EFFECTS OF RHIZOSPHERE INUNDATION ON THE GROWTH AND PHYSIOLOGY OF WETAND DRY-SITE ACER-RUBRUM (RED MAPLE) POPULATIONS

Six-wk-old Acer rubrum L. (red maple) seedlings, grown from fruits col lected on paired wet and dry sites on the Coastal Plain, Piedmont, and Ridge and Valley physiographic regions of Virginia, were flooded to d etermine whether there are ecotypic differences in growth and physiolo gy between seedlings from wet and dry sites. Periodic harvests were co nducted over 3 mo to measure growth of flooded and unflooded seedlings derived from three trees per site. Shoot water potential and gas exch ange were measured for 2 wk to determine if the physiology of seedling s from wet and dry sites were affected differently by flooding. Floodi ng adversely affected seedling growth and physiology resulting in shor ter (18%) and lighter (30% less leaf mass, 14% less stem mass and 68% less root mass) seedlings that had higher water potentials (20%) and r educed photosynthetic rates (50%). Significant differences developed b etween seedlings from wet and dry sites with the wet site seedlings ha ving lower water potentials and taller, heavier shoots. However, no si gnificant interactions between flooding and maternal hydrologic condit ions were found that would indicate genetic differences in flood respo nse between wet and dry site seedlings. This lack of a differential gr owth or physiological response to waterlogging by the distinct populat ions strongly suggests that young Acer rubrum seedlings do not exhibit ecotypic differences in flood tolerance.