Abstract
Taxicity of oxygen species such as free radicals and H2O2 has been invoked to explain a number of degradative processes in plants, most involving photo‐oxidation. Since catalase is a major protectant against accumulation and toxicity of H2O2, we examined alterations in catalase activity in several plant species (Pisum sativum L. cv. Greenfeast, Vigna radiata (L.) R. Wilcz, Cucumis sativus L. cv. Heinz Pickling, and Passiflora spp.) during chilling, and compared this change to change in H2O2 content. Catalase activity was reduced in a range of chilling sensitive and tolerant species by exposure to low temperature. This reduction in catalase activity correlated better with the onset of visible symptoms than with the treatment itself. Visible injury in turn was dependent on light and temperature differences. Hydrogen peroxide concentrations invariably decreased with low temperatures.Reduction in catalase activity therefore does not necessarily imply accumulation of H2O2 to damaging levels. The absence of a clear inverse relationship between catalase activity and H2O2 concentration suggests the continued activity of other reactions that remove H2O2 and these may be important in the tolerance of plants to oxidative attack. Loss of catalase activity may result from the inability of damaged peroxisomal membranes to transport catalase precursors into the peroxisome.
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