Arun Shanker

Main objective is to deliver information for developing strategies to combat crop stress * Bridges the mechanistic aspects (what do we know) of stresses with the strategic aspects (what do we do) * Presents both abiotic and biotic stresses in a single volume Crops experience an assortment of environmental stresses which include abiotic viz., drought, water logging, salinity, extremes of temperature, high variability in radiation, subtle but perceptible changes in atmospheric gases and biotic viz., insects, birds, other pests, weeds, pathogens (viruses and other microbes). The ability to tolerate or adapt and overwinter by effectively countering these stresses is a very multifaceted phenomenon. In addition, the inability to do so which renders the crops susceptible is again the result of various exogenous and endogenous interactions in the ecosystem. Both biotic and abiotic stresses occur at various stages of plant development and frequently more than one stress concurrently affects the crop. Stresses result in both universal and definite effects on plant growth and development. One of the imposing tasks for the crop researchers globally is to distinguish and to diminish effects of these stress factors on the performance of crop plants, especially with respect to yield and quality of harvested products. This is of special significance in view of the impending climate change, with complex consequences for economically profitable and ecologically and environmentally sound global agriculture. The challenge at the hands of the crop scientist in such a scenario is to promote a competitive and multifunctional agriculture, leading to the production of highly nourishing, healthy and secure food and animal feed as well as raw materials for a wide variety of industrial applications. In order to successfully meet this challenge researchers have to understand the various aspects of these stresses in view of the current development from molecules to ecosystems. The book will focus on broad research areas in relation to these stresses which are in the forefront in contemporary crop stress research.

World population is growing at an alarming rate and is anticipated to reach about six billion by the end of year 2050. On the other hand, agricultural productivity is not increasing at a required rate to keep up with the food demand. The reasons for this are water shortages, depleting soil fertility and mainly various abiotic stresses. The fast pace at which developments and novel findings that are recently taking place in the cutting edge areas of molecular biology and basic genetics, have reinforced and augmented the efficiency of science outputs in dealing with plant abiotic stresses. In depth understanding of the stresses and their effects on plants is of paramount importance to evolve effective strategies to counter them. This book is broadly dived into sections on the stresses, their mechanisms and tolerance, genetics and adaptation, and focuses on the mechanic aspects in addition to touching some adaptation features. The chief objective of the book hence is to deliver state of the art information for comprehending the nature of abiotic stress in plants. We attempted here to present a judicious mixture of outlooks in order to interest workers in all areas of plant sciences.

Plants, unlike animals, are sessile. This demands that adverse changes in their environment are quickly recognized, distinguished and responded to with suitable reactions. Drought, heat, cold and salinity are among the major abiotic stresses that adversely affect plant growth and productivity. In general, abiotic stress often causes a series of morphological, physiological, biochemical and molecular changes that unfavorably affect plant growth, development and productivity. Drought, salinity, extreme temperatures (cold and heat) and oxidative stress are often interrelated; these conditions singularly or in combination induce cellular damage. To cope with abiotic stresses, of paramount significance is to understand plant responses to abiotic stresses that disturb the homeostatic equilibrium at cellular and molecular level in order to identify a common mechanism for multiple stress tolerance. This multi authored edited compilation attempts to put forth an all-inclusive biochemical and molecular picture in a systems approach wherein mechanism and adaptation aspects of abiotic stress are dealt with. The chief objective of the book hence is to deliver state of the art information for comprehending the effects of abiotic stress in plants at the cellular level.

A field experiment was conducted in a randomized block design at the National Research Centre for Agroforestry, Jhansi (UP) during two consecutive years (2000 - 01 and 2001 - 02). The experiment comprised eight treatments: T1 - trees allowed to grow normally + crop, T2 - pruning of trees up to 70% plant height + crop, T3 - trees allowed

ABSTRACT A study on seasonal variation in nitrate reductase activity and total nitrogen was conducted at National Research Centre for Agroforestry, Jhansi, India, on Albizia amara, a fodder yielding, drought resistant and fire hardy tree of the arid and semi-arid regions of the country. Total nitrogen did not exhibit a distinct linear relationship with nitrate reductase activity although they were directly related. Significant variation in nitrate reductase activity due to season was observed. Nitrate reductase activity was lowest in May and June. ...

