ABSTRACT
Phenotypic plasticity affords invasive plant species the ability to
colonize a wide range of habitats, but physiological plasticity of their
stems is seldom recognized. Investigation of the stem plasticity of
invasive plant species could lead to a better understanding of their
invasiveness. We performed a pot
experiment involving defoliation treatments and an isolated culture
experiment to determine whether the invasive species Mikania
micrantha exhibits greater plasticity in the stems than do three native
species that co-occur in southern China and then explored the mechanism
underlying the modification of its stem photosynthesis. Our results
showed that the stems of M. micrantha exhibited higher plasticity
in terms of either net or gross photosynthesis in response to the
defoliation treatment. These effects were positively related to an
increased stem elongation rate. The enhancement of stem photosynthesis
in M. micrantha resulted from the comprehensive action involving
increases in the Chl a /b ratio, D1 protein and stomatal
aperture, changes in chloroplast morphology and a decrease in
anthocyanins. Increased plasticity of
stem photosynthesis may improve the survival of M. micranthaunder harsh conditions and allow it to rapidly recover from defoliation
injuries. Our results highlight that phenotypic plasticity promotes the
invasion success of alien plant invaders.
Keywords : chloroplasts, ETR, Mikania micrantha ,
pigments, plasticity, stem photosynthesis