水体无机碳条件对常见沉水植物生长和生理的影响

为了解水华引起的水体无机碳变化对沉水植物生长的影响,对8种沉水植物:金鱼藻、穗花狐尾藻、篦齿眼子菜、光叶眼子菜、微齿眼子菜、伊乐藻、菹草和黑藻在不同无机碳浓度下的生物量、株高、叶绿素以及光合和呼吸速率进行了比较研究.结果表明8种沉水植物均能利用HCO3-作为光合无机碳源,在1.5 mmoL/L外源HCO3-浓度下能促进金鱼藻、菹草和伊乐藻的生长,提高其光合速率;在2.5 mmol/L外源HCO3-浓度下能促进狐尾藻、光叶眼子菜、黑藻、微齿眼子菜和蓖齿眼子菜的生长,提高其光合速率.在CO32-为优势碳源时,8种沉水植物表现出不同的适应性,发现微齿眼子菜、篦齿眼子菜和黑藻在整个实验范围内生长未受抑制,且在不同浓度下表现生长和光合速率的促进,说明这三种沉水植物对[HCO3-]/[CO32-]比值和pH具有较广适应范围.而当CO32-成为优势碳源时,金鱼藻和伊乐藻的生长受到抑制,狐尾藻、菹草和光叶眼子菜均死亡,表明[HCO3-]/[CO32-]比值和pH是这5种沉水植物生长的重要限制因子.

Physiological effects of dissolved inorganic carbon on common submerged Macrophytes

Dissolved inorganic carbon (DIC) is a fundamental resource for photosynthesis of plants. The forms of DIC in water include CO2, HCO3- and CO32-. Recent studies have shown that DIC potentially limited the growth and photosynthesis of several submerged macrophytes. In order to elucidate the impacts of the states of DIC in hyper-eutrophic lakes caused by water bloom on the growth of submerged macrophytes, the growth, chlorophyll and photosynthetic and respiration rates of eight species of submerged macrophytes, including Ceratophyllum demersum, Myriophyllum spicatum, Potamogeton pectinatus, Potamogeton lucens, Potamogeton maackianus, Elodea nattalii, Potamogeton crispus and Hydrilla verticillata, were investigated under different DIC conditions. The results indicated that HCO3- could be used as a carbon source by all the submerged macrophytes tested. Improvement of growth and photosynthetic rates was found on C. demersum, P. crispus and E. nattalii under exogenous HCO3- below 1.5mmol/L, and also on M. spicatum, P. lucens, H. verticillata, P. maackianus and P. pectinatus under exogenous HCO3- below 2.5 mmol/L, however, when CO32- acted as the dominate carbon source, different effects were found on the eight kinds of submerged macrophytes. Growth and photosynthetic rates of P. maackianus, P. pectinatus and H. verticillata were not inhibited, and showed improvement under certain CO32- concentrations, which indicated that the three species of macrophytes could adapt to a wide range of [HCO3-]/ [CO32-] ratio and pH value. In contrast, the growth of C. demersum and E. nattalii were inhibited, and M. spicatum, P. crispus and P. lucens were died under the conditions of CO32- as dominate carbon source, indicating [HCO3-]/ [CO32-] ratio and pH values were the important limiting factors of growth for the above 5 species of submerged macrophytes.