Growth, lipid peroxidation, H2O2 produciton and the response of the antioxidant enzymes and metabolites of the ascorbate glutathione pathway to oxidative stress caused by two concentrations (50 and 100 µM) of Cr(III) and Cr(VI) was studied in 15 day old seedlings of sorghum (Sorghum bicolor (L.) Moench cv CO 27) after 10 days of treatment. Cr accumulation in sorghum plants was concentration and organ dependant. There was no significant growth retardation of plants under 50 µM Cr(III) stress. 100 µM Cr(VI) was most toxic of all the treatments in terms of root and leaf growth and oxidative stress. 50 µM Cr(VI) treated roots exhibited high significant increase in superoxide dismutase (SOD), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) (p < 0.01) and significant increases in catalse (CAT), ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) (p < 0.05). A high increase in ascorbic acid (AA) level was seen in roots of 50 µM Cr(VI) treated plants in comparison with control. Levels of reduced glutathione (GSH) showed a varied and complex response in all the treatments in both plant parts. GSH/GSSG ratio was not affected by Cr(III) treatment in leaves, in contrast, roots exhibited significant reduction in the ratio. Results indicate that GSH depletion increased sensitivity to oxidative stress (Cr(VI) roots and leaves and Cr(III) 100 µM roots) and AA in tandem with APX compensated for GSH depletion by acting directly on H2O2 and the mechanism of defensive response in roots as well as leaves varied in its degree and effectiveness due to the concentration dependant differences observed in translocation of the element itself, reactive oxygen species (ROS) generation and enzyme inhibition based on the oxidation state supplied to the plants.

Selenium (Se) is regarded as an antioxidant in animals and plants, even though considered as non-essential element in plants. To test its ability to counteract senescence related oxidative stress in soybean a pot culture experiment was conducted. The soybean plant was sprayed with sodium selenate (50 ppm) at 78 days after sowing (DAS). Soybean leaves were harvested at 80 and 90 DAS for analysis of oxidant production and antioxidative enzymes activity. Se positively promoted growth and acted as antioxidant by inhibiting lipid peroxidation and per cent injury of cell membrane. The antioxidative effect was associated with an increase in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes activity. Significant increase in antioxidant enzyme activity was positively related to Se content. The decrease in antioxidative enzymes at 90 DAS was much faster in control plants than Se-sprayed plants. The reduction in SOD and GSH-Px may be associated with senescence-induced oxidative burst.

Abstract An experiment was taken up at National Research Centre for Agroforestry, Jhansi, to determine suitable species of Albizia and an optimum pruning practice for increased natural forage production under tree canopy. Three species for Albizia (A. amara, A. lebbek and A. procera) were evaluated under four pruning heights (0, 25, 50 and 75% from the ground level) in split plot design with three replications. There were no significant differences in survival percentages, growth of Albizia spp.

Selenium (Se) is regarded as an antioxidant in animals and plants, even though considered as non-essential element in plants. To test its ability to counteract senescence related oxidative stress in soybean a pot culture experiment was conducted. The soybean plant was sprayed with sodium selenate (50? ppm) at 78? days after sowing (DAS). Soybean leaves were harvested at 80 and 90 DAS for analysis of oxidant production and antioxidative enzymes activity.

A study was conducted to analyse the association of osmotic adjustment (OA) with drought tolerance and yield in castor (Ricinus communis L.). Hybrids (GCH4, DCH32 and DCH177) and their respective parents (VP-1, 48-1, LRES17, DCS5, DPC9 and DCS9) were assessed for their osmotic adjustment, leaf water relations, accumulation of compatible solutes in relation to seed yield in response to moisture stress at primary spike development stage.

Drylands of the world are affected in addition to the impending climate change by various other inherent biotic and abiotic limitations like water availability, declining soil quality and pest and disease infestations. The challenges facing dryland agriculture, global food security and the sustainable management of natural resources are many and are interrelated. Productivity of dryland crops can be increased only if the problems are understood well and in turn combated effectively.

ABSTRACT A pot culture experiment was conducted in the glass house of Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore to study the potential chromium (Cr) phytoaccumulatory capabilities of four promising agroforestry trees species viz., Albizia amara, Casuarina equisetifolia, Tectona grandis, Leucaena luecocephala. Both biologically stable speciation of Cr (trivalent and hexavalent) were used in addition to tannery effluent.

