Changes in Catalase Activity in Higher Plants and Fungi treated with Oxygen at High Pressure

Abstract

IT has been shown by Caldwell^1,2 and by Robb³ that the inhibition of growth of fungi by oxygen at high pressure (HOP) can be reversed after quite prolonged periods of treatment. Thus many fungi can resume growth after treatment with oxygen at 10 atm. for 14 days. On the other hand, higher plant tissues, with the exception of dormant tissues such as seeds, are usually killed by treatment with oxygen at 10 atm. for 1–2 days or less⁴. Studies on the metabolic effects of HOP on higher plants^5,6 and on micro-organisms^7,8 (and also on mammalian tissues^9,10) suggest that the primary effect of treatment is the same in all cases, namely inhibition of the enzymes involved in the metabolism of pyruvic acid, leading to a rapid inhibition of respiration. This primary inhibition is very rapid and can readily be reversed after short periods of treatment in higher plant tissues and micro-organisms. The irreversible effects of more prolonged HOP treatment are probably brought about by a different mechanism. The available evidence suggests that hydrogen peroxide is not involved in the primary enzyme inhibition⁹, but the irreversible inhibition of growth and metabolism may be due to the accumulation of peroxide under HOP conditions¹¹. The ability of fungi to survive much longer periods of HOP treatment than higher plants can tolerate could be due, therefore, to a protective mechanism preventing peroxide accumulation. Our studies on the changes in catalase activity in two higher plants (Lepidium sativum and Elodea canadensis) and in two fungi (Mucor racemosus and Candida utilis) support this idea.