叶位和叶序对海草光合作用和无机碳利用的影响

Effects of Leaf Position and Leaf Order on Photosynthesis and Inorganic Carbon Utilization in Seagrass

摘要:

为探讨叶位和叶序对热带海草光合作用和无机碳利用的影响，对同一生境中泰来草(Thalassia hemprichii)和圆叶丝粉草(Cymodocea rotunda)叶片不同部位的光响应曲线、光合荧光、pH漂移和HCO₃^–利用等进行了研究。结果表明，海草叶片中部具有较高的净光合速率(P_n)，基部的高于顶部，幼叶高于成熟叶；叶片顶部的最大光合效率(F_v/F_m)低于其他部位；叶片中部的光合色素含量高于顶部和基部，幼叶的光合色素含量高于成熟叶。2种海草叶片均能有效利用海水中的HCO₃^–作为碳源，但成熟叶利用HCO₃^–的能力优于幼叶，叶片中部利用HCO₃^–的能力优于顶部和基部。因此，虽然2种海草在相同的生境中发展出了相似的光能和HCO₃^–利用策略，但随叶位和叶序的不同，其光合作用和无机碳利用能力存在差异。

Abstract:

To explore the effects of leaf position and leaf order on the photosynthesis and inorganic carbon utilization of tropical seagrasses, the light response curves, photosynthetic fluorescence, pH drift and HCO₃^– utilization of different parts of the leaves of Thalassia hemprichii and Cymodocea rotunda in the same habitat were studied. The results showed that the middle part of the seagrass leaves had a higher net photosynthetic rate (P_n), the base was higher than the top, and the young leaves were higher than the mature leaves; the maximum photosynthetic efficiency (F_v/F_m) of the leaf top was lower than that of other parts; the photosynthetic pigment content in the middle part of the leaves was higher than that in the top and base, and the photosynthetic pigment content in the young leaves was higher than that in the mature leaves. Both seagrass species could effectively utilize HCO₃^– in seawater as a carbon source, but the mature leaves had a better ability to utilize HCO₃^– than the young leaves, and the middle part of the leaves had a better ability to utilize HCO₃^– than the top and base. Therefore, although the two seagrass species have developed similar strategies for light energy and HCO₃^– utilization in the same habitat, their photosynthesis and inorganic carbon utilization capabilities vary with leaf position and leaf order.