Differences in tissue concentrations of hydrogen peroxide in the roots and cotyledons of annual and perennial species of flax (Linum)

Abstract

Short-lived annuals should allocate more resources towards reproduction, whereas long-lived perennials should allocate more resources towards tissue maintenance. Although ecological data support this hypothesis, no studies have examined the physiological basis for lifespan differences between annuals and perennials. Based on the oxidative theory of aging, hydrogen peroxide (H2O2) levels should be lower in perennating tissues (e.g., basal roots) — but not nonperennating tissues (e.g., cotyledons) — from perennials compared with annuals. We tested this prediction using two annual and two perennial species of flax ( Linum ). As predicted, H2O2concentrations were lower in roots from perennials than from annuals, reflecting higher catalase activity in roots from perennials. In cotyledons, contrary to our predictions, H2O2concentrations were actually higher in perennials than in annuals, despite higher catalase activity in perennials as well, likely reflecting higher H2O2production via peroxisomes and chloroplasts. Therefore, we propose that, consistent with the oxidative theory of aging, perennial flax species have a lower oxidative burden in their roots, but this comes at the cost of a greater oxidative burden in their shoots. As we demonstrate, perenniality is ancestral in Linum, and so derivation of the annual condition likely involved a physiological shift towards a more equitable oxidative burden between roots and shoots.