Brodribb Timothy J, McAdam Scott A M, Jordan Gregory J, Feild Taylor S
School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia.
Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Knoxville, TN, 37919, USA.
New Phytol. 2009 Aug;183(3):839-847. doi: 10.1111/j.1469-8137.2009.02844.x. Epub 2009 Apr 23.
The stomata of angiosperms respond to changes in ambient atmospheric concentrations of CO(2) (C(a)) in ways that appear to optimize water-use efficiency. It is unknown where in the history of land plants this important stomatal control mechanism evolved. Here, we test the hypothesis that major clades of plants have distinct stomatal sensitivities to C(a) reflecting a relatively recent evolution of water-use optimization in derived angiosperms. Responses of stomatal conductance (g(s)) to step changes between elevated, ambient and low C(a) (600, 380 and 100 micromol mol(-1), respectively) were compared in a phylogenetically and ecologically diverse range of higher angiosperms, conifers, ferns and lycopods. All species responded to low C(a) by increasing g(s) but only angiosperm stomata demonstrated a significant closing response when C(a) was elevated to 600 micromol mol(-1). As a result, angiosperms showed significantly greater increases in water-use efficiency under elevated C(a) than the other lineages. The data suggest that the angiosperms have mechanisms for detecting and responding to increases in C(a) that are absent from earlier diverging lineages, and these mechanisms impart a greater capacity to optimize water-use efficiency.
被子植物的气孔对环境大气中二氧化碳（C(a)）浓度的变化做出反应，其方式似乎能优化水分利用效率。目前尚不清楚这种重要的气孔控制机制在陆地植物演化历史中的哪个阶段出现。在此，我们检验这样一个假设：植物的主要类群对C(a)具有不同的气孔敏感性，这反映了在衍生的被子植物中水分利用优化是相对较新才演化出来的。我们比较了在系统发育和生态方面具有多样性的高等被子植物、针叶树、蕨类植物和石松类植物中，气孔导度（g(s)）对高、环境和低C(a)（分别为600、380和100微摩尔每摩尔）阶跃变化的响应。所有物种在低C(a)时都会通过增加g(s)做出反应，但只有被子植物的气孔在C(a)升高到600微摩尔每摩尔时表现出显著的关闭反应。因此，在C(a)升高的情况下，被子植物的水分利用效率增幅明显大于其他类群。数据表明，被子植物具有检测和响应C(a)增加的机制，而早期分化的类群则没有这些机制，并且这些机制赋予了被子植物更大的优化水分利用效率的能力。
