Growth and physiological acclimation to shade in young plants of Adesmia bijuga Phil., a critically endangered species in central Chile

Abstract

Adesmia bijuga Phil. is an endemic and endangered shrub species of central Chile. Its potential shade intolerance is one of the leading hypotheses for its vigor loss when the species grows beneath closed canopies. The objective of this study was to assess the growth and physiological acclimation to the shade of young plants of A. bijuga. A nursery experiment was established with three light levels based on the interception of photosynthetic active radiation (PAR) (TRT0: control at full sun; TRT60: 60% shaded; TRT90: 90% shaded), and maintained for 71 days during the summer season. Growth and leaf morpho-physiological responses were evaluated at the beginning, at the middle, and at the end of the experiment. The shading treatment increased plant height (H), live crown percentage (Lcrown), and specific leaf area (SLA) compared to the control treatment at full sun. However, light-saturated photosynthetic rate (Amax), dark respiration rate (Rd), and light compensation point (Γi) were higher in TRT60 than in the other treatments, while no differences were found among treatments for the apparent quantum yield (α). At this stage of plant development, our results suggest high acclimation plasticity of A. bijuga to light levels; however, a semi-shade environment (i.e., TRT60) favored a better performance of the species.

Keywords

• Adesmia bijuga
• Shade Tolerance
• Photosynthesis
• Light Acclimation
• Forest Restoration