芦苇与入侵植物互花米草的光合特性比较

A comparison of photosynthetic characteristics between an invasive plant Spartina alterniflora and an indigenous plant Phragmites australis

以上海崇明东滩湿地外来入侵植物互花米草与本地种芦苇为研究对象,对它们的光合特性进行了比较研究,结果表明:(1)与芦苇相比,互花米草具有更高的表观量子效率(AQY)、CO2羟化效率(CE)和最大净光合速率(pmax);(2)生长季节初期,互花米草午间时段的光合、气孔导度和蒸腾速率均高于芦苇,各指标与光、温的变化基本一致;(3)互花米草的净光合速率曲线呈“单峰”型,测定指标在强光合辐射、高温条件下迅速上升,芦苇则表现出明显的“午休”现象;(4)在生长季节初期(5月份)和活跃期(9月份),互花米草的净光合速率显著高于芦苇,而在生长季节后期(11月份)则低于芦苇。该项研究有利于解释互花米草生长迅速,生产力高,竞争性强的生理生态学特性。

As a consequence of rapid globalization, greatly increased emphasis is being placed on research into the ecology of invasive plants. Since Spartina alterniflora was introduced into Chongming Dongtan in 1995, it has gradually occupied a large area of the Phragmites australis zone, and has became a threat to the intertidal vegetation.. In this study, the photosynthetic characteristics of an invasive plant, Spartina alterniflora, and an indigenous plant, Phragmites australis, were measured during the growing season of 2004 by a Li-6400 Portable Photosynthesis （LI-COR inc, USA. ） at Chongming Dongtan Nature Reserve, Shanghai, between 31°25′－31°38′N and 121°50′－ 122°05′E. The results showed that： （1） Compared with the local plant Phragmites australis, the invasive plant Spartina alterniflora had a significantly higher apparent quantum yield （AQY） carboxylation efficiency （CE） and maximum net photosynthetic rate （Pnmax）; （2） In the early growing season, the curves of net photosynthetic rate （Pn）, leaf stomatal conductance （Gs） and transpiration rate （Tr） of Spartina alterniflora during midday displayed a “single-peak” pattern, which was generally consistent with the changes in light intensity and temperature. In contrast, Phragmites australis showed a distinct “noon-break” phenomenon after reaching the peak, which was not consistent with the changes in light intensity and temperature; （3） The net photosynthetic rate （Pn）, leaf stomatal conductance （Gs） and transpiration rate （Tr） of Spartina alterniflora were higher than those of Phragmites australis during the measurement period. In particular, Spartina alterniflora had a stronger photosynthetic capability above PAR 1 600 μmol/（m^2·s）; （4） These two plants had their own distinctive photosynthetic characteristics at different stages of the growing season. The average Pn for these two plants reached the maximum value in September, while the average Gs and Tr were the highest in May. In general, the photosynthetic parameters of Spartina alterniflora measured in May and September were significantly higher than those of Phragmites australis, while Phragmites australis exceeded Spartina alterniflora later in the growing season （November）. The results from this study have important ecological implications in terms of the fast growth rate, high productivity and a strong competitive ability of the invasive plant Spartina alterniflora, which could provide a sound basis for formulating effective control measures on this species.