为确定菘蓝(Isatis indigotica Fort.)种植过程中氮肥的合理施用方式,对正常供氮(对照,Hoagland 基本营养液培养15 d)、缺氮(缺氮营养液培养15 d)和复氮(先用Hoagland 基本营养液培养6 d,然后用缺氮营养液培养4 d,最后用Hoagland 基本营养液培养5 d)条件下菘蓝幼苗的生长、光合和气体交换参数及相关酶活性指标进行分析。结果表明:经缺氮和复氮处理后菘蓝幼苗的单株根和叶片的鲜质量和干质量均高于对照组;其中,经复氮处理后单株根鲜质量及单株叶片鲜质量和干质量均最高,经缺氮处理后单株根干质量最高,且均与对照组有显著差异。经缺氮和复氮处理后叶片的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)均显著低于对照组;其中,复氮组的Pn值最低,缺氮组的Gs 和Tr 值均最低;而3 个处理组间的胞间CO2 浓度(Ci)无显著差异。经缺氮和复氮处理后叶片的谷氨酸脱氢酶(GDH)、谷氨酸合成酶(GOGAT)、过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性均低于对照组,丙二醛(MDA)含量显著高于对照组;其中,复氮组叶片的GDH、GOGAT 和CAT 活性均最低,而缺氮组叶片的POD 和SOD 活性均最低,且均与对照组有显著差异。研究结果显示:缺氮处理有利于菘蓝幼苗的干物质积累,但不利于其光合作用和气体交换,对GDH 等相关酶活性也均有一定的抑制作用;而经复氮处理后叶片的气体交换参数及部分酶活性均有所提高,因此,在菘蓝栽植过程中建议采用短期缺氮的施肥方式以提高其产量。

In order to confirm reasonable application mode of nitrogen fertilizer during planting process of Isatis indigotica Fort., indexes of growth, photosynthetic and gas exchange parameters and related enzyme activities of I. indigotica seedlings were analyzed under conditions of normal nitrogen supplying (the control, cultured for 15 d by Hoagland basic nutrient solution), nitrogen deficiency (cultured for 15 d by nitrogen deficiency nutrient solution) and nitrogen recovery (firstly, cultured for 6 d by Hoagland basic nutrient solution, then, cultured for 4 d by nitrogen deficiency nutrient solution, finally, cultured for 5 d by Hoagland basic nutrient solution). The results show that after nitrogen deficiency and nitrogen recovery treatments, fresh and dry weights of root and leaf per plant of I. indigotica seedlings all are higher than those of the control group. In which, fresh weight of root per plant, fresh and dry weights of leaf per plant after nitrogen recovery treatment all are the highest, dry weight of root per plant after nitrogen deficiency treatment is the highest, and all of them have significant differences to those of the control group. After nitrogen deficiency and nitrogen recovery treatments, net photosynthetic rate (Pn),stomatal conductance (Gs) and transpiration rate (Tr) of leaf all are significantly lower than those of the control group. In which, Pn value of nitrogen recovery group is the lowest, both Gs and Tr values of nitrogen deficiency group are the lowest, while there is no significant difference in intercellular CO2 concentration ( Ci) among three treatment groups. After nitrogen deficiency and nitrogen recovery treatments, activities of glutamic dehydrogenase ( GDH), glutamate synthase ( GOGAT), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) in leaf all are lower than those of the control group, and malondialdehyde (MDA) content is significantly higher than that of the control group. In which, activities of GDH, GOGAT and CAT in leaf of nitrogen recovery group all are the lowest, while both activities of POD and SOD in leaf of nitrogen deficiency group are the lowest with significant difference to those of the control group. It is suggested that nitrogen deficiency treatment is beneficial for I. indigotica seedlings to accumulate dry matter, but is not beneficial to its photosynthesis and gas exchange, and has a certain inhibition effect on related enzyme activities such as GDH, etc. While after nitrogen recovery treatment, gas exchange parameters and some enzyme activities of leaf have a little increase. Therefore, it is suggested that taking short-term nitrogen deficiency mode during planting process of I. indigotica is feasible to increase its yield.