Abstract Arabidopsis Thaliana HARDY (AtHRD) is a gene with an APETELA 2/Ethylene Responsive Factor (AP2/ERF) domain linked to improved performance under drought in rice. We hypothesized that the sorghum genome could possess a similar gene product and were motivated to conduct a computational genome scale mining for the protein and analyse its structural and functional properties. AtHRD sequence was used as a query to BLAST against the sorghum genome dataset followed by multiple alignment analysis.

Abstract A thorough and extensive wild germplasm exploration survey was undertaken and 50 high yielding candidate plus trees (CPTs) of Pongamia pinnata (L.) Pierre from different locations from a latitudinal and longitudinal spread between 12° 41′ and 22° E longitude and 77° and 84° 40′ N latitude covering 11 locations in an area spread of 150,000 km 2 were collected for evaluating genetic association and variability in seed and growth characters.

Biotic and abiotic stresses in crops are a major hurdle in attaining potential yield worldwide. Finding an approach to sustain high yields of crop plants under biotic and abiotic stresses is an important goal of agriculture researchers and stakeholders alike. Among the abiotic stresses, drought, salinity, temperature and heavy metal accumulation are the major environmental stresses, which adversely affect plant growth and productivity.

Résumé/Abstract In greenhouse experiments, selenium (Se) has been shown to defend plants against detrimental effects of heavy UV-B radiation stress. The aim of this study was to investigate whether this positive effect can be found in open-field conditions with enhancement of UV-B radiation.

Abstract Above and belowground competition for growth resources between tree and crop can be minimized by pruning, putting soil barrier between tree and crop and avoiding moisture stress through providing required irrigation to the crop. The role of these management practices on production of understorey crop in agrisilviculture might be less during initial years but their effect may be increased with increasing age of trees.

Abstract: Expression of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2) has been shown to increase WUE in rice by Karaba et al 2007 (PNAS, 104: 15270–15275). We conducted a detail analysis of the complete sorghum genome for the similarity/presence of either DNA, mRNA or protein product of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2).

Abstract: Expression of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2) has been shown to increase WUE in rice by Karaba et al 2007 (PNAS, 104: 15270–15275). We conducted a detail analysis of the complete sorghum genome for the similarity/presence of either DNA, mRNA or protein product of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2).

Abstract A reproducible and highly efficient protocol for genetic transformation mediated by Agrobacterium has been established for greengram (Vigna radiata L. Wilczek). Double cotyledonary node (DCN) explants were inoculated with Agrobacterium tumefaciens strain LBA 4404 harboring a binary vector pCAMBIA 2301 containing neomycin phosphotransferase (npt II) gene as selectable marker, β-glucuronidase (GUS) as a reporter (uidA) gene and annexin 1 bj gene.

Members of the family Musaceae (bananas and plantains) have a major contribution towards the world's total food production1 and are an important staple food for millions of people inhabiting the humid and sub-humid tropics2. These are amongst the world's leading fruit crops, with an annual global production of about 88 million metric tonnes from an area of approximately 10 million ha. More than 100 countries throughout the tropical and sub-tropical regions cultivate bananas3 and

Chromium has received relatively little attention from plant scientists compared to other heavy metals in recent times in spite of it being a very a hazardous environmental pollutant. One of the reasons for this is the complexity of the metals interactions with biological systems and the difficulty in studying them. Although the possible mode of entry into the plants, resultant toxicity mechanisms and tolerance potential has been worked out in plants there is still a need to get a complete picture of the Cr–plant interactome. With the advent of hyphenated technologies and global gene/protein and metabolite expression/quantification techniques, studies to elucidate the complete metallome are possible albeit resource intensive. This minireview focuses on the recent developments in the field of Cr–plant interactions and proposes a model using a systems biology and integrated -omics approach to decipher the intricacies of Cr–plant interaction.

Changes in climate can be expected to have significant impacts on crop yields through changes in
temperature and water availability. The purpose of mitigation and adaptation measures is therefore to attempt a
gradual reversal of the effects caused by climate change and sustain development. There are several mitigation
and adaptation practices that can be effectively put to use to overcome the effects of climate change with
desirable results. These methods fall into the broad categories of under crop/cropping system-based
technologies, resource conservation-based technologies and socio-economic and policy interventions. These
measures are discussed to suggest effective strategies among them to combat climate change with specific
reference to India