Photosynthetic physiological and ecological responses of the invasive Sphagneticola trilobata and the native Sphagneticola calendulacea to experimental shading

Affected by global climate change and human activities, biological invasion has become a serious global problem that not only occurs in cities and wastelands but also in forests, severely endangering biodiversity. Sphagneticola trilobata (L.) Pruski, 1996, is a common invasive plant in South China that can adapt to high light and high temperature environments, but its photosynthetic physiological response to shaded environments, such as forest margins, remains unclear. This study investigates the photosynthetic physiology and oxidative damage of S. trilobata and the native species Sphagneticola calendulacea (L.) Pruski, 1996, in a low-irradiance environment. The results show that, compared with the full-light group, photosynthetic gas exchange parameters (including net photosynthetic rate, stomatal conductance and transpiration rate) and chlorophyll fluorescence parameters (maximal quantum yield and actual quantum yield of PSII) of plants in the low-light group significantly decreased after shading, while intercellular CO 2 and nonphotochemical quenching increased; of note, S. trilobata experienced smaller changes. The malonaldehyde content of S. calendulacea increased, while phenols and the total antioxidant capacity of S. trilobata declined more significantly than those of the native species tested . These results further indicate that, compared with S. calendulacea , S. trilobata exhibited a lower loss in photosynthesis and less oxidative damage under shading. This may explain why S. trilobata tends to spread to forests in South China.