木质部导水系统效率-安全权衡主导生物量分配——棉花对土壤质地的适应

Safety vs. efficiency trade-off in xylem hydraulic conductance system controls plant biomass allocation:A case study of cotton acclimation to soil texture

植物表型的发育受到植物维管网络几何特征的制约。在不同的环境中,植物维管网络在安全-效率之间做出结构和功能上权衡,发育出不同的维管网络特征,从而引起表型的可塑性响应。虽然植物表型适应与植物维管网络的关系非常重要,但对它的研究却在总体上被忽略了。本文设置了3个土壤质地(沙土、黏土和两者的1∶1混合土)环境梯度,以棉花(Gossypium herbaceum L.)为研究对象,分析了土壤质地对根茎木质部导管几何结构的影响,及其与植物表型之间的关系。结果表明:增加土壤颗粒直径将会导致维管网络结构显著变化,引起导管直径和长度的改变。将3个土壤处理的植物相比较,结果表明这种结构性差异显著影响了(或者相关于)棉花的根系导水率、地上导水率、整株导水率、纹孔阻力等导水系统功能,同时也显著改变了叶面积、根长和根叶比等表型特征。这些结果表明,土壤颗粒直径增加,棉花没有发育更有效的导水系统,反而以牺牲导水效率为代价,构建了更加安全的导水系统(效率-安全权衡)。

The development of phenotype is restricted by the geometry of plant vascular network. In different environments, plant vascular network makes the structural and functional tradeoff between efficiency and safety, develops different network characters, and thus, induces the plastic responses of phenotype. Despite the importance of vascular network structural acclimation in modifying plant phenotype, this topic has largely been neglected. In this paper, an environmental gradient of three soil textures （sandy soil, clay soil, and 1∶1 sandy soil and clay soil） was installed to study the effects of soil texture on the geometry of root and stem xylem vessels of cotton （Gossypium herbaceum L.） plants as well as the relationships among soil texture, xylem vessel size, and biomass allocation. The results showed that long-term exposure to the soil texture gradient led to a significant change in the vessel traits. The comparison of the plants in the three treatments indicated that the structural differences of the vessels could significantly affect （or wererelated to） the root, shoot, and whole plant hydraulic conductance, end-wall resistance, leaf area, and plant height. These results demonstrated that an increased soil particle size tended to result in a safer hydraulic system rather than a more efficient hydraulic system （safety and efficiency tradeoff）.