干出状态下羊栖菜的光合作用特性

Photosynthetic Characteristics of Hizikia fusiformis Under Emersed State

生长于低潮带的海藻羊栖菜(Hizikiafusiformis)在低潮时常处于干出状态。羊栖菜在干出状态下可进行有效的光合CO2同化作用,虽然光合活性比在海水状态时小。在干出状态下羊栖菜藻体发生脱水作用,在脱水15%以内时,光合活性没有显著变化,但随着进一步的脱水,光合活性急剧下降。在脱水率为38%时,光合活性下降至初始干出时的一半。现有大气中CO2浓度不能饱和羊栖菜在干出状态下的光合作用,且这种CO2限制随着藻体的严重脱水而加剧,其CO2羧化效率也随严重的脱水而急剧下降。减少脱水的因素如海浪、藻体相互重叠等)以及大气(CO2浓度升高有利于促进羊栖菜在干出状态下的光合作用。

The seaweed Hizikia fusiformis growing at the low intertidal zone will be exposed to an emersion state during low tide. Emersed H. fusiformis could photosynthesize efficiently, although the photosynthetic activity was lower under the emersed state than under submersed state. Water would be lost from H. fusiformis under emersed state. While 15 % of water loss could hardly affect photosynthetic activity, further desiccation reduced it significantly. The photosynthetic activity was reduced by half of its initial value when H. fusiformis lost 50 % of water. The present atmospheric CO2 level couldn't saturate the emersed photosynthesis of H. fusiformis, and such a CO2-limition became greater with severe desiccation. At the same time, the CO2 carboxylating efficiency declined drastically with further desiccation. It was concluded that the factors alleviating desiccation such as sea spray and shingle-overlapping, and increasing atmospheric CO2 concentration would benefit the emersed photosynthesis of H. fusiformis.