02147naa a2200265 a 450000100080000000500110000800800410001910000180006024501550007826000090023352013560024265000120159865000190161065000160162965000180164565000180166365000170168165300110169865300220170965300170173165300210174870000180176970000220178777300720180917851481995-07-31       1974    bl ---       0--  u    #d1 aLUDLOW, M. M.  aStudies on the productivity of tropical pasture plants. V. Effect of shading on growth, photosynthesis and respiration in two grasses and two legumes.  c1974  aTwo grasses and two legumes were grown at three illuminances: one grass one legume in a growth cabinet (100, 50 and 34% relative illuminance) and one of each in a grassland (100, 30 and 10% relative illuminance). The response to shading was investigated by using classical growth analysis techniques, and the photosynthesis-respiration balance obtained by Watson and Hayashi's method. Shading caused a reduction in the proportion of root and a corresponding increase in the proportion of leaf, and an increase in the shoot/root ratio in all species except green panic. The relative growth rates of grasses (which were only clearlya superior at the highest illumainance) were affected more by shading than were those of legumes, and the greater shading effect from a greater decrease in net assimilation rate, and to a lesser extent, from a smaller compensatory increase in leaf area ratio in the grasses athana ain the legumes. The greater sensitivity of net assiamilation rate of grasses to shading arose from a stronger dependence of the photosynthetic rate on illuminance. The significance of these findings for pasture productiona is discussed. Both tiller and runner production were dependent upon the total amount of radiant energy received by the plant, and in growth cabinet, at least, were independent of its intensity, duration and sequence.  alegumes  aphotosynthesis  aCrescimento  aFotossíntese  aProdutividade  aRespiração  aGrowth  aPastagem tropical  aProductivity  aTropical pasture1 aWILSON, G. L.1 aHESLEHURST, M. R.  tAustralian Journal of Agricultural Researchgv.25, p.425-433, 1974.