Ritte Gerhard, Raschke Klaus
Universität Göttingen, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Untere Karspüle 2, 37073 Göttingen, Germany.
Current address: Universität Potsdam, Institut für Biochemie und Biologie, Abt. Pflanzenphysiologie, Karl-Liebknecht-Str. 24-25, Haus 20, 14476 Golm, Germany.
New Phytol. 2003 Jul;159(1):195-202. doi: 10.1046/j.1469-8137.2003.00789.x.
• Stomatal opening is caused by guard cell swelling due to an accumulation of osmotica. We investigated the release of carbon from guard cell chloroplasts as a source for the production of organic osmotica. • Photosynthetically active chloroplasts were isolated from guard cell protoplasts of Vicia faba. Export of metabolites into the surrounding medium was analyzed by silicone oil filtering centrifugation and spectrophotometrically by coupled metabolite assays. Effects of external oxaloacetate and 3-phosphoglycerate on photosynthetic electron transport were examined by recording chlorophyll fluorescence. • In the light, guard cell chloroplasts exported triose phosphates, glucose, maltose and hexose phosphates. The presence of phosphate in the medium was essential for the release of phosphorylated compounds and also strongly enhanced the export of glucose and maltose. Total efflux of carbon from illuminated guard cell chloroplasts was on average 486 µatom C (mg Chl) h , which was significant with respect to the carbon requirement for stomatal opening. • Metabolites released by illuminated guard cell chloroplasts originated predominantly from starch breakdown. Photosynthetic electron transport provided redox power for the reduction of oxaloacetate and 3-phosphoglycerate.
• 气孔开放是由于渗透物质积累导致保卫细胞肿胀引起的。我们研究了保卫细胞叶绿体中碳的释放，作为有机渗透物质产生的来源。
• 从蚕豆保卫细胞原生质体中分离出具有光合活性的叶绿体。通过硅油过滤离心法和耦合代谢物测定分光光度法分析代谢物向周围培养基中的输出。通过记录叶绿素荧光来检测外部草酰乙酸和3-磷酸甘油酸对光合电子传递的影响。
• 在光照下，保卫细胞叶绿体输出磷酸丙糖、葡萄糖、麦芽糖和磷酸己糖。培养基中磷酸盐的存在对于磷酸化化合物的释放至关重要，并且还强烈增强了葡萄糖和麦芽糖的输出。光照下保卫细胞叶绿体的总碳流出量平均为486 μatom C/（mg Chl）·h，这对于气孔开放所需的碳量而言是显著的。
• 光照下保卫细胞叶绿体释放的代谢物主要源自淀粉分解。光合电子传递为草酰乙酸和3-磷酸甘油酸的还原提供了氧化还原能力。
