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 CO₂-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 CO₂ 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.