and increase availability to plant roots (Chen et al. 2017). Therefore, both the soluble fraction of Zn and Cd and their labile solid fractions affect their availability to roots (Chen et al. 2017; Nolan et al. 2005).

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Zinc and Cd differ in their affinities towards organic ligands. In the presence of Zn, Cd is dominantly bound to sulphate ligands, like phytochelatin or glutathione (Wiggenhauser et  al. 2016). In contrast, Zn preferably bound with N- and O-containing functional groups of organic ligands, like nicotianamine and phytosiderophores released by wheat (Marković et al. 2017). Composition of root exudates and their ability to bind metals differ from crop to crop. In maize, root exudates do not significantly affect the availability of Zn, but these do increase the availability of Cd to some extent (Redjala et al. 2011).

Root Uptake Different cultivars of cereals behave differently in Cd and Zn uptake and accumulation. In durum and bread wheat, for example, Cd and Zn compete to enter in the plasma membrane of roots (Hart et al. 2002). However, bread wheat is more capable of Cd accumulation in higher amounts than durum wheat. In addition, Cd translocation in different root sections of durum wheat may also be decreased when Zn concentration is greater than 1 μM in soil solution (Welch et al. 1999). According to Chaney (2015), however, Zn has less ability to restrict Cd transport in rice than other crops. The mechanisms of root Cd uptake are poorly known. To develop low-Cd genotypes, it is necessary to study transport pathways and other processes that result in high Cd accumulation in plant tissues (Li et al. 2017). Cadmium is thought to enter plant roots through different pathways. (a) From epidermal cells of roots where H2CO3 dissociates into H+ and HCO3− followed by absorption of Cd in exchange with H+ (Song et al. 2017). This process is rapid and occurs without any energy. After the exchange of ions, Cd follows the apoplastic pathway to enter into roots. This pathway does not face any physical barrier if Cd is taken up from developing root tips with no Casparian strip (Mahajan and Kaushal 2018). (b) Cadmium is transported from apoplastic space to cytosol via transporters localised in the plasma membrane. Cadmium may enter root cells through Zn2+, Fe2+ and Ca2+ channels (Sadana et al. 2003). These channels support Cd entry at a specific concentration of Cd in soil solution. (c) In the rhizosphere, the plant secretes various low-molecular-­ weight organic compounds that may chelate Cd and make it available with the help of transport proteins specific for the transport of chelated ions (Feng et al. 2017). Nutrients and water availability significantly affect bioavailability and uptake of soil Cd (Reeves and Chaney 2008). The mineral nutrients dissolved in soil solution can be easily transported across the plasma membrane of roots (Li et  al. 2017). However, plants hinder the entry of Cd into root cells. For example, as compared to Cd, Zn is present at a hundred times higher concentration in natural soil environments. However, Cd concentration should be equal to Zn to transport through Zn transporters on the plasma membrane (Song et al. 2017). This strategy protects a plant externally from the harmful effect of Cd. Plants may show Cd tolerance by maintaining active plant metabolism in the presence of Cd in plant cells. In metal

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tolerance, several physiological mechanisms are conferred that enable a plant to cope with the toxic level of metals. It is generally believed that metal transports on plasma membrane regulate Cd transporter (Belcastro et al. 2009). Cadmium accumulation and tolerance depend on the activity of such transporters. These transporters are present in all plant parts and regulate Cd uptake from soil to root and then accumulation into grains. Most often, general cation transporters or transporters of metal nutrients (e.g. Zn transporters) mediate Cd transport in plants (Sasaki et al. 2014). Cadmium may also be taken up by root epidermis cells via Ca channels. It is known that a high concentration of Ca or blockage of Ca channels restricts Cd uptake into roots of wheat (Li et al. 2017). However, root uptake of Cd occurs mainly through ZRT1 and other Zn transporters. Given below is a brief description of three transporters that mediate transportation of both Zn and Cd.

