PREMISE 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.

中文翻译：

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下加利福尼亚半岛南部肉质灌木的叶子和光合茎的功能特征

前提 光合茎代表来自炎热和干燥环境的植物中额外碳的来源，但对于亚热带系统中叶子和光合茎在光合能力、性状协调和对季节性干旱的反应方面有何不同，我们知之甚少。方法我们研究了来自南下加利福尼亚州肉质灌木丛的 12 种植物的叶子和光合茎的光合、水力、形态测量（比叶面积 [SLA]、木材密度 [WD]）和生化（C 和 N 同位素）特征。墨西哥半岛，分干湿两季。结果 根据叶绿素荧光性状评估，叶和茎具有相似的平均光合能力，表明叶和茎光合作用的投资相似。我们没有发现茎水力传导率与叶或茎光合特性之间的关系。然而，我们发现 WD 与茎水力传导率和 SLA 之间的资源分配权衡。叶和茎的光合性状不随季节变化，但比茎面积是少数几个在季节之间变化最大的性状之一——它在旱季增加了 154%，表明蓄水量很大。结论 我们的结果表明，所有 12 个物种的叶片和光合茎的光合能力和干物质的投资比例相同。我们在这个季节性地点确定了多种策略，物种范围从一端的高 WD、低 SLA、低导水率和高特定树皮面积到另一端的相反特性。