γ–氨基丁酸浸种对高氮处理下白菜生长及硝酸盐代谢的影响

Regulation of γ-aminobutyric Acid on Growth and Nitrate Metabolism of Pak-choi Treated with High Nitrogen Application

在营养液中添加硝态氮模拟设施白菜(Brassica campestris ssp.chinensis Makino)生产中氮肥施用量,采用5、10 mmol·L^(-1)γ–氨基丁酸(GABA)浸泡种子,研究GABA对白菜生长以及硝酸盐代谢过程中物质含量和关键酶活性、基因表达和蛋白表达的影响。结果表明:与对照和未经GABA浸种的高氮处理相比,GABA浸种显著促进了高氮条件下白菜的生长,并通过显著提高叶片硝酸还原酶(NR)、亚硝酸还原酶(NiR)、谷氨酸脱羧酶(GAD)等关键酶活性以及NR、GAD基因和蛋白表达量,诱导硝酸盐、亚硝酸盐含量显著降低,但铵态氮(NH_4^+-N)、谷氨酸(Glu)和内源GABA含量仍维持较高水平。进一步分析表明,GABA浸种降低硝酸盐的效果存在时效性和浓度差异,在高氮处理0~12 d时效果较明显,5 mmol·L^(-1) GABA处理效果较好;并且GABA对NR、GAD基因、蛋白表达的影响早于酶活性的变化。结果证明GABA浸种在促进植株生长的同时,通过提高叶片NR、GAD等代谢关键酶的活性、基因和蛋白表达量,加速了无机氮的还原和同化,从而降低叶片硝酸盐含量,提高白菜的产量和品质。

To explore the effect of 7-aminobutyric acid （GABA） on the growth, substance content related to nitrate metabolism, key enzyme activities as well as gene and protein expression in pak-choi （Brassica campestris ssp. chinensis Makino）, the plants grown in nutrient solution with high nitrate nitrogen were used as sample materials after the seeds were soaked with GABA at the concentration of 5 and 10 mmol · L-1. The results showed that compared with the control and nitrate application treatments,GABA soaking significantly improved the growth of the pak-choi, increased the activities of nitrate reductase （NR） and nitrite reductase （NiR）, glutamic acid decarboxylase （GAD）, and gene and protein expression in leaves. As a result, GABA soaking treatment decreased the contents of nitrate and nitrite nitrogen in leaves, but the contents of ammomium nitrogen （NH4-N）, glutamate （Glu） and endogenous GABA maintained at a higher level. Further analysis showed that the effect of GABA soaking on nitrogen metabolism varied with treatment time and concentration. It showed the better result at 0-12 days after high nitrate application, and the GABA soaking effect at concentration of 5 mmol · L-1; meanwhile, GABA influenced the key enzyme gene and protein expression was earlier than that of enzyme activities. The results indicated that GABA soaking treatment promoted plant growth as well as the metabolism of nitrate reduction and assimilation through the increase of NR and GAD activities, gene and protein expression, and consequently, reduced nitrate content in leaves, improved yield and quality of pak-choi.