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Potassium fertilizer improves drought stress alleviation potential in cotton by enhancing photosynthesis and carbohydrate metabolism

Zahoor, Rizwan, Dong, Haoran, Abid, Muhammad, Zhao, Wenqing, Wang, Youhua, Zhou, Zhiguo
Environmental and experimental botany 2017 v.137 pp. 73-83
Gossypium hirsutum, beta-fructofuranosidase, biomass production, carbon dioxide, cotton, cultivars, drought, flowering, leaves, nutrient management, photosynthesis, potassium, potassium fertilizers, ribulose-bisphosphate carboxylase, soil, starch, stomatal conductance, sucrose, sucrose synthase, sucrose-phosphate synthase, water content, water stress
Under drought, limited photo-assimilates synthesis and their poor partitioning is a main constraint to final yield production in cotton (Gossypium hirsutum L.). To study the potassium (K) role in photo-assimilation and carbohydrate metabolism in cotton under soil drought stress during flowering and boll formation stage, a two-year pot experiment was conducted in 2015 and 2016. Two cotton cultivars namely Simian 3 (low-K tolerant) and Siza 3 (low-K sensitive) were grown under three K rates (0, 150 and 300kgK2Oha−1). Plants were exposed to well-watered [(75±5%) soil relative water content (SRWC)] and water stress (35–40% SRWC) for 7days followed by re-watering to SRWC (75±5%). The results showed that water-stressed plants under K0 application exhibited significant decline in net photosynthesis, stomatal conductance, intercellular CO2 concentration and ribulose-1,5-bisphosphate carboxylase (Rubisco) activity and resulting in reduced photo-assimilates synthesis and partitioning towards reproductive organs in both cultivars. Conversely, K application decreased the decline in photosynthesis, Rubisco activity and biomass accumulation and partitioning. The positive effects of K application increased as increasing K rates, and that was more pronounced in Siza 3 than Simian 3. Drought stress decreased starch content but increased sucrose content; whereas, K application maintained higher concentration of sucrose in leaves of water-stressed plants through the regulation of higher sucrose phosphate synthase (SPS), sucrose synthase (SuSy) and lower soluble acid invertase (SAI) activities. The results of the study concluded that K application regulated the photo-assimilation and translocation process along with the related enzymes activities in cotton. The study suggests that K nutrient management strategy has the potential to minimize the impacts of drought stress in cotton.