Effect of water deficit stress on an Indian wheat cultivar (Triticum aestivum L. HD 2967) under ambient and elevated level of ozone.

The response of a wheat cultivar (HD 2967) under the combination of elevated ozone (O) and water deficit stress (WS) was evaluated in terms of morphological, physiological and yield parameters along with nutrient uptake and their redistribution to different plant parts. An open-top chamber experiment has been conducted under O exposures (ambient (A) and ambient +20 ppb O (E)) along with two different water regimes (well-watered; WW and water deficit with 50% of soil capacity; WS). Most of the growth parameters showed significant reductions due to elevated O under both WW and WS conditions. Stomatal conductance and assimilation rate reduced significantly under the combined stress as compared to their controls (AWW). The maximum decrease in grain yield was observed under the additive effect of both the stresses of water deficit and elevated O (-43.6%), followed by water deficit stress (-19.8%) and elevated O (-17.9%) as compared to the control (AWW). Furthermore, the study displayed that reduced water availability has checked the uptake of nutrients in the roots, shoot and leaves, while, a higher carbon accumulation has been observed with subsequent increases in C: N and C: K ratios in the leaves. Such limitation of nutrients uptake and photosynthates availability weakened the antioxidative defense system of the test cultivar, making it more sensitive against combined stresses. Besides, the study displayed that the defense system has been remarkably suppressed under the presence of interactive stress factors, which allowed us to predict that the distribution of limited carbon pool has inverse relationship between the plant's defense system and growth.