Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Jaén, Spain.
Plant Biol (Stuttg). 2014 Mar;16(2):354-64. doi: 10.1111/plb.12064. Epub 2013 Aug 19.
During photosynthesis, respiration and transpiration, gas exchange occurs via the stomata and so plants face a trade-off between maximising photosynthesis while minimising transpiration (expressed as water use efficiency, WUE). The ability to cope with this trade-off and regulate photosynthetic rate and stomatal conductance may be related to niche differentiation between closely related species. The present study explored this as a possible mechanism for habitat differentiation in Iberian columbines. The roles of irradiance and water stress were assessed to determine niche differentiation among Iberian columbines via distinct gas exchange processes. Photosynthesis-irradiance curves (P-I curves) were obtained for four taxa, and common garden experiments were conducted to examine plant responses to water and irradiance stress, by measuring instantaneous gas exchange and plant performance. Gas exchange was also measured in ten individuals using two to four field populations per taxon. The taxa had different P-I curves and gas exchange in the field. At the species level, water stress and irradiance explained habitat differentiation. Within each species, a combination of irradiance and water stress explained the between-subspecies habitat differentiation. Despite differences in stomatal conductance and CO2 assimilation, taxa did not have different WUE under field conditions, which suggests that the environment equally modifies photosynthesis and transpiration. The P-I curves, gas exchange in the field and plant responses to experimental water and irradiance stresses support the hypothesis that habitat differentiation is associated with differences among taxa in tolerance to abiotic stress mediated by distinct gas exchange responses.
在光合作用、呼吸作用和蒸腾作用过程中，气体通过气孔进行交换，因此植物在最大限度地提高光合作用的同时，必须尽量减少蒸腾作用（用水分利用效率 WUE 表示）。植物应对这种权衡的能力以及调节光合速率和气孔导度的能力，可能与其密切相关的物种之间的生态位分化有关。本研究探索了这是否是伊比利亚鹤望兰在栖息地分化中的一种可能机制。通过不同的气体交换过程来评估光照和水分胁迫的作用，以确定伊比利亚鹤望兰之间的生态位分化。对四个分类群进行了光合作用-光照曲线（P-I 曲线）的测定，并进行了共同栽培实验，通过测量瞬时气体交换和植物性能，研究了植物对水分和光照胁迫的反应。还对 10 个个体进行了气体交换测量，每个分类群使用两个到四个野外种群。这些分类群在 P-I 曲线和野外的气体交换方面存在差异。在种的水平上，水分胁迫和光照解释了栖息地的分化。在每个物种内，光照和水分胁迫的组合解释了亚种之间的栖息地分化。尽管气孔导度和 CO2 同化存在差异，但在野外条件下，分类群的 WUE 没有差异，这表明环境同样可以调节光合作用和蒸腾作用。P-I 曲线、野外的气体交换以及植物对实验水分和光照胁迫的反应支持了这样一种假设，即栖息地分化与不同分类群对生物胁迫的耐受能力有关，这种耐受能力是通过不同的气体交换反应介导的。
