01749naa a2200229 a 450000100080000000500110000800800410001910000180006024500870007826000090016552011500017465000170132465000160134165000120135765000170136965000150138665000180140165000180141965000100143765000150144777300570146216462812023-04-20       1958    bl uuuu     u00u1 u    #d1 aWATSON, D. J.  aThe dependence of net assimilation rate on leaf-area index.h[electronic resource]  c1958  aThe leaf-area index (leaf area por unit area of land, L) of field crops of kale and sugar-beet was varied experimentally by removing different fractions of the plant population distributed iniformly through the crop. The net assimilation rate (E) was determined in susequent periods of Io-14 days. For kale, E decreased nearly linearly with increase of L throughout the range fron i to 5. E of sugar-beet was less affected by change in L and was apparently not decreased until L rose above about 3. Because of this dependence of E on L, the rate of dry-matter production per unit area of land, or crop growth-rate (C = EL), showeda curved relation to L; for kale it increased to a maximum when L was between 3 and 4 and fell again at higher values of L. Maximal C for suar-beet crops problaby lies near the upper limit of the current agricultural range, so there is little, if any, scope for increasing the dry-matter yiel by further increase in L. For heavy kale crops L is already far in excess of the optimum, and it may be possible to increase the total dry-matter yield of kale by repeated thinning or defoliation to hold L near the optmum.  aÁrea Foliar  aCrescimento  aDoença  aFertilizante  aFisiologia  aFotossíntese  aMatéria Seca  aPraga  aProdução  tAnnals of Botany, Oxfordgv.22, n.85, p.37-54, 1958.