Understanding the invasion mechanism of malignant alien weed Mikania micrantha from the perspective of photosynthetic capacity of stems

Mikania micrantha (mile-a-minute weed) is recognized as one of the top 10 malignant weeds in the world. One of its remarkable characteristics is the rapid growth of its stems. The inherent advantages of the photosynthetic characteristics of M. micrantha stems were analyzed in the study. The results indicated that comparing with model plant ( Arabidopsis thaliana ), vines ( Vitis vinifera and Ipomoea nil ), C3 plants ( Oryza sativa ), Crassulacean Acid Metabolism (CAM, Ananas comosus ) plants and Asteraceae ( Lactuca sativa ), M. micrantha had more genes involved in the photosynthetic pathway, light energy capture, carbon fixation and chlorophyll synthesis . From the photosynthetic physiology, with compared to associated vines, M. micrantha stems had a strong net photosynthetic rate ( P n ), and had certain advantages in photosynthetic pigment and chlorophyll fluorescence parameters. In a test under high light (HL) conditions, differently from Ipomoea nil , M. micrantha stems showed higher values of P n , the maximum photochemical efficiency of PSII (F v /F m ) and contents of flavonoids, total phenols and anthocyanin, while lower hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA) and relative conductivity. The qPCR results further showed that chlorophyll a light-harvesting complex ( LHCA ), chlorophyllide a oxygenase ( CAO ) and Ribulose-1,5-bisphosphate carboxylase/oxygenase ( Rubisco ) gene expression levels were decreased in the two species under HL treatment and that the downregulation range was smaller in M. micrantha stems. The inherent advantage of the strong photosynthetic ability of stems is a favorable condition for further enhancing the rapid growth of plants, which may be an important invasion mechanism and provides a new idea for researchers to pay attention to the control strategy of M. micrantha in the future.