氮素水平对茶树叶片氮代谢关键酶活性及非结构性碳水化合物的影响

以福鼎大白茶(FD)、保靖黄金茶1号(HJ1)、白毫早(BHZ)为材料,设置不施氮N_0(0 g)、低氮N1(11 g)、中氮N_2(22 g)和高氮N_3(33 g)4个氮素水平的盆栽实验,研究了铵态氮对3个品种茶树的根系活力、氮代谢关键酶及非结构性碳水化合物(NSC)的影响。结果表明:随着施氮水平的提高,N_2、N_3处理的茶树根系活力较对照N0显著增加(P0.05),但二者间无显著差异;叶片谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)活性总体呈上升趋势;与对照比较,茶树叶片全氮和可溶性蛋白含量增加,其中HJ1在N_2和N_3处理后显著增加(P0.05);在3个茶树品种中,非结构性碳水化合物中可溶性总糖含量均呈上升趋势,淀粉含量具有品种特异性,施氮处理后3个茶树品种氮代谢关键酶活性及NSC含量变化存在差异,以HJ1的氮同化关键酶GS、GOGAT酶活性较高、根系活力较强,氮代谢产物显著增加,表明其具有较高的氮同化速率。施氮后HJ1的总NSC的含量及碳氮比的变化幅度较另外2个品种小,能够更好的保持碳氮平衡,游离氨基酸含量增幅较高,品质更优。因此,通过茶树氮代谢关键酶活性及非结构性化合物的研究能为茶树品种的品质评价以及提高茶树的品质和氮素利用效率提供依据。

Effects of nitrogen levels on key enzyme activities and non-structural carbohydrates in nitrogen metabolism in tea leaves

We investigated the effects of nitrogen on root activity, key enzyme activities of nitrogen metabolism, and non-structural carbohydrates (NSC) in 3 tea varieties (Fuding dabai tea (FD),Baojing huangjin tea 1# (HJ1) and Baihaozao (BHZ)) with 4 ammonium nitrogen (N) treatments:without N deposition:N₀ (0 g), low N deposition:N₁ (11 g), medium N deposition:N₂ (22 g), and high N deposition:N₃ (33 g). The results showed that root activity increased significantly in N₂ and N₃ compared with the control, however, there were no differences between these two treatments. The GS and GOGAT activities in tea leaves increased after N treatment. Compared with the control, the total nitrogen content and soluble protein content in tea leaves generally increased following nitrogen treatment, significantly in the case of N₂ and N₃ in HJ1 (P<0.05). As the mass of N in the treatment increased, the NSC and total soluble sugars presented a tendency of increasing. However, the changes in starch content displayed varietal specificities in FD, HJ1 and BHZ. Changes in key enzymes involved in nitrogen metabolism and NSC content were observed after nitrogen treatment, which were different in the 3 tea varieties. Following N treatment, HJ1 showed higher GS and GOGAT activities, higher root activity, and a significant increase of nitrogen metabolites compares to FD and BHZ, which indicates a higher rate of nitrogen assimilation. The total NSC content and C/N changed less in HJ1, which had a better quality of higher free amino acid content, implying that HJ1 better maintain a carbon-nitrogen balance. Therefore, research on the activities of key enzymes involved in nitrogen metabolism and NSC in tea plants can provide a basis for evaluating the quality of tea varieties and improving the quality and nitrogen use efficiency of tea plants.