Foliar nitrogen and potassium applications improve photosynthetic activities and water relations in sunflower under moisture deficit condition

This study investigated the influence of foliar supplementation of nitrogen (n) potassium (k) and their combination on photosynthetic activities,physiological indices and water relations of two sunflower (helianthus annuus l.) hybrids hysen-33 and lg-5551under water deficit condition. studies were conducted in a wire-house at nuclear institute for agriculture and biology,faisalabad,pakistan. treatments were two water stress levels [100 (control) and 60% field capacity (water deficit)],six levels of foliar spray (no spray,water spray,1% n,1% k,0.5% n + 0.5% k and 1% n + 1% k) and each treatment was replicated three times. results showed that water stress reduced the photosynthetic activities: pn (photosynthetic rate),e (rate of tanspiration) and gs (stomatal conductance) and water relations i.e.,ψw (water potential),ψs (osmotic potential) and ψp (turgor potential). soil moisture deficit also significantly reduced the plant height,root length,fresh and dry matter which consequently affected the plant height stress tolerance index (phsi),root length stress tolerance index (rlsi) and dry matter stress tolerance index (dmsi) in both sunflower hybrids. however,foliar supplementation with n and k or n+k improved the photosynthetic activities,water relations and physiological indices of both the sunflower hybrids. the findings of present study suggest that application of n+k is necessary to have high plant productivity. © 2016,pakistan botanical society. all rights reserved.