Changes of photosynthetic characteristics in leaves of Jussiaea repens to waters with different eutrophica level

Китайский. 对水龙在不同富营养水体中生长时的光合生理生态特征变化进行了测定。结果表明，水龙可以在一定的富营养水平下正常生长，光合速率及表观量子产额表现为上升的趋势，叶绿素含量也相应增加；但在超富营养条件下，水龙植株的生长受到抑制，光合速率及呼吸速率均呈现出显著的下降趋势，气孔导度表现为上升的趋势，表观量子产额呈下降趋势，叶绿素含量尤其是叶绿素a含量受到显著影响；培养至38d后，植株全部死亡。

Английский. The photosynthetic ecophysiological response of Jussiaea repens to two waters with different nutrient level was measured. The results showed that there were some difference between the variation of photosynthetic characteristics under different nutrient level. The obvious decrease of net maximal photosynthetic rate（Pmax） and respiration rate were found in the supereutrophic water. The apparent quantum yield（AQY） and the chlorophyll content of J. repens decreased with the duration of exposure to the supereutrophyieation. But under lower nutrient level, no significant difference were found in maximum photosynthetic rate, dark respiration rate（Rd）, the apparent quantum yield and the chlorophyll content. In the supereutrophic water, the significant reduction of net photosynthetic rate followed by increase of stomatal conductanee（gs） suggested that the non-stomatal limitation may be the main reason for the deficiency of photosynthesis. The decrease of chlorophylla content, the dark respiration rate and the apparent quantum yield in the supereutrophic water provides the evidence for this elucidation. In the experiment, the the yellowish and decomposition was found in the leaf of J. repens seedling until it died in the supereutrophic water. However, the seedlings grew well in the eutrophic water. Based on the observation above, it was concluded that J. repens can grow well in eutrophic condition, but the higher concentration of N and P in supereutrophic water will restrict the growth of J. repens.