Effect of Shading on Chlorophyll Fluorescence Parameters in Leaves of Seedlings of Eight Mangrove Species

Abstract:

The restoration and reconstruction of mangrove wetland ecosystems is one of the key research fields in ecological restoration in the coastal zones of South China. How to optimize the assembly of mangrove species is the priority to be concerned in the restoration and transformation of mangrove forest community. In order to reveal the ecophysiological strategies to light conditions of mangrove plant species and provide theoretical guidance for optimal assembly of mangrove community structure, the characteristics of leaf chlorophyll fluorescence parameters in seedlings of eight mangrove plant species, such as Sonneratia apetala, Kandelia candel, Bruguiera gymnorrhiza, Aegiceras corniculatum, Acanthus ilicifolius, Acrostichum aureum, Heritiera littoralis and Hibiscus tiliaceus, under different light intensities (100%, 45%, 30%, and 10% of natural sunlight) were studied using shading control experiment. The results showed that all of eight mangrove plant species appeared a significantly higher maximal photochemical efficiency of PSII (F_v/F_m) and actual photochemical efficiency of PSII (ΦPSII) in shading treatments, while the significant lower electron transport rate (ETR) was found in shading treatments in seedlings of eight mangrove species. Under 100% light intensity, S. apetala, K. candel, A. corniculatum, Heritiera littoralis and Hibiscus tiliaceus had higher F_v/F_m than the other three mangrove plant species, while A. corniculatum and Heritiera littoralis had higher ΦPSⅡ and ETR than B. gymnorrhiza, A. ilicifolius and A. aureum. Therefore, Sonneratia apetala, K. candel, A. corniculatum, Heritiera littoralis and Hibiscus tiliaceus had high light energy utilization, while A. corniculatum and Heritiera littoralis could make better use of high light and dissipate excess light energy to protect photosynthetic organs, thus these five mangrove species are suitable to be planted as upper layer tree species in mangrove forests. In contrast, the ΦPSII of B. gymnorrhiza, A. ilicifolius and A. aureum were lower than 0.2, and ETR was only 20%-33% of those of sun plant species like S. apetala, indicating that they are suitable to be used as understory species in dense mangrove forests.