Periploca sepium leaf dry weight, area, and thickness scale differently under different light environments in Taohe riparian forests

Abstract

Understanding the variation in plant morphological characteristics under heterogeneous light environments is important to comprehend the adaptation strategies of riparian forest plants. Among the plant parts, leaves are the most sensitive to changes in the environment, and their functional traits and correlations among them can reflect the pathways and mechanisms of a plant's response to environmental changes. The allometric relationship between leaf dry weight (LDW), leaf area (LA) and leaf thickness (LT) in Periploca sepium under three natural habitat conditions, namely, under canopy, gap, and full sun areas in the Taohe riparian forest, was examined by using the standardized major axis (SMA) estimation method and correlation analysis. In the under canopy area, LDW and LA showed an allometric growth relationship (SMA slope < 1), whereas LDW and LT displayed an isometric relationship (SMA slope = 1). In the gap area, LDW was isometrically related to the LA and LT (SMA slope = 1). In the full sun area, LDW and LT showed an allometric relationship (SMA slope > 1), whereas LDW and LA showed an isometric relationship (SMA slope = 1). LA, LT, and LDW decreased by 34.3%, 45.0%, and 40.4%, respectively, in plants from the under canopy area to the full light area. Moreover, the transpiration rate (Tr), net photosynthetic rate (Pn), stomatal conductance (Gs), and vapour pressure deficit (VPD) of Periploca sepium increased 1.29-fold, 13.5%, 63.2%, and 29.7%, respectively, from the under canopy area to the full sun area. Periploca sepium developed large, thick leaves in the under canopy area, and small, thin leaves in the full sun area, demonstrating the investment trade-off mechanism of plant leaf functional traits to adapt to the heterogeneous light environment.