Photosynthetic and Growth Responses of Silver Maple (Acer saccharinum L.) Seedlings to Flooding

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Abstract
Flooding affected several growth parameters of silver maple seedlings. Root biomass and leaf area were sharply reduced. Photosynthetic rates of recently germinated seedlings decreased significantly after 21 days of root-flooding and after only 3 days of submersion. In some treatments, reduced net photosynthesis/transpiration ratios after flooding indicated a decline in water use efficiency. Seedlings submersed in water containing suspended sediments had lower rates of photosynthesis than plants submersed in clear water. The timing of flooding treatments (spring vs. late summer) had no apparent effect on the pattern of decline in net photosynthesis. Two-year-old seedlings had a greater capacity for net photosynthesis after flooding than recently germinated seedlings, suggesting that recovery of normal physiological function after flooding is an important survival feature of older silver maple seedlings. Light conditions had minimal effect on seedling growth and photosynthesis. Seedlings had relatively high rates of photosynthesis over a broad range of photosynthetically active photon flux density and developed a shade leaf morphology when grown at low intensity. Duration of flooding is the most important characteristic of the flood cycle affecting the survival and establishment of silver maple seedlings in floodplain habitats.