Photosynthesis, Productivity, and Environmental Stress E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 787

Veröffentlichungsjahr: 2019

Beschreibung

A guide to environmental fluctuations that examines photosynthesis under both controlled and stressed conditions Photosynthesis, Productivity and Environmental Stress is a much-needed guide that explores the topics related to photosynthesis (both terrestrial and aquatic) and puts the focus on the basic effect of environmental fluctuations. The authors--noted experts on the topic--discuss photosynthesis under both controlled and stressed conditions and review new techniques for mitigating stressors including methods such as transgeneics, proteomics, genomics, ionomics, metabolomics, micromics, and more. In order to feed our burgeoning world population, it is vital that we must increase food production. Photosynthesis is directly related to plant growth and crop production and any fluctuation in the photosynthetic activity imposes great threat to crop productivity. Due to the environmental fluctuations plants are often exposed to the different environmental stresses that cause decreased photosynthetic rate and problems in the plant growth and development. This important book addresses this topic and: * Covers topics related to terrestrial and aquatic photosynthesis * Highlights the basic effect of environmental fluctuations * Explores common stressors such as drought, salinity, alkalinity, temperature, UV-radiations, oxygen deficiency, and more * Contains methods and techniques for improving photosynthetic efficiency for greater crop yield Written for biologists and environmentalists, Photosynthesis, Productivity and Environmental Stress offers an overview of the stressors affecting photosynthesis and includes possible solutions for improved crop production.

Leseprobe

Photosynthesis, Productivity, and Environmental Stress

Edited by

Parvaiz Ahmad

Department of Botany and Microbiology, King Saud University, Riyadh, Saudi Arabia

and

Department of Botany, S. P. College, Srinagar, Jammu and Kashmir, India.

Mohammad Abass Ahanger

College of Life Science, NorthWest A & F University, Yangling Shaanxi, China.

Mohammed Nasser Alyemeni

Department of Botany and Microbiology, King Saud University, Riyadh, Saudi Arabia.

Pravej Alam

Department of Biology, Prince Sattam bin Abdul Aziz University, Alkharaj, Riyadh, Saudi Arabia.

Copyright

This edition first published 2020

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Library of Congress Cataloging‐in‐Publication Data

Names: Ahmad, Parvaiz, editor. | Ahanger, Mohammad Abass, editor. | Alyemeni, Mohammed Nasser, editor. | Alam, Pravej, editor.

Title: Photosynthesis, productivity, and environmental stress / edited by Parvaiz Ahmad, Mohammad Abass Ahanger, Mohammed Nasser Alyemeni, Pravej Alam.

Description: First edition. | Hoboken : Wiley, 2019. | Includes index.

Identifiers: LCCN 2019024513 (print) | LCCN 2019024514 (ebook) | ISBN 9781119501770 (cloth) | ISBN 9781119501831 (adobe pdf) | ISBN 9781119501824 (epub)

Subjects: LCSH: Photosynthesis–Research. | Plants–Effect of stress on–Research.

Classification: LCC QK882 .P385 2019 (print) | LCC QK882 (ebook) | DDC 572/.46072–dc23

LC record available at https://lccn.loc.gov/2019024513

LC ebook record available at https://lccn.loc.gov/2019024514

Cover Design: Wiley

Cover Image: © Matteo Senesi/Getty Images

List of Contributors

Parvaiz Ahmad

Department of Botany and Microbiology,

King Saud University, Riyadh,

Saudi Arabia

and

Department of Botany, S.P. College,

Srinagar, Jammu and Kashmir

India

Ifthekhar Ali

Department of Soil and Environmental Sciences,

Gomal University,

Dera Ismail Khan,

Pakistan

Shafaqat Ali

Department of Environmental Sciences and Engineering,

Government College University Allama Iqbal Road Faisalabad,

Pakistan

Tofig Idris Allahverdiyev

Research Institute of Crop Husbandry,

Ministry of Agriculture of the Republic of Azerbaijan,

Pirshagi settlement, Sovkhoz, Baku AZ, Azerbaijan,

Muhammad Azam

Department of Horticulture,

University of Agriculture,

Faisalabad, Pakistan

Hasan Garib Babayev

Institute of Molecular Biology and Biotechnologies,

Azerbaijan National Academy of Sciences, Matbuat Avenue, Baku AZ, Azerbaijan.

Aditya Banerjee

Post Graduate Department of Biotechnology,

St. Xavier's College (Autonomous),

Mother Teresa Sarani, Kolkata, West Bengal, India

Shahnigar Mikayil Bayramov

Institute of Molecular Biology and Biotechnologies,

Azerbaijan National Academy of Sciences, Matbuat Avenue, Baku AZ, Azerbaijan.

Amanda A. Cardoso

Department of Botany and Plant Pathology,

Purdue Center for Plant Biology,

Purdue University, West Lafayette, IN, USA

Laury Chaerle

Department of Physiology,

Laboratory of Functional Plant Biology,

Ghent University,

K. L. Ledeganckstraat, Ghent Belgium

Biswanath Dari

Aberdeen Research and Extension Center,

University of Idaho,

Aberdeen, ID, USA

Cristiane J. da‐Silva

Departamento de Botânica,

Instituto de Biologia, Universidade Federal de Pelotas,

Pelotas, RS, Brasil

Letúzia M. de Oliveira

Soil and Water Science Department,

University of Florida,

Gainesville, FL, USA

Murat Dikilitas

Department of Plant Protection,

Harran University,

Sanliurfa, Turkey

Ulduza Ahmad Gurbanova

Institute of Molecular Biology and Biotechnologies,

Azerbaijan National Academy of Sciences,

Matbuat Avenue, Baku AZ, Azerbaijan.

