effect of spraying zinc on photosynthetic pigments and grain yield of chickpea under level different irrigation

in order to study the effect of foliar zinc spraying on photosynthetic pigments and yield of chickpea under water stress conditions, a factorial experiment carried out based on randomized completely block design (rcbd) with three replications in university of mohaghegh ardabili agricultural research station in 2012. the treatments consisted of three levels of irrigation (irrigated at planting, planting + before flowering, planting + before flowering + pod initiation) and three zinc spraying rates (zero, 3 and 6 kg znso4 ha-1) in two plant growth stages. results showed that water limitation reduced photosynthetic pigments and grain yield. applications of 6 kg znso4 ha-1 effectively reduced adverse effects of drought stress through increasing content of chlorophyll a, total chlorophyll, carotenoids and spad index. chlorophyll fluorescence affected by water stress and zn. water stress reduced the instantaneous fluorescence (fv), maximum fluorescence (fm) and the quantum yield (fv/fm), whereas zn enhanced instantaneous fluorescence and maximum fluorescence. zinc application had no significantly effect on the quantum yield. results also showed, chlorophyll a content had the greatest impact on spad index and it had a quadratic correlation with spad index. among the measured photosynthetic pigments, carotenoids content had the highest contribution to the stress in the yield prediction. also zinc reduced the effect of chlorophyll and increase carotenoid content in yield prediction. generally zinc spraying improved crop yield by alleviating drought stress and enhancing factors that are effective on the photosynthetic pigments production under the water stress.