Bota Josefina, Medrano Hipólito, Flexas Jaume
Laboratori de Fisiologia Vegetal, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, Km 7.5, 07122 Palma de Mallorca, Balears, Spain.
New Phytol. 2004 Jun;162(3):671-681. doi: 10.1111/j.1469-8137.2004.01056.x.
• Whether decreases in Rubisco activity and the availability of ribulose-1,5-bisphosphate (RuBP) regeneration are responsible for drought-induced depression of photosynthesis is under debate. • Here, leaf water potential and relative water content, gas exchange, chlorophyll fluorescence, initial and total Rubisco activity and RuBP content were determined during the time course of drought development in five C species: Rhamnus alaternus, Rhamnus ludovici-salvatoris, Nicotiana sylvestris, Phaseolus vulgaris and Vitis vinifera. Water was withheld until photosynthesis approached zero (between 6 and 12 d depending on the species). • Relative water content and water potential progressively dropped with drought in Rhamnus and Vitis, but not in the other two species. While RuBP content and Rubisco activity remained constant, declining eventually only in the more severe drought situations, light-saturated stomatal conductance (g ) and photosynthesis (A ) decreased progressively during drought in all species. This strongly suggests a dominant role of decreased g in photosynthesis downregulation during drought in these species, which is supported by increased electron transport to A ratio. • It is concluded that impairment of Rubisco activity and RuBP content do not limit photosynthesis until drought is very severe. Moreover, the relative water content at which these mechanisms are impaired is strongly species-dependent.
• 核酮糖-1,5-二磷酸羧化酶（Rubisco）活性的降低以及1,5-二磷酸核酮糖（RuBP）再生能力的下降是否是干旱导致光合作用受抑制的原因仍存在争议。• 在此，对五种C植物（互生鼠李、鲁氏鼠李、野生烟草、菜豆和葡萄）在干旱发展过程中的叶片水势和相对含水量、气体交换、叶绿素荧光、初始和总Rubisco活性以及RuBP含量进行了测定。停止浇水直至光合作用接近零（根据物种不同，在6至12天之间）。• 鼠李和葡萄中的相对含水量和水势随干旱逐渐下降，但其他两个物种则不然。虽然RuBP含量和Rubisco活性保持恒定，最终仅在更严重的干旱情况下才下降，但在干旱期间所有物种的光饱和气孔导度（g）和光合作用（A）均逐渐降低。这强烈表明气孔导度降低在这些物种干旱期间光合作用下调中起主导作用，这一点得到了电子传递与A比率增加的支持。• 得出的结论是，在干旱非常严重之前，Rubisco活性和RuBP含量的损害不会限制光合作用。此外，这些机制受损时的相对含水量强烈依赖于物种。