Irada Mammad Huseynova

Institute of Molecular Biology and Biotechnologies,

Azerbaijan National Academy of Sciences, Matbuat Avenue, Baku AZ, Azerbaijan.

Meeshaw Hussain

Institute of Molecular Biology and Biotechnology,

Bahauddin Zakariya University,

Multan, Pakistan

Syed Sarfraz Hussain

Department of Biological Sciences,

Forman Christian College (A Chartered University) Lahore,

Pakistan

Muhammad Irfan

Department of Biological Sciences,

Forman Christian College (A Chartered University),

Lahore, Pakistan

Anjana Jajoo

School of Life Science and School of Biotechnology,

Devi Ahilya University,

Indore, Madhya Pradesh, India

Yachana Jha

Department of Biotechnology, Genetics and Bioinformatics,

N. V. Patel College of Pure and Applied Sciences, S. P. University,

V. V. Nagar, Anand (Gujarat), India

Sema Karakas

Department of Soil Science and Plant Nutrition,

Harran University,

Sanliurfa, Turkey

Naser Karimi

Laboratory of Plant Physiology,

Department of Biology, Faculty of Science,

Razi University, Kermanshah, Iran

Mumtaz Khan

Department of Soil and Environmental Sciences,

Gomal University,

Dera Ismail Khan, Pakistan

Belur Satyan Kumudini

Department of Biotechnology, School of Sciences,

JAIN (Deemed‐to‐be University),

Bengaluru, India

Avinash Mishra

Division of Biotechnology and Phycology,

CSIR‐Central Salt and Marine Chemicals Research Institute,

G. B. Marg, Bhavnagar, Gujarat, India

Neeha Nawaz

Department of Environmental Sciences and Engineering,

Government College University Allama Iqbal Road Faisalabad,

Pakistan

Savita Veeranagouda Patil

Department of Biotechnology, School of Sciences,

JAIN (Deemed‐to‐be University),

Bengaluru, India

Muhammad Rizwan

Department of Environmental Sciences and Engineering,

Government College University,

Faisalabad, Pakistan

Aryadeep Roychoudhury

Post Graduate Department of Biotechnology,

St. Xavier's College (Autonomous),

Mother Teresa Sarani, Kolkata West Bengal, India

Aykut Saglam

Department of Molecular Biology and Genetics,

Karadeniz Technical Univeristy,

Trabzon, Turkey

Bujun Shi

School of Agriculture, Food and Wine, Waite Campus,

University of Adelaide,

Adelaide, SA Australia

Debjani Sihi

Environmental Sciences Division,

Oak Ridge National Laboratory,

Bethel Valley Rd, Oak Ridge, TN, USA

Eray Simsek

Department of Plant Protection,

Harran University,

Sanliurfa, Turkey

Bhupendra Singh

School of Life science,

Devi Ahilya University,

Indore, Madhya Pradesh, India

Zahra Souri

Laboratory of Plant Physiology,

Department of Biology, Faculty of Science,

Razi University, Kermanshah, Iran

Rupal Singh Tomar

School of Life science,

Devi Ahilya University,

Indore, Madhya Pradesh, India

Roland Valcke

Laboratory of Molecular and Physical Plant Physiology,

Faculty of Sciences,

Hasselt University,

Diepenbeek, Belgium

Dominique Van Der Straeten

Laboratory of Functional Plant Biology,

Department of Physiology,

Ghent University,

K. L. Ledeganckstraat, Ghent Belgium

Rinukshi Wimalasekera

Department of Botany, Faculty of Applied Sciences,

University of Sri Jayewardenepura,

Gangodawila, Sri Lanka

Sonam Yadav

Division of Biotechnology and Phycology,

CSIR‐Central Salt and Marine Chemicals Research Institute,

G. B. Marg, Bhavnagar, Gujarat, India

Preface

Plants due to their sessile nature are exposed to different environmental stresses. These environmental stresses (biotic and abiotic) have been reported to decrease plant growth and development and massive crop loss worldwide. Environmental stress imposes ionic, osmotic stress and in severe cases causes oxidative stress in plants. Oxidative stress is generated by the production of reactive oxygen species (ROSs). These ROSs are highly reactive and can attack biomolecules and change their structural and functional utility. However, plants are equipped with defense mechanisms like osmolytes, osmoprotectants and antioxidants that enable them to withstand the negative effects of osmotic and oxidative stress. Genes and proteins related to defence mechanisms are up and downregulated and leads to plant tolerance against the particular stress.

Plant growth and development is regulated by different physio‐biochemical and molecular processes which are dependent on photosynthesis. All environmental stresses, irrespective of their targets and nature of perception in plants, algae, and cyanobacteria bring perturbation in the cellular energy homeostasis. The stress‐adaptive mechanisms developed by these photosynthetic organisms are primarily based on reestablishment of cellular energy balance. In this background photosynthesis, the energy‐producing process, plays a central role in modulating energy signaling and balance, which have significant implications for energy homeostasis of the whole organism.

Therefore, this book is compiled to acquaint readers with the latest update and future goals of photosynthetic research and also some of the scientific challenges that still exist in photosynthesis and living organism's interactions. The book is a compilation of 14 chapters.