ZIP Proteins Zinc-regulated transporter (ZRT) and iron-regulated transporter (IRT)-like proteins are known as ZIP proteins. These transporters play a crucial role in metal uptake from extracellular spaces of root cells into their cytoplasm. The ZIP transporters are identified in all major cereals (Zheng et al. 2018). The first member of ZIP family is IRT1, which is involved in the transport of Fe2+ and other divalent cations, e.g. Zn2+, Cu2+, Cd2+ and Mn2+. In rice, IRT1 mediates the transport of both Zn2+ and Cd2+ across the root cell membrane (Lee and An 2009; Nakanishi et al. 2006). OsIRT1 gene increases Cd uptake in Fe-deficient conditions. Similarly, ZRT1 increases Cd uptake in Zn-deficient environments. In total, about 17 ZIP transporters have been recognised in rice while in maize 9 ZIP-coding genes have been identified (Li et al. 2013). Many ZIP transporters are also known for wheat (Sanaeiostovar et al. 2011).

YSL Proteins Yellow strip-like (YSL) transporters are involved in the transport of Zn-nicotianamine from phloem to endosperm or from endosperm to aleurone cells (Palmgren et al. 2008). These are also involved in Cd uptake by root cells and transportation of Cd-nicotianamine complexes through root membrane. Therefore, Cd when bound to nicotianamine and other low-molecular-weight organic ligands is transported through YSL proteins (Sasaki et al. 2011; Zheng et al. 2012).

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NRAMP Proteins The natural resistance-associated macrophage protein (NRAMP) is a family of metal transporters in plants. In rice, NRAMP transporters are present in roots that regulate the transmembrane transfer of Cd (Sasaki et al. 2011). The OsNRAMP1 is involved in the differences in Cd accumulation of different rice cultivars (Ishimaru et  al. 2012a, b). OsNRAMP5 has recently been recognised as a major Cd transporter in rice. This transporter is localised to the plasma membrane at the lateral side of root exodermis and endodermis. From sequence analysis, it is revealed that mutants of genotypes had many mutations of the same gene (OsNRAMP5). Functional analysis revealed that the mutants encoded defective transport proteins that decreased the uptake of Cd from roots (Ishikawa et  al. 2012). The suppression of OsNRAMP5 resulted in Cd translocation from roots to shoots (Ishimaru et al. 2012a). In rice, Cd is also absorbed by Mn transporter, NRAMP5.

Xylem Transport After passing through root surface, metal ions cross apoplastic barriers like Casparian strips in the root epidermis and enter into the symplastic pathway (Nocito et al. 2011). From there, ions are transported to xylem cells (Akhter et al. 2014) and move in ionic form in xylem along with water flow. Cadmium and Zn may also be directly delivered into xylem elements in root apex, where Casparian strips are not completely developed (Redjala et al. 2009). Regardless of the pathway, root xylem loading is the most critical step in Cd transport towards aboveground plant parts (Verbruggen et al. 2009; Yamaguchi et al. 2011). Both Cd and Zn generally follow the same mechanism of transport, but less Cd is transported towards xylem because a major portion of the root-absorbed Cd is compartmentalised into vacuoles and inactive root parts. Due to its high solution activity, however, Zn moves towards upper plant parts through xylem (Yoneyama et al. 2010, 2015). Xylem loading is mediated through P-type ATPase, HMA2, HMA4, and YSL proteins. These proteins are mainly involved in Cd pumping into xylem and mediate root-to-shoot transport of Cd. In rice, OsHMA2 is involved in both Zn and Cd loading into xylem and translocation from roots to shoots. The disturbance in its functioning resulted in less accumulation of Cd in shoots and grains (Curie et al. 2009; Hussain et al. 2004; Mills et al. 2012). OsZIP7 also plays an important role in root-to-xylem loading of both Zn and Cd. It is present in stele in rice roots and in vascular bundle cells of nodes. Additionally, OsZIP1 is present in the pericycle and overlapped with OsZIP7 (Satoh-Nagasawa et  al. 2012; Takahashi et  al. 2012b; Uraguchi et  al. 2011). So, these transporters cooperate in root-to-xylem loading of Zn and Cd. Due to similarity in transportation pathway, Zn competes with Cd for these transporters.

