Effects of soil water condition on photosynthesis, ultrastructure and physiological characteristics of Jatropha curcas L. seedlings

Abstract

The photosynthesis, ultrastructure and physiological characteristics of Jatropha curcas L. seedlings were investigated with different soil water contents (80%, 50% and 30% of field capacity (FC)) in pots. The results indicated that under 80% FC, the net photosynthesis rate (Pn), content of chlorophyll pigment, stable carbon isotope ratio (Ω 13C), nitrogen (N) content and water use efficiency (WUE) of J. curcas were the lowest, while malonaldehyde (MDA), hydrogen peroxide (H 2O2) content, stomatal conductance (gg) intercellular CO2 concentration (C1) and transpiration rate (Tr) were the highest; Larger starch grains in chloroplast were observed, and chloroplast membrane was damaged. Under 50% FC, MDA and H 2O2 content, gg, Ci and T r of J. curcas were significantly higher than those under 30% FC, while N content and ω13C were nearly as same as those under 30% FC. J. curcas under 30% FC had the maximal Pn, pigment content, leaf N content and WUE, and the least MDA and H2O2 content; Moreover, the ultrastructure of chloroplast was always in order, and there were small chloroplasts and osmiophilic granules in chloroplast under 30% FC. Based on the economic value of J. curcas mostly coming from its seed and the soil nutrient conditions of Panxi regions, it was concluded that the suitable soil water content for J. curcas plantation ranged between 30%∼50% FC, under which the photosynthesis, N content and WUE of J. curcas were the highest. Excessive water supply might lead to an excessive vegetative growth because 80% FC would hurt the physiological and biochemical functions.