不同pH值高氮营养液培养下外源γ-氨基丁酸对小白菜叶片无机氮代谢的影响

Effects of exogenous γ-aminobutyric acid on inorganic nitrogen metabolism in leaves of pakchoi(Brassica campestris ssp.chinensis)cultured with different pH and high nitrogen nutrition conditions

在不同pH值高氮营养液条件下,研究了外源GABA对小白菜‘五月慢’(Brassica campestris ssp.Chinensis)叶片无机氮代谢的影响。结果表明:在pH 6.5条件下,与正常营养液处理相比,高氮营养液(pH6.5+N)培养6和12d后,小白菜叶片NR、NiR活性以及NO-3-N、NO-2-N、NH+4-N、游离氨基酸含量显著增加,但是GAD活性变化不显著。与pH 6.5+N处理相比,2.5mmol/L GABA处理加速了小白菜叶片硝酸盐的代谢,表现为NR、NiR、GAD活性和NH+4-N、游离氨基酸含量显著增加,NO-3-N、NO-2-N含量显著降低。但GABA对小白菜叶片硝酸盐的代谢受pH值的影响较大,以pH 6.5+N条件下GABA处理效果最好,其次为pH 4.5+N处理,而pH 8.5+N条件下GABA处理效果最差;不同pH处理12d的效果较明显。结果证明外源GABA对小白菜叶片无机氮代谢的诱导受pH值的影响,其中pH 6.5是GABA降低高氮条件下小白菜叶片硝态氮含量的适宜酸碱环境,且GABA最佳添加时期为采收前12d。

The effects of exogenous GABA on the inorganic nitrogen metabolism in leaves of pakchoi(Brassica campestris ssp.chinensis)were studied under different pH and high nitrogen conditions.The results showed that under the condition of pH 6.5,compared with the normal nutrient solution,the activities of NR,NiR,along with the contents of NO-3-N,NO-2-N,NH+4-N and free amino acid were significantly enhanced in leaves of pakchoi after 6 days and 12 days of high nitrogen nutrition(pH 6.5+N),but no significant change in GAD.Compared with pH 6.5+N treatment,the addition of application treatment increase the activities of NR,NiR,GAD and the contents of NH+4-N,free amino acid significantly,but decrease the contents of NO-3-N and NO-2-N obviously,which indicated that 2.5 mmol/L GABA treatment accelerected the metabolism of nitrate in pakchoi leaves.However,pH condition is the major factor of GABA on nitrate metabolism of pakchoi leaves.The effect of 2.5 mmol/L GABA treatment was the best under the condition of pH 6.5+N,followed by pH 4.5+N condition;and the worst effect was in pH 8.5+N.Moreover,the effect of GABA treatment for 12 d was more prominent than that for 6 d under three different pH conditions.The results showed that exogenous GABA could induce the change of inorganic nitrogen metabolism in pakchoi leaves,and this effect affected by pH in rhizosphere condition and treatment time;pH 6.5 and treatment for 12 d was the suitable for GABA decreasing the nitrate content of pakchoi leaves under high nitrogen condition.