Brassinosteroids constitute naturally occurring plant hormones that are involved in the regulation of various metabolic functions associated with morphological, physiological, and developmental processes in plants. The polyhydroxylated steroidal hormones occur widely in the plant kingdom and exhibit structural variations. The recent advancement in different molecular approaches has led to the understanding of various processes involving BR synthesis, signaling, and pathways in plants. BRs not only play an important role in the growth and development of plants but also in providing tolerance against various abiotic and biotic stresses. Current trends indicate a myriad role of BRs in the amelioration of drought stress in plants that results in systematic stress management under fluctuating environmental conditions. This chapter provides insights into drought stress and its effect on the growth of plants. Further, the chapter focuses on the role of BRs in mitigating the negative effect of drought stress that critically hampers the growth and metabolism of plants.

Technogenic advances have led to the exploitation and contamination of soil/water ecosystems. The alleviation of heavy metal contaminants from polluted soils through non-conventional methods is a cost-effective and eco-friendly approach. Phytoremediation is a prominent green technology employed to remediate contaminated soil/water ecosystems. Rhizospheric microorganisms are omnipresent and can tolerate a wide range of contaminants, hence they can facilitate the removal of noxious contaminants. Microorganism-assisted phytoremediation is a safe and innovative method for remediation of toxic substances. Microorganisms like bacteria and fungi in the rhizosphere can sense signals and enable the plants to tolerate metal-induced toxicity along with growth promotion. These rhizosphere microbes can accumulate, transform or detoxify the toxic substances. In this chapter, we discuss heavy metal-induced toxicity, microorganism–plant interactions and microorganism-assisted phytoremediation of contaminated ecosystems. This chapter is also intended to give an overview of the recent findings, challenges and opportunities in microorganism-assisted plant-based reclamation of contaminated soils.

Abiotic stresses have become a major concern now a days as they act as the limiting factors in plant growth and development. Due to the advancement of science, intensive research has been carried out globally to explore the underlying mechanisms of plant nutrient uptake, their metabolism, homeostasis and protection against abiotic stresses. Plants require trace elements at very low concentrations for growth and other physiological activities. Exogenous supplementation of trace elements in plant systems mitigates various stress conditions of plant species. Trace elements not only improve plant physiological processes and growth, but also play vital roles in improving plant tolerance toward varied abiotic stresses. The addition of trace elements ameliorates plant antioxidant response to counter oxidative stress. This chapter presents the plant responses to different abiotic stresses and the beneficial effects of different trace elements in conferring plant tolerance against various abiotic stresses.

Cadmium (Cd) is a nonbiodegradable, toxic trace element that occurs widely in the environment. The transfer of Cd along the food chains poses serious harm to the ecosystem. The increased anthropogenic activities such as mining, smelting, use of fertilizers, pesticides have elevated Cd concentrations in the environment. Cd stress in plants leads to reactive oxygen species (ROS) generation that damages cellular machinery and different biomolecules in plants. These negative effects of Cd lead to inhibition of physiological mechanisms, growth, and overall development in plants. ROS generation triggers plant defense mechanism that activates different enzymatic (catalase, superoxide dismutase, ascorbate peroxidase) and nonenzymatic (glutathione, phytochelatins, phenols) antioxidants in plants. This chapter aims to provide critical information on recent studies related to Cd stress in plants. Additionally, the important strategies, tolerance mechanisms adopted by plants to combat Cd-induced toxicity are also discussed in this chapter.

Copper (Cu) is an essential element for humans and plants when present in lesser amount, while in excessive amounts it exerts detrimental effects. There subsists a narrow difference amid the indispensable, positive and detrimental concentration of Cu in living system, which substantially alters with Cu speciation, and form of living organisms. Consequently, it is vital to monitor its bioavailability, speciation, exposure levels and routes in the living organisms. The ingestion of Cu-laced food crops is the key source of this heavy metal toxicity in humans. Hence, it is necessary to appraise the biogeochemical behaviour of Cu in soil-plant system with esteem to their quantity and speciation. On the basis of existing research, this appraisal traces a probable connexion midst: Cu levels, sources, chemistry, speciation and bioavailability in the soil. Besides, the functions of protein transporters in soil-plant Cu transport, and the detrimental effect of Cu on morphological, physiological and nutrient uptake in plants has also been discussed in the current manuscript. Mechanisms related to detoxification strategies like antioxidative response and generation of glutathione and phytochelatins to combat Cu-induced toxicity in plants is discussed as well. We also delimits the Cu accretion in food crops and allied health perils from soils encompassing less or high Cu quantity. Finally, an overview of various techniques involved in the reclamation and restoration of Cu-contaminated soils has been provided. (C) 2020 Elsevier Ltd. All rights reserved.