The volume entitled “Photosynthesis, Productivity, and Environmental Stress” has a wide variety of chapters with updated information related to the relevant topics. This book has been planned to fulfill the gap of knowledge in relation to photosynthesis, crop productivity, and environmental stress. Chapter 1 of this book describes the effects of organic pollutants (OPs) on photosynthesis. The authors have worked very hard and have provided information on the characteristics of the OPs, sources of OPs, uptake and accumulation of OPs by plants, and effects of OPs on plant growth. Chapter 2 demonstrates the photosynthetic processes under cold stress and the authors have discussed the aspects of primary targets of cold stress in plants, cold stress infiltration of the chloroplast membrane integrity, damage to photosynthetic apparatus, effects on carbon dioxide (CO2) fixation, and strategies to ameliorate cold stress and improve photosynthesis. Chapter 3 deals with high‐temperature stress and photosynthesis under the pathological impact with the main focus on high‐temperature stress on crop plants, photosynthesis mechanisms, the impact of pathogens on photosynthesis mechanisms under temperature stress, and genomic, biochemical, and physiological approaches for crop plants under temperature and pathogenic stresses. Chapter 4 describes differential photosynthetic responses to light intensity with the thrust on characteristics of light, light absorption, and pigments, light absorption by leaves, light and photosynthetic responses. Chapter 5 deals with a case study of the effect of mineral mobilizing bacteria on photosynthesis and other physiological attributes under salinity stress. Chapter 6 narrates the regulation of photosynthesis under metal stress and the authors explain the ill effects of metals on photosynthesis and the mechanisms of photosynthesis regulation under metal stress. Heavy metals and photosynthesis: recent developments is the subject of Chapter 7. The authors take the opportunity to explain the heavy metals and hyperaccumulation, characteristics of hyperaccumulator plants, hyperaccumulation and photosynthesis, and the effect of heavy metals on chloroplast structure, gas‐exchange, photosynthetic pigments, photosystems (PSI and PSII), key photosynthetic enzymes, and antioxidant defence mechanism from the photosynthetic systems. Chapter 8 deals with the regulation of photosynthesis under abiotic stresses. Different abiotic stresses like, drought, salinity, cold, and heat stress have been considered with a focus on photosynthesis. Overexpression of photosynthesis related genes and transcription factors have also been explained very well. Chapter 9 describes the regulatory roles of miRNAs for enhancing photosynthesis in plants under environmental stresses. miRNAs involved in photosynthesis and other downstream biological processes, effect of abiotic stresses on photosynthesis and plant productivity, genome wide miRNA profiling under abiotic stresses, functional characterization of miRNAs associated with photosynthesis and the role of MiRNAs in shoot/tiller development, root development, controlling stomatal density, hormone signaling, and controlling nodule development in leguminous crops are the thrust area of this chapter. Chapter 10 explains mineral mobilizing bacteria (MMB) mediated regulation of secondary metabolites for proper photosynthesis in maize under stress. The main focus of the chapter is on MMB mediated regulation of nutrients, chlorophyll content, carbon/sugar metabolite, nitrogen metabolite, and gene expression for secondary metabolites production and photosynthesis. MMB mediated regulation of secondary metabolites production and photosynthesis under biotic and abiotic stresses is also explained. Chapter 11 discusses the improvement of photosynthesis with phytohormones. The authors explain phytohormones: watchdogs of plant growth and development, the role of phytohormones in photosynthesis and abiotic stress tolerance. Chapter 12 deals with thermal and chlorophyll fluorescence imaging with respect to drought, salt, light, herbicides, pathogens, herbivory, and air pollutant stresses. Chapter 13 is about the biotechnological approach of introgression of C4 pathway gene(s) in C3 plants to improve photosynthetic carbon assimilation for crop improvement. The authors explain CO2 assimilation in C3 and C4 plants, evolution of C4 metabolism in higher plants, the effect of elevated CO2 on C3 and C4 plants, and ectopic expression of C4 photosynthesis genes in C3 plants. Chapter 14 describes a case study regarding the interaction of photosynthesis, productivity, and the environment. Here the authors explain the effect of drought stress on some physiological traits, yield, and yield components of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes, subcellular localization of the NADP‐ME and NAD‐ME activity in the leaves of the wheat genotypes under soil drought conditions physico‐chemical parameters of NADP‐ME and NAD‐ME in the leaves of the Barakatli 95 and Garagylchyg 2 genotypes under soil drought conditions.

Although we have tried our best to gather the information and recent updated discoveries related to photosynthesis, crop productivity, and environmental stress in this volume. We believe however, that there still must be some scope for expansion; therefore, valuable suggestions from the readers and researchers are welcome, which we would include in our future editions and volumes. Last but not the least, we are very much thankful to the contributors and the entire publication team of Wiley who helped in every possible way to make this project possible and valuable for publication.

Dr. Parvaiz Ahmad

Dr. Mohammad Abass Ahanger

Dr. Mohammed Nasser Alyemeni

Dr. Pravej Alam

About the Editors

Dr. Parvaiz Ahmad is the Senior Assistant Professor in Department of Botany at Sri Pratap College, Srinagar, Jammu and Kashmir, India. Dr. Ahmad has completed his Master of Science in Botany in 2000 at Jamia Hamdard, New Delhi, India. After receiving a Doctorate degree from the Indian Institute of Technology (IIT), Delhi, India, he joined the International Centre for Genetic Engineering and Biotechnology, New Delhi, in 2007. His main research area is Stress Physiology and Molecular Biology. He has published more than 75 research papers in peer‐reviewed journals and 60 book chapters. Dr. Ahmad has published 21 books with different International publishers, like Elsevier, Springer, Wiley, Taylor and Francis, etc. He is a recipient of the Junior Research Fellowship and Senior Research Fellowship by CSIR, New Delhi, India. Dr. Parvaiz has been awarded the Young Scientist Award under the Fast Track scheme in 2007 by the Department of Science and Technology, of the Government of India. Dr. Parvaiz is actively engaged in studying the molecular and physio‐biochemical responses of different agricultural and horticultural plants under environmental stress.

