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The physiological and nutrient uptake performance of two wheat (Triticum aestivum L.) cultivars (Lasani-2008 and Auqab-2000) to foliar application of 1% potassium (K) at three different growth stages (tillering, flower initiation and grain filling) was investigated under water limited environment in a wire house experiment at the Nuclear Institute for Agriculture and Biology, Faisalabad. The aim was to find out the best K application stage for improvement in drought tolerance potential. Drought stress was created by withholding irrigation at the three growth stages and then K was sprayed with carboxymethyl cellulose as a sticking agent, whereas Tween-20 was used as a surfactant for foliar spray. At maturity, aboveground nitrogen, phosphorus, K, sodium and calcium uptakes by the crop were measured. Besides, water potential, osmotic potential and turgor potential of crop were also estimated. The results indicated that the drought stress at all three critical growth stages of wheat adversely affected plant's nutrient uptake, water potential, osmotic potential and turgor potential of wheat plants. The exogenous application of K under drought stress at all three critical growth stages enhanced tolerance of wheat by reducing toxic nutrient's uptake and improving the physiological efficiency. In this regards, both varieties showed uniform behavior. Maximum improvement in all the recorded nutrients uptake and physiological parameters was achieved when K was applied at grain filling stage of both cultivars.

Exposure of plants to long periods of water scarcity, mainly in arid and semi-arid regions, is one of the major reasons for over 50% reduction in average yields. Proper management of Brassica napus to enhance its ability to survive under drought and high temperature stress at early growth stages, besides development of tolerant genotypes, could improve its production in the rainfed areas. In the present study, we report the interactive effects of Ca 2+ , K + and N supplementation and water availability on the fresh biomass, N and C content, as well as C/N ratio of crop plants. Exposure to water stress significantly reduced the fresh biomass, Nitrogen (N), Carbon (C) content and the C/N ratio. Ca 2+ and K + supplementation before drought positively affected fresh biomass by stimulating N uptake and C assimilation. However, the C/N ratio was reduced after supplementation with Ca 2+ and K +. The N supplementation before drought imposition, though enhanced the N uptake, but the excessive damage to cell membranes and electrons leakage from Electron Transport Chain (ETC) during photosynthesis resulted in a decrease in C assimilation. Consequently, there was a decrease in the C/N ratio in seedlings exposed to drought after supplementation with N.

Supply of adequate moisture is one of the most important factors limiting agricultural extension and productivity. Ca 2+ and K + are both essential plant nutrients required in a number of developmental and metabolic processes. Both of these nutrients play an important role in ameliorating drought stress in crop plants. This experiment was designed to study whether exogenous application of Ca 2+ and K + before the drought could enhance the potential of plants to survive under limiting water conditions. Brassica napus L. cv Bulbul-98 seedlings were exposed to drought stress for 10 days after exogenous application of different concentrations of Ca 2+ , K + and N through irrigation water. Exogenous Ca 2+ and K + application was associated with increased relative water content, membrane stability and chlorophyll content in seedlings exposed to water deficit. Though the quantity of Pro and activities of APX (EC: 1.11.1.11) and CAT (EC: 1.11.1.6) were increased after K + application, they were strongly induced in seedlings supplemented with Ca 2+ in a dose dependent manner. Increasing quantity of N application, however, had a negative effect on these parameters.