Keeley J, Morton B, Babcock B, Castillo P, Fish B, Jerauld E, Johnson B, Landre L, Lum H, Miller C, Parker A, Van Steenwyk G
Department of Biology, Occidental College, 90041, Los Angeles, USA.
Oecologia. 1981 Mar;48(3):332-333. doi: 10.1007/BF00346490.
In the leaves (but not corms) of the submerged aquatic Isoetes storkii malic acid concentration fluctuated from 22 μeg g FW in the evening to 171 μeg g FW in the morning. Associated with this was a change in titratable acidity of 152 μeg g FW between morning and evening. C carbon was fixed in both the light and the dark, though the amount of carbon fixed in the light was more than that fixed in the dark. Autoradiographs show 88% of CO fixed in the dark is recovered after 1 h, in malic acid and the remainder in one other unidentified product, whereas these two products contain less than 15% of the C fixed after 1 h exposure to CO in the light. It is suggested that CAM metabolism in this aquatic species may be related to the low availability of CO for photosynthesis during the day in its aquatic environment and that this metabolic pathway may prove common in the genus Isoetes.
在沉水水生植物斯托克水韭的叶片（而非球茎）中，苹果酸浓度从傍晚时的22微克/克鲜重波动至早晨时的171微克/克鲜重。与此相关的是，可滴定酸度在早晨和傍晚之间变化了152微克/克鲜重。碳在光照和黑暗条件下均会被固定，不过光照下固定的碳量多于黑暗中固定的碳量。放射自显影片显示，黑暗中固定的二氧化碳在1小时后，88%在苹果酸中回收，其余在另一种未鉴定的产物中，而在光照下暴露于二氧化碳1小时后固定的碳中，这两种产物所含不到15%。有人认为，这种水生植物中的景天酸代谢可能与其水生环境中白天光合作用时二氧化碳的低可用性有关，并且这种代谢途径可能在水韭属中很常见。
