Department of Soil, Plant, and Environmental Quality, Institute of Agricultural Sciences, Spanish National Research Council (ICA-CSIC), Serrano 115-bis, 28006 Madrid, Spain.
Department of Plant Biology I, Universidad Complutense de Madrid, José Antonio Nováis 10, 28040 Madrid, Spain.
Tree Physiol. 2021 Sep 10;41(9):1641-1657. doi: 10.1093/treephys/tpab034.
Photoprotection is a plant functional mechanism to prevent photooxidative damage by excess light. This is most important when carbon assimilation is limited by drought, and as such, it entails a trade-off between carbon assimilation vs stress avoidance. The ecological adaptation of plants to local water availability can lead to different photoprotective strategies. To test this, we used different provenances of Caesalpinia spinosa (Mol.) Kuntze (commonly known as 'tara') along a precipitation gradient. Tara is a Neotropical legume tree with high ecological and commercial value, found in dry tropical forests, which are increasingly threatened by climate change. Morphological and physiological responses of tara provenances were analysed under three different treatments of drought and leaflet immobilization, i.e., light stress, in a common garden greenhouse experiment. Tara quickly responded to drought by reducing stomatal conductance, evapotranspiration, photochemical efficiency, carbon assimilation and growth, while increasing structural and chemical photoprotection (leaflet angle and pigments for thermal dissipation). Leaflet closure was an efficient photoprotection strategy with overall physiological benefits for seedlings as it diminished the evaporative demand and avoided photodamage, but also entailed costs by reducing net carbon assimilation opportunities. These responses depended on seed origin, with seedlings from the most xeric locations showing the highest dehydration tolerance, suggesting local adaptation and highlighting the value of different strategies under distinct environments. This plasticity in its response to environmental stress allows tara to thrive in locations with contrasting water availability. Our findings increase the understanding of the factors controlling the functional ecology of tara in response to drought, which can be leveraged to improve forecasts of changes in its distribution range, and for planning restoration projects with this keystone tree species.
光保护是一种植物功能机制，可防止过量光引起的光氧化损伤。当碳同化受到干旱限制时，这一点尤为重要，因此，这需要在碳同化与避免胁迫之间进行权衡。植物对当地水分可用性的生态适应会导致不同的光保护策略。为了检验这一点，我们沿着降水梯度使用了不同的金合欢属 spinosa（Mol.）Kuntze（俗称“塔拉”）起源。塔拉是一种具有高生态和商业价值的新热带豆科树，分布在干燥的热带森林中，这些森林正受到气候变化的日益威胁。在一个普通花园温室实验中，我们对三种不同的干旱和小叶固定处理（即光胁迫）下的塔拉起源进行了形态和生理响应分析。塔拉通过降低气孔导度、蒸散、光化学效率、碳同化和生长来快速应对干旱，同时增加结构和化学光保护（小叶角度和热耗散色素）。小叶闭合是一种有效的光保护策略，对幼苗具有整体生理益处，因为它减少了蒸发需求并避免了光损伤，但也通过减少净碳同化机会来带来成本。这些响应取决于种子的起源，来自最干旱地区的幼苗表现出最高的脱水耐受性，表明存在局部适应，并突出了不同策略在不同环境下的价值。这种对环境胁迫的响应可塑性使塔拉能够在具有不同水分可用性的地方茁壮成长。我们的研究结果增加了对控制塔拉在干旱条件下功能生态学的因素的理解，这可以用来提高对其分布范围变化的预测，并为这个关键树种的恢复项目规划提供依据。
