Effects of Several Abiotic Stresses on Photosynthetic Rate and Other Physiological Indexes in Jatropha curcas L. Seedlings

Abstract:

The dynamic changes in several physiological indexes, such as net photosynthetic rate (Pn), transpiration rate (Tr), etc., in Jatropha curcas L. seedlings under different abiotic stresses were studied. The results showed that under phosphorus deficiency, Pn of J. curcas contained about 90% of control, and stomata conductance (Gs) and intercellular CO₂ concentration (Ci) increased 20%-40% and 4%-16% after 2 days, respectively, and little change in Tr. The P content decreased from 55% to 85% under phosphorus deficiency, whereas dry weight only decreased 3% after 17 days. Under nitrogen deficiency, Pn decreased to the lowest level at the 9th day, and then maintained at about 64% of control. Gs increase significantly about 15%-57% treated after 2 to 7 days, and then decreased to control. Ci rose about 4% to 24% from the 2nd day compared with the control, and there was little change in Tr. N content decreased 22% to 53% under nitrogen deficiency and plant dry weight decreased about 23% after 17 days. Under salt stress, Pn decreased to 54% of control at the 5th day, and then maintained about 48%. The changes in Gs, Ci and Tr were consistent with that in Pn. The content of P in petiole and stem increased 37%-54%, while K⁺/Na⁺ decreased 87%-96% in different tissues, and dry weight decreased 18% of control after 17 days. Under drought stress, Pn decreased rapidly to 29% at the 6th day, and the changes in Gs, Ci and Tr were consistent with that of Pn. The cell membrane permeability increased 67% at the 7th day and dry weight decreased 55% of control at the 17th day. Meanwhile, leaves became curly and pendulous, and old leaves fall off. Among all of stresses, Pn of J. curcas reached relative stable state at first under phosphorus deficiency stress, followed by salt stress and nitrogen deficiency. It suggested that the J. curcas had good adaptability to phosphorus deficiency stress, and relatively poor to nitrogen deficiency stress. The salt tolerance of J. curcas should belong to the gathered salt type, which is a type of avoiding salt damage, while the drought adaptation of J. curcas belongs to drought avoidance type.