THE FLORAL NECTAR