Dr. Mohammad Abass Ahanger is currently working as Guest Lecturer in the Education Department, Government of Jammu and Kashmir India. Dr. Ahanger completed his Postgraduate education in Botany from Jiwaji University, Gwalior, India in 2010 specializing in plant stress physiology. After receiving M Phil, Dr Ahanger completed his Ph D in 2016 from the same university. His main research interests are elucidation of tolerance mechanisms in plants for improved abiotic stress tolerance. He has published more than 15 research publications in reputed national and international journals, and has contributed several book chapters to internationally published volumes from publishers like Springer, Elsevier, and Wiley.

Dr. Pravej Alam has completed his PhD in Biotechnology from the Department of Biotechnology, Jamia Hamdard (Hamdard University) New Delhi, India in 2012. Dr. Alam did his doctoral research focused on biosynthesis of secondary metabolite production in plants and microbes through a genetic engineering approach. Dr. Alam has been awarded Dr. D.S. Kothari Postdoctoral Fellowship by UGC‐Govt. of India. He also served as an Assistant Professor (Guest) in Biotechnology Department, Jamia Millia Islamia, New Delhi, India from 2012 to 2015. In 2015, he has finally joined as Assistant Professor, Biology Department, College of science Prince Sattam bin Abdulaziz University, Saudi Arabia. Dr. Alam has published a good number of articles in high impact factor journals of plant science.

Prof. Dr. Mohammed Alyemeni is currently a Professor of Ecophysiology at Department of Botany and Microbiology – King Saud University. He received his Bachelor of Science from King Saud University, Saudi Arabia, his Master of Philosophy from Reading University in United Kingdom, and his PhD degree in Plant Ecology from Edinburgh University – United Kingdom. His research interest is focused in plant ecology, stress physiology, and plant hormones. He has taught university students at all levels for over 38 years and has guided many students to the award of MSc and PhD degrees. He has been the principal investigator of the various projects and has contributed extensively to the world plant ecology and physiology literature with over 90 publications appearing in ISI Web of Science Index Journals. He has also published several books in the area of plant ecology and physiology in Arabic and English.

1Effects of Organic Pollutants on Photosynthesis

Rupal Singh Tomar 1, Bhupendra Singh 1, and Anjana Jajoo 1,2

1 School of Life Science, Devi Ahilya University, Indore, Madhya Pradesh, India

2 School of Biotechnology, Devi Ahilya University, Indore, Madhya Pradesh, India

1.1 Introduction to Organic Pollutants

Life on earth is powered by the process of photosynthesis. For more than billion years, life on earth has been transformed by the photosynthetic organisms. Photosynthetic organisms like cyanobacteria, algae, and plants harvest sunlight and produce oxygen and organic molecules, which are responsible for life on earth. Photosynthesis starts with the absorption of light of the visible region coming from the sun. It includes several partial processes such as splitting of water to molecular oxygen, electrons, and protons, which participate directly in the electrochemical reactions leading to phosphorylation and fixation of carbon dioxide into sugars.

Plants are sessile organisms that cannot move and thus cannot avoid exposure to fluctuating environmental conditions. Plants face several abiotic stress factors, such as water deficit (drought), excess water (flooding/water logging), extremes of temperatures (cold, chilling, frost, heat), high salt, mineral deficiency, and toxicity. Because of climate changes, it is predicted that these abiotic stresses may become more intense and frequent. Climate change, occurring either naturally or anthropogenically, poses serious challenges for agriculture all over the world.

During the last decades, environmental contamination has become one of the major problems on this planet. Anthropogenic activities have led to an abundance of soil, water, and air pollutants, factors that directly affect plants. Amongst these, environmental organic pollutants (OPs) have an immense effect on plant growth and development. OPs and their transformation products have been the most investigated environmental pollutants in last two decades. They accumulate in humans, animals, and plants as they are hydrophobic and lipid‐soluble, and they biomagnify as they move up the food chain. OPs can be found everywhere on earth as they can travel great distances in both air and water. OPs have been found to cause serious disorders in mammals such as cancer and endocrine disorders. It is therefore essential to understand how these contaminants enter and move in the ecosystem and environment. Plants are capable of taking up, transforming, and accumulating environmental pollutants such as OPs. Several physiological and biochemical reactions in plants are influenced by OPs in the same way as other toxic compounds such as metals. They can change the energetic metabolism of plants and are associated with growth and development. About 90% of the OPs accumulate in the soil due to their hydrophobic nature, because of which they rapidly associate with solid particles of soil and permeate to bottom sediments. Several studies have been carried out on the uptake of OPs by plants and their toxicity to plants cells. Here we present an updated account of these studies, focusing on (i) the uptake of OPs by the plants and (ii) their harmful effects on the photosynthetic reactions.

