Effects of shading on the photosynthetic characteristics and leaf structure of Ranunculus ternatus Thunb.

Abstract

Abstract [Objective] The study aims to investigate the effects of different shading levels on the photosynthetic characteristics and leaf anatomical structure of wild plant Ranunculus ternatus Thunb. and provide a theoretical basis for the in-depth understanding of its shading tolerance and large-scale planting. [Methods] This experiment adopts the method of controlling variables with R. ternatus Thunb. as materials. Five shading treatments full light (CK), 30% shading (T1), 50% shading (T2), 70% shading (T3), and 90% shading (T4), were applied. [Results] (1) With the increase of shading, the leaf area reached the maximum under T3 environment. Plant height and stem diameter were decreased with the decrease of light. (2) With the increase of shading, the leaf apparent quantum efficiency (AQE) of R. ternatus was first increased and then decreased, and was lower than other treatments under T4 treatment. Light saturation point (LSP), light compensation point (LCP), dark respiration rate (Rd), and maximum net photosynthetic rate (Pn,max) were decreased gradually. Maximum fluorescence (Fm), variable fluorescence (Fv), maximized chemical efficiency (Fv/Fm), and PSⅡ potential activity (Fv/Fo) were increased first and then decreased, while the electron ratio of heat dissipation (φDo) and the initial fluorescence (Fo) was decreased first and then increased. (3) With the increase of shading, the stomatal density of R. ternatus was first decreased and then increased, and reached the minimum value at T3 treatment. The thickness of the upper and lower epidermis and the thickness of the sponge gradually were decreased, the tissue structure compactness (CTR) was decreased first and then increased, and the tissue structure porosity (SR) was first increased and then decreased. (4) Leaf palisade tissue, sponge tissue, leaf thickness, and upper, and lower epidermal thickness were positively correlated with Rd. Sponge tissue thickness (ST), CTR, and SR were positively correlated with Pn,max. P/S and SR were positively correlated with AQE. However, sponge tissue thickness (ST) and SR were negatively correlated with Fo. [Conclusion] R. ternatus can improve its shading tolerance by reducing photosynthetic rates and changing leaf structures; it grows well in full light and adapts to 30%-70% shading environment.

Keywords

• ranunculus ternatus thunb.
• shading
• photosynthetic characteristics
• leaf anatomical structure