为解析氮（N）素形态和弱光胁迫对茶树生长代谢的影响,以2年生龙井43扦插苗为试验材料,通过溶液培养分别供给NH4+-N和NO3--N 2种不同形态N源,以及正常光照和弱光2种光照强度。结果表明：（1）茶苗净光合速率主要受N素形态影响,正常光照条件下,NH4+-N处理明显高于NO3--N处理;相同氮素条件下,与正常光照相比,弱光胁迫有减弱茶苗净光合速率的趋势。（2）茶苗新梢叶绿素含量主要受氮素形态和光照共同影响,弱光胁迫有助于提高叶绿素含量。正常光照时NH4+-N处理的茶苗新梢叶绿素含量显著高于NO3--N处理,但叶绿素a（Chl a）和叶绿素b（Chl b）含量的比值（Chl a/b）基本不变,弱光胁迫后新梢叶绿素含量增加,但NH4+-N处理的新梢Chl a/b值明显提高,而NO3--N处理的Chl a/b值略有下降,茶树施用NO3--N比施用NH4+-N更具有耐荫性。（3）茶苗N素吸收主要受N素形态和光照共同影响,弱光胁迫有助于提高茶苗新梢N素的累积。正常光照时NH4+-N处理的茶苗新梢N含量要明显高于NO3--N处理,弱光胁迫明显增加茶树地上部N含量。（4）新梢品质成分变化主要受到光照影响,但酚氨比的变化受光照和氮源的共同作用影响。正常光照下NH4+-N处理新梢游离氨基酸总量和咖啡碱含量明显高于NO3--N处理,而酚氨比则低于NO3--N处理。弱光胁迫后新梢中游离氨基酸和咖啡碱含量进一步升高,而茶多酚含量和酚氨比降低,NO3--N处理新梢中游离氨基酸总量增加速率和茶多酚含量、酚氨比下降速率更快。研究结果为解析其机制提供理论依据。
In order to analyze the effects of N form and weak light stress on the tea plant growth and metabolism, the two-year-old cutting seedlings of ‘Longjing 43’ were taken as experimental materials, and two different forms of N sources (NH4+-N and NO3--N) and two light intensities (normal light and weak light) were supplied under solution culture. The results show that: (1) the net photosynthetic rate of tea seedlings was mainly affected by the N form under normal light intensity. The net photosynthetic rate of tea seedlings treated with NH4+-N was significantly higher than that treated with NO3--N. Under the same nitrogen conditions, compared to normal light, weak light stress had a tendency to reduce the net photosynthetic rate of tea seedlings. (2) Under normal light intensity, the chlorophyll content in young shoots treated with NH4+-N was significantly higher than that treated with NO3--N, but the chlorophyll a (Chl a)/chlorophyll b (Chl b) ratio was basically unchanged. The chlorophyll content increased significantly after weak light stress, but Chl a/b ratio under NH4+-N treatment was significantly increased, while Chl a/b ratio under NO3--N treatment was slightly decreased. NO3--N treated tea plants showed better shade tolerance than that treated with NH4+-N. (3) N uptake by tea seedlings was mainly influenced by both N form and light, and weak light stress helped to improve the accumulation of N in new shoots of tea seedlings. The N content of NH4+-N treated tea seedlings was significantly higher than that treated with NO3--N under normal light. Weak light stress significantly increased the above-ground N content in tea plants. (4) Under normal light intensity, the contents of free amino acids and caffeine in young shoots treated with NH4+-N were significantly higher than those treated with NO3--N, while the ratio of tea polyphenol to free amino acids was lower. After weak light stress, the contents of free amino acid and caffeine in shoots further increased, while the contents of tea polyphenol and the ratio of tea polyphenol to free amino acids continued to decline. The increase rate of total free amino acid and descent rate of tea polyphenol and tea polyphenol/free amino acids ratio were faster in young shoots treated with NO3--N than those treated with NH4+-N. The composition of shoot quality was mainly affected by light intensity, but tea polyphenol-free amino acids ratio was influenced by both light intensity and N form. The research results provide theoretical basis for the analysis of its mechanism.
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