Behrens P W, Xu F, Werner M, Hoffman T, Marsho T V, Mackay A B
Department of Biological Sciences, University of Maryland Baltimore County (U.M.B.C.), Catonsville, Maryland 21228.
Plant Physiol. 1985 Oct;79(2):441-4. doi: 10.1104/pp.79.2.441.
The effect of water stress (reduced osmotic potential) on photosynthetic nitrite reduction was investigated using intact, isolated spinach (Spinacia oleracea) chloroplasts. Nitrite-dependent O(2) evolution was inhibited 39% at -29.5 bars osmotic potential, relative to a control at -11 bars. In the presence of an uncoupler of photophosphorylation this inhibition was not seen. Reduced osmotic potential did not inhibit either methyl viologen reduction or photosynthetic O(2) reduction. These results indicate that an inhibition of electron transport to ferredoxin cannot account for the observed inhibition of nitrite-dependent O(2) evolution. In vitro assay of nitrite reductase activity showed that the interaction of the enzyme with nitrite was not affected by changes in the concentrations of ions or molecules that might be caused by water stress conditions. These results indicate that the most likely site for the effect of water stress on chloroplastic nitrite reduction is the interaction of ferredoxin with nitrite reductase.
利用完整的、分离的菠菜（Spinacia oleracea）叶绿体研究了水分胁迫（渗透势降低）对光合亚硝酸盐还原的影响。相对于-11巴的对照，在-29.5巴渗透势下，亚硝酸盐依赖的氧气释放被抑制了39%。在存在光合磷酸化解偶联剂的情况下，未观察到这种抑制作用。渗透势降低既不抑制甲基紫精还原，也不抑制光合氧气还原。这些结果表明，电子传递至铁氧还蛋白的抑制不能解释所观察到的亚硝酸盐依赖的氧气释放的抑制。亚硝酸盐还原酶活性的体外测定表明，该酶与亚硝酸盐的相互作用不受水分胁迫条件可能引起的离子或分子浓度变化的影响。这些结果表明，水分胁迫对叶绿体亚硝酸盐还原作用的最可能位点是铁氧还蛋白与亚硝酸盐还原酶的相互作用。
