Abstract:
A survey of photosynthetic pigments, including 86 species from 64 families, was conducted for leaves of neotropical vascular plants to study sun-shade patterns in carotenoid biosynthesis and occurrence of alpha-carotene (alpha-Car) and lutein epoxide (Lx). Under low light, leaves invested less in structural components and more in light harvesting, as manifested by low leaf dry mass per area (LMA) and enhanced mass-based accumulation of chlorophyll (Chl) and carotenoids, especially lutein and neoxanthin. Under high irradiance, LMA was greater and beta-carotene (beta-Car) and violaxanthin-cycle pool increased on a leaf area or Chl basis. The majority of plants contained alpha-Car in leaves, but the alpha- to beta-Car ratio was always low in the sun, suggesting preference for beta-Car in strong light. Shade and sun leaves had similar beta,epsilon-carotenoid contents per unit Chl, whereas sun leaves had more beta,beta-carotenoids than shade leaves. Accumulation of Lx in leaves was found to be widely distributed among taxa: >5 mmol mol Chl(-1) in 20% of all species examined and >10 mmol mol Chl(-1) in 10% of woody species. In Virola elongata (Benth.) Warb, having substantial Lx in both leaf types, the Lx cycle was operating on a daily basis although Lx restoration in the dark was delayed compared with violaxanthin restoration.
