敖汉和维多利亚紫花苜蓿对低磷环境应激机制的比较

为了探索紫花苜蓿在低磷环境下的表现及响应机制,以期为提高苜蓿磷利用效率及磷吸收效率提供参考。试验以耐低磷较强的敖汉苜蓿和耐低磷较弱的维多利亚苜蓿为研究对象,以正常磷(500 μmol·L^-1 KH₂PO₄)处理为对照,低磷(5 μmol·L^-1 KH₂PO₄)胁迫处理10、15、20 d后,分别观测其形态特征及生理指标的变化,比较两个品种在低磷胁迫下的差异,综合分析其耐低磷机制。结果表明,低磷胁迫下,敖汉和维多利亚的株高、地上生物量及磷含量有所下降,地下生物量、根冠比、总根长、根表面积及磷利用率有所提高,二者净光合速率、气孔导度和蒸腾速率显著下降(P<0.05),但是敖汉的下降幅度都远小于维多利亚;二者的酸性磷酸酶活性都极显著增强(P<0.01),但敖汉的酸性磷酸酶活性极显著高于维多利亚(P<0.01)。综合表明,低磷胁迫抑制了苜蓿的地上部分生长,促进了地下部分生长,敖汉较维多利亚耐低磷主要表现在光合作用受低磷影响较小、磷酸酶活性增强幅度较大。通过两个品种在低磷胁迫下的不同表现,为紫花苜蓿的耐低磷机制研究提供一定的理论依据。

Comparison of response mechanisms to low inorganic phosphate stress between alfalfa varieties Aohan and Victoria

In order to compare the performance and adaptive mechanisms of two varieties of alfalfa under low inorganic phosphate (low-Pi) conditions, and to provide more information for improvement of Pi utilization efficiency and absorption efficiency in alfalfa, the varieties Aohan and Victoria were grown under low-Pi (5 μmol·L^-1 KH₂PO₄) and normal Pi (500 μmol·L^-1 KH₂PO₄) conditions. Morphological and physiological traits were measured at 10, 15 and 20 days. It was found that, the height, aboveground biomass and Pi content of both Aohan and Victoria were decreased under low-Pi stress; while the underground biomass, root-shoot ratio, total root length, root surface area and Pi utilization were increased. The net photosynthetic rate, stomatal conductance and transpiration rate were decreased significantly under low-Pi (P<0.05), but the decrease was much smaller in cultivar Aohan than in cultivar Victoria. The acid phosphatase activity of both was significantly enhanced (P<0.01), and for Aohan was significantly higher than that of Victoria (P<0.01). To sum up, low-Pi stress inhibited the growth of the above ground plant organs and promoted growth of the underground parts. The greater low-Pi tolerance of Aohan compared to Victoria is associated with greater increase in acid phosphatase activity under low-Pi in Aohan, and a lower reduction in photosynthesis under low-Pi. The contrasting responses of the two varieties under low-Pi stress indicate a potential mechanism for alfalfa tolerance to low-Pi.