The rapid growth in chemical and agrochemical industries has resulted in the release of a large number of new and toxic chemical compounds into the environment. These OPs are getting significant attention in environmental and engineering research. Several countries and international organizations have published lists of harmful pollutants, which are at alarming levels and should be controlled immediately. The group of organic chemicals discussed here include the pesticides, antibiotics, bisphenol A (BPA) and polycyclic aromatic hydrocarbons (PAHs) (Figure 1.1). Several internal and external factors regulate normal development and productivity of plants. External factors include natural and man‐made chemicals that have detrimental effects on plants. OPs are a major threat in terrestrial as well as aquatic ecosystems. They quite easily cross the cell membrane of plant and animal cells due to their lipophilic character resulting in substantial bioconcentration. Plant roots and leaves serve as a major sink for these pollutants. Plants and bacteria are both involved in the biogeochemical cycling of OPs. Uptake of OPs depends on cell size, temperature, and their hydrophobicity (Dachs et al. 2002; Gang and Xitao 2005). The toxic effect of OPs may be a result of direct interaction, or some OPs may accumulate into the plant tissue to a toxic level and can affect the plant development at any stage (Hanano et al. 2015). OPs contaminate water, soil, and sediments and thus become a major environmental problem that needs to be rectified. In more recent years, the studies with these OPs are more focused on the characterization of toxicity response in a variety of plant and animal species. Scientists are also trying to explore some plants species to degrade or at least to detoxify (phytoremediation) these OPs to protect other organisms from the adverse effects of these compounds.

Figure 1.1 Broad classification of organic pollutants (OPs), based on their effects on plants and photosynthetic machinery.

1.2 Characteristics of the Organic Pollutants

All OPs are synthetic chemicals, many are pesticides, while some others are products or by‐products of industrial processes or of incomplete combustion. They are quite persistence in the environment, and it may take a long time, up to several decades or even centuries, for their degradation. OPs have been found in tissues or environmental samples from almost all parts of the world. They are lipophilic in nature and have a tendency to remain in lipid‐rich tissues. This affinity for the fat tissues suggests that most likely, OPs will accumulate, persist, and bioconcentrate, and eventually could reach toxicologically significant amounts. In nature, OPs enter the food chain and prove to be toxic to plants, animals, and human beings.

Because of their unique physicochemical characteristics, OPs are either adsorbed on atmospheric particles or exist in the vapor phase, which facilitates their transport over larger distances in the atmosphere. Very low water solubility and high affinity for lipids lead to their accumulation in the tissues (El‐Shahawi et al. 2010). From the atmosphere, they can be transferred to the ground surface either by dry (e.g. flying ashes) or by wet (through rainout/washout) deposition. They are, however, easily deposited on solid particles such as ash, dust, and soil. They have fair solubility in organic fluids such as fats, oils, and liquid fuels. This implies that there will be more OP content if more solid particles and organic liquids are present in the water (Katsoyiannis and Samara 2005). Interestingly, they have also been detected in snow and ice at the North Pole, along with the animals of the North Sea. This shows that they traveled long distances to reach that location, as nobody has used them in the polar regions (Kumar et al. 2005; Katsoyiannis and Samara 2005). It is reported that from the environment, 45% of PAHs are taken up by the plants (Wagrovski and Hites 1997).

1.3 Sources of Organic Pollutants

Two possible natural sources of OPs are volcanic activity and forest fires. Several industrial sources also pave the way for their entry e.g. power stations, incinerating plants, agricultural sprays, and thermal stations. Sometimes, humans also contribute to OPs unintentionally through chemical factories, wastes from the use of obsolete oil, fly ash, cement plants, sewage sludge, products from incinerators, and burning of fossil fuels (Ying et al. 2005; Wenzel et al. 2006).

Thus, important emission sources of OPs are: combustion processes, industrial production processes, energy production emissions, and open burning process emissions. These sources account for just over half of total PAH emissions and more than one third of the total dioxin and furan emissions. Apart from these, there are agriculture sources and waste incineration emissions too. Industrial processes and product use sources account for half of the polychlorinated biphenyl (PCB) emissions.

1.4 Uptake and Accumulation of Organic Pollutants in Plants

About 80% of the land surface on earth is covered with green vegetation having a cuticle rich in lipids. Plants have a significant role in global distribution and cycling of various OPs. Plants absorb OPs either from soil (through roots) or air (through leaves) (Figure 1.2). OPs, such as PAHs, BPA and antibiotics are mainly absorbed by plants through roots because of their low volatility. The plant root generally comes in contact with OPs first and so absorption through roots is the commonest way of uptake. Plants may sequester these pollutants through several routes. It includes (i) uptake from soil, transfer to plant roots and thereafter translocation within the xylem, (ii) deposition from the atmosphere on the leaf surface or uptake through stomata and further translocation through the phloem (Simonich and Hites 1994, 1995). The route of uptake depends on the physicochemical properties of the pollutant, property of the soil, and the plant species. For lipophilic OPs, however, the main pathway of accumulation is transfer from atmosphere to plant (Ockenden et al. 1998). Large amounts of OPs are continuously released into the environment. Plants form the basal step of the terrestrial food web and are therefore important for agricultural as well as natural ecosystems. Bioconcentration is defined as the uptake and concentration of compounds from the environment into a living organism (Bernes 1998). The concentration in plant tissues is related to the plant species in relation to physiology, leaf area, root depth, and growing time period, etc. (White 2002; Gonzales et al. 2003). The pathway by which OPs enter the plants varies with the hydrophobic nature, solubility in water, vapor pressure, and environmental conditions, such as organic content of the soil and temperature. Through their foliage, plants present a large area for uptake from the atmosphere. Many of the highly toxic pollutants are hydrophobic in nature and the lipid cover on the surface of leaves provides an ideal sink for deposition and accumulation of these compounds. Through stomata, gaseous molecules diffuse inside and outside thereby interacting with a large hydrophobic area. After entering the food chain of ecosystems, OPs are biomagnified from one trophic level to the next. Plant species which offer a high surface‐to‐volume ratio accumulate more organic air pollutants compared to the species which have compact leaves. A well‐established link between photosynthesis and plant growth is reported (Huang et al. 1997; Marwood et al. 2001).

