Department of Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA, 92521, USA.
Evolution, Ecology and Organismal Biology Graduate Program, Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, CA, 92521, USA.
Am J Bot. 2020 Oct;107(10):1410-1422. doi: 10.1002/ajb2.1546. Epub 2020 Oct 14.
Photosynthetic stems represent a source of extra carbon in plants from hot and dry environments, but little is known about how leaves and photosynthetic stems differ in terms of photosynthetic capacity, trait coordination, and responses to seasonal drought in subtropical systems.
We studied photosynthetic, hydraulic, morphometric (specific leaf area [SLA], wood density [WD]), and biochemical (C and N isotopes) traits in leaves and photosynthetic stems of 12 plant species from a sarcocaulescent scrub in the southern Baja California Peninsula, Mexico, in wet and dry seasons.
Leaves and stems had similar mean photosynthetic capacity, as evaluated by chlorophyll fluorescence traits, indicating similar investment in leaf and stem photosynthesis. We did not find a relationship between stem hydraulic conductivity and leaf or stem photosynthetic traits. However, we found resource allocation trade-offs, between WD and both stem hydraulic conductivity and SLA. Leaf and stem photosynthetic traits did not change with season, but specific stem area was one of the few traits that changed the most between seasons-it increased during the dry season by as much as 154% indicating substantial water storage.
Our results indicate the same proportional investment in photosynthetic capacity and dry matter in both leaves and photosynthetic stems across all 12 species. We identified multiple strategies at this seasonal site, with species ranging from high WD, low SLA, low hydraulic conductivity, and high specific bark area on one end of the spectrum and opposite traits on the other end.
光合作用茎代表了来自炎热干燥环境的植物的额外碳源，但对于叶片和光合作用茎在光合能力、性状协调以及对亚热带系统季节性干旱的响应方面的差异，知之甚少。
我们研究了墨西哥下加利福尼亚半岛南部 sarcocaulescent 灌丛中 12 种植物的叶片和光合作用茎的光合、水力、形态（比叶面积[SLA]、木材密度[WD]）和生化（C 和 N 同位素）特性，在湿季和干季。
叶片和茎具有相似的平均光合能力，这可以通过叶绿素荧光特性来评估，表明叶片和茎的光合作用具有相似的投资。我们没有发现茎水力传导率与叶片或茎光合特性之间的关系。然而，我们发现了资源分配的权衡，即 WD 与茎水力传导率和 SLA 之间的权衡。叶片和茎的光合特性没有随季节变化，但特定茎面积是少数几个变化最大的特征之一，在旱季增加了 154%，表明有大量的水分储存。
我们的结果表明，在所有 12 个物种中，叶片和光合作用茎的光合能力和干物质的比例投资相同。我们在这个季节性地点确定了多种策略，其中一些物种的 WD 较高，SLA 较低，水力传导率较低，特定树皮面积较高，而另一些物种则相反。