Being sessile organisms, plants are persistently confronted by a diverse array of biotic agents, including viruses, bacteria, fungi, herbivores, and nematodes. Understanding the mechanism of host-pathogen interactions is essential for improving plant resistance against these biotic factors. In this review, we have discussed various means and mechanisms by which pathogens influence the host plant defense. A virulent pathogen can reduce the growth and development of a plant, which eventually lowers its yield by multiple processes, like enhancement in cell death, as well as modification of plant architecture. This review also explains the various strategies used by plants to control pathogen-caused diseases. These mainly include either resistance or tolerance by activating cell signaling pathways, which further regulate the synthesis and accumulation of several cellular products, such as phytohormones, enzymes, proteins, and secondary metabolites. To minimize the influence of infection on their vigor, plants also exhibit immunity regardless of the amount of pathogen multiplication. The current review provides an important insight into the mechanisms of host-pathogen interaction, which is very significant for efficient disease management.

During the entire life span, plants tolerate diverse abiotic stresses. Heavy metal contamination of soil and water ecosystems is a major abiotic stress faced by the plants. Among the heavy metals, cadmium (Cd) stress in plants is a critical concern due to its easy uptake, root to shoot transport and toxicity. Cd toxicity in plants has now become a constraint to the productivity, quality and yield of the food grains. Increasing population, rapid industrialization, urbanization and innate food demand has further worsened the situation. Cd toxicity poses pessimistic effects on the morphological, physiological, biochemical and molecular status of the plants. High Cd regimes disturb plant water relations, promote the generation and accumulation of reactive oxygen species that induce oxidative outburst in plants by altering antioxidant plant defense mechanisms. The counterbalance of Cd toxicity in plants needs effective mechanisms at physiological, biochemical and molecular levels so as to improve the quality and productivity of the crops. This chapter summarizes the recent findings and mechanisms on (i) Cd speciation, its uptake and transport in plants, (ii) the effect of Cd toxicity on the morphological, physiological and biochemical attributes of the plants and (iii) tolerance strategies adopted by plants to combat Cd toxicity.

Anthropogenic activities and natural processes pollute soil and aquatic environments with high quantity of organic pollutants or substances such as pesticides, solvents, halogenated compounds, petroleum hydrocarbons, and phthalate esters. The use of traditional or conventional approaches like physical and chemical methods for remediation of these organic pollutants is economically challenging process. In this regard, remediation with biological agents poses promising alternative. Enzyme-based technologies are crucial for metabolism and degradation of organic substances. They can be used in metabolism of simple and complex organic pollutants. This chapter provides an overview on different plant enzymatic alternatives for decontamination of soils and their role in transformation and metabolism of organic pollutants.

Chapter 19Token Access Restoring Ecosystem Services of Degraded Forests in a Changing Climate Smita Chaudhry, Institute of Environmental Studies, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this authorGagan Preet Singh Sidhu, Centre for Applied Biology in Environment Sciences, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this authorRashmi Paliwal, Institute of Environmental Studies, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this author Smita Chaudhry, Institute of Environmental Studies, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this authorGagan Preet Singh Sidhu, Centre for Applied Biology in Environment Sciences, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this authorRashmi Paliwal, Institute of Environmental Studies, Kurukshetra University, Kurukshetra, Haryana, IndiaSearch for more papers by this author Book Editor(s):Majeti Narasimha Vara Prasad, School of Life Sciences, University of Hyderabad (an Institution of Eminence), Hyderabad, Telangana, IndiaSearch for more papers by this author First published: 21 May 2021 https://doi.org/10.1002/9781119678595.ch19 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Summary Forests serve as repositories for carbon and provide intangible and valuable ecological services for humans and other living organisms. Their diversity plays a crucial role in regulating various ecological processes. The carbon sequestration potential of forests is important for both adaptation and mitigation of global climate change. Recent human impacts on the extent and types of forest degradation in India and the impact of climate change in further enhancing degradation require attention. Restoring degraded forest ecosystems is crucial for maintaining ecological services at the local, regional, and global scales. Successful restoration is possible by taking appropriate steps to maintain and integrate the environmental components of forest ecosystems for their proper functioning. This chapter highlights the alterations in soil nutritional status, hydrological protection, carbon sequestration potential, and other ecological services caused by the degradation of forest ecosystems. Various techniques and policies for restoring and enhancing forest quality are discussed in light of projected climate change. Handbook of Ecological and Ecosystem Engineering RelatedInformation