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Metabolism in Plant Tissues Plants can tolerate an ultra-low level of Cd by certain defensive mechanisms like Cd compartmentalisation in plant roots (Hart et al. 2005), chelation, regulating enzyme activities (Ekmekçi et al. 2008) and activating genes that regulate transport proteins (Martos et al. 2016). Cadmium has the ability to bind specific proteins and replace certain cations from binding sites. In this way, it directly affects metabolic activities in the plant by inactivation of enzymes and production of reactive oxygen species (ROS). Cadmium-induced oxidative stress increased malondialdehyde (MDA) and H2O2 contents in wheat (Zhao et al. 2005a), rice (Hassan et al. 2005a) and maize (Anjum et al. 2016). Photosynthetic rate is also decreased by Cd exposure to plant. All parameters that determine photosynthesis, including contents of photosynthetic and accessory pigments (chlorophyll a, b and carotenoids), stomatal conductance, transpiration rate and internal CO2 concentration, are adversely affected by prolonged Cd exposure. In maize, Cd toxicity reduced chlorophyll contents by about 65% that ultimately decreased the rate of photosynthesis (Ekmekçi et al. 2008). Zinc has ameliorative effects on Cd stress in plants. Zinc application decreased oxidative damage due to Cd stress in plants (Lin and Aarts 2012). In winter wheat, Cd-induced oxidative stress was decreased by Zn that activated antioxidant enzymes, like ascorbate peroxidase, guaiacol peroxidase and catalase (Cherif et  al. 2011; Hassan, Zhang, et al. 2005; Saifullah et al. 2014; Wu et al. 2020; Zhao et al. 2005a). Moreover, Cd-induced low protein contents in wheat were increased by foliar-­ applied Zn-EDTA (Forster et al. 2018). In Cd-stressed plants, application of Zn significantly increases the net photosynthetic rate and all related physiological processes. In wheat, due to a high Cd uptake, the net photosynthetic rate was decreased from 29 to 24 μmol CO2 m−2 s−1 (Zhou et al. 2019). Zinc application restored it to 27 μmol CO2 m−2 s−1. Similarly, in rice, decrease in photosynthetic rate was up to 32% after 7 days of Cd exposure and up to 48% after 21 days of Cd exposure (Hassan et al. 2005b). Application of Zn, under such conditions, significantly increased photosynthetic rate and plant growth.

Phloem Transport Transport of Cd and Zn from xylem to phloem is a key process in the determination of Cd accumulation in cereal grains. Nodes are very important for nutrient distribution to developing regions or panicles through phloem loading. In nodes, vascular bundles are of three types, e.g. enlarged, transit and diffuse vascular bundles (Yamaguchi et al. 2011). Inter-transfer of these metals occurred from enlarged to diffuse vascular bundles that help in their transfer from the lower node to upper nodes of rice and other cereals.

