Effects of Different Nitrate Form on the Growth and Physiological Characteristics for Quercus mongolica Seedlings

To reveal the effects of different nitrogen forms on growth and physiology of Quercus mongolica, the biomass, photosynthesis, chlorophyll and soluble protein contents were measured in annual seedlings by cultivating in green house. The results showed that increasing the proportion of ammonium nitrogen could significantly increase the seedling biomass, photosynthesis, chlorophyll contents and soluble protein contents. The effect of different nitrogen forms ratios on the biomass was significantly different. The whole plant biomass was the highest when the ratio of NO^-₃-N/NH⁺₄-N was 2∶6. The biomass was 1.27 and 1.34 times respectively that the pure nitrate and the pure ammonium. But the difference was not significant between NO^-₃-N/NH⁺₄-N of 4∶4. The photosynthetic rate（Pn） and transpiration rate（Tr） reached the maximum when the ratio of NO^-₃-N/NH⁺₄-N was 4∶4. The Pn was 2.65 and 1.88 times of pure nitrate and pure ammonium. The Tr was 3.11 and 2.13 times of pure nitrate and pure ammonium. The contents of chlorophyll a, carotenoid and soluble protein appeared highest at NO^-₃-N/NH⁺₄-N ratio of 4∶4. These results suggested that the equal mixing of ammonium and nitrate can promote the growth of Quercus mongolica seedlings.