Figure 1.2 Schematic presentation of various pathways of uptake of OPs by plants.

1.5 Effects of Organic Pollutants on Plant Growth

Plant growth is also influenced by nutritional, genetic, hormonal, and environmental conditions. It has been shown that exposure to certain environmental pollutants could promote or inhibit the growth, seed germination, elongation of pollen tubes, rate of photosynthesis, and content of hormones in the plants.

Being a vital organ of plants, roots absorb not only water and nutrients from soil, but also absorb and transfer several pollutants. In comparison to aerial parts of the plant, roots in the soil are directly exposed to OPs present in the soil. Several studies are reported which give an assessment of global effects of OPs on plants (Yildiztekin et al. 2015; Du et al. 2006; Liu et al. 2009; Kreslavski et al. 2017; Tang et al. 2006; Jajoo et al. 2014; Jajoo 2017). Recent research on the effects of OPs on plant cells mainly targets the detrimental effects on the process of photosynthesis (Kreslavski et al. 2017; Tomar and Jajoo 2013a; Sharma et al. 2017), protein synthesis, lipids, nucleic acids, (Pašková et al. 2006), and hormones (Váňová et al. 2011; Kummerova et al. 2010). However different plant species sequester pollutants at different rates and extents (Kömp and McLachlan 1997). OPs affect plants by inhibiting several biological processes such as, mitosis, germination, the function of enzymes, production of hormones, root growth, leaf formation, synthesis of pigments, photosynthetic proteins or DNA, destruction of cell membranes, and promoting uncontrolled growth (Figure 1.3). OPs like pesticides can affect the germination process thereby altering physiological, biochemical, and enzymatic reactions that ultimately inhibit the yield and also lead to accumulation of OPs in plants, vegetables, fruits, and different organisms. Moreover, UV exposure causes photooxidation of some OPs such as PAHs. The photoproducts have more toxic effects on plants (Grenvald et al. 2013; Tomar and Jajoo 2015).

Figure 1.3 General effects of OPs on growth and photosynthesis in plants.

As in the case of other abiotic stress (e.g. heavy metal, high temperature, and high salt), OP induced oxidative stress stimulates accumulation of reactive oxygen species (ROS), (Liao and Chen 2007; Ye et al. 2003; Zhang et al. 2007), which in turn induce DNA/RNA damage, membrane damage and lipid peroxidation (LPO). The effects of PAHs (pyrene) on ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA) and proline were studied in various parts such as roots, stems, and leaves of Bruguiera gymnorrhiza (L.) Savigny. At different level of stress, the activities of antioxidant enzymes in PAH‐treated stems and roots varied and fluctuated. The levels of the antioxidant enzymes SOD and APX in leaves increased under PAH stress exhibiting a positive relationship. Kreslavski et al. (2017) studied the effects of PAHs on pea leaves. The study revealed an increase of H2O2 formation in pea leaves by naphthalene. They concluded that it might be because of a disturbance in the lipid bilayer of the plasma membrane and membrane of cell organelles, particularly thylakoid membranes. According to Liu et al. (2009) activity of the SOD increased while CAT activity was relatively unaffected. POD and APX exhibited peak enzyme activities at lower concentrations of phenanthrene and declined at higher concentrations. There was a dose‐dependent H2O2 accumulation seen in 3,3′‐diaminobenzidine (DAB) staining due to phenanthrene as evident from high activity of glutathione (GSH), and MDA. Microarray results suggested several perturbations in signaling and metabolic pathways which regulate ROS and responses related to pathogen defense. Wei et al. (2014) investigated effects of phenanthrene on LPO, chlorophyll content, antioxidant enzymes and accumulation of H2O2 in wheat. Phenanthrene elevated the levels of LPO and induced H2O2 accumulation in leaf tissues with increased dose. Li et al. (2008) suggested that the presence of PAHs caused enhanced content of soluble protein and induced SOD activities in rice. Zhang et al. (2016) reported in soybean that a low dose of BPA caused some peroxidation of membrane lipids but did not activate antioxidant systems. However, a high dose of BPA increased levels of ROS and caused LPO in membranes at all stages of plant growth. Application of BPA induced oxidative stress in chickpea roots (Dogan et al. 2010). This study demonstrated more H2O2 formation, which was quantitatively correlated with POD activity, MDA activity, and non‐protein SH groups as a result of BPA treatment. Yildiztekin et al. (2015) studied effects of pesticides on the oxidative defence system in tomato (Solanum lycopersicum L.). Application of pesticides resulted in a significant increase in free proline content of leaves and electrolyte leakage. The foliar application of pesticides caused enhanced accumulation of MDA. Doses of pesticides promoted the activities of enzymes such as CAT, POD, and SOD in most of the cases. These results clearly suggest that the application of pesticides at higher doses provoked oxidative and antioxidative systems in tomato plants.

1.6 Effects of Organic Pollutants on Photosynthesis

Photosynthesis is an important metabolic process in plants, which is directly correlated with biomass. Unfortunately it is highly sensitive to stress conditions. Any stress which affects this process negatively will result in a decreased crop yield. Photosynthesis is inhibited by many environmental pollutants such as metals, herbicides, and organic contaminants (Jajoo 2017; Marwood et al. 2001, 2003).

