Volume 5 Special Issue 1 2011
PLANT NUTRITION and ABIOTIC STRESS TOLERANCE III

ISBN 978-4-903313-61-0

How to reference: Gill SS, Khan NA, Anjum NK, Tuteja N (2011) Amelioration of Cadmium Stress in Crop Plants by Nutrients Management: Morphological, Physiological and Biochemical Aspects. In: Anjum NA, Lopez-Lauri F (Eds) Plant Nutrition and Abiotic Stress Tolerance III. Plant Stress 5 (Special Issue 1), 1-23

Guest Editors

Naser A. Anjum

Aligarh Muslim University, India

www.amu.ac.in

Centre for Environmental and Marine Studies (CESAM) & Department of Chemistry, University of Aveiro, Portugal

www.cesam.ua.pt/

Félicie Lopez-Lauri

Université d’Avignon et des Pays de Vaucluse, France

www.univ-avignon.fr

CONTENTS AND ABSTRACTS

Sarvajeet Singh Gill, Nafees A. Khan, Naser A. Anjum, Narendra Tuteja (India) Amelioration of Cadmium Stress in Crop Plants by Nutrients Management: Morphological, Physiological and Biochemical Aspects (pp 1-23)

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ABSTRACT

Invited Review: Plants are sessile organisms therefore, cannot avoid adverse environmental conditions (such as soil salinity, drought, heat, cold, flooding and heavy metal contamination). These stress factors are a menace for plants, prevent them from reaching their full genetic potential and limit crop productivity worldwide. Soil contamination with heavy metals has become a world wide problem leading to losses in agricultural yield and hazardous health effects as they enter the food chain. Among heavy metals, Cadmium (Cd) is a ubiquitous environmental pollutant and is a non-essential highly toxic metal for plants. It significantly damages general plant metabolism and induces oxidative stress. In response to Cd stress, the cells of Cd-resistant plant species can produce metallothioneins, phytochelatins and stress proteins to detoxify Cd ions. The plant cells can also resort to other defense systems to detoxify Cd ions, e.g., exclusion of Cd through the action of plasma membrane, the immobilization of Cd by cell wall and compartmentalization of Cd to vacuols. It has also been found that mineral nutrient status of plants can play a critical role in increasing plant resistance to environmental stress factors. Among mineral nutrients, sulfur (S) and nitrogen (N) are major macronutrients necessary for the plant life cycle, the two processes the uptake and assimilation of S and N in higher plants are the crucial factors determining plant growth and vigor, crop yield and these nutrients play a particular role in contributing to the survival of crop plants under environmental stress conditions. In this review, we focus on the alterations in morphological, physiological and biochemical characteristics in crop plants under Cd stress. Further, the importance of plant mineral nutrients especially S and N in the amelioration of Cd stress has also been reviewed.

Cesar Arrese-Igor (Spain/USA), Esther M. González (Spain), Daniel Marino (France), Rubén Ladrera, Estíbaliz Larrainzar, Erena Gil-Quintana (Spain) Physiological Responses of Legume Nodules to Drought (pp 24-31)

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ABSTRACT

Invited Review: Legumes include important agricultural crops, as their high protein content is of primary importance for human food and animal feed. In addition, the ability of most of them to establish symbiotic relationships with soil bacteria allows them to obtain their N requirements from nitrogen fixation in nodules and, therefore, avoids the use of nitrogen fertilizers. Thus, legumes are also essential to improve the soil fertility and quality of agricultural lands and to reclaim eroded or barren areas, making them crucial for agricultural and environmental sustainability. However, legume nitrogen fixation in crop species is very sensitive to environmental constraints and drought, in particular. The present contribution reviews our current knowledge on the processes involved in this inhibition, with particular emphasis on oxygen, nitrogen and carbon physiology. Emerging aspects such as oxidative damage, C/N interactions and sulphur metabolism together with future prospects are also discussed.

Elizamar Ciríaco da Silva, Rejane Jurema Mansur Custódio Nogueira, Marcelle Almeida da Silva, Manoel Bandeira de Albuquerque (Brazil) Drought Stress and Plant Nutrition (pp 32-41)

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ABSTRACT

Invited Mini-Review: Drought is a climatic phenomenon that can occur periodically in all climatic zones, but with a higher frequency in tropical and sub-tropical regions, causing physiological damage to plants in both ecosystems and agroecosystems. Due to these climate changes more frequent and prolonged drought events are expected in several parts of the world, leading to weaker crop yields and, in more severe cases, food shortages. Despite the water deficiency itself, which already causes grave constraints to plant development and production, problems with mineral nutrition can occur as a secondary effect. In higher plants most mineral nutrient transport from soil solution to the roots is dependent on soil moisture. Nutrient transport from the roots to the shoots is also limited by drought-induced decreases in the transpiration rate, imbalance in active transport and membrane permeability. All these factors acting together have serious consequences in plant development, affecting several physiological processes. A better understanding about the effects of water stress on plant nutrition should be a useful tool to develop strategies to ameliorate the injuries caused by drought and consequent nutrient deficiency. Thus, this review intends to discourse about some aspects of water stress on uptake and physiological responses of plants.

