Effect of abiotic stresses on growth, metabolic alterations and tolerance mechanisms in rice crop

Abstract

Rice is a staple food crop for the majority of world population. Abiotic stressful conditions of the environment such as salinity, drought, heat, chilling, anaerobiosis, metal toxicity impose limitations on productivity of rice in the regions which are prone to such constraints. The manifestations of these stresses include non-expression of full genetic potential, differential transcription of many genes, induction of stress responsive genes leading to cellular metabolic changes, alteration in activity behaviours of many enzymes, overproduction of several compatible metabolites like amino acids, sugars, polyamines, phytochelatins, organic acids, increased synthesis of many enzymes and stress specific proteins. Salinity and drought are prime stressful conditions for rice crop in arid and semi arid regions of the world. Changes in temperature rhythm impose heat or chilling injury. Soil flooding or submergence causes oxygen deprivation leading to anaerobic stress. Metal ions such as Pb, Cd, Hg, As, Ni are key pollutants of the soil, whereas Al toxicity is a problem in acid upland soils. Most of the abiotic stresses cause overproduction of reactive oxygen species (ROS) within the cell which cause oxidative damage to membranes and biomolecules. Increased accumulation of compatible solutes, overproduction of antioxidative enzymes, overexpression of transcription factors have been shown to confer tolerance in rice plants to a wide range of stresses like salinity, drought and low temperature. Stress induced gene products those involved in stress tolerance and those involved in signal transduction or as transcription regulators have served as basis to engineer stress tolerant plants. To contribute to food security and sustainability in rice production, it is essential to produce stress tolerant rice plants suitable for cultivation in stress prone areas. This needs a detail understanding of physiological and molecular mechanisms associated with stress tolerance more specially gene products involved in stress tolerance and signal transduction. Transcriptome profiling of rice seedlings has helped in great way in understanding how rice plants respond to abiotic stresses. Successful attempts have been made to produce transgenic rice plants tolerant to different abiotic stresses. However, with the rapid progress in the areas of functional genomics, proteomics and metabolomics a more improved understanding of novel stress responsive genes and their expression under various stresses is anticipated which will provide the basis of new strategies to produce genetically engineered rice plants tolerant to a single or multiple of abiotic stresses. © 2009 Nova Science Publishers, Inc.