Ribas-Carbo Miquel, Taylor Nicolas L, Giles Larry, Busquets Silvia, Finnegan Patrick M, Day David A, Lambers Hans, Medrano Hipólito, Berry Joseph A, Flexas Jaume
Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Universitat de les Illes Balears, Spain.
Plant Physiol. 2005 Sep;139(1):466-73. doi: 10.1104/pp.105.065565. Epub 2005 Aug 26.
The effect of water stress on respiration and mitochondrial electron transport has been studied in soybean (Glycine max) leaves, using the oxygen-isotope-fractionation technique. Treatments with three levels of water stress were applied by irrigation to replace 100%, 50%, and 0% of daily water use by transpiration. The levels of water stress were characterized in terms of light-saturated stomatal conductance (g(s)): well irrigated (g(s) > 0.2 mol H(2)O m(-2) s(-1)), mildly water stressed (g(s) between 0.1 and 0.2 mol H(2)O m(-2) s(-1)), and severely water stressed (g(s) < 0.1 mol H(2)O m(-2) s(-1)). Although net photosynthesis decreased by 40% and 70% under mild and severe water stress, respectively, the total respiratory oxygen uptake (V(t)) was not significantly different at any water-stress level. However, severe water stress caused a significant shift of electrons from the cytochrome to the alternative pathway. The electron partitioning through the alternative pathway increased from 10% to 12% under well-watered or mild water-stress conditions to near 40% under severe water stress. Consequently, the calculated rate of mitochondrial ATP synthesis decreased by 32% under severe water stress. Unlike many other stresses, water stress did not affect the levels of mitochondrial alternative oxidase protein. This suggests a biochemical regulation (other than protein synthesis) that causes this mitochondrial electron shift.
利用氧同位素分馏技术,研究了水分胁迫对大豆(Glycine max)叶片呼吸作用和线粒体电子传递的影响。通过灌溉设置了三个水分胁迫水平的处理,分别替代蒸腾作用每日耗水量的100%、50%和0%。水分胁迫水平通过光饱和气孔导度(g(s))来表征:充分灌溉(g(s) > 0.2 mol H₂O m⁻² s⁻¹)、轻度水分胁迫(g(s)在0.1至0.2 mol H₂O m⁻² s⁻¹之间)和重度水分胁迫(g(s) < 0.1 mol H₂O m⁻² s⁻¹)。尽管在轻度和重度水分胁迫下净光合作用分别下降了40%和70%,但在任何水分胁迫水平下,总呼吸耗氧量(V(t))均无显著差异。然而,重度水分胁迫导致电子从细胞色素途径显著转向交替途径。通过交替途径的电子分配在充分浇水或轻度水分胁迫条件下从10%增加到12%,在重度水分胁迫下接近40%。因此,在重度水分胁迫下,计算得出的线粒体ATP合成速率下降了32%。与许多其他胁迫不同,水分胁迫并未影响线粒体交替氧化酶蛋白的水平。这表明存在一种(除蛋白质合成之外的)生化调节机制导致了这种线粒体电子转移。