Research On The Effect Of Nitrogen Form On Growth Physiology And Nitrogen Absorption-utilization In Four Tea Varieties (Camellia Sinensis L.)

It was a hot focus that the effect of different forms nitrogen application on the growth physiology. The effect of nitrogen form on growth of plant spring shoots, main chemical components, content of mineral elements, nitrogen metabolism and photosynthetic physiology were studied in plot experiment, with four different tea varieties. The physiology and biochemical bases for the reason that tea prefers to using ammonium was discussed. The main results were concluded as follows:1. The height growth of tea plant and time of keeping tenderness were greatly affected by nitrogen form, comparing the little effect on girth growth. The photosynthetic capacity, such as Pn, Gs and Tr, and GS activity were enhanced when the proportion of ammonium nitrogen was high. But when the ammonium proportion was higher than 70%, the capacity and GS activity reduced obviously.The diurnal variations of Pn with pure nitrate and NO3--N:NH4+-N7:3 application were one peak type, and others were double peaks. The annual dynamic of GS and GOGAT activity with different treatment were similarly.2. The total absorption area (St), active absorption area (Sa), the kinetics of ammonium and nitrate uptake in root and efficiency of nitrogen usage were affected by nitrogen form significantly, comparing the effect on ratio of Sa/St, specific surface area, and nitrogen transportation ratio was small. And the comprensive ability of nitrogen absorbing and utilization was relatively better with NO3--N:NH4+ -N5:5 application. The effect of nitrogen form on total nitrogen (TN) was significant. And the effect on TP and TK was relatively small.3. The increment of ammonium nitrogen in plot experiment will lead to the increasing of free amino acids and caffeine content, and the decrement of tea polyphenol content. These contents were high under the NO3--N:NH4+-N7:3 or 5:5 treating. But the contents were low when the proportion of NH4+-N exceeding 70%. The annual dynamic of chemical components was similar among different treatments. And the tea polyphenol/free amino acids had small difference.4. The effect of nitrogen form on physiological mechanism of tea grow manifested at the comprehensive influence on tea plant. When the NH4+-N proportion was increasing, the kinetics of ammonium and nitrate uptake was changed greatly. The root activity was promoted. The activity of key enzymes in ammonium assimilation progress in leaves were affected, especially the GS activity was affected larger than GOGAT activity. TN in leaves was also changed greatly with nitrogen form treating. Both the enzymes and the mineral content in leave, with the moderating mixed nitrogen application, were all better than pure nitrogen using. And the photosynthetic capacity was promoted greatly when the ratio of different nitrogen was suitable. Then, the individual and spring shoot growth was improved. But when the proportion of ammonium was too high, the growth and physiology of these plants was not very googd. These effects on tea plant might be related to the NO3- played as a signal role to regulating these physiological mechanisms.