Sanchez Adriana, Mercado Lina M, Posada Juan M, Smith William Kirby
Departamento de Biología, Facultad de Ciencias Naturales, Universidad del Rosario, Bogotá, Colombia.
Faculty of Environment, Science, and Economy, University of Exeter, Exeter, United Kingdom.
Front Plant Sci. 2025 Apr 14;16:1529852. doi: 10.3389/fpls.2025.1529852. eCollection 2025.
Dry and rainy seasons in many ecosystems differ significantly in cloudiness, precipitation, and incident sunlight. These seasonal variations can influence photosynthesis by altering light availability and water stress. This study examines whether light availability or water stress is the primary limiting factor for photosynthesis in páramo plants during the dry and rainy seasons. We measured photosynthetic carbon gain per unit leaf area ( ), stomatal conductance ( ), chlorophyll fluorescence (ϕPSII), and leaf water potentials, in two dominant páramo species, and , across both seasons. Photosynthetic light-response curves were generated for each species, and statistical analyses assessed the relative influence of environmental factors such as light, temperature, and vapor pressure deficit on An. Contrary to our expectations, An was higher in the dry season despite increased water stress, suggesting that light availability is a stronger driver of carbon assimilation. However, light-response curves showed that exhibited higher potential carbon uptake during the dry season, while had greater uptake during the rainy season. Statistical analyses indicated that light was the primary factor influencing in both seasons, though temperature and vapor pressure deficit also played a role for in the rainy season. The combination of high solar radiation and elevated leaf temperatures in the dry season facilitated greater carbon assimilation, particularly in . In contrast, the cloudier conditions of the rainy season limited photosynthesis despite reduced water stress. Although exhibited high during the dry season, it appeared vulnerable to high radiation and desiccation. These findings emphasize that cloud cover and light availability, rather than water stress alone, are key drivers of páramo plant carbon uptake, with important implications for predicting climate change effects in high-altitude ecosystems.
许多生态系统的旱季和雨季在云量、降水量和入射阳光方面存在显著差异。这些季节变化会通过改变光照可用性和水分胁迫来影响光合作用。本研究探讨了在旱季和雨季，光照可用性或水分胁迫是否是帕拉莫植物光合作用的主要限制因素。我们在两个主要的帕拉莫物种（ 和 ）中，测量了两个季节的单位叶面积光合碳同化量（ ）、气孔导度（ ）、叶绿素荧光（ϕPSII）和叶水势。为每个物种生成了光合光响应曲线，并通过统计分析评估了光照、温度和蒸汽压亏缺等环境因素对 的相对影响。与我们的预期相反，尽管水分胁迫增加，但旱季的 更高，这表明光照可用性是碳同化的更强驱动因素。然而，光响应曲线表明， 在旱季表现出更高的潜在碳吸收能力，而 在雨季的吸收能力更强。统计分析表明，光照是两个季节影响 的主要因素，尽管温度和蒸汽压亏缺在雨季对 也有作用。旱季高太阳辐射和升高的叶片温度相结合，促进了更大的碳同化，特别是在 中。相比之下，雨季多云的条件尽管水分胁迫降低，但限制了光合作用。尽管 在旱季表现出高 ，但它似乎易受高辐射和干燥的影响。这些发现强调，云层覆盖和光照可用性，而非单独的水分胁迫，是帕拉莫植物碳吸收的关键驱动因素，对预测高海拔生态系统中的气候变化影响具有重要意义。
