Intermittent water availability characterizes the canopy habitat, but few studies have focused on how C₃ epiphytic bromeliads deal with drought. In this context, we investigated how water deficits affect the photosynthetic responses of the epiphytic bromeliad Vriesea gigantea regarding its physiological and anatomical traits that can minimize the effects of stomatal closure. In a controlled experiment in which bromeliads were submitted to 21 days of drought, we demonstrated a reduction in the leaf water content followed by strong reductions in net CO₂ exchange and the efficiency of the photochemical system. However, there were increases in the yield of non-photochemical quenching and the activities of hydrophilic antioxidants. We observed substomatal chambers connected with air channels reaching the chlorophyllous parenchyma. Our findings indicate that the low net CO₂ exchange and the energy imbalance possibly increased the cyclic transport of electrons and activated the thermal dissipation of energy to avoid damage to the photosynthetic apparatus. Additionally, the aeration channels may passively store CO₂ to facilitate its re-assimilation. Because most epiphytic bromeliads are C₃ plants and drought is frequent in the canopy, we speculate that some attributes of V. gigantea may occur in other C₃ species, favouring their radiation in the epiphytic environment.

中文翻译：

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C ₃附生罐凤梨科植物对干旱有何反应？

间歇性的水供应是冠层栖息地的特征，但是很少有研究集中于C ₃附生凤梨如何应对干旱。在此背景下，我们研究了水赤字是如何影响附生的光合反应凤梨Vriesea巨关于它的生理解剖特点，可以最大限度地减少气孔关闭的影响。在一项将凤梨科植物置于干旱21天的对照实验中，我们证明了叶片含水量减少，然后净CO _2大量减少交换和光化学系统的效率。然而，非光化学猝灭的产率和亲水性抗氧化剂的活性增加。我们观察到与气道相连的气孔下腔到达叶绿素薄壁组织。我们的发现表明，低净CO ₂交换和能量不平衡可能会增加电子的循环传输并激活能量的热耗散，从而避免损坏光合装置。另外，曝气通道可以被动地存储CO _2，以促进其重新同化。由于大多数附生凤梨科植物都是C ₃植物，而且树冠层经常发生干旱，因此我们推测了V. gigantea的某些属性可能在其他C ₃物种中发生，有利于它们在附生环境中辐射。