胞质碱化介导了外源一氧化氮诱导的蚕豆气孔关闭

以蚕豆(Vicia faba L.)为材料，利用pH荧光探针SNARF-1-AM和激光共聚焦显微镜研究外源一氧化氮(nitric oxide，NO)对表皮条保卫细胞胞质pH变化以及pH对NO诱导气孔关闭的影响。结果表明，与对照相比，100 μmol L–1 NO供体硝普钠(sodium nitroprusside, SNP)可显著增加保卫细胞胞质pH (从6.91升高到7.19，增加约0.28个单位)，并诱导气孔关闭。NO清除剂c-PTIO和弱酸丁酸均能显著抑制SNP诱导的保卫细胞胞质碱化和气孔关闭，而弱碱苄胺则促进NO诱导的胞质碱化和气孔关闭，另外，不产生NO的SNP结构类似物Fe(II)CN和Fe(III)CN不能诱导保卫细胞胞质碱化和气孔关闭，说明保卫细胞胞质碱化介导了外源NO诱导的气孔关闭。未发现NO诱导保卫细胞胞质碱化过程中液泡和细胞壁的pH发生显著变化，说明该过程中，胞质的质子可能主要不是进入液泡或细胞壁。

Cytoplasmic Alkalization Mediates Exogenous Nitric Oxide-Induced Stomatal Closure in Vicia faba

The effects of exogenous NO on changes in cytosolic pH of guard cells from epidermal fragments and of the pH on NO-induced stomatal closure in Vicia faba were investigated by using a pH specific fluorescence probe SNARF-1-AM and a confocal laser scanning microscopy. The results showed that treatments with 100 μmol L^–1 sodium nitroprusside (SNP), a widely used NO donor, led to a significant increase in cytosolic pH (from 6.91 to 7.19, i.e. 0.28 pH unit) and stomatal closure in comparison with the control. Furthermore, SNP-induced cytosolic alkalization and stomatal closure were significantly inhibited by NO scavenger c-PTIO or weak acid butyrate, and promoted by the weak base benzylamine. Whereas two structural analogs of SNP such as Fe(II)CN and Fe(III)CN, which can not release NO, failed to induce guard cell cytoplasmic alkalization and stomatal closure. These findings suggest that cytoplasmic alkalization of guard cells mediates NO-induced stomatal closure. In addition, pH in guard cell vacuoles and cell walls was measured during the cytosolic alkalization. However, no significant changes of pH in the two regions were found, implying that the cytoplasmic protons of guard cells may not go into vacuoles or cell walls during the NO-promoted alkalization in Vicia faba.