Pasala Ratnakumar, Vincent Vadez, L. Krishnamurthy, G. Rajendrudu (India) Semi-arid Crop Responses to Atmospheric Elevated CO₂ (pp 42-51)

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ABSTRACT

Invited Mini-Review: Semi-arid tropics host most of the poor and small-holding farmers of the developing world. Global warming is seen largely as a consequence of continuous increase in the emission of carbon dioxide and other greenhouse gases into the atmosphere leading to unusual changes in global temperatures and rainfall patterns. This in turn is expected to increase the water scarcity in the environment, affecting plant growth and metabolism. In this context, we reviewed semi-arid crop responses to elevated CO₂ levels in terms of growth, yield components, physiological, biochemical and molecular changes. Predicted rise of carbon-dioxide in the atmosphere may benefit the plants by increasing the crop water use efficiency and net photosynthesis leading to greater biomass, yield and harvest index. C₃ and C₄ crop plants vary in their degree of response to elevated CO₂, which will likely affect the proportion of land area occupied by these crops in future. Stomatal conductance will probably be reduced at higher CO₂ concentrations reducing transpiration per unit leaf area and consequently increasing the leaf temperature. The high CO₂ is an ameliorative of the adverse effects of drought and acts by altering the plant, biochemical and molecular systems. Understanding of the direct effects of elevated CO₂ and its interactions with the other climate variables is needed in order to predict the impact of climate change scenarios on crop growth and food security in future.

Renu Khanna-Chopra, Srivalli Singh (India) Approaches to Increase Water Use Efficiency in Horticultural and Grain Crops – An Overview (pp 52-63)

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Invited Review: Water use efficiency (WUE) is an important component of drought resistance and breeding. Horticultural crops consume more water than grain crops and hence are more susceptible to reduced water availability both in terms of yield and quality as well. Although management techniques are playing an important role in enhancing water use and WUE in horticultural crops, it is important to complement this by improving this characteristic at the whole plant level. Potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.) are the ideal model horticultural crops important for studying water use and WUE. Knowledge of the traits contributing towards drought resistance of a crop need to be defined as these are often stage-dependent. Biotechnological approaches such as increasing the plant photosynthetic capacity and transferring important genes involved in metabolic pathways related to osmolyte synthesis, stress proteins and/or regulatory genes may also help to improve cellular stress tolerance. However, translating this advantage at the field level may require a coordinated approach involving other traits such as phenology, deep root system, optimum WUE, etc. Selecting genotypes having high WUE alone may not be rewarding, as it may be associated with low biomass. Hence, selecting genotypes with high biomass potential and having high WUE under a stress environment may be more appropriate. Understanding the mechanism enabling root growth in a water deficit environment and linking it with molecular markers may help to select this trait in segregating populations. Hence, a multidisciplinary approach is desired which helps in pyramiding traits imparting drought tolerance while retaining the productivity potential in an irrigated environment in a genotype.

Afaq A. Mian, Prasad Senadheera, Frans J. M. Maathuis (UK) Improving Crop Salt Tolerance: Anion and Cation Transporters as Genetic Engineering Targets (pp 64-72)

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ABSTRACT

Invited Review: Plant exposure to high levels of NaCl results in osmotic stress and creates ion toxicity mainly due to Cl^- and, in particular, Na⁺ accumulation. In addition, salt stress impacts on nutritional homeostasis of minerals such as, Ca²⁺ and K⁺. The large detrimental effects of salinity on agriculture require understanding of the underlying genes and mechanisms to improve crop tolerance. A large number of potentially important genes has been identified using forward and reverse genetics, yeast complementation and transcriptomics approaches. The present review gives an overview of membrane transporters that have been assigned functions in uptake, efflux, compartmentation and translocation of Na⁺ and Cl^-. Subsequently, the review critically evaluates how specific genes were identified and assesses whether these would provide valuable targets to improve plant tolerance.

