Plant Drought Stress: Effects, Mechanisms and Management

Abstract

-Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO 2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO 2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance. drought response / stomatal oscillation / osmoprotectants / hormones / stress proteins / drought management / CO 2

Mining expressed sequence tags of rapeseed (Brassica napus L.) to predict the drought responsive regulatory network

“…Among the abiotic stresses, drought has a crucial devastating impact on agricultural production (Farooq et al 2009;Farooq et al 2012). Plants recruit complex overlapping mechanisms to reprogram their gene expression to cope with drought stress (Ahuja et al 2010;Golldack et al 2011).…”

Influencing of Water Stress and Micronutrients on Physio-Chemical Attributes, Yield and Anatomical Features of Common Bean Plants ( Phaseolus vulgaris L.)

“…These increments would be attributed to the major role of the applied microelements in photosynthesis activation, pigments formation and carbohydrates assimilation converted to the grains which optimize the economic part of the plant (Hilman & Asandhi, 1987). Farooq et al (2009) reported that water stress leads to severe decrease in yield components of crop plants probably by disrupting leaf gas interchange properties which not only restricted the size of the source and sink tissue show ever the phloem loading, assimilate translocation and dry matter distribution are also impaired. Thalooth et al (2006) illustrated that the foliar spray with zinc sulfate under drought condition have the positive effect on yield and its components of mungbean plant.…”

Effect of Restricted Irrigation on Water Relation Traits and Antioxidant Activity

“…When plant expose to adverse environment (drought) reactive oxygen species (ROS) such as superoxide (O 2 • ), hydrogen peroxide (H 2 O 2 ), hydroxyl radicals (OH • ) and singlet oxygen ( 1 O 2 ) are produced (Faize et al 2011). Multiple antioxidant enzymes like superoxide dismutases (SOD), catalases (CAT) and peroxidases (POX) are involved in the enzymatic scavenging of ROS (Apel and Hirt, 2004;de Carvalho, 2008;Farooq et al 2009). (Jiang and Jhang, 2004).…”