Abstract:To further understand the growth strategies of semi-parasitic species and their interactions with their host species, the leaf functional traits of two common Loranthaceae species in the Chengdu Plain, China, Taxillus nigrans and Scurrula parasitica, were examined with their four primary host species, Chimonanthus praecox, Magnolia grandiflora, Osmanthus fragrans, and Ligustrum lucidum, in the urban areas of Chengdu to identify variations in leaf functional traits among the mistletoe species across different categories and types of hosts. Furthermore, a comparative assessment of these traits was conducted under diverse parasitism scenarios, encompassing both parasitized and non-parasitized host branches. Among mature mistletoe plants, there were significant differences in flavonoid content, leaf nitrogen content, leaf thickness, specific leaf area, and leaf dry matter content among different host plants. The nitrogen content in the leaves of mature mistletoe individuals parasitizing on the nitrogen-fixing host species, Robinia pseudoacacia, was significantly lower than that parasitizing on the non-nitrogen-fixing host species, M. grandiflora. However, except for the flavonoid content in mistletoe leaves parasitizing on shrubs being significantly higher than those on trees, host type (evergreen or deciduous, broadleaved or coniferous, tree or shrub) did not significantly affect leaf functional traits of the mistletoe plants, including leaf nitrogen content, chlorophyll content, specific leaf area, dry matter content, and leaf thickness. Mistletoe leaves on different host plants exhibited diverse leaf economic spectrum characteristics. Those on M. grandiflora displayed a "quick investment-return" strategy, whereas those on Prunus cerasifera 'Atropurpurea' and Chaenomeles speciosa followed a "slow investment-return" strategy. Meanwhile, mistletoes on other host plants did not exhibit typical leaf economic spectrum traits. For the juvenile individuals, the leaf chlorophyll and leaf nitrogen contents of T. nigrans were significantly higher than those of mature individuals. The responses of leaf chlorophyll content, nitrogen content, thickness, and the specific leaf area of proximal and distal leaves infected on host plants O. fragrans, M. grandiflora, and C. praecox to the mistletoe infection were not influenced by the relative position of the mistletoes. Therefore, it would be essential to understand the survival strategies of semi-parasitic plants and their interactions with host species.
