Eco-physiological characteristics of Tetracentron sinense Oliv. saplings in response to different light intensities

Abstract

The regeneration of Tetracentron sinense Oliv. is poor in the understory and in open areas due to the characteristics of natural regeneration of the species on forest edges and in gaps. It is unclear whether different light intensities in various habitats affect eco-physiological characteristics of saplings and their natural regeneration. In this study, the light intensity in T. sinense habitats was simulated by artificial shading (L1: 100% NS (natural sunlight) in the open; L2: 50% NS in a forest gap or edge; L3: 10% NS in understory) to investigate differences in morphology, leaf structure, physiology, and photosynthesis of 2-year-old saplings, and to analyze the mechanism of light intensity on sapling establishment. Significant differences were observed in morphology (including leaf area, and specific leaf area) under different light intensities. Compared to L1 and L3, chloroplast structure in L2 was intact. With increasing time, superoxide dismutase (SOD) and catalase (CAT) activities in L2 became gradually higher than under the other light intensities, while malondialdehyde (MDA) content was opposite. Shading decreased osmoregulation substance contents of leaves but increased chlorophyll. The results suggest that light intensities significantly affect the eco-physiological characteristics of T. sinense saplings and they would respond most favorably at intermediate levels of light by optimizing eco-physiological characteristics. Therefore, 50% natural sunlight should be created to promote saplings establishment and population recovery of T. sinense during in situ conservation, including sowing mature seeds in forest edges or gaps and providing appropriate shade protection for seedlings and saplings in the open.