盐胁迫下囊果碱蓬和陆地棉硝态氮低亲和吸收速率的差异及其生理分析

采用常规离子耗竭方法,以陆地棉(Gossypium hirsutum L.)为对照,在不同Cl-和NO3--N营养状况下,研究了盐生植物囊果碱蓬(Suaeda physophora Pall.)NO3-低亲和吸收动力学特征,探讨了盐胁迫下囊果碱蓬NO3-高效吸收的调控机制。结果表明:两种植物NO3-的低亲和吸收动力学呈线性吸收,且囊果碱蓬NO3-的净吸收速率和硝酸还原酶的活性显著高于陆地棉,说明囊果碱蓬具有较高的氮需求;10 mmol L-1KNO3预处理2 h后,囊果碱蓬和陆地棉地上部全氮的含量分别增加30.6%和36.8%;NO3-的净吸收速率分别降低了46.6%和45.5%,说明两种植物氮的吸收受到体内氮营养的负反馈调节;NaCl长期胁迫30 d显著抑制NO3-的吸收,陆地棉NO3-的净吸收速率下降幅度显著高于囊果碱蓬,而根系Cl-的含量显著高于囊果碱蓬;NO3-的净吸收速率与植物根系Cl-的含量呈显著性负相关,说明囊果碱蓬根系拒Cl-的能力显著高于陆地棉;NaCl或KCl短期胁迫2 h对囊果碱蓬NO3-的净吸收速率没有显著影响,但陆地棉NO3-的净吸收速率分别降低了43.8%和37.5%。研究结果证明了盐胁迫下囊果碱蓬NO3-的高效吸收与植物内部的高氮需求和Cl-的累积有关,而培养介质中Cl-的浓度对NO 3-的低亲和转运系统影响较小。

Difference between Suaeda physophora and Gossypium hirsutum in low affinity absorption rate under salt stress and its physiological analysis

NO3- low affinity absorption dynamics of Suaeda physophora Pall. and mechanism of the high NO3- absorption efficiency were studied using the conventional ion depletion method with Gossypium hirsutum L. as control in the nutrient solutions different in Cl- and NO3--N concentration. Results show that the NO3- uptake rate of S. physophora and G. hirsutum increased linearly with KNO3 concentration from 1 to 50 mmol L-1 in the solution. But the net NO3- uptake rate and nitrate reductase activity were significantly higher in S. physophora than in G. hirsutum, which implies that S. physophora has a higher demand for nitrate than G. hirsutum does. After 2 h of pre-treatment with 10 mmol L-1 KNO3, the total nitrogen concentrations increased by 30.6% and 36.8% in the shoots of G. hirsutum and S. physophora, respectively, meanwhile, the net NO3- uptake rates of the two reduced by 46.6% and 45.5%, respectively, which suggests that N uptake of the two species were regulated by negative feedback of the N nutrition of these plants. When G. hirsutum and S. physophora were put under NaCl stress for 30 days, NO3- uptake was significantly inhibited, more in G. hirsutum than in S. physophora. The net NO3- uptake rate exhibited a significant negative correlation with Cl- concentration in the roots of G. hirsutum and S. physophora, indicating that the ablility of the root of S. physophora to resist Cl- was higher than that of G. hirsutum. Temporary NaCl or KCl stress for 2 hours did not affect much the net NO3- uptake of S. physophora, but did decrease that of G. hirsutum by 43.8% and 37.5%,, respectively. The findings indicate that the high-efficiency nitrate uptake by S. physophora roots is related to the high N demand and Cl- accumulation of the plant, and Cl- concentration in the nutrient solution does not have much impact on NO3- low-affinity transport system.