γ‐Aminobutyric acid addition alleviates ammonium toxicity by limiting ammonium accumulation in rice (<i>Oryza sativa</i>) seedlings

Physiologia Plantarum - Tập 158 Số 4 - Trang 389-401 - 2016
Xiaoling Ma1, Changhua Zhu1, Na Yang1, Lijun Gan1, Kai Xia1
1College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China

Tóm tắt

Excessive use of nitrogen (N) fertilizer has increased ammonium (NH4+) accumulation in many paddy soils to levels that reduce rice vegetative biomass and yield. Based on studies of NH4+ toxicity in rice (Oryza sativa, Nanjing 44) seedlings cultured in agar medium, we found that NH4+ concentrations above 0.75 mM inhibited the growth of rice and caused NH4+ accumulation in both shoots and roots. Use of excessive NH4+ also induced rhizosphere acidification and inhibited the absorption of K, Ca, Mg, Fe and Zn in rice seedlings. Under excessive NH4+ conditions, exogenous γ‐aminobutyric acid (GABA) treatment limited NH4+ accumulation in rice seedlings, reduced NH4+ toxicity symptoms and promoted plant growth. GABA addition also reduced rhizosphere acidification and alleviated the inhibition of Ca, Mg, Fe and Zn absorption caused by excessive NH4+. Furthermore, we found that the activity of glutamine synthetase/NADH‐glutamate synthase (GS; EC 6.3.1.2/NADH‐GOGAT; EC1.4.1.14) in root increased gradually as the NH4+ concentration increased. However, when the concentration of NH4+ is more than 3 mM, GABA treatment inhibited NH4+‐induced increases in GS/NADH‐GOGAT activity. The inhibition of ammonium assimilation may restore the elongation of seminal rice roots repressed by high NH4+. These results suggest that mitigation of ammonium accumulation and assimilation is essential for GABA‐dependent alleviation of ammonium toxicity in rice seedlings.

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Thông tin xuất bản

Physiologia Plantarum

Tập 158 Số 4

389-401

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