钙离子对紫花苜蓿及苜蓿根瘤菌耐酸能力的影响

土壤酸性是阻碍苜蓿根瘤菌与其宿主紫花苜蓿之间高效共生固氮的重要环境因子.本文研究了Ca2 对紫花苜蓿及苜蓿根瘤菌耐酸能力的影响.结果表明:加入一定浓度的Ca2 (5和10mmol·L-1)能提高苜蓿根瘤菌的生长速率,使苜蓿根瘤菌提前进入对数生长期.中性pH条件下,Ca2 的加入对苜蓿根毛变形率无显著影响;低pH条件下,加入2、5和10mmol·L-1的Ca2 均可提高根毛变形率,Ca2 浓度越高,其影响越显著,说明低pH下Ca2 可能会促进苜蓿根瘤菌与其宿主之间的识别.低pH条件下加入Ca2 可以使苜蓿结瘤提前,结瘤率提高;结瘤动力学检测结果表明,加入一定浓度的Ca2 可以使同期结瘤数增加,越是结瘤后期,环境pH越低,这种表现越明显.

Effects of Ca2+ on acid tolerance of Medicago sativa and Rhizobium meliloti

Soil acidity is an important environmental factor hampering the effective symbiotic nitrogen fixation of Rhizobium meliloti and its host plant Medicag sativa. The study on the effects of Ca2 + on the acid tolerance of M. sativa and R. meliloti showed that applying 5 and 10 mmol . L(-1) of Ca2+ could promote the growth of R. meliloti and advance its log growth phase. Under neutral pH condition, applying Ca2+ didn't have any significant effects on root hair deformation, while under low pH condition, Ca2+ demonstrated positive functions. The higher the Ca2+ concentration, the more significantly it affected, indicating that Ca2+ might play an important role in the recognition between R. meliloti and its host plant. Applying Ca2+ under low pH made the nodulation ahead of time and the nodulation rate enhanced. Definite concentration of Ca2+ could increase the number of nodules in the same period, which was more obvious at anaphase stage or under lower pH condition.