[Effect of salicylic acid on photosynthesis, physio-biochemistry and quality of Panax ginseng under full sun shine in spring].

In order to search for a new pathway to improve the yield of ginseng through growing at the full sun shine accompanied by salicylic acid (SA), the net photosynthetic rate (P(n)), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), malondialdehyde (MDA) in Panax ginseng leaves, and the content of ginsenosides in roots were compared under various concentrations of SA and full sun shine with the traditional shade shed. Under the full sun shine, 0.05, 0.2 mmol x L(-1) SA increased net photosynthetic rate to a great extent. Under the cloudy day, the average net photosynthetic rate increased by 127.8% and 155.0% over the traditional shade shed, 13.9% and 27.5% over the treatment without SA respectively; under the clear day, 23.5% and 30.4% over the traditional shade shed, 8.6% and 14.6% over the treatment without SA, particularly obvious in the morning and late afternoon. With such concentration, SA increased activities of SOD, CAT, POD, and decreased the contents of the MDA. This difference resulted from different light intensity, rise of light saturation point, and fall of compensation point. Full sun shine decreased ginsenosides contents, but with SA, the ginsenosides regained, the content of Rg1 and Re, Rb1, total six types of ginsenosides in SA 0.2 mmol x L(-1) group were higher than those in the control group (P < 0.05) and other groups. The application of 0.2 mmol x L(-1) SA under full sun shine during a short time has little threat to the P. ginseng in spring, and could enhance the resistance to the adversity, which would improve the yield of ginseng heavily.