THE POSSIBLE ROLE OF EMBRYO SAC DEGENERATION IN YIELD REDUCTION OF SUMMER TURNIP RAPE CULTIVAR CANDLE

When pollination occurred within 24 h after anthesis, 69.2% of the pod s of Brassica rapa cultivar Candle contained at least 50% fertilized o vules. If pollination occurred later than 4 d after anthesis, an occas ional ovule near the base of the pistil was fertilized; however, no si gnificant seed set was observed. Pollen tubes were observed entering t he locules of the ovary from pollinations carried out as late as 5 d a fter anthesis. At 3 d after anthesis, in unpollinated flowers, a gener al deterioration of the embryo-sac contents began and gradually increa sed to include integumentary cells by 6 d after anthesis. Some ovules swelled as though they were fertilized, but no embryos were present. T he results suggest that yield reductions in this species may occur bec ause of the reduction of fertilization potential through rapid degener ation of embryo sacs following anthesis.