Effect Of Different Types Of Shades On Photosynthetic Characteristics Of Farmland Ginseng Leaves

3-year-old ginseng was used as material to set up four kinds of shade treatment(P1M1: arch shed covered with blue films; P1M2: arch shed covered with yellow films; P2M1: trapezoidal shed covered with blue films; P2M2: trapezoidal shed covered with yellow films), Li-6400 portable photosynthesis system was used to detect the net photosynthetic rate 、 photon flux density、stomatal conductance and transpiration rate, intercellular CO2 concentration, as well as environmental factors such as air temperature, relative humidity, air CO2 concentration and so on. Test results were as follows:The results showed that the net photosynthetic rate presents bimodal curve in the whole growth of farmland ginseng leaves. The peak appeared at full un-folding and green fruit stage,the flowering is slightly decline, the curve decreased after red fruit, and the lowest is yellowing leaves. The net photosynthetic rate of farmland ginseng has significant differences under different shades, showing that P1M1 is highest, followed by P2M1 treated, and the lowest is P2M2 process. Net photosynthetic rate throughout P1M1 treated is respectively higher 15.02%,48.99% and 81.97% than the average of P2M1, P1M2 and P2M2 processing in growth stage; net photosynthetic rate throughout P2M1 processed is respectively higher 29.53% and 58.20% than the P1M2 and P2M2 processing. Transpiration rate, water use efficiency and Pn/Ci of farmland ginseng under different shades are the same with net photosynthetic rate.The net photosynthetic rate of Panax ginseng un-folding leaves was in the range of 0.50~3.05 μmol·m-2·s-1 in green fruit. Diurnal changes of the net photosynthetic rate, stomatal conductance and transpiration rate all showed a rise in the morning, a decrease at a low level at noon, a gradual decrease in the afternoon, and the photosynthetic rate in the morning higher than that in the afternoon. From 6:00 to17:00, the net photosynthetic rate was significantly positively correlated with photo flux density(PFD).Correlation coefficient were 0.5912*;The net photosynthetic rate has the same trends with air temperature in the morning and afternoon sessions.Photo flux density and air temperature are major environmental factors influencing diurnal changes of net photosynthetic rate. In the control cultivation patterns the effect of light intensityand temperature on the growth of ginseng should be focused on.In the process farmland ginseng leaves response under different shades. The results showed that as the change of light environment was good, the net photosynthetic rate of ginseng leaves increased slowly after the first rapid increase and at the last in a stable trend, and light saturation point was at 400 μmol·m-2·s-1 or so. Gas exchange characteristics of ginseng leaves also changes followed light intensity increases, the same with the net photosynthetic rate. The net photosynthetic rate of ginseng leaves was found the highest under the arch shed covered with blue films, trapezoidal shed covered with blue films is second, the lowest is trapezoidal shed covered with yellow films.The results of this experiment showed that shed cover with blue film is the most conducive to the growth of ginseng either from observation of diurnal variation of ginseng leaves photosynthesis or the results determined in the growth period. It is recommended to widely use in production practices.