SEEDLING DEVELOPMENT OF <em>GONOSTYLUS</em> <em>BANCANUS</em> (RAMIN MELAWIS) IN RESPONSE TO LIGHT INTENSITY AND SPECTRAL QUALITY

Abstract

We studied seedling development of Gonostylus bancanus (ramin melawis, Thymeliaceae) in response to shade conditions, to learn about the tree's functional ecology. Shadelight comprises reductions in solar irradiance (photosynthetic photon flux density, 400-700 nm, or PFD) and changes in spectral quality, as reductions in the red:far-red ratio (or R:FR). We studied the separate and interactive effects of PFD and R: FR on seedling development by growing them under six different replicated shadehouse treatment conditions. Seedlings grew least at low light levels and full sunlight. Seedling branching was not strongly affected by the light treatments, but stem robustness was promoted by PFD, and leaf area/stem length was decreased by low R:FR. Photosynthate allocation to leaves was low, and was primarily reduced by increasing PFD. Most of the effects on development were influenced by PFD; only internode length and leaf area/stem length were more influenced by R:FR. Seedlings of ramin malawis are intolerant of extreme shade and direct sunlight, growing most rapidly in partial shade, with daily percentages of 40 % and more of full sunlight. Such seedlings are probably only at a competitive advantage in the inundated soils of their natural distribution.