Gas exchange, photochemical efficiency, and yield of Jatropha curcas irrigated with saline water

Abstract

Jatropha curcas L. is a rustic plant with great potential for energy source. In semi-arid regions, where water scarcity has been one of the major problems, saline water is an alternative source in agriculture, although it causes losses in crop development and yield. This study was developed to evaluate the photochemical efficiency, gas exchange, and yield of Jatropha curcas irrigated with saline water. The experiment was carried out under five levels (L) of water electrical conductivity: L1 = 1.2, L2 = 1.8, L3 = 2.4, L4 = 3.0, and L5 = 3.6 dS m-1, (calibrated at 25 ºC). We conducted physiological assessments such as photochemical efficiency of photosystem II, gas exchange through stomatal conductance, transpiration, CO2 internal concentration and leaf net photosynthesis rate after application of saline water and following prunning. J. curcas production was measured based on the following variables, number of bunches per plant, number of fruits per plant, number of fruits per bunch, weight of shells per plant and weight of seeds per plant. Continuous application of saline water after J. curcas pruning caused a drastic reduction of up to 31.1% in gas exchange (A, gs, E, Ci, and A/Ci). Photochemical efficiency of photosystem II was restricted by salinity at 2.4 dS m-1 level. Increasing electrical conductivity in irrigation water at levels above 1.20 dS m-1 significantly reduced J. curcas production components by up to 77.3%. Irrigation with saline water up to the level 1.20 dS m-1 did not damage gas exchange and fruit production of Jatropha curcas crop.