The Effect of Hypoxia and Sulphide on Culture-Grown Wetland and Non-Wetland Plants: II. METABOLIC AND PHYSIOLOGICAL CHANGES

Pearson, J. and Havill, D. C. 1988. The effect of hypoxia andsulphide 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 fivewetland species (Oryza sativa, Aster tripolium, three Salicorniaspp.) were grown in aerated, unaerated and sulphide-treatedculture 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 sulphideincreased ADH activity by 900–1 800%, whereas COase activitydecreased by 80–92% of the aerated control. In the wetlandspecies, except S. europaea which was not affected, hypoxiaincreased ADH activity by 350–550%, while COase activitywas little affected. Generally, when treated with sulphide theactivity of ADH increased to about 750% in most of the wetlandspecies, but increases as low as 175% (S. europaea) and as highas 1400% (S.fragilis) were recorded. The effect of sulphideon the COase activity in the wetland plants was not as markedas in the non-wetland plants. The Salicornia spp. were the leastaffected by the sulphide treatment and they also had intrinsicallyhigher levels of COase activity than the other species sampled.Of the wetland plants the Salicornia species had the lowestvalue for root aerenchyma, 3–6%. Therefore, there wasno correlation between the possession of aerenchyma and thephysiological changes measured. Measurement of malate, lactateand ethanol in roots of the first four species listed abovegave no evidence for alternative anaerobic fermentation pathways.While in the flood-intolerant species, high ADH activities werenot able to maintain the energy charge. It is suggested thatmaintenance of relatively high COase activity in wetland plantsmay help to ‘scavenge’ any available oxygen withinroots and thus help reduce energy loss. Key words: Cytochrome oxidase, alcohol dehydrogenase, metabolic adaptation