Effect of Nitrogen Fertilizer and Plant Density on Diurnal Variation of Photosynthetic Characteristics of Salvia miltiorrhiza

In order to provide theoretical basis for normalized cultivation of Salvia miltiorrhiza,the effect of nitrogen fertilizer and plant density on diurnal variation of photosynthetic characteristics of purple flower Salvia miltiorrhiza was studied.The results showed that,the diurnal variation of net photosynthetic rate of Salvia miltiorrhiza presented double-apex curve,and had a phenomenon of photosynthetic noon breaking.During photosynthetic noon breaking,stomatal conductance,transpiration rate and air CO2 concentration decreased,but photosynthetically available radiation increased.Under high nitrogen fertilization condition,stomatal conductance was the main limiting factor affecting the photosyntheticnoon breakingof Salvia miltiorrhiza,and net photosynthetic rate was higher in plant density of 8×104 plants/ha.Under low nitrogen fertilization condition,net photosynthetic rate of Salvia miltiorrhiza was affected by several factors together,and net photosynthetic rate was higher in plant density of10×104 plants/ha.Net photosynthetic rate was higher under high nitrogen fertilizer condition than that under low nitrogen fertilizer condition when the plant density was same.This result indicated that interaction between nitrogen fertilizer and plant density had significant effects on the net photosynthetic rate of Salvia miltiorrhiza.So,in a range of soil fertility amount,plant density can be regulated to compensate or substitute fertilization.