Inductive flood tolerance in swamp tupelo (Nyssa sylvatica var
Under flooding or anoxia the newly initiated roots of swamp tupelo produce et hanol and lactio acid and oxidize their rhizosphere. Unflooded roots produce less ethanol than flood roots and do not oxidize their rhizosphere. Oxygen enters the stem via the lenticels and appears to be diffused or transported via the cortex or phloem. Flood roots have less suberization in the epidermis in the terminal 2-cm section and casparian strips were less evident than in the same sections in unflooded roots. Swamp tupelo roots tolerated 10 per cent CO2 without adverse effects but 31 per cent CO2 reduced the initiation of new roots, rate of O2 uptake, and transpiration rate. Tolerance to high CO2 around the root seemed to be related to the oxidation of the rhizosphere by new roots. The combined adaptations of accelerated anaerobic respiration in the absence of O2, oxidation of the rhizosphere, and CO2 tolerance of new roots appear to be sufficient conditions to account for flood tolerance in this species.