干旱生境中接种丛枝菌根真菌对三叶鬼针草(Bidens pilosa L.)光合特征的影响

Photosynthetic responses of AMF-infected and AMF-free Bidens pilosa L. to drought stress conditions

为阐明丛枝菌根真菌对石灰岩地区适生植物三叶鬼针草(Bidens pilosaL.)光合作用的影响,设置正常浇水(A)、中度干旱胁迫(B)和重度干旱胁迫(C)3个水分处理梯度,比较了不同水分处理条件下接种丛枝菌根真菌Glomus mosseae和未接种三叶鬼针草之间净光合速率、气孔导度、蒸腾速率、胞间CO2浓度、羧化效率、水分利用效率等特征的差异。结果表明,水分胁迫显著降低三叶鬼针草的净光合速率、气孔导度、蒸腾速率和羧化效率。胞间CO2浓度在处理的前期(7d)因干旱胁迫而降低,在后期随土壤含水量的降低而升高;水分利用效率则是中度胁迫的植株、正常浇水处理植株、重度胁迫植株依次降低。在正常浇水条件下接种G.mosseae对三叶鬼针草光合参数没有产生显著性影响;在中度胁迫条件下,接种植株较未接种植株在水分处理的前28d有更高的净光合速率、气孔导度、蒸腾速率和羧化效率;在重度胁迫条件下,虽然净光合速率、气孔导度、蒸腾速率和羧化效率接种植株高于未接种植株,但是二者并不显著。研究认为,干旱胁迫对三叶鬼针草光合作用的影响在水分处理的前期表现为气孔因素制约,在后期则主要是非气孔因素的影响;在正常浇水条件下接种G.mosseae对三叶鬼针草的光合作用没有显著性影响,在干旱胁迫条件下,丛枝菌根真菌通过改善三叶鬼针草气孔导度和羧化效率等减弱干旱胁迫对植株的伤害,但是这种保护作用因为土壤水分的严重匮乏以及土壤干旱的时间延长而受到限制。

To reveal the effects of vesicular- arbuscular mycorrhizal fungi （AMF） on the photosynthesis of Bidens pilosa L., three drought treatments were imposed ： well watered （ A ）, intermediate drought treatment （ B ） and serious drought treatment（ C ）. Net photosynthetic rate （ Pn ）, stomatal conductance （ Gs ）, transpiration rate （ Tr）, intercellular CO2 concentration（ Ci）, carboxylation efficiency（CE） and water use efficiency （WUE） were compared between plants infected with Glomus mosseae （AM plants） and those not infected （Non-AM plants）, under different water treatments. The results showed that the Pn, Gs, Tr, CE of plants decreased significantly under drought stress. Ci decreased at the early stage of drought stress （7d）, but rose as the soil water content decreased at the late stage of drought stress. The water use efficiency （WUE） of intermediate drought stress plants was higher than control, while the WUE of seriously stressed plants was lower than that of control plants. The photosynthetic parameters of well watered plants were not significantly affected by G. mosseae infection. During the first 28d of the drought treatment, AM plants had higher Pn, Gs, Tr and CE than non-AM plants under intermediate drought stress, but they showed no significant difference under serious drought stress. It was concluded that drought stress did affect the photosynthesis of Bidens pilosa L. because of stomatal resistances at the early stage of treatment and nonstomatal limitation at the later stage of treatment. The photosynthesis of well watered plants was not affected by G. mosseae infection. However, under drought stress, AMF improved the Gs and CE of plants to compensate for the injury caused by drought, whilst this compensatory response was limited by the more severe and longer drought treatment.