光照强度对2种来源的空心莲子草生长的影响

研究了空心莲子草(Alternanthera philoxeroides)匍匐茎片段(来源于水体)和宿根片段(来源于陆生环境)萌生苗在不同光照强度下的生长。主要结果为:2种来源的空心莲子草幼苗(陆生苗和水生苗)在相同的光照强度下(全光照、33%光照、9%光照),具有基本相同的生长格局,对光照强度的变化也具有相似的反应。随着光照强度的降低,甚至在9%光照时,空心莲子草的总分枝数、最长枝长、节间长度、叶片数没有显著差异,而空心莲子草的叶绿素相对含量显著降低,地上茎直径显著减小;在中等光照条件下(33%光照),其叶面积发生补偿性增大;就生物量的分配而言,随着光强的减弱,根生物量和总生物量显著减少,而茎、叶的生物量只有在光强极低的条件下(9%光照)才显著减少。这些结果表明,在不同的光照强度下,一方面空心莲子草的生长表现出一定程度的形态可塑性,另一方面,空心莲子草基本的空间生长格局特征具有相对稳定性,这种生长策略上的权衡可能是空心莲子草成功入侵的一个重要机制。

Influence of Light Intensity on Growth of Alternanthera philoxeroides,an Alien Invasive Plant

The shoots growth of alligatorweed(Alternanthera philoxeroides)was studied under different light intensity.The results showed that alligatorweed shoots,whether from stem fragments of aquatic alligatorweed or root fragments of terrestrial alligatorweed,had a similar growth pattern in response to the same light intensity(full light,33% light intensity and 9% light intensity).The total number of the branches,maximum length of the branches,internodes length,leaves number had no significant difference as the light intensity decreased.While the chlorophyll relative content,aboveground stems diameter,total biomass and root biomass decreased dramatically as the light intensity decreased.Furthermore,leaves area under 33% light intensity condition was larger than that under other light intensity,biomass of the stems and leaves significant decreased only when the light intensity decreased to 9%.According to the above results,the growth of alligatorweed revealed some degree of phenotypic plasticity in response to different light intensity,but the basic growth pattern of alligatorweed had relative stability.This kind of trade-off at growth strategy might be an important mechanism,by which alligatorweed could invade new habitat successfully.