外来入侵种加拿大一枝黄花及其伴生植物光合特性研究

Comparison of basic photosynthetic characteristics between exotic invasive weed Solidago canadensis and its companion species

使用LCA4光合蒸腾测定系统测定外来入侵杂草加拿大一枝黄花（Solidago canadensis）及其16种伴生杂草的光合作用指标．结果发现：①加拿大一枝黄花实测最大净光合速率为19．22μmolCO2·m^-2·s^-1,低于一年蓬（Erigeron annuus）、野塘蒿（Conyza bonariensis）和小飞蓬（Conyza canadensis）3种外来入侵杂草，但是高于马缨丹（Lantana camara）、空心莲子草（Alternanthera philoxeroides）、北美车前（Plantago virginica）和苦苣菜（Sonchus oleraceus）等外来入侵杂草；②该外来种在五月下旬净光合速率的日进程与空心莲子草相似，有较弱的光合午休现象；③加拿大一枝黄花的光补偿点为48．36μmol·m^-2·s^-1，表明是一种喜阳性杂草；④在中等光强（300-400μmol·m^-2·s^-1）和强光（1300-1800μmol·m^-2·s^-1）照射下，加拿大一枝黄花位于植株中部叶片的净光合速率最高，处于弱光（15～45μmol·m^-2·s^-1）下，植株基部叶片的净光合速率较高，反映出基部叶片比中上部叶片具有较低的光补偿点；⑤与阴生环境中的植株相比，阳生环境中的加拿大一枝黄花株高、叶数增加较快，净光合速率相对较高．加拿大一枝黄花植株通过提高叶绿素总含量来适应阴生环境；⑥阳生环境下，与加拿大一枝黄花植株净光合速率关系最大的环境因子依次为叶面光合有效辐射、蒸腾速率和叶面温度，而在阴生环境下，与该种净光合速率关系最大的环境因子依次为叶面光合有效辐射、空气相对湿度、蒸腾速率和气孔导度．

Photosynthetic indices of Solidago canadensis and its companion species were determined using LCA- 4 portable photosynthesis and transpiration system （ADC, England）. Results were as follows： （i） The actual maximal net photosynthetic rate of S, canadensis is 19.22 μmol·m^-2·s^-1 , lower than those of Erigeron annuus, Conyza bonariensis, Conyza canadensis, but higher than those of Lantana camara, Alternathera philoxeroides, Plantago virginica and Sonchus oleraceus ; （ii） During the last ten-day period of May, the daily course patterns of net photosynthetic rates of S. canadensis was characterized by its weak double-peak type,similar to that of Alternanthera philoxeroides ; （iii）The light compensation point of S. canadensis was 48. 36 μmol·m^-2·s^-1, revealing its well-adapted to sunny environments; （iv） For S. canadensis, under leaf photosynthetic active radiation （PAR） of 1300-1800μmol·m^-2·s^-1and PAR of 300-400 μmol·m^-2·s^-1, the net photosynthetic rates of middle leaves are higher than those of the upper leaves and the basal leaves, while under PAR of 15-45 μmol·m^-2·s^-1, the basal leaves had higher net photosynthetic rates than the middle and upper leaves, which indicates that the basal leaves have lower light compensation point and could more effectively absorb weak light; （v） Compared with those in shady environments, the individuals of S. canadensis in sunny environments increased fast in the plant height and leaf number because of their higher net photosynthetic rates. Additionally, the individuals of S. canadensis in the shady environment have higher total chlorophyll content than those in sunny environment; （vi） According to the correlation coefficients with the net photosynthetic rate, in the sunny environment, the environmental variables influencing the net photosynthetic rate of S. canadensis rankes as leaf photosynthetic active radiation, leaf transpiration rate and leaf temperature; while in the shady environment, the environmental variables ranks as leaf photosynthetic active radiation, relative humidity, transpiration rate and stomatic conductivity.