Abstract
The present investigation was aimed to understand the physiological and biochemical basis of water-deficit stress tolerance in pearl millet [Pennisetum glaucum (L.) R. Br.] hybrid ICMH 356 and its parents ICMR 356 (♂) and ICMB 88004 (♀) in response to and recovery from drought stress and also to comprehend crop adaptation under dryland conditions. A field experiment was conducted in a split plot design with moisture levels as the main plot and genotypes as the sub plots. A comparative analysis of hybrid and parents under well-watered and water-deficit stress conditions revealed that the hybrid was superior over the parents in terms of leaf water relations, excised leaf water retention capacity, accumulation of compatible solutes, photosynthesis, membrane stability index and antioxidative enzyme viz., superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) activities. ANOVA for these parameters was also found to be significant for genotypes, treatments and their interactions at 0.01% level. Maintenance of superiority in terms of these physiological and biochemical parameters coupled with better recovery ability upon stress relief are crucial physiological mechanisms contributing to water deficit stress tolerance in pearl millet. Simple correlation coefficient analysis revealed significant positive association of yield at 0.01% level with relative water content, leaf water potential, stomatal conductance, photosynthesis, proline, total soluble sugars, free amino acids, membrane stability index, leaf area index and total biomass, while a significant negative association with solute potential and malondialdehyde content, under water-deficit stress clearly indicated that such relationships can be positively attributed to drought tolerance.
Highlights
Abiotic stresses such as extreme temperatures, low water availability, flooding and high salt levels are the major limiting factors for plant growth and productivity
A comparative analysis of hybrid and parents under well-watered and water-deficit stress conditions revealed that the hybrid was superior over the parents in terms of leaf water relations, excised leaf water retention capacity, accumulation of compatible solutes, photosynthesis, membrane stability index and antioxidative enzyme viz., superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) activities
The ability to withstand Water deficit stress (WDS) was studied in terms of water relations, photosynthesis, membrane stability index (MSI), accumulation of compatible solutes and activity of AOX enzymes
Summary
Abiotic stresses such as extreme temperatures, low water availability, flooding and high salt levels are the major limiting factors for plant growth and productivity. Osmotic adjustment (OA) is an important mechanism which alleviates some of the detrimental effects of water stress due to the accumulation of osmolytes like proline, TSS and FAA Apart from their role in OA, they play a role in reactive oxygen species (ROS) signaling [3]. SOD is the front-line enzyme in ROS attack, since it rapidly scavenges superoxide, dismutating it to oxygen and H2O2 which in turn activates downstream antioxidative enzymes there by scavenging ROS [6] These physiological and biochemical mechanisms of stress response are common to all the plants, major differences exist in terms of strategies adapted by different crop species to cope with drought stress [7]. The present study was aimed to assess the effect of water-deficit stress and its relief on different physiological and biochemical processes along with the assay of antioxidative enzymes to ascertain their role in stress tolerance
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