GROWTH AND PHOTOSYNTHETIC RESPONSES OF 4 VIRGINIA PIEDMONT TREE SPECIES TO SHADE

To determine the effects of shade on biomass, carbon allocation patter ns and photosynthetic response, seedlings of loblolly pine (Pinus taed a L.), white pine (Pinus strobus L.), red maple (Acer rubrum L.), and yellow-poplar (Liriodendron tulipifera L.) were grown without shade or in shade treatments providing a 79 or 89% reduction of full sunlight for two growing seasons. The shade treatments resulted in less total b iomass for all species, with loblolly pine showing the greatest shade- induced growth reduction. Yellow-poplar was the only species to show i ncreased stem height growth in the 89% shade treatment. The shade trea tments increased specific leaf area of all species. Quantum efficiency , dark respiration and light compensation point were generally not aff ected by the shade treatments. Quantum efficiency, dark respiration, m aximum photosynthesis and light compensation point did not change cons istently between the first and second growing seasons. We conclude tha t differences in shade tolerance among these species are not the resul t of changes in the photosynthetic mechanism in response to shade.