AM真菌对烟草砷吸收及根际pH的影响

采用矿区3种砷(As)含量土壤水提液的琼脂培养基变色试验,研究接种土著(Glomus spp.,Acaulospora spp.)与外源(Glomus caledonium)AM真菌对煳草(Nicotiana tabacum L.)As吸收以及根际pH的影响.结果表明,除无As水平下的烟草对照苗根际pH持续升高外,其它处理的烟草化苗根际pH都有先升高后降低的规律,而且菌根化苗根际pH的降低速度快于对照苗.烟草地上部分As含量在所有处理中没有表现出显著的差异.在无As水平下,烟草地下部分As含量依次为外源菌根化苗>土著菌根化苗>对照苗.在低As、中As、高As水平下,土著菌根化苗的地下部分As含量显著高于外源菌根化苗以及对照苗.可见,接种AM真菌可以降低烟草根际pH,从而影响烟草的As吸收,这也显示了AM真菌应用于烟草安全的可能性.此外,本研究表明土著AM真菌与外源AM真菌对培养基质中的同一As水平有着不同的响应.

Effects of arbuscular mycorrhizal inoculation on arsenic uptake and rhizosphere pH of Nicotiana tabacum L.

A culture experiment using agar plates was conducted to study arsenic (As).uptake and rhizosphere pH of tobacco (Nico-tiana tabacum L) seedlings inoculated with indigenous and nonindigenous arbuscular mycorrhizal (AM) fungi. In most cases, rhizosphere pH of seedlings, measured by a pH indicator contained in the agar, increased during the first hours and then decreased until the end of the experiment, while it increased continuingly in the case of nonmycorrhizal seedlings without As stress. No sig-nificant differences in shoot As concentrations were observed among all treatments. However, root As concentrations followed the markedly decreasing order: nonindigenous mycorrhizal seedlings > indigenous mycorrhizal seedlings > nonmycorrhizal seedlings in treatments without As stress. And, it was much higher in indigenous mycorrhizal seedlings than in nonindigenous mycorrhizal and nonmycorrhizal seedlings under low, medium and high As levels. These results indicated that AM fungi could affect As uptake of tobacco via regulating its rhizosphere pH, and with this form protect their host during As stress. Furthermore, the responses of AM fungi with different origins were observed different to the same As level.