B. K. Garg, Uday Burman (India) Physiological Basis of Yield Improvement of Arid Zone Crops through Nutrient Management (pp 73-81)

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Invited Review: About 62% of Indian arid zone lies in western Rajasthan where low annual rainfall and its erratic distribution result in widespread and recurring droughts of varying intensity and magnitude. Crops in the arid and semi-arid areas suffer from both moisture and nutrient stresses. As nutrient and water requirements are intimately linked therefore, the interaction between soil moisture deficits and nutrient uptake that is of paramount importance has been extensively studied. Our investigations have established significant positive response of plants of these zones to improved soil fertility. However, the degree of yield response varied with rainfall pattern, drought intensity and crop species. Advantages of fertilizer application under arid conditions might be realized in situations where both dry and wet phase exist during the growing period. However, the benefits of nutrients under such conditions are generally less than in well irrigated crops. Fertility-induced metabolic efficiency coupled with higher photosynthetic and nitrate reductase activity are considered to be the control mechanisms for enhanced growth and yield of rainfed crops. Studies suggested that tissue hydrature was not an infallible index of metabolic efficiency as nutritional status of plants was more critical under water deficits for leaf metabolism, photosynthesis, growth and yield in different crops where nitrogen moisture interactions were explored. Alleviation of drought effects in arid legumes has been achieved through phosphorous (P) application which favourably modulates various physiological and biochemical processes. Similarly, applied potassium (K) mitigates the adverse effects of water stress by favourably influencing internal tissue moisture, photosynthetic rate and nitrogen metabolism in legumes. Thus, significant yield improvement can be obtained even under low soil moisture conditions through adequate nutrient management.

Helen Belefant-Miller (USA) Non-nutritive Mineral Effects on Rice (pp 82-91)

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Invited Review: The study of the responses of rice (Oryza sativa L.) to non-nutritive minerals has numerous benefits. With the sequencing of the rice genome, rice is the current model plant for genomic studies of crops and changes in genetic regulation in rice may reflect changes in other plants. The growth of rice is largely determined by the presence or absence of nutritive elements. Some of these are macronutrients while others are required in such small amounts as to be called micronutrients. However, the presence or absence of other, non-nutritive minerals can also influence rice growth. Their presence tends to be by human intervention and a selected few have been studied. Studies on the uptake and transport of non-nutritive elements can often provide correlative information on the nutritive minerals. Genetic information regarding mineral transport proteins in rice has been particularly valuable in understanding transport in other organisms. This paper presents an overview of the following minerals that have been studied and for which a physiological response in rice has been observed: aluminum, arsenic, cadmium, cesium, chlorine, chromium, germanium, mercury, iodine, lanthanum, nickel, lead, selenium, strontium, and vanadium.

Allen V. Barker, Ellen J. Pader (USA) Health Correlates of Nutrients in Soils and Foods (pp 92-97)

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Invited Mini-Review: Utilizing food systems to improve nutrition without the need for artificial fortification of food or use of dietary supplements of mineral nutrients is important in ending malnutrition. Malnutrition from deficiencies of mineral elements is reported to be on the rise worldwide, even in the United States. It is estimated that half of the world population suffers from incidences of mineral nutrient deficiencies. These deficiencies limit the physical, intellectual, and mental health activities of the affected people. The deficiencies appear to derive from diminished contents of mineral nutrients in foods of plant (vegetables, fruits) or animal (meats, milk, cheese) origins. With fruits and vegetables, the decline in nutrients is related in part to depletion of nutrients from soils without adequate replenishment with fertilization. Some of the diminished nutrient contents in fruits and vegetables may be related to genetics of new cultivated varieties of produce. Research is needed to develop systems of food crop production that will supply adequate mineral nutrition directly through crop-related foods and from meats and dairy products from livestock and poultry that are provided with adequate mineral nutrition.

Ramzi Murshed, Franck Lacroix, Huguette Sallanon, Félicie Lopez-Lauri (France) Effect of Water Deficit and Salt Stress on Oxidative Parameters and Antioxidant Systems in Tomato (Solanum lycopersicum L.) Fruits (pp 98-106)

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ABSTRACT

Original Research Paper: In this study, the differential behaviour of antioxidant systems between water stress and salt stress, considering two stages of development of the fruit was investigated. The activities of superoxide dismutase (SOD) and catalase (CAT), as well as the activities and the relative transcript levels of the enzymes of ascorbate-glutathione cycle: ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), the levels of ascorbate pool and hydrogen peroxide (H₂O₂) and malonyldialdehyde (MDA) contents were studied in fruits of tomato plants (Solanum lycopersicum L. cv. ‘Micro-Tom’) subjected to water and salt stresses. Water deficit was induced by holding off the irrigation for 3 and 6 days. To apply salt stress, plants were treated with 100 mM of NaCl for 3 and 6 days. H₂O₂ content was generally increased with both water and salt stresses, however, MDA content was increased only with salt stress. Changes in ascorbate pool were noted in plants subjected to salt stress more than in plants subjected to water stress. Moreover, changes in SOD and CAT activities and in DHAR, MDHAR, APX and GR activities and relative transcript levels were depending on the type and period of stress and the fruit development stage. Moreover, the changes in enzyme activities in response to stress were not directly related to changes in the corresponding gene expressions. These results suggest that water and salt stress lead to oxidative stress and modulates the antioxidative responses of tomato fruits.