Abstract
Wheat is an important global staple food crop; however, its productivity is severely hampered by changing climate. Erratic rain patterns cause terminal drought stress, which affect reproductive development and crop yield. This study investigates the potential and zinc (Zn) and silicon (Si) to ameliorate terminal drought stress in wheat and associated mechanisms. Two different drought stress levels, i.e., control [80% water holding capacity (WHC) was maintained] and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar-applied Zn-Si combinations (i.e., control, water spray, 4 mM Zn, 40 mM Si, 4 mM Zn + 40 mM Si applied 7 days after the initiation of drought stress). Results revealed that application of Zn and Si improved chlorophyll and relative water contents under well-watered conditions and terminal drought stress. Foliar application of Si and Zn had significant effect on antioxidant defense mechanism, proline and soluble protein, which showed that application of Si and Zn ameliorated the effects of terminal drought stress mainly by regulating antioxidant defense mechanism, and production of proline and soluble proteins. Combined application of Zn and Si resulted in the highest improvement in growth and antioxidant defense. The application of Zn and Si improved yield and related traits, both under well-watered conditions and terminal drought stress. The highest yield and related traits were recorded for combined application of Zn and Si. For grain and biological yield differences among sole and combined Zn-Si application were statistically non-significant (p>0.05). In conclusion, combined application of Zn-Si ameliorated the adverse effects of terminal drought stress by improving yield through regulating antioxidant mechanism and production of proline and soluble proteins. Results provide valuable insights for further cross talk between Zn-Si regulatory pathways to enhance grain biofortification.
Highlights
Wheat (Triticum aestivum L.) is one of world’s most important staple food crops
I.e., control (80% water holding capacity (WHC) maintained throughout the growing season) and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar applied Zn-Si combinations
Photosynthetic pigments and relative water contents (RWC) of flag leaves were reduced under drought stress (Fig 1)
Summary
Wheat (Triticum aestivum L.) is one of world’s most important staple food crops. Overall, yield potential of wheat is limited due to climate change effects, especially abiotic stresses, including heat, salinity and drought [1]. All environmental stresses negatively affect the growth and development of wheat, terminal drought stress hampers reproductive development and grain yield [2]. In arid and semi-arid region, there is deficiency of water for wheat crop during the late season, which is considered as terminal drought that occurs at reproductive and grain-filling growth phases. Reproductive and grain-filling phases are considered as most sensitive to drought [3], and prolonged terminal drought can cause significant reduction in wheat yield [2,3]. Drought stress affects at all growth stages of wheat, and reproductive stage, grain filling stage is the most sensitive where onset of drought leads to fewer and smaller grains in wheat [3]. Plants have evolved physiological (like production of osmolytes and soluble sugars) and antioxidant defense mechanisms (like ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) to combat the toxicity of ROS [10]
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