| Red maple (Acer rubrum L.) is a frequently planted street tree often recommended for wet sites, yet in its native habitat it is a dominant forest species in both wetlands and dry uplands. Is red maple a generalist species, able to acclimate to wet and dry sites, or have different ecotypes evolved, each adapted to its specific habitat? To investigate these questions seeds were collected from 3 wet sites (WS) and 3 dry sites (DS) surrounding Ithaca, New York.;Germination trials indicated that wet site red maple seeds are non-dormant upon dispersal, while dry site seeds required 1 or 2 stratification periods to germinate. Differences in germination between seeds collected from wet and dry sites suggest that the hydrology of the collection site may have acted as an agent of selection and is a good predictor of red maple germination strategy.;Flooding resulted in changes in leaf ion levels, lower net photosynthesis, lower stomatal conductance, a near complete cessation in growth, and lower leaf chlorophyll for trees from both wet and dry sites. Wet site seedlings limited the uptake of potentially toxic ions, Al, Na, and Fe when flooded while DS seedlings had much higher levels of these ions compared to controls.;After 90 days of continuous flooding, WS trees had higher net photosynthesis, stomatal conductance, and chlorophyll levels than did DS trees. When trees were flooded for 22 days and then drained, net photosynthesis and stomatal conductance recovered more quickly and to a higher level in WS trees.;Differences in ion uptake and gas exchange may be due to differences in adventitious root development since wet site seedlings produced more adventitious roots than DS seedlings. This difference in phenotypic plasticity and the corresponding differences in physiology suggest that ecotypic differentiation has occurred between WS and DS populations of red maple.;Cultivar studies also suggest there is genetic variation for characters associated with flood tolerance within red maple. |
