Guralnick Lonnie J, Gladsky Kate
Department of Biology, Roger Williams University, Bristol, RI 02809 USA.
Heliyon. 2017 Apr 13;3(4):e00293. doi: 10.1016/j.heliyon.2017.e00293. eCollection 2017 Apr.
L. is a dominant facultative CAM species growing in the Southeastern Cape of South Africa. is well adapted to regions of the Spekboom thicket in areas of limited and sporadic rainfall. populations occur in isolated drainages. We hypothesized the utilization of CAM would vary in the different populations in response to rainfall and temperature gradients. Carbon isotope composition can be used to determine the contribution of CAM in leaf tissue. leaves of populations were analyzed in transects running south to north and east to west in locations from the coast to elevations of 1400 m. Carbon isotope values ranged from -16.1‰ in Plutosvale to -21.0‰ to -22.7‰ in Port Alfred and Grahamstown populations respectively with some values reaching -25.2‰. These values indicated an estimated variable contribution of the CAM pathway ranging from 23% to almost 60%. The results indicate a much greater range of variability than previously reported. The carbon isotope values showed no direct correlation with rainfall or maximum or minimum day/night temperatures in the summer or winter for the different locations. The results indicated the microclimate may play a more significant role in determining CAM utilization. We present evidence that CAM is a continuous trait in and CAM is operating continuously at low levels during C photosynthesis which may explain the high variability in its carbon isotope composition. populations illustrate a large phenotypic plasticity and further studies may indicate genotypic differences between populations. This may be valuable in ascertaining the genetic contribution to its water use efficiency and possible use in engineering higher water use efficiency in C plants. The results revealed here may explain ' ability to sequester carbon at high rates compared to more mesic species.
L.是一种优势兼性景天酸代谢（CAM）植物，生长在南非东开普省。它非常适应斯佩克博姆灌木丛中降雨有限且零星的地区。其种群分布在孤立的排水区域。我们推测，景天酸代谢的利用情况会因不同种群对降雨和温度梯度的响应而有所不同。碳同位素组成可用于确定景天酸代谢在叶片组织中的贡献。我们在从海岸到海拔1400米的地点，沿着南北向和东西向的样带对种群的叶片进行了分析。碳同位素值范围从普鲁托斯韦尔的-16.1‰到阿尔弗雷德港和格雷厄姆斯敦种群的-21.0‰至-22.7‰，有些值达到-25.2‰。这些值表明景天酸代谢途径的贡献估计在23%至近60%之间变化。结果表明，其变异性范围比先前报道的要大得多。不同地点的碳同位素值与夏季或冬季的降雨量、日/夜最高或最低温度均无直接关联。结果表明，小气候在决定景天酸代谢的利用方面可能发挥更重要的作用。我们提供的证据表明，景天酸代谢在L.中是一种连续性状，并且在C3光合作用期间景天酸代谢以低水平持续运行，这可能解释了其碳同位素组成的高变异性。L.种群表现出很大的表型可塑性，进一步的研究可能会揭示种群之间的基因型差异。这对于确定其对水分利用效率的遗传贡献以及在提高C3植物水分利用效率方面的可能应用可能具有重要价值。此处揭示的结果可能解释了L.与更多中生植物相比具有高固碳率的能力。
