The central Chilean Andes are located in a Mediterranean-type climate zone, characterized by dry summers and high irradiance. This creates a contrasting elevational gradient because higher elevations get more solid precipitation and lower temperatures, resulting in higher soil humidity along the growing season compared with severe drought at lower elevations. Therefore, species with wide elevational distributions, such as Phacelia secunda, must have developed specific adaptations to cope with contrasting severity of drought stress-induced photoinhibition at different elevations. We hypothesize that P. secunda from lower elevation, is more tolerant to drought stress-induced photo-damage than plants from high elevation. This higher tolerance will be associated to a higher diversity of photoprotective strategies in plants that naturally suffers severe drought every growing season. To test this hypothesis, plants from 2700 and 3600 m in the central Chilean Andes were grown under the common garden and then subjected to water restriction. We measured stress indicators, photochemistry of PSII and PSI and estimate alternative electron sinks. Drought affected P. secunda photosynthetic performance differentially depending on the elevation of provenance. Plants from lower elevation exhibited higher drought tolerance than higher elevation ones. This was related to higher levels of heat dissipation and alternative electron sinks exhibited by plants from lower elevation under drought stress. We concluded that plants naturally subjected to recurrent drought are better adapted to respond to drought stress using additional photochemical photoprotective mechanisms and confirm the role of alternative electron sinks ameliorating photodamage.

中文翻译：

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对干旱的光保护策略取决于Phacelia secunda的海拔高度

智利中部安第斯山脉位于地中海型气候区，夏季干燥，辐射度高。这会产生相反的海拔梯度，因为较高的海拔会获得更多的固体降水和较低的温度，与较低海拔的严重干旱相比，整个生长季节的土壤湿度会更高。因此，具有高海拔分布的物种（例如Phacelia secunda）必须已开发出特定的适应性，以应对干旱胁迫在不同海拔引起的光抑制的严重程度的对比。我们假设P. secunda低海拔地区的植物比高海拔地区的植物更能耐受干旱胁迫引起的光害。在每个生长季节自然遭受严重干旱的植物中，较高的耐​​受性将与较高的光保护策略多样性相关。为了检验这一假设，智利安第斯山脉中部2700年至3600 m的植物在共同的花园下生长，然后进行水分限制。我们测量了应力指标，PSII和PSI的光化学性质，并估计了其他电子沉陷。受干旱影响的P. secunda光合性能根据出处的高低而不同。低海拔植物比高海拔植物表现出更高的抗旱性。这与干旱胁迫下较低海拔的植物表现出的较高的散热水平和替代性电子吸收有关。我们得出的结论是，自然遭受反复干旱的植物更适合使用其他光化学光保护机制来应对干旱胁迫，并证实替代电子宿子减轻光害的作用。