Analysis of post-flowering compensatory growth in winter oilseed rape (Brassica napus)

Abstract

SUMMARYPatterns of assimilate distribution in single plants of winter oilseed rape (Brassica napus L.) cv. Mikado, following a reduction in sink capacity at flowering were investigated in two field experiments during the 1985/86 and 1986/87 growing seasons at Cockle Park Experimental Station, Northumberland. Plants demonstrated considerable compensatory growth following the removal of flowers from the terminal raceme and primary branches.Flower removal from lower branches did not significantly reduce total seed weight. Plants with a pod-bearing terminal raceme and one, two or three productive higher-order branches yielded a similar amount of seed. When seed production was confined to the terminal raceme and first four primary branches, seed yield per plant was greatly increased. Removal of flowers from the terminal raceme and uppermost branches of plants increased the number and productivity of lower-order branches but not enough to offset the overall loss in seed yield potential per plant. Indeed, when flowers were removed from higher-order racemes, the reduction in total seed weight per plant, was directly related to the degree of flower removal. The additional seed yield obtained from individual branches of modified plants in both experiments arose largely through an increase in fertile pod number and seed number per pod. Flower removal treatments did not greatly influence mean seed weight.The results clearly demonstrated that the loss of flowers from lower-order branches could be tolerated and may even be beneficial. Conversely, the removal of flowers from higher-order branches resulted in significant yield reductions. The production of lower branches should be restricted, therefore, in order to increase the superiority of the terminal raceme and uppermost branches and to increase the overall production efficiency of the crop canopy.