水菜花异形叶片叶绿素荧光特征与HCO3-利用能力的研究

以生长发育过程中具有异形叶的水生植物水菜花（Ottelia cordata（Wall.）Dandy）为材料，利用叶绿素荧光技术和pH-漂移（pH-drift）实验测定具有两型叶片的水菜花正常沉水叶（submerged leaves，S）、正常浮水叶（floating leaves，F）、处于淹没状态的浮水叶（submerged floating leaves，SF）以及只有浮水叶植株的浮水叶（floating leaves only，OF）的叶绿素荧光特征与HCO₃^-利用能力。快速光曲线分析结果显示：沉水叶（S）的相对电子传递速率（rETR）显著低于其他类型的叶片，且随着光强的增强，差异增大；由光化学引起的荧光淬灭q_P、潜在最大电子传递速率（rETR_max）、半饱和光强（E_k）等指标均为沉水叶（S）显著低于浮水叶（F）。沉水叶（S）与淹没状态的浮水叶（SF）表征HCO₃^-利用能力的C_T/Alk值显著低于两种浮水叶（F和OF）。研究结果表明水菜花成年期的浮水叶比幼年期的沉水叶具有更高的光合效率，并且更适合在高光强下生长；当水位发生波动时被淹没的浮水叶会增强对HCO₃^-的利用能力以适应淹水低浓度CO₂环境。

Chlorophyll fluorescence characteristics and HCO3- utilization capability of heteromorphic leaves of Ottelia cordata

Ottelia cordata (Wall.) Dandy, a species with heteromorphic leaves during growth and development, was used as the study material. Chlorophyll fluorescence and pH-drift were used to measure chlorophyll fluorescence characteristics and HCO₃^- utilization capability of different shaped leaves of O. cordata:i.e., submerged leaves (S), floating leaves (F), submerged floating leaves (SF), and floating leaves only (OF). Rapid light curve (RLC) results showed that the relative electron transport rate (rETR) of submerged leaves (S) was significantly lower than that of the other leaves, and the gap increased with light intensity; photochemical fluorescence quenching (q_P), maximum rETR (rETR_max), and light-saturation coefficient (E_k) of submerged leaves (S) were also significantly lower than that of floating leaves (F). The C_T/Alk value of submerged leaves (S), which can show HCO₃^- utilization capability, was significantly lower than that of both types of floating leaves (F and OF). These results indicated that the mature floating leaves (F) of O. cordata had higher photosynthetic efficiency than juvenile submerged leaves (S), and floating leaves (F) were more adapted to high light. These results also suggest that submerged floating leaves (SF) can enhance HCO₃^- utilization capability to adapt to low CO₂ in water.