Globally, environmental contamination by potentially noxious metalloids like arsenic is becoming a critical concern to the living organisms. Arsenic is a non-essential metalloid for plants and can be acclimatised in plants to toxic levels. Arsenic acquisition by plants poses serious health risks in human due to its entry in the food chain. High arsenic regimes disturb plant water relations, promote the generation of reactive oxygen species (ROS) and induce oxidative outburst in plants. This review evidences a conceivable tie-up among arsenic levels, speciation, its availability, uptake, acquisition, transport, phytotoxicity and arsenic detoxification in plants. The role of different antioxidant enzymes to confer plant tolerance towards the enhanced arsenic distress has also been summed up. Additionally, the mechanisms involved in the modulation of different genes coupled with arsenic tolerance have been thoroughly discussed. This review is intended to present an overview to rationalise the contemporary progressions on the recent advances in phytoremediation approaches to overcome ecosystem contamination by arsenic.

Global climate change is identified as a major threat to survival of natural ecosystems. Climate change is a dynamic, multifaceted system of alterations in environmental conditions that affect abiotic and biotic components of the world. It results in alteration in environmental conditions such as heat waves, intensity of rainfall, CO2 concentration and temperature that lead to rise in new pests, weeds and pathogens. Climate change is one of the major constraints limiting plant growth and development worldwide. It impairs growth, disturbs photosynthesis, and reduces physiological responses in plants. The variations in global climate have gained the attention of researchers worldwide, as these changes negatively affect the agriculture by reducing crop productivity and food security. With this background, this review focuses on the effects of elevated atmospheric CO2 concentration, temperature, drought and salinity on the morphology, physiology and biochemistry of plants. Furthermore, this paper outlines an overview on the reactive oxygen species (ROS) production and their impact on the biochemical and molecular status of plants with increased climatic variations. Also additionally, different tolerance strategies adopted by plants to combat environmental adversities have been discussed.

The gradual increase in environmental contamination by toxic heavy metals is a serious concern for biotic communities, and since plants are immobile and stationary, they are highly exposed to heavy metal toxicity during changing environmental conditions. Thus efforts are being made to recognize plant stress response and tolerance strategies to cope with heavy metal stress. Plants produce low-molecular weight thiols that show high affinity for toxic metals. This chapter highlights the significance of thiol compounds in relation to metal hyperaccumulation and tolerance in plants. The most important biological thiols discussed are glutathione (GSH), cysteine, phytochelatins (PC), and metallothioneins (MT). Further, this chapter overviews the future perspectives related to role of thiol compounds in metal phytoextraction or hyperaccumulation mechanisms in plants.

Soil is a substantial constituent of the environment, accumulating an excessive amount of pollutants, especially heavy metals. Both natural and anthropogenic activities increase the heavy metal content in soil. Biomagnification of metals through the food chain affects both flora and fauna. This chapter provides a composite and analytical evaluation of heavy metal contamination by employing different pollution indices, such as enrichment factor, geoaccumulation index, contamination factor, pollution index, potential contamination index, and modified pollution index. Further, different methodologies adopted for the assessment of risk related with metals in soil, such as the potential ecological risk index and modified potential ecological risk index, are also discussed in this chapter. Finally, the chapter also summarizes the status of contamination indices and ecological risk assessment in agricultural, urban, roadside, and industrial soils.

Given their sessile nature, plants continuously face unfavorable conditions throughout their life cycle, including water scarcity, extreme temperatures and soil pollution. Among all, metal(loid)s are one of the main classes of contaminants worldwide, posing a serious threat to plant growth and development. When in excess, metals which include both essential and non-essential elements, quickly become phytotoxic, inducing the occurrence of oxidative stress. In this way, in order to ensure food production and safety, attempts to enhance plant tolerance to metal(loid)s are urgently needed. Nitric oxide (NO) is recognized as a signaling molecule, highly involved in multiple physiological events, like the response of plants to abiotic stress. Thus, substantial efforts have been made to assess NO potential in alleviating metal-induced oxidative stress in plants. In this review, an updated overview of NO-mediated protection against metal toxicity is provided. After carefully reviewing NO biosynthetic pathways, focus was given to the interaction between NO and the redox homeostasis followed by photosynthetic performance of plants under metal excess.

