The Effect of Hypoxia and Sulphide on Culture-Grown Wetland and Non-Wetland Plants

Abstract

Pearson, J. and Havill, D. C. 1988. The effect of hypoxia and sulphide on culture-grown wetland and non-wetland plants. II. Metabolic and physiological changes.—J. exp. Bot. 39: 431-439. Two non-wetland (Agropyron pungens, Hordeum vulgare) and five wetland species (Oryza sativa, Aster tripolium, three Salicornia spp.) were grown in aerated, unaerated and sulphide-treated culture solution. Changes in the activity of alcohol dehydrogenase (ADH) and cytochrome oxidase (COase) in the roots were measured. In the non-wetland species, treatment with hypoxia or sulphide increased ADH activity by 900-1800%, whereas COase activity decreased by 80-92% of the aerated control. In the wetland species, except S. europaea which was not affected, hypoxia increased ADH activity by 350-550%, while COase activity was little affected. Generally, when treated with sulphide the activity of ADH increased to about 750% in most of the wetland species, but increases as low as 175% (S. europaea) and as high as 1400% (S.fragilis) were recorded. The effect of sulphide on the COase activity in the wetland plants was not as marked as in the non-wetland plants. The Salicornia spp. were the least affected by the sulphide treatment and they also had intrinsically higher levels of COase activity than the other species sampled. Of the wetland plants the Salicornia species had the lowest value for root aerenchyma, 3-6%. Therefore, there was no correlation between the possession of aerenchyma and the physiological changes measured. Measurement of malate, lactate and ethanol in roots of the first four species listed above gave no evidence for alternative anaerobic fermentation pathways. While in the flood-intolerant species, high ADH activities were not able to maintain the energy charge. It is suggested that maintenance of relatively high COase activity in wetland plants may help to 'scavenge' any available oxygen within roots and thus help reduce energy loss. Key words—Cytochrome oxidase, alcohol dehydrogenase, metabolic adaptation. Correspondence to: Department of Biology (Darwin Building), University College, Gower Street, London WC1E 6BT, U.K.