An investigation on possible effect of leaching fractions physiological responses of hot pepper plants to irrigation water salinity

BACKGROUND: The modification effect of leaching fraction (LF) on the physiological responses of plants to irrigation water salinity (EC(iw)) remains unknown. Here, leaf gas exchange, photosynthetic light–response and CO(2)–response curves, and total carbon (C) and nitrogen (N) accumulation in hot pepper leaves were investigated under three EC(iw) levels (0.9, 4.7 and 7.0 dS m(− 1)) and two LFs treatments (0.17 and 0.29). RESULTS: Leaf stomatal conductance was more sensitive to EC(iw) than the net photosynthesis rate, leading to higher intrinsic water use efficiency (WUE) in higher EC(iw), whereas the LF did not affect the intrinsic WUE. Carbon isotope discrimination was inhibited by EC(iw), but was not affected by LF. EC(iw) reduced the carboxylation efficiency, photosynthetic capacity, photorespiration rate, apparent quantum yield of CO(2) and irradiance–saturated rate of gross photosynthesis; however, LF did not influence any of these responses. Total C and N accumulation in plants leaves was markedly increased with either decreasing EC(iw) or increasing LF. CONCLUSIONS: The present study shows that higher EC(iw) depressed leaf gas exchange, photosynthesis capacity and total C and N accumulation in leaves, but enhanced intrinsic WUE. Somewhat surprisingly, higher LF did not affect the intrinsic WUE but enhanced the total C and N accumulation in leaves.