In the past few decades, cadmium (Cd) as soil contaminant is a major problem for the mankind. Cd contamination of soil and food crops is a critical environmental concern as it deteriorates the soil quality and creates threat to the food safety and human health. High Cd concentration in soils pose negative effects on the plants at physiological, structural and molecular levels. Secretion of certain secondary metabolites in the rhizosphere is a survival mechanism adopted by plants to tolerate and encounter Cd toxicity. Under metal-stressed conditions, secretion of root exudates in soil increases the external detoxification strategies of the plants. The secreted phytochemicals are gaseous compounds, inorganic and especially organic in composition. In plants, the role of these metabolites to confront Cd toxicity and induce tolerance under Cd distress is underrated. The review paper focuses on Cd sources, factors that affect its bioavailability, uptake and toxicity in the plants. Furthermore, it also highlights the contemporary progression in our understanding on the mechanisms of root exudation in plants and the effect of Cd toxicity on the root exudation. Finally, the review provides important information on the role of different root exudates to subsist Cd stress in plants naturally, particularly by reducing the dependence on synthetic amendments to enhance Cd-tolerance and its aquisition in plants.

Salicylic acid (SA) is a very simple phenolic compound (a C7H6O3 compound composed of an aromatic ring, one carboxylic and a hydroxyl group) and this simplicity contrasts with its high versatility and the involvement of SA in several plant processes either in optimal conditions or in plants facing environmental cues, including heavy metal (HM) stress. Nowadays, a huge body of evidence has unveiled that SA plays a pivotal role as plant growth regulator and influences intra- and inter-plant communication attributable to its methyl ester form, methyl salicylate, which is highly volatile. Under stress, including HM stress, SA interacts with other plant hormones (e.g., auxins, abscisic acid, gibberellin) and promotes the stimulation of antioxidant compounds and enzymes thereby alerting HM-treated plants and helping in counteracting HM stress. The present literature survey reviews recent literature concerning the roles of SA in plants suffering from HM stress with the aim of providing a comprehensive picture about SA and HM, in order to orientate the direction of future research on this topic.

Plants face a variety of abiotic stresses, which generate reactive oxygen species (ROS), and ultimately obstruct normal growth and development of plants. To prevent cellular damage caused by oxidative stress, plants accumulate certain compatible solutes known as osmolytes to safeguard the cellular machinery. The most common osmolytes that play crucial role in osmoregulation are proline, glycine-betaine, polyamines, and sugars. These compounds stabilize the osmotic differences between surroundings of cell and the cytosol. Besides, they also protect the plant cells from oxidative stress by inhibiting the production of harmful ROS like hydroxyl ions, superoxide ions, hydrogen peroxide, and other free radicals. The accumulation of osmolytes is further modulated by phytohormones like abscisic acid, brassinosteroids, cytokinins, ethylene, jasmonates, and salicylic acid. It is thus important to understand the mechanisms regulating the phytohormone-mediated accumulation of osmolytes in plants during abiotic stresses. In this review, we have discussed the underlying mechanisms of phytohormone-regulated osmolyte accumulation along with their various functions in plants under stress conditions.

Soil is substantive component of biosphere, which is exposed to plethora of pollutants including heavy metals. These are added by natural as well as anthropogenic activities. Upsurge in heavy metal content affects all organisms by biomagnification. So, it becomes vital to create a database of heavy metals concentration in soil. This is relevant in countries where unsustainable intensive agriculture, industrial and urban development is in progress. The present review of the scientific literature from 1991 to 2018 on heavy metals in soils in India shows that Zn and Pb exceeded their limits for Indian natural soil guidelines (Zn 22.1 and Pb 13.1 μg/g), Canada (Zn 200 μg/g), Swedish (80 μg/g) and Poland (Zn 300 μg/g) soil guidelines. The mean values of As and Cu for all soil types except for roadside soils, exceeded the limits. The average value of Cd for all soil types exceeded their limit. The mean values obtained for soils of India are Fe (23774.84 μg/g), Mn (872.54 μg/g), Zn (359.94 μg/g), Cu (183.67 μg/g), Cr (161.42 μg/g), As (148.70 μg/g), Ni (112.41 μg/g), Pb (61.87 μg/g), Co (37.63 μg/g) and Cd (14.16 μg/g). Cluster analysis and factor analysis were employed to different soil types and showed multiple sources of these metals. The contamination factor (CF), enrichment factor (EF) and potential contamination index (Cp) showed that Cd and As are the main contaminants. The results of ecological risk index indicated that Cd is the main pollutant in the different soils of India.