PJB-2022-369
The photosynthetic eco-physiological adaptability of the endangered plant Tetracentron sinense Oliv. to different habitats and altitudes
Rui Chen
Abstract
Tetracentron sinense Oliv, the only tall deciduous tree in the family Tetracentraceae, is listed as a national second-grade key protected plant in China and an endangered species. It is a constructive species in the community, but the natural regeneration of T. sinense is poor, and niche overlap between T. sinense and its associated species results in fierce competition for natural resources like light and CO2. It is not clear whether the photosynthetic capacity of T. sinense differs from its associated species, and how does this affect the natural regeneration of T. sinense population. Additionally, light intensity and temperature vary with altitude and this could lead to difference in the light adaptation of T. sinense growing at different altitudes. In this study, a Li-6400 portable photosynthetic meter was used to measure the photosynthetic eco-physiological adaptability of T. sinense to different habitats and altitudes. The light saturation point (LSP), maximum net photosynthetic rate (), carboxylation efficiency (CE), saturation point of carbon dioxide (), and light respiration rate () of T. sinense in forest gap (FG) were higher than those in the forest edge (FE) and understory (US). In FE, the net photosynthetic rate () , light compensation point (LCP), LSP, CE, , and of T. sinense were lower than those of Pterocarya stenoptera, while the LSP, CE, , of T. sinense in US were lower than those of Acer pictum . The specific leaf area (SLA) of T. sinense decreased with decrease in the light intensity. With increasing altitude, the , LSP, and SLA of young T. sinense trees (YT) increased, while the LCP of YT increased first and then decreased. The trend of LCP and SLA of mature trees (MT) was the same as that of the YT, whereas the LSP of MT first increased and then decreased, and the gradually decreased with increasing altitude. The results showed that (1) the photosynthetic capacity of T. sinense in FE and US was weaker than that of its associated species, and its ecological range of light adaptation was also narrower than its associated species, placing T. sinense at a competitive disadvantage, which may be one of the important reasons for its poor regeneration; and (2) the environmental conditions at higher altitude can contribute to the growth and survival of T. sinense. Therefore, active artificial intervention should be undertaken to expand the area of FG for T. sinense and transplant its seedlings at higher altitude areas to promote the growth of T. sinense and population regeneration.
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