Deciduous and evergreen perennials have higher antioxidant levels and more reactive oxygen species-susceptible chlorophyll-binding proteins

Abstract

Perennials live longer than annuals, yet the underlying physiological mechanisms responsible are poorly understood. We gathered data from published reports to investigate two hypotheses based on the oxidative stress theory of ageing. The first hypothesis was that perennials maintain higher antioxidant levels to neutralize reactive oxygen species (ROS) better, before they cause oxidative damage. Although carotenoid levels did not differ between annuals and perennials, we found that deciduous perennials had higher activity of the ascorbate–glutathione cycle, and evergreen perennials had higher activity of superoxide dismutase (SOD, EC 1.15.1.1). The second hypothesis was that chlorophyll-binding proteins of perennials have a lower proportion of ROS-susceptible amino acids to protect chlorophyll better from oxidative damage. Contrary to our predictions, although LHCI, LHCII, CP26, and CP29 showed no difference in amino acid composition between annuals and perennials, D1 protein and CP24 had a higher proportion of ROS-susceptible amino acids in both deciduous and evergreen perennials. By being more susceptible to ROS attack, these proteins might minimize oxidative damage to chlorophyll and/or contain oxidative damage within the photosystems such that it does not spread to other cell regions.