ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
PHYSIOLOGICAL RESPONSE OF RED AND FREEMAN MAPLES TO WATER DEFICIT STRESS |
| Authors: | M.E. Reaves, T.H. Whitlow |
| Keywords: | Acer rubrum, Acer x Freemanii, drought stress, genotypic variation, cultivars, gas exchange, water relations |
| Abstract:
Recent research suggests that genotypic variation in response to drought stress exists between populations of Acer rubrum as a result of selection pressures at the site of origin. We believe that the range of drought tolerance currently found in commercial cultivars may not represent the full range of drought tolerance existing within the species. Three Acer rubrum cultivars: ‘Northwood’, ‘October Glory’, ‘Autumn Flame’; three Acer x Freemanii (A. rubrum x A. saccharinum) cultivars ‘Scarlet Sentinel’, ‘Morgan’, ‘Armstrong’; and two naturally occurring ecotypes representing hydrological extremes were evaluated for gas exchange and water relations during drought. When water was withheld, all genotypes exhibited decreased stomatal conductance, photosynthetic rates, and water potential. A ranking based on photosynthetic reduction (% vs. well watered control) at 18 days of drought appears as: ‘Northwood’ (9.5%), ‘Dry site ecotype’ (23%), ‘October Glory’ (26%), ‘Autumn Flame’ (35%), ‘Scarlet Sentinel’ (45%), ‘Morgan’ (85%), ‘Armstrong’ (93%), and ‘Wet site ecotype’ (97%). In a series of single-degree-of-freedom contrasts, red maple cultivars had significantly higher Anet (4.94 μmol m–2 s-1) and gs (0.05 mol m–20 s-1) versus Freeman maples on the last day of drought. The wet site and dry site ecotypes showed average photosynthetic reductions of 9.42 and 1.30 (μmol m–2 s-1), respectively. Predawn stem water potentials ranged from –0.42 to –2.89, with the dry site having the highest values and the wet site having the most negative. Evidence from this study suggests that it is possible to develop a selection of red maple with improved drought tolerance. Additionally, we recommend the cultivar ‘Northwood’ for planting in dry locations. | |
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