Flexas Jaume, Medrano Hipólito
Laboratori de Fisiologia Vegetal, Departament de Biologia, Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07071 Palma de Mallorca, Spain. Corresponding author; email:
Laboratori de Fisiologia Vegetal, Departament de Biologia, Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07071 Palma de Mallorca, Spain.
Funct Plant Biol. 2002 Oct;29(10):1209-1215. doi: 10.1071/FP02015.
A general quantification of the relative contribution of different light energy dissipation processes to total dissipation under different drought conditions is lacking. Here we compare six studies, including enough data for such a general quantification, to build up a general pattern of the relative importance of several energy dissipation mechanisms in response to drought in C3 plants. Such a general pattern apparently emerges independently of specific acclimation to drought, but largely dependent on CO2 availability in the chloroplasts, which may be regulated under drought by adjustments in stomatal and mesophyll conductances. Under irrigation and saturating light, more than 50% of absorbed light is thermally dissipated, while photosynthesis dissipates 20-30% and photorespiration 10-20%. Under mild drought, the contribution of photosynthesis decreases, and that of photorespiration increases in a compensatory manner. During moderate to severe drought, the contribution of both photosynthesis and photorespiration decreases, and thermal dissipation increases up to 70-90% of the total light absorbed. The contribution of other processes, like the Mehler reaction, is shown to be very low under both irrigation and drought. Therefore, in C3 plants subjected to different degrees of drought, more than 90% of the total energy absorbed by leaves is dissipated by the sum of thermal dissipation, photorespiration and photosynthesis.
目前尚缺乏对不同干旱条件下不同光能耗散过程对总耗散的相对贡献进行总体量化的研究。在此，我们比较了六项研究，这些研究包含了足够的数据以进行此类总体量化，从而建立起C3植物中几种能量耗散机制在响应干旱时相对重要性的总体模式。这种总体模式显然独立于对干旱的特定适应性出现，但在很大程度上取决于叶绿体中的二氧化碳可用性，而叶绿体中的二氧化碳可用性在干旱条件下可能通过气孔和叶肉导度的调节来控制。在灌溉和饱和光照条件下，超过50%的吸收光通过热耗散，而光合作用耗散20%-30%，光呼吸耗散10%-20%。在轻度干旱条件下，光合作用的贡献降低，光呼吸的贡献以补偿方式增加。在中度至重度干旱期间，光合作用和光呼吸的贡献均降低，热耗散增加至吸收总光量的70%-90%。在灌溉和干旱条件下，其他过程（如梅勒反应）的贡献都非常低。因此，在遭受不同程度干旱的C3植物中，叶片吸收的总能量中超过90%通过热耗散、光呼吸和光合作用的总和进行耗散。
