Growth of axillary buds of Brussels sprouts (Brassica oleraceavar.bullatasub var.gemmifera)

Abstract

SUMMARYIn 1984 and 1985, the growth of axillary buds of Brussels sprouts plants was studied at Cockle Park, Northumberland, UK. Bud growth commenced in late September or early October and continued at all nodes until the final harvest in December. Total bud yield increased at a broadly constant rate until late November but at a decreasing rate thereafter. Plants producedc.100 nodes with buds ≥ 5 mm diameter. The largest buds werec.40 mm diameter and 25 g fresh weight. Bud size increased from the base of the stem upwards to between the 20th and 40th nodes and then decreased towards the apex. Nodes 20–40 (20% of the total) producedc.40–45% of total bud yield. The size profile of leaves along the stem followed a similar pattern to the buds and the largest buds were in the axils of the largest leaves. There were close relationships between bud fresh weight and size,bud fresh weight and size, bud fresh weight and volume and log10bud fresh weight and log10bud size (r2≥ 0·995). The density of buds wasc.0·8 and bud fresh weight doubled for each 5 mm increase in bud diameter.Current photosynthesis of the leaf canopy was apparently the major source of assimilates for bud growth. A C14tracing experiment suggested that growth of individual buds was mainly supported by their subtending leaves. There was no evidence of re-translocation of dry matter from dying leaves or the stems to buds or of substantial production of dry matter by the buds themselves. Rates of bud photosynthesis were only about 10% of the rate of leaves. The continued increase in bud fresh weight and size at the lowest nodes when leaves were senescing rapidly and after they had abscissed was probably mainly the result of water uptake rather than dry matter accumulation.