| Abstract: | The competitive effects of varying the density on the developmentof Vicia faba have been studied in a series of multifactorialexperiments where the spacing both between and within rows wassimultaneously altered. Over densities ranging from 11 to 67plants per metre2 seed production on an area basis tended tobe maximal at 35–45 plants per metre2 in the winter typeand at the highest density for the spring type. As the densityincreased the number of pods per plant and the extent of branchingfell progressively but there was no appreciable change in eitherseed size or the number of seeds per pod: thus seed productionwas solely governed by the number of mature pods formed. Thenumber of flowers per plant was more dependent on the numberof inflorescences than on the number of flowers per inflorescence.Increasing the population diminished the number of nodes bearinginflorescences particularly in the upper part of the shoot,while the size of the inflorescence was decreased to a lesserextent. The number of flowers forming mature pods was very small(9–14 per cent.). At the top of the shoot the flowerswere infertile, while above the middle node most of the podsformed were shed while still immature. Thus the primary effectof increasing density was to depress the number of nodes onthe lower half of the stems which produced mature pods. By thetime the flowering stage was reached plant height was alreadycorrelated with density due more to a change in internode lengththan an alteration in the number of differentiated nodes; atmaturity the differences in height were smaller due to the greaternumber of nodes in the widely spaced plants. For a given density,alterations in the distance between rows had little influenceon development. The possible physiological factors responsiblefor the changing pattern of development brought about by varyingdensity are discussed. |
