Root Respiration Characteristics of Flood-tolerant and Intolerant Tree Species1

Red maple ( Acer rubrum L.) and baldcypress ( Taxodium distichum (L.) Rich.) seedlings were very tolerant of extended flooding, whereas shoots of sugar maple ( Acer saccharum Marsh) seedlings experienced desiccation after 8 days of flooding, and leaf death after 14 days. Shoot desiccation occurred after 14 days of flooding. Roots of all 3 species utilized O 2 with similar efficiency prior to flood stress. However, the respiratory capacity of sugar maple roots declined substantially during the first 8 days of flooding, and more gradually from 8 to 22 days, at 21, 5, or 0.5% O 2 . Red maple roots declined gradually in respiratory capacity over the entire flooding period at 21 and 5%, but not at 0.5% O 2 . After an initial sharp decline, baldcypress roots gradually regained capability to utilize O 2 from 8 to 22 days of flooding at all 3 levels of O 2 . When tested at 21% O 2 , both red maple and baldcypress roots had 2- to 3-fold higher respiratory capacities than did sugar maple roots after 22 days of flooding. Presoaking root sections from flooded red and sugar maple in a sucrose solution mildly stimulated respiration rates measured at 21% O 2 , but did not fully restore respiratory capacity lost by flooding either species.