CO2浓度升高对沉水克隆植物生长速率及营养元素积累的影响

 研究在不同CO2浓度下水生克隆植物刺苦草（Vallisneria spinulosa）整个生活周期中生长的动态变化及对营养元素积累情况。在不损伤植物体的前提下，采用刺苦草形态学指标组合史估计了植株生物量的动态变化。结果表明：刺苦草鳞茎的萌发不受CO2浓度变化的影响。在高浓度CO2即(1000±50) μmol·mol-1下，刺苦草源株地上部分生长速率在整个生长前期和中期都远远高于低浓度CO2即(400±20) μmol·mol-1，而在后期则出现相反的现象，其中一个原因是因为高浓度CO2下后期光合物质向地下大量转移形成鳞茎引起地上部分生长减慢。但高浓度CO2下克隆株中的初级和次级分株生长速率均高于低浓度CO2。在两种CO2浓度下相同克隆植株构件中的总碳含量没有明显差异；除鳞茎外，根、叶、匍匐茎中的总磷含量随CO2浓度升高显著增加；由于各构件生物量增加有明显差异，导致叶和鳞茎因为生物稀释作用而使其含氮量降低了12%～14%，但根和茎中含量基本保持不变。在高浓度CO2中植株总生物量显著升高，所以总碳、总氮和总磷吸收量均显著大于在低浓度CO2中的吸收量。研究结果揭示，大气CO2浓度升高对沉水克隆植物生长的促进，有利于提高水生克隆植物在群落中的竞争能力；水生植物克隆生长将增加水生生态系统中碳的沉积；水环境中N、P含量将直接影响到水生克隆植物生长。

RESPONSE OF GROWTH RATE AND NUTRIENT ELEMENTS ACCUMULATION IN SUBMERGED CLONAL MACROPHYTE UNDER ELEVATED CO2

A submerged clonal plant, Vallisneria spinulosa, was grown for three months in greenhouse under ambient CO2 (400±20) μmol·mol-1 and elevated CO2 (1000±50) μmol·mol-1 to test the dynamic change of its growth and nutrient accumulation during its life cycle. It is credible to estimate the biomass of the submerged macrophyte continuously by multiplex parameters of morphology without destroying the experimental material. The sprouting of turions had not been affected by elevated CO2. The growth rate of ortet above-ground responded positively to elevated CO2 during prophase and metaphase of life cycle, while the opposite result occurred during anaphase because much more photosynthetic substance transferred to blow-ground to reproduce turions under elevated CO2 condition. Both primary and secondary ramets had higher growth rate under elevated CO2 than under ambient CO2. There was no difference in C content of the same clonal modules under two experimental conditions. Elevated CO2 significantly stimulated P accumulation in all modules of V. spinulosa except turion compared with ambient CO2. However, due to bio-dilute resulted from quickly increasing biomass, a 12％ 14% of N content of leaf and turions reduced under elevated CO2, while no significant difference in root and rhizome under both CO2 concentrations was detected. Total C, N and P accumulated in submerged plant under elevated CO2 were much more than those under ambient CO2 because the growth rate of plant increased quickly under the former condition. It is concluded, therefore, from the present study that (i) elevated CO2 significantly stimulates V. spinulosa clonal growth which will be of great benefit to its competition with other species among the community; (ii) more carbon will sink in the water-ecosystem because aquatic plants biomass increases; (iii) the content of N、P will influence directly aquatic clonal plants’ growth in the global climate change.