铝胁迫下大豆根系分泌物对根际土壤微生态的影响

EFFECT OF SOYBEAN(GLYCINE MAX) ROOT EXUDATION ON RHIZOSPHERIC MICROBIAL ECOSYSTEM UNDER ALUMINUM STRESS

通过对19个不同基因型大豆品种的耐铝性筛选实验,选择耐铝型的浙春2号和敏感型的浙春3号作为实验材料;设置5个铝处理浓度(0,0.2,0.4,0.6,0.8 g kg-1,即土壤总Al3+浓度分别为0.293,0.493,0.693,0.893,1.093 g kg-1)土壤,大棚种植大豆30d后,取大豆根际、非根际土壤和外源根系分泌物作用下的土壤样品,对各类微生物生理群进行分析,同时测定土壤呼吸速率、纤维分解作用、氨化作用、硝化作用,以及酸性磷酸酶、过氧化氢酶和蔗糖酶等土壤重要酶类的活性。结果显示,土壤铝含量较低条件下(0.2,0.4g kg-1),大豆根系分泌物的应激分泌促使土壤微生物数量增多、微生物物质转化能力增强和土壤酶活性增大;土壤铝含量较高(0.8 g kg-1)时,根系分泌物的分泌相对受抑制,土壤微生物活性和土壤酶活性相应地受到抑制。实验结果还表明,外源根系分泌物也能影响土壤微生态,引起土壤微生物数量和土壤酶活性的变化,以及各种土壤生化作用(如硝化作用等)的改变,显示出一定的缓解铝毒能力,从而减少铝毒对植物的伤害。

Out of 19 different genotypes of soybeans （ Glycine max）, Variety Zhechun No.2 （Al-resistant） and Variety Zhechun No.3 （M-sensitive） were screened and selected as subjects in this study, which was designed to have 5 different aluminum （Al3^＋ ） treatments 0, 0.2, 0.4, 0.6, and 0.8 g kg^-1, （i. e. 0.293, 0.493, 0.693, 0. 893, and 1.093 g kg^-1, respectively, in soil total Al3^＋） and 3 parallel treatments （non-rhizospheric soils, rhizospheric soils and bulk soils with exogenous soybean exudation）. Thirty days after the treatment, respiration rate, cellulose hydrolysis efficiency, ammonification rate, nitrification rate of the soils, and activities of acid phosphatase, catalase, and sucrase were measured. Results indicate that in treatments low in soil A1 （0.2 and 0.4 g kg^-1）, irritated secretion from the soybean roots increased the population of soil microbes, strengthened their capability of material transformation and stimulated the activity of soil enzymes, whereas in treatments high in soil Al （0.8 g kg^-1） , root exudation was restrained comparatively, resulting in inhibition of the activity of microorganisms and soil enzymes. The results also demonstrated that exogenous root exudation could also influence the microbial ecosystem, triggering changes in activity of the soil enzymes and in major biochemical functions of the soil, thus mitigating aluminum poison to soybean, which is convincing evidence that root exudation obviously affects the microbial ecosystem.