Light Response Characteristics of Seedlings Leaves of Eight Mangrove Species Under Different Light Intensities

Abstract:

Mangrove species are a group of trees, shrubs or herbs that grow in intertidal zones of tropical and subtropical coasts. They are generally categorized into true mangrove and semi-mangrove species according to their distribution. Understanding the eco-physiological strategies of light adaptation of mangrove species is of important theoretical significance to revealing the community assembly mechanisms of mangrove forests, and can provide scientific guidance for the reconstruction and transformation of mangrove forests. In order to reveal the physiological and ecological strategies to light conditions of mangrove plant species and provide theoretical guidance for optimal assembly of mangrove community structure, the light response characteristics in leaves of eight mangrove seedlings, such as Sonneratia apetala, Kandelia candel, Bruguiera gymnorrhiza, Aegiceras corniculatum, Acanthus ilicifolius, Acrostichum aureum, Heritiera littoralis and Hibiscus tiliaceus, grown under different light intensities, including 100%, 45%, 30%, and 10% of natural sunlight, were studied using shading control experiment. The results showed that the effects of growth light intensities on the photosynthetic light response characteristics were different among mangrove species. Shading significantly increased the maximum net photosynthetic rate (P_max) of K. candel and B. gymnorrhiza, but had no significant effects on P_max of other mangrove species. Kandelia candel had a higher P_max under 45% light intensity treatment, while B. gymnorrhiza had higher P_max under 45% and 30% light intensities. With the decrease of growth light intensity, the light saturation point of leaves of K. candel seedlings significantly increased, the light compensation points of B. gymnorrhiza, Acanthus ilicifolius and Acrostichum aureum appeared a decreasing trend, the apparent quantum yield of B. gymnorrhiza and Acrostichum aureum showed an increasing pattern, and the dark respiration rate of B. gymnorrhiza and Acrostichum aureum decreased. Therefore, it was suggested that B. gymnorrhiza, Acanthus ilicifolius and Acrostichum aureum are suitable for planting under forest with high canopy density, while S. apetala, K. candel, Aegiceras corniculatum, Heritiera littoralis and Hibiscus tiliaceus are suitable to be planted as upper layer species in mangrove forests or planted under forest with low canopy density.