铁添加对喀斯特土壤中天蓝苜蓿生长及柠檬酸分泌的影响

Effect of Iron Application on the Growth and Citrate Secretion of Medicago lupulina Grown in Karst Soil

喀斯特土壤中铁亏缺常常发生,本研究通过添加FeCl_2和FeCl_3盐后,比较天蓝苜蓿柠檬酸代谢和生长的差异。结果表明:与对照相比,添加Fe Cl_2和FeCl_3后,增加了叶片数量,而单位叶面积干重和叶绿素无显著差异;光饱和点(light saturation point, LSP)、最大净光合速率(maximum net photosynthetic rate, Pmax)显著高于对照。对照处理叶片和根系分泌物中的柠檬酸含量显著高于FeCl_2和FeCl_3。特别地,FeCl_2处理的根际土中柠檬酸含量显著低于其他处理。XRD分析发现对照、FeCl_2和FeCl_3中铁离子的结晶度分别为24%、69%和81%。本研究结论初步表明:天蓝苜蓿在缺铁环境下根系分泌柠檬酸促进对Fe的吸收;同时,Fe2+铁盐对植物生理生长的影响优于Fe3+铁盐。

Iron deficiency is widespread in karst soils. A comparison of difference between citric acid metabolism and the growth of Medicago lupulina after application of FeCl2 and FeCl3were undertaken. The results showed that application of FeCl2 and FeCl3increased the number of leaves compared with the control, while the dry weight per unit leaf area(LMA) and the chlorophyll content were not significantly changed. The light saturation point(LSP)and maximum net photosynthetic rate(Pmax) with added Fe Cl2 and Fe Cl3 were significantly higher than those in the control. In contrast, the citric acid content in the leaf and root exudates in the control were significantly higher than those after application of FeCl2 and FeCl3. In particular, the citric acid content in the rhizosphere soil after application of FeCl2 was significantly lower that after other treatments. XRD analysis showed that the crystallinities of iron ions in the control, application of Fe CL2, and FeCl3 groups were 24%, 69%, and 81%, respectively. The conclusions of this study initially indicated that the critic acid secreted from roots in an iron-deficient environment could promote Fe uptake. In addition, Fe2+showed more favorable effects on the growth of plants than Fe3+.