乌桕对南方根结线虫与地上不同食性昆虫互作的光合生理响应

本文通过比较乌桕对两种地上不同食性昆虫(专食性癞皮夜蛾、广食性斜纹夜蛾)与南方根结线虫互作的光合生理响应,分析不同空间植食性生物间的互作关系及植物的响应机制。结果表明:无南方根结线虫胁迫下,2种地上不同食性昆虫对乌桕的净光合速率(P_n)、气孔导度(G_s)及胞间CO_2浓度(C_i)的影响与对照组无显著差异;而南方根结线虫胁迫下,2种地上昆虫显著降低了乌桕G_s及C_i。其中,与对照组及癞皮夜蛾处理组相比,南方根结线虫与斜纹夜蛾的共同胁迫显著降低了乌桕P_n、G_s及C_i。此外,斜纹夜蛾为害增加了乌桕叶绿素含量,南方根结线虫胁迫降低了叶绿素含量。因此,南方根结线虫与斜纹夜蛾间形成一种加性效应,并对乌桕光合生理产生了拮抗效应,而这种效应在南方根结线虫与癞皮夜蛾间并不显著。由此可见,乌桕对地上-地下植食性生物胁迫形成不足补偿机制,且具体的响应机制与植食性生物的食性相关。

Photosynthetic physiology responses of Sapium sebiferum to the interactions between Meloidogyne incognita and aboveground herbivores with different diet breadths

To compare the interactive patterns of herbivores from different spaces and plant response mechanisms, the photosynthetic physiology responses of Sapium sebiferum to the interactions between two aboveground herbivores with different diet breadths (the specialist Gadirtha inexacta and the generalist Spodoptera litura) and Meloidogyne incognita were compared. The results showed that, without M.incognita herbivory, there was no significant differences in the net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) of S.sebiferum among the two aboveground herbivores and the control. With the presence of M.incognita, the two aboveground herbivores significantly reduced the Gs and Ci of S.sebiferum. Compared with the control and the G.inexacta herbivory, the synergistic herbivory by M.incognita and S.litura significantly reduced Pn, Gs and Ci. Furthermore, S.litura herbivory increased the chlorophyll content, while M.incognita significantly decreased the chlorophyll content of S.sebiferum. Therefore, M.incognita and S.litura exerted an additive effect on each other, resulting in an antagonistic effect on the photosynthetic physiology of S.sebiferum. However, this pattern was not found between M.incognita and G.inexacta. Therefore, S.sebiferum formed an insufficient compensation mechanism to respond above-and below-ground herbivore interactions, and the specific responses are closely related to the diet breadths of herbivores.