Intraspecific variation of drought adaptation in brittlebush: leaf pubescence and timing of leaf loss vary with rainfall
Intraspecific variation of drought adaptation in brittlebush: leaf pubescence and timing of leaf loss vary with rainfall
复制标题
脆灌木干旱适应的种内变化：叶子的柔毛和叶子损失的时间随降雨量的变化而变化
作者：
D. Sandquist;J. Ehleringer
摘要荒漠灌木粉刺的反射叶被毛降低了叶温和植物水分损失，被认为是适应干旱环境的。然而，对这一性状的种内变异知之甚少。在横跨非常宽的降水梯度的粉针茅北部的三个种群中，叶片吸收率的变化和干旱诱导的叶片损失时间的差异都与气候变异性广泛相关。年平均降雨量最大的地方，干旱导致的叶片损失最早，但这些植物的种群水平平均叶片吸收值也较高。较高的吸收率增加了对潜热传递(蒸腾冷却)的相对依赖性，但也提供了更大的瞬时碳同化。最干燥地点的植物达到较低的叶片吸收值，并在干旱期间保持叶片更长时间。较低的叶片吸水率减少了水分消耗，延长的叶片寿命可能会缓冲在最干燥的地点所经历的生长条件的不可预测性。这些观察结果与一种权衡方案是一致的，即来自较潮湿地区的植物可能会牺牲节水来换取更高的瞬时碳增量，而来自较干燥地区的植物则减少了水分消耗并延长了叶片寿命，以在不可预测的生长条件下保持光合作用活性。
Abstract Reflective leaf pubescence of the desert shrub Encelia farinosa (brittlebrush) reduces leaf temperature and plant water loss, and is considered adaptive in xeric environments. Yet, little is known about intraspecific variation in this trait. Among three populations in the northern range of E. farinosa, which span a very broad precipitation gradient, both leaf absorptance variation and differences in the timing of drought-induced leaf loss were broadly associated with climatic variability. Where mean annual rainfall was greatest, drought-induced leaf loss was earliest, but these plants also had higher population-level mean leaf absorptance values. Higher absorptance increases the relative dependence on latent heat transfer (transpirational cooling), but it also provides greater instantaneous carbon assimilation. Plants at the driest site reached lower leaf absorptance values and maintained leaves longer into the drought period. Lower leaf absorptance reduces water consumption, and extended leaf longevity may buffer against the unpredictability of growing conditions experienced in the driest site. These observations are consistent with a trade-off scenario in which plants from wetter regions might trade off water conservation for higher instantaneous carbon gain, whereas plants from drier regions reduce water consumption and extend leaf longevity to maintain photosynthetic activity in the face of unpredictable growing conditions.