Alcohol dehydrogenase activity in the roots of marsh plants in naturally waterlogged soils

Abstract

The aim of this work was to discover whether oxygen tensions in the roots of marsh plants in flooded soils are high enough to allow fully acrobic metabolism. Activity of alcohol dehydrogenase (ADH), a protein synthesised in anoxic plants, was measured in roots of marsh plants growing in habitats where the availability of oxygen to the roots would be expected to differ. Roots of Carex riparia in standing water had ADH activities about 2.5 times higher than those of phosphofructokinase, and comparable to ADH activities of Poa trivialis, Urtica dioica and Ranunculus repens roots in dry soil. Removal of the oxygen supply via aerenchyma to Carex roots caused a 30-fold increase in ADH activity relative to that of phosphofructokinase. There was no change in ADH activity with depth in Carex roots in waterlogged soil, but in Filipendula ulmaria roots activity was 14 times higher below 10 cm depth than near the surface. Urtica roots in waterlogged soil had alcohol dehydrogenase activities 26 times higher than roots in dry soil, but for Poa and Ranunculus roots this figure was only 1.7 and 4.2, respectively. These results indicate that the oxygen tensions in the roots of marsh plants in waterlogged soil differ considerably among species. Ethanol was the major product of fermentation in roots of all species studied. There was no correlation between ADH activity and the rate of ethanol production under anoxia of Urtica roots. The physiological significance of high ADH activities in roots is thus unclear.

Regulation of root anaerobiosis and carbon translocation by light and root aeration in Isoetes alpinus

“…Alcoholic fermentation is the primary pathway for carbohydrate metabolism in anoxic roots in both flood‐tolerant and flood‐sensitive species (Smith & ap Rees 1979). ADH activity increases when the oxygen supply to roots is impaired (Smith et al . 1986), and is responsive to the extent to which oxygen transport can prevent hypoxia in species growing in anoxic soils (McKee et al .…”

“…The ADH activity found in I. alpinus was similar to that found by McKee et al . (1989) for emergent wetland species well‐adapted for internal oxygen transport, and much lower than that developed in flood‐intolerant species subject to acute oxygen deficiency after flooding (Smith et al . 1986; McKee et al .…”

“…1990). ADH activity is often not closely correlated with ethanol production (Smith et al . 1986), due to limitation of fermentation rates by the supply rate of substrates, duration of exposure to hypoxia (Drew et al .…”

Salinity and waterlogging tolerances in three stem-succulent halophytes (Tecticornia species) from the margins of ephemeral salt lakes

“…Ethanolic fermentation rates in the three species of Tecticornia were relatively high in comparison with rates observed in other species, such as in 10 mm root tips of Lophopyrum elongatum at 2.84 μmol g −1 fresh mass h −1 (at 20°C, McDonald et al 2001), and rates in 20-40 mm root tips of five wetland species removed from waterlogged soil ranged from 0.84 μmol g −1 fresh mass h −1 in Poa trivalis to 2.65 μmol g −1 fresh mass h −1 in Filependula ulmaria (at 25°C, Smith et al 1986), although the larger proportion of fully expanded cells in these larger tips (i.e. less cytoplasmic volume per unit fresh mass) would likely have lowered rates expressed on a fresh mass basis (cf.…”

Flooding tolerance in halophytes

“…Thus, at least ADH in roots of halophytes appears to respond similarly to that in roots of some freshwater marsh species (e.g. Smith et al, 1986). We expect that other aspects of anoxic metabolism in halophytes will probably reflect those in glycophytes, although further studies, particularly to measure rates of ethanol production in anoxia and of pyruvate decarboxylase activity (the rate-limiting enzyme in conversion of pyruvate to ethanol, , should also be assessed for a range of halophytic species.…”