Drought Stress: An Impact of Climate Change, Its Consequences and Amelioration Through Silicon (Si)

Abstract

The eighteenth century simultaneously with the onset of industrial revolution and introduction of steam engines witnessed a meteoric upsurge in urbanization coupled with harmful anthropogenic activities which in turn subsequently steered climatic changes prompting calamitous floods, drought, global warming and altered CO2 concentration in air. Drought is one of the most imperative abiotic stresses wherein water availability recedes the optimum water requirement to an extent causing significant reduction in yield potential. The augmentation of harmful reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and the superoxide and hydroxyl radicals, leads to an alteration in various morphological, physiological, biochemical and molecular pathways consequently triggering the accumulation of numerous compatible osmolytes such as glycine-betaine, soluble sugars and proline and regulated expression of other genes. Drought, most importantly, influences the process of photosynthesis through the depletion of photosynthetic pigments, distortion of the structure and morphology of mesophyll cells altering the photosynthesis and gas-exchange processes as well as diminishing the reduction (electron transfer) efficiency of PSII. Silicon, in conditions of drought stress, has emerged to be a magical bullet compensating the yield loss to a great extent. Furthermore, it contributes to the amelioration of photosynthetic efficiency through the optimization of thylakoid membrane protein components. It is perceived to enhance seed germination in lentil and form a Si-cuticle double-layer diminishing transpiration rate and water flow rate in xylem vessels improving WUE up to 35% in case of maize under water stress. Silicon thus can be ascertained as a promising component to exterminate the hostile consequences of drought stress.