Effect of different nitrogen forms and their proportion on biological characteristics of Isatis indigotica Fort

To provide a theoretical basis of efficient utilization of nitrogen fertilizer for cultivation and production of Isatis indigotica, effects of different nitrogen forms and their proportion on biological characteristics of I. indigotica were studied by using sand culture. There were four different concentrations of three nitrogen forms,NH+4-N,NO-3-N and［CO(NH2)2-N］. The dry weights of leaves and roots, lengths and diameter of taproots, chlorophyll content and photosynthetic parameters were used as indicators. The results show that the nitrogen treatments could increase the dry weights of leaves and roots, the effect of NH4+\|N on taproot length and number of lateral root is the most significant, the effect of amide nitrogen and nitrate nitrogen on taproot diameters is similar, and the effect ofNO-3-N on dry weights of leaves and roots and root/shoot ratio is the most significant. The nitrogen treatments could significantly improve the chlorophyll content and net photosynthetic rate which affect chlorophyll and net photosynthetic rate of nitrate nitrogen, stomatal conductance and transpiration rate of amide nitrogen, and the concentration of carbon dioxide in the intercellular of ammonium nitrogen, respectively. Different nitrogen forms affect the growth through the effects of chlorophyll content and photosynthetic parameters, and in which nitrate nitrogen is the most significant nitrogen form.