The process of photosynthesis occurs in two stages: light reactions are associated with the thylakoid membranes that capture light energy and convert it into chemical energy in the form of reducing power, nicotinamide adenine dinucleotide phosphate (NADPH), and energy, adenosine triphosphate (ATP), accompanied with oxygen evolution. In a sequence of reactions, dark reactions utilize NADPH and ATP to drive endergonic process leading to the formation of hexose sugar from CO2.

In plants, the photosynthetic process occurs inside chloroplasts found in the mesophyll cells, which contain about 50 or more chloroplasts per cell. Each chloroplast is surrounded by an inner and an outer membrane with a diameter of approx. 5–10 μm, though many different sizes and shapes can be seen in different plants. Inside the chloroplast is the thylakoid membrane that contains proteins, required for the light reactions. The stacks of thylakoid membranes are called grana while the surrounding aqueous phase is called stroma. The proteins required for the fixation and reduction of CO2 are located in the stroma. Oxygenic photosynthetic organisms have several multi‐subunit protein complexes associated with thylakoid membranes. These are: photosystem II (PSII), photosystem I (PSI), cytochrome b6f, (Cyt b6f), and ATP‐synthase (Nelson and Ben‐Shem 2004; Dekker and Boekema 2005). In plants, CO2 enters the leaves through small holes called stomata, and reaches the mesophyll cells. Then CO2 diffuses into the stroma of the chloroplast where the organic molecule glucose is synthesized using ATP and NADPH.

OPs cause serious damage to the photosynthetic apparatus. Many studies have demonstrated the effect of different stresses on photosynthetic organisms, particularly higher plants. Environmental stress conditions, such as scarcity of water, high temperature, and high salt have been extensively studied (Faraloni et al. 2011; Oukarroum et al. 2012). There are many research works available that have demonstrated the effects of organic compounds, such as PAHs, pesticides, etc., on plant photosynthesis (Figure 1.4) (Bi et al. 2012; Jajoo et al. 2014; Kreslavski et al. 2014, 2017; Kumar and Han 2011; Magnusson et al. 2010; Naumann et al. 2010; Qiu et al. 2013; Tomar and Jajoo 2014).

Figure 1.4 Effects of selective OPs on light and dark reactions in photosynthetic machinery of plants.

1.6.1 Effects of Pesticides on the Light Reactions

Use of pesticides is very common in agriculture fields to protect crops from pest induced damage. However, excessive use of pesticides may cause toxicity, which can have deleterious effect on plant growth and development. Literature reveals that the application of pesticides reduced the content of pigments like chlorophyll and carotenoids in Vitis vinifera L. and Nicotiana tabacum L., respectively (Garcia et al. 2003; Saladin et al. 2003a). Similarly, a reduction in photosynthetic pigments in maize was observed when pyriproxyfen was applied (Coskun et al. 2015). Application of the pesticides aldicarb, phorate fensulfothion, etc. in chickpea (Tiyagi et al. 2004) and tricyclazole in tomato also led to reduced pigment content (Shanmugapriya et al. 2013). Benomyl, a systemic fungicide, also inhibited pigment biosynthesis in Helianthus annuus L. (Ahmed et al. 1983). The inhibition of photosynthetic pigment content by pesticides can lead to a reduced photosynthetic efficiency in plants. Photosystem II (or water‐plastoquinone oxidoreductase) is the first protein complex in the photosynthetic machinery and is one of the most susceptible components to various stresses.

Xia et al. (2006) observed significant changes in photosynthetic parameters measured by chlorophyll a (Chl a) fluorescence technique in cucumber (Cucumis sativus L.) when it was exposed to nine different pesticides. The maximal quantum efficiency of PSII (Fv/Fm) was significantly inhibited by paraquat, while other pesticides showed no significant effect on the value of Fv/Fm. The quantum efficiency of PSII (YII) was significantly reduced by most of the pesticides and this decrease was mostly due to an inhibited photochemical quenching coefficient (qP). Non‐photochemical quenching, (NPQ), was inhibited by paraquat and haloxyfop, whereas an up‐regulation was seen after exposure to other pesticides. The effect of dichloro‐diphenyl‐trichloroethane (DDT) and dichloro‐diphenyl‐dichloroethylene (DDE) (a metabolite of DDT) on electron transport in chloroplasts was investigated (Bowes 1972; Owen et al. 1977). The photosynthetic electron transport chain (ETC) in isolated spinach and barley chloroplasts (Owen et al. 1977) and from macroscopic green algae, Codium fragile (Suringar) Hariot and Chaetomorpha aerea (Dill.) Kuetz, (Bowes 1972) was inhibited by both compounds. Photoreduction and photophosphorylation showed 50% inhibition with DDT and DDE. The addition of uncouplers such as ammonium ions and carbonyl cyanide m‐chlorophenyl hydrazone could not overcome the inhibition. Some herbicides such as isoproturon and metolachlor caused lower quantum efficiency of PSII in aquatic photosynthetic organisms (Laviale et al. 2011; Thakkar et al. 2013).

