Abstract
The realized productivity of crop plants is generally lower than the potential productivity due to the influence of one or more external stresses (biotic and abiotic). Simultaneous occurrence of combination of abiotic stresses, which is more common under field condition, results in compounded effect on functional processes. Main focus of the present work is the combined effect of drought and light (irradiance) on rice plants. Potted seedlings of four selected rice lines (viz., IR36, N22, CRD40 and Bhootmuri) were exposed to three different levels of drought stress (50%, 25%, 12.5% of water) along with control (100%) in combination with three different light intensities (high, medium and low) during experimental period. After 7 days of stress, plant height and relative water content (RWC) were relatively low while root length increased with increasing water stress level and light intensity. Protein content increased with increasing water stress and light intensity, while chlorophyll level was higher at higher light intensities. Malondialdehyde (MDA) content, indicative of lipid peroxidation, increased with water stress only at high light intensities. Superoxide dismutase (SOD), peroxidase (POX) and ascorbate peroxidase (APX) activities increased with combined drought and light stress level, whereas catalase (CAT) activity was higher at higher light intensities. On the other hand, superoxide (O2.-) production, but not hydrogen peroxide (H2O2) production was higher with increasing water stress and light intensity. It appears that light-induced ROS (O2.-) production under drought condition provoked oxidative stress, though a potential mechanism of tolerance was apparent through antioxidant system.
Highlights
Recent issues of global warming and associated climate errors have been a big alert for crop plants, which are increasingly subjected to different biotic and abiotic stresses and their combinations affecting growth and yield [1,2,3,4]
Superoxide dismutase (SOD), peroxidase (POX) and ascorbate peroxidase (APX) activities increased with combined drought and light stress level, whereas catalase (CAT) activity was higher at higher light intensities
Considering only light intensity, shoot growth increased with increasing light intensity except for S3, increase was less at high light intensity
Summary
Recent issues of global warming and associated climate errors have been a big alert for crop plants, which are increasingly subjected to different biotic and abiotic stresses and their combinations affecting growth and yield [1,2,3,4]. Plants are always likely to be exposed to different types of abiotic stresses viz. Under field conditions, stresses may often occur in combinations, like drought along with heat or high light intensity, conditions which are very common to most of the crop growing areas, in India. Impact of such combinations may not always be additive, depending on the nature of interacting stresses [3, 9,10,11,12,13]. A stress matrix has been developed considering the responses of plants due to interactions among different stresses reflecting both the negative and positive impacts on plant growth and development [1, 14]
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