Degradation and repair/resynthesis rates of chlorophyll in response to oxidative stress and complete darkness differ between annual and perennial flax

Abstract

Among plants, there is considerable variation in maximum lifespan, with annuals living less than one year and perennials living up to 43 600 years. This lifespan variation may reflect differential investment of limited energy resources, with perennials investing more energy into biomolecular damage prevention and/or repair than annuals in order to ensure their persistence over multiple seasons. The present study evaluated this prediction using chlorophyll from annual and perennial flax (Linum L.). We investigated the degradation and repair/resynthesis rates of chlorophyll in response to two different stressors: oxidative stress and complete darkness. Chlorophyll levels were measured using two different techniques: image colour analysis and spectrophotometry. While chlorophyll degradation rates in response to oxidative stress did not differ between annuals and perennials, chlorophyll repair rates following such exposure were significantly higher in perennials, for both chlorophyll a and b, consistent with our predictions. When plants were subjected to complete darkness, chlorophyll degradation rates were significantly lower in perennials than annuals, as predicted; however, when plants were subsequently reintroduced to natural photoperiod, chlorophyll resynthesis rates did not consistently differ between annuals and perennials, though they tended to be higher in the latter, as expected. Overall, our study illuminates that evolutionary transitions between life history strategies in plants have been accompanied by some physiological modifications to chlorophyll dynamics that permit perennial species to better maintain chlorophyll levels in the face of exogenous stressors, which may contribute to their increased longevity.