Chauhan et al. (2013) observed several photochemical changes in potato upon exposure to pesticides. Photosynthesis is greatly inhibited due to inefficient biosynthesis of chlorophyll content that results in leaf chlorosis (Mitra and Raghu 1998). A decrease in content of pigments Chl a, Chl b, and Chl a + b in tomato plants was observed when sprayed with a high dose of pesticides (Yildiztekin et al. 2015). Several amino phosphonate herbicides used on cucumber at a concentration of 0.25 mM caused a decrease of the chlorophyll content by 30–55% (Bielecki et al. 2001). The chlorophyll content of wheat plants treated with 50 μM of the herbicide acifluorfen (diphenylether) was reduced by 44% five days after the treatment (Pascal et al. 2000). The herbicides norflurazon (pyridazinone) and amitrole (triazole) were used on barley leaves at 100 and 125 μM respectively (La Rocca et al. 2000). Both herbicides caused a photooxidation of chloroplasts which made them photosynthetically nonfunctional. Chl a, Chl b and carotenoid contents were strongly affected by amitrole and were completely degraded after the norflurazon treatment. Thylakoid membranes were dramatically altered by amitrole and totally degraded with norflurazon. The effect of herbicide treatments, atrazine, isoproturon, and metribuzin on chlorophyll content was studied by Khan et al. (2006). They proposed that a decrease in the amount of photosynthetic pigments could be one of the most important reasons for inhibition in photosynthesis. Moreover, a decrease in photosynthetic pigments may also cause a decline in the nutrition value of the pepper plant, since chloroplasts are the site for vitamin synthesis.

Sharples et al. (1997) demonstrated that the accumulation of pesticides in plants affected plant growth and caused metabolic disorders. For example, electron transfer from quinone to plastoquinone in PSII is blocked by metribuzin (Fedtke 1982). This prevents the reduction of NADP required in dark reactions, ultimately inhibiting photosynthesis. Further, the deficiency of pigment in green gram plants may be caused by photobleaching (Barry et al. 1990). Kaushik and Inderjit (2006) found that mung beans grown in soil treated with herbicides showed a decrease in chlorophyll content with a high dose of herbicide. Significant reduction in the content of carotenoids was reported in other plants under pesticide stress (Shakir et al. 2016; Garcia et al. 2003; Saladin et al. 2003a). It was concluded that the photochemical changes due to the pesticides were mainly due to chlorophyll degradation and activation of the oxidation process. Carotenoids also protect plants from photodynamic damage under stress condition. Oxygen evolution was inhibited in a concentration dependent manner by dimethoate (Mishra et al. 2008). In the same experiment, the activity of PSII and ETC decreased in chloroplasts in response to various concentrations of dimethoate. The herbicide chlorotoluron blocked the photosynthetic ETC (Fuerst and Norman 1991) and damaged the reaction center (RC) of PSII (Barry et al. 1990).

1.6.2 Effects of Pesticides on the Dark Reactions

The effect of OPs on photosynthesis, particularly on PSII activity, has been well documented. However, there are still very few studies on changes in the carbon assimilation reaction in response to OPs. Gas exchange measurement is one of the common ways to study the dark reactions of photosynthesis. Diffusion of gases from the air to the leaves is the major uptake pathway for the entry of lipophilic OPs (Jensen et al. 1992; Wild and Jones 1992; Wild et al. 2005). Many works reported that herbicides can also affect the dark reactions of photosynthesis. Several parameters such as gas exchange, photosynthetic pigment content, or carbohydrate levels are used to evaluate the effects of OPs on the dark reactions of photosynthesis. Foliar application of pesticides partially block stomatal pores and inhibit photosynthesis by hindering the exchange of gases. The phytotoxicities of several pesticides on photosynthesis were investigated by Xia et al. (2006) in cucumber (Cucumis sativus L. cv. Jinyan No. 4) by gas exchange measurements. A reduction in net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) were affected to varying degrees with different pesticides (Xia et al. 2006). Three‐year‐old grapevines were treated weekly three times with the herbicide chlorsulfuron (sulfonylurea) used at 0.01% of the dose usually applied on adjacent wheat fields. A 33% reduction of the net leaf photosynthesis and a 60% increase in the stomatal resistance were registered (Bhatti et al. 1997). The pre‐emergence herbicide clomazone (isoxazolidinone) used on wheat seedlings reduced concomitantly the photosynthetic rate and carotenoid content by more than 50% and the chlorophyll content by 70% in primary leaves (Kaňa et al. 2004). Six‐week‐old grapevines grown in vitro were exposed to the herbicide flumioxazin (N‐phenylphthalimide) at a lower concentration than in the field (Saladin et al. 2003b). Three weeks after the treatment, gas exchange and photosynthetic pigment contents were still reduced by 90% and 80% respectively. Moreover, plastids were strongly affected, exhibiting a spherical shape, thylakoid disorganization and the accumulation of many plastoglobules. Similarly, grapevine fruiting cuttings treated with the herbicide flumioxazin exhibited a decrease of CO2 fixation (Saladin et al. 2003b). However, in the vineyard the plants responded oppositely to the herbicide treatment since the CO2 assimilation and the photosynthetic pigment content were stimulated by 13% and 25% respectively (Saladin et al. 2003b). The enzymes involved in the photosynthesis process are not well documented after pesticide exposure. Nevertheless, it was shown that the herbicide propachlor (chloroacetanilide) used at the field dose on bean plants caused a reduction of Rubisco activity by 25% (Scarponi et al. 2002). Hydrolysis of the carbohydrate reserves takes place after a decrease in photosynthesis by which the plants counteract the loss due to sugar synthesis. Bean plants treated with the chloroacetanilide herbicide propachlor exhibited a loss of soluble carbohydrate and starch content (50% and 10% respectively) after 16 days (Scarponi et al. 2001). Imazamox, an imidazolinone herbicide used on maize at the recommended dose caused a starch hydrolysis of 20% and a parallel accumulation of soluble carbohydrates by 32% within 96 hours after the treatment (Scarponi et al. 2001