| 论文摘要： |
Ottelia alismoides (Hydrocharitaceae) is a heterophyllous freshwater macrophyte which shows heteroblastic heterophylly during plant development, and differs in carbon dioxide-concentrating mechanisms (CCMs) at different stage. This study investigated the anatomy and CCMs in the first stage of leaf during O. alismoides development, linear juvenile leaves. It comprised three layers of cell and enriched air spaces, but not significantly affected by CO2 concentration ([CO2]), while leaf thickness and chloroplast ultrastructure were significantly affected by [CO2]. The linear juvenile leaves could perform C-4 photosynthesis at low [CO2]; the two types of chloroplasts distributed in epidermal and mesophyll cells respectively, with different shape and starch content, might provide the structural basis for C-4 operation. The pH-drift data showed that the linear juvenile leaves could use HCO3- regardless of [CO2]. Whereas, CAM and C-4 operation could only be induced at low [CO2]. When compared the CCMs among all the heteromorphic leaves in O. alismoides, it is shown that CCMs in the O. alismoides heteromorphic leaves become more diversified during the plants development: HCO3- use was present in all leaf-types regardless of the [CO2]; CAM and C-4 were only induced at low [CO2] and became more efficient in mature leaves. The anatomy was also regulated to adapt to the functions of CCMs, and ultimately, the ovate mature leaves can operate C-4 constitutively. |