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In rice nodes, OsZIP7 regulates the transfer of Zn and Cd from nodes to developing parts and grains (Tan et al. 2019). OsZIP7 also cooperates with OsHMA2 and OsZIP3 for intervascular transfer of Zn and Cd in nodes (Yamaji and Ma 2014). Xylem-to-phloem loading also occurs through OsHMA2 transporter located at nodes in rice (Yoneyama et al. 2010). Both Zn and Cd are transported through this same transport protein; therefore, phloem transport of Cd is affected by Zn supply (Gomes et al. 2002). Low-affinity cation transporters (such as LCT1) are also involved in the xylem-­ to-­phloem loading of both Zn and Cd. This transporter has higher transport activity for Cd than Zn in rice. A downregulation of LCT1 decreased Cd accumulation in leaves and grains. In rice, OsLCT1 has been recently recognised as a gene facilitating Cd transport from xylem to phloem. In wheat, LCT1 is localised around vascular bundles and in stem during the reproductive phase (Uraguchi et  al. 2011). This transporter is highly expressed in plant nodes near maturity stage where most of the exchange process occurred from xylem to phloem. Inactivation of this transport protein resulted in a substantial decrease in grain Cd concentration without any adverse effect on the concentration of other nutrients and crop yield (Uraguchi et al. 2011). In the whole route of transport, OsHMA3 and OsLCT1 are the specific Zn transporters that also transport Cd from roots to shoots. High Zn concentration in xylem or phloem led to low Cd transport through these transporters into rice grains (Adil et al. 2020; Bashir et al. 2019). Long-distance transport of Cd in phloem occurs as Cd-chelator complexes. In the phloem, complexes of both Cd and Zn are transported via YSL transporters (Kato et al. 2010). Thiols, that make complexes with Cd in the phloem, are present in phloem in high quantities during the exposure to high Cd. Cadmium is also mobilised in the form of complexes with phytochelatin (Palmgren et al. 2008). Zinc, however, prefers to form complexes with nicotianamine in the phloem. Overall, Cd is less mobile in phloem than Zn (Habib 2009).

Grain Accumulation Grain Cd concentration over 0.1 mg kg−1 in wheat and 0.2 mg kg−1 in other cereals is considered toxic for human consumption (Codex Alimentarius Commission 2017). Depending on the level of soil contamination, grain Cd concentration varies in cereal grains from permissible to toxic levels (Hussain et al. 2019a, b). At toxic levels of Cd, increase in the concentration of ROS causes damage to membranes and increases translocation of Cd towards grains. Among various strategies, high Zn supply is one of the well-known strategies to limit Cd loading into grains. Soil-applied Zn decreased Cd concentration in grains of wheat by 42%, from 0.71 to 0.50 mg kg−1 (Murtaza et al. 2017). Both soil and foliar application of Zn significantly decreases Cd accumulation in cereal grains (Adiloglu 2002; Hussain et al. 2019a; Qaswar et al. 2017; Saifullah et al. 2014; Tavarez et al. 2015). Therefore, Zn supply at grain-filling stage increases the grain

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Zn concentration and restricts the remobilisation of Cd from other plant parts (Jiang et al. 2007; Saifullah et al. 2016). The decrease in grain Cd accumulation with Zn supply can be considered as an additive effect of Zn on Cd transport across plant barriers placed from root surfaces to developing grains.

Partitioning Within a Plant Cadmium sequestration and translocation from roots, and its accumulation in cereal grains, largely depend on genetic variations (Nocito et  al. 2011; Uraguchi et  al. 2011). Absorbed metal ions are retained in roots by the process of metal sequestration, presence of chelating molecules and apoplastic barriers in roots. During maturation of endodermis and exodermis, root cell walls are impregnated with suberin that restricts Cd mobility to root stele. Besides this, vacuolar sequestration is also demonstrated as a major factor for major variation in Cd accumulation in grains of different varieties of rice and other cereals (Lux et  al. 2011). Transport protein OsHMA3 is involved in the vacuolar storage of Cd which retained most of the absorbed Cd into roots and restricted its mobility to shoots and grains (Takahashi et al. 2012a). It is found that some metal chelators bound Cd in rice roots and do not allow translocating towards rice grains. The partitioning of Cd in plant organs is influenced by Zn supply. At grain-filling stage, in a low-Cd-accumulator wheat, sufficient Zn supply (10  μM) in solution decreased grain Cd by 16% and bract Cd by 6%, while increased rachis Cd accumulation by 40% (Hart et  al. 2005). In another study, application of sufficient Zn (10  μM) resulted in 6–52% Cd partitioning in roots, 40–90% in lower leaves, 0.8–6% in stems and 0.3–3% in flag leaves while