酸、铝和盐胁迫对夏季豆科绿肥作物种子萌发及根瘤菌抗氧化酶活性的影响

在逆境土壤,种子的成功萌发与根瘤的形成是确保豆科作物正常生长的关键。本试验选择4种夏季豆科绿肥作物,包括竹豆、绿豆、田菁和豇豆,研究了种子萌发及其根瘤菌抗氧化酶活性(SOD,超氧化物歧化酶;POD,过氧化物酶;CAT,过氧化氢酶;GR,谷胱甘肽还原酶)对逆境胁迫的响应机制。种子萌发设置4个pH水平,即4,5,6,7;4个 NaCl胁迫水平,即0、40、120和200 mmol·L^-1;4个活性铝(Al³⁺)水平,即0、50、100和200 mg·L^-1。根瘤菌培养设置4个pH水平,即4,5,6,7;5个NaCl水平,即0、10、20、30和40 g·L^-1;5个活性铝(Al³⁺)水平,即0、25、50、75和100 μmol·L^-1。结果表明,酸、铝、盐胁迫显著影响几种豆科绿肥作物的种子发芽率及其根瘤菌的抗氧化酶活性,其中根瘤菌抗氧化酶活性较发芽率对胁迫敏感。不同夏季豆科绿肥品种中,田菁不耐酸,但对盐胁迫有一定耐受性;竹豆、绿豆和豇豆对低浓度的盐和弱酸性环境有一定耐受性;但是所有品种对活性铝浓度增加较为敏感。在酸性和盐碱化土壤,较高浓度的H⁺、活性铝或NaCl抑制种子萌发,减缓根瘤菌的生长,降低根瘤菌对有害物质的抗氧化能力,最终限制豆科绿肥作物的早期生长。

Responses of seed germination and rhizobia antioxidative enzyme activities in legumes to acidity and aluminum and NaCl stresses

It is important for legumes to germinate and form nodules successfully under adverse soil conditions. In the current study, four summer legume crops used for green manure; Phaseolus calcaratns, Vigna radiata, Sesbania cannabina and Vigna unguiculata were utilised to investigate the responses of seed germination and the antioxidative enzyme activities of their rhizobia to soil acidity and NaCl stress. Four pH levels (4, 5, 6, 7), four Al³⁺ levels (0, 50, 100 and 200 mg·L^-1), and four NaCl levels (0, 40, 120 and 200 mmol·L^-1) were assessed for their effects on seed germination. Similarly, four pH levels (4, 5, 6, 7), five Al³⁺ levels (0, 25, 50, 75 and 100 μmol·L^-1), and five NaCl levels (0, 10, 20, 30 and 40 g·L^-1) were assessed for the influence on antioxidative enzymes. The results indicated that the seed germination and rhizobia antioxidative enzyme activities were significantly influenced by low soil pH and increased concentrations of Al³⁺ and NaCl. Overall, the antioxidative enzyme activities of rhizobia were more sensitive than seed germination to these stresses. Among the four plant species, seed germination and rhizobia of S. rostrat were comparatively sensitive to soil pH and Al³⁺ but was relatively tolerant to NaCl stress; those of P. calcaratns, V. radiate and V. unguiculata were relatively tolerant to low levels of NaCl and high levels of soil pH, whereas those of all plant species were sensitive to increased Al³⁺ concentrations. In acid or alkaline soils, higher concentrations of H⁺ and Al³⁺ or NaCl inhibited seed germination, retarded rhizobia growth, reduced the oxidation resistance of rhizobia, and limited the early growth of legume seedlings.