Premise of research. Epiphytic bromeliads endure intense seasonal environmental changes in the canopy of dry tropical deciduous forests. The analysis of the physiological responses of these epiphytes to environmental changes can be useful in assessing their plasticity, vulnerability, and adaptations to such extreme habitats. Methodology. We measured microenvironmental variables and water relations for plants of the epiphytic bromeliad Tillandsia brachycaulos in three microhabitats within the canopy of a dry tropical forest. We measured individual plants for seasonal and spatial differences in light, leaf temperature, osmotic potential, cell wall elasticity, and relative capacitance as indications of their physiological responses to the changing environment. Pivotal results. We detected greater physiological differences for leaves of T. brachycaulos among seasons than among microhabitats. Osmotic potential decreased in the early dry season, especially in the low and middle strata within the canopy, and leaf relative capacitance increased. Conclusions. Individuals of T. brachycaulos displayed modest leaf physiological responses to the strong seasonal environmental changes within the canopy of this tropical forest. Such responses are in agreement with the observation that when water is available, it has high water potential, and thus water storage is the main strategy for surviving in such extreme conditions.

中文翻译：

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炎热但不干燥：热带干燥落叶林附生凤梨科植物水分关系的适度变化

研究的前提。附生凤梨科植物在干燥的热带落叶林的树冠中承受强烈的季节性环境变化。分析这些附生植物对环境变化的生理反应有助于评估它们的可塑性、脆弱性和对此类极端栖息地的适应性。方法。我们测量了干燥热带森林树冠内三个微生境中附生凤梨科植物 Tillandsia brachycaulos 植物的微环境变量和水分关系。我们测量了单个植物在光、叶温度、渗透势、细胞壁弹性和相对电容方面的季节性和空间差异，作为它们对不断变化的环境的生理反应的指标。关键结果。我们检测到 T 叶的更大生理差异。brachycaulos 在季节之间比在微生境中。旱季初期渗透势下降，尤其是冠层内中低层，叶片相对电容增加。结论。T. brachycaulos 个体对热带森林冠层内强烈的季节性环境变化表现出适度的叶片生理反应。这种反应与观察结果一致，即当有水可用时，它具有高水势，因此储水是在这种极端条件下生存的主要策略。brachycaulos 对这片热带森林树冠内强烈的季节性环境变化显示出适度的叶子生理反应。这种反应与观察结果一致，即当有水可用时，它具有高水势，因此储水是在这种极端条件下生存的主要策略。brachycaulos 对这片热带森林树冠内强烈的季节性环境变化显示出适度的叶子生理反应。这种反应与观察结果一致，即当有水可用时，它具有高水势，因此储水是在这种极端条件下生存的主要策略。