基质养分对寄生植物南方菟丝子生长的影响

群落中各营养级的相互作用在群落结构形成中起了重要作用.以南方菟丝子(Cuscuta australis R.Br.)和三叶鬼针草(Biden pilosa L.)为研究对象,采用完全随机区组实验设计方法,测定并分析基质养分(不施肥与施肥)对寄生植物生长的影响,探讨寄生植物生物量与寄主生长特性、生物量和光源捕获能力的相关性.结果表明,施肥显著增加寄生植物南方菟丝子的吸器数量、缠绕圈数、相对盖度、营养器官生物量、生殖器官生物量和总生物量,但对生殖器官的生物量比无显著影响.施肥显著增加寄主植物的根、茎、叶生物量和总生物量、叶生物量比、比叶面积和叶绿素含量,但显著降低根冠比与根生物量比.南方菟丝子生物量与三叶鬼针草生物量、叶生物量比、比叶面积以及相对叶绿素含量之间均存在显著正相关,与根生物量比和根冠比存在显著负相关.研究结果表明施肥可以提高寄主植物的光资源捕获能力,将更多地生物量分配至叶等光合机构上,从而促进寄主植物(生产者)的生长,并间接促进寄生植物(初级消费者)的生长.

Effects of nutrients on the growth of the parasitic plant Cuscuta australis R.Br.

Interspecific interactions at different trophic levels play important roles in the structure and dynamics of communities. Studying such multitrophic interactions at the individual level could help to better model complicated interactions across trophic levels at the community level. Parasitic plants are one type of consumer that interacts with other species at different trophic levels in natural communities. Bidens pilosa L. (Compositae), an annual forb native to South America, has invaded subtropical south-western China, where it is now common. Cuscuta australis (Convolvulaceae), a holoparasitic plant, has been identified as a potential biological control agent of such invasive plants. Here, we conducted a common pot experiment to investigate how fertilization of host plants indirectly affected the growth of parasitic plants and the possible mechanisms related to the growth, biomass allocation patterns, and light-resource capture abilities of the hosts. The number of coils around the stems of the host plants, the number of haustoria, and the relative cover of C. australis on fertilized B. pilosa were higher than on non-fertilized B. pilosa. Fertilization significantly increased the vegetative biomass, reproductive biomass, and total biomass of C. australis, but had no significant effect on the reproductive mass ratio. The biomass of leaves, stems, roots, total biomass, leaf mass ratio, specific leaf area, and relative chlorophyll content of the fertilized host were significantly higher than those of non-fertilized hosts, but the root/shoot ratio and root mass ratio were lower than those of the non-fertilized host. The vegetative biomass, reproductive biomass, and total biomass of C. australis were significantly positively correlated with the biomass of the roots, stems, leaves, total biomass, leaf mass ratio, relative chlorophyll content, and specific leaf area of the host plant and significantly negatively correlated with the root/shoot ratio and root mass ratio. Our results suggested that fertilization could improve the light-resource usage and allocation of biomass to photosynthetic organs of invasive plants, which could result in rapid growth of these invasive hosts (producer) and thus indirectly promote the growth of parasitic plants (primary consumer).