A Study on the Control of Exotic Weed Mikania micrantha by Using Parasitic Cuscuta campestris Change of soil microbial biomass and enzyme activities in the community invaded by Mikania micrantha, due to Cuscuta campestris parasitizing the invader The Harm Caused by Mikania micrantha and Its Control by Cuscuta campestris Influence of the obligate parasite Cuscuta campestris on the leaf stomatal behavior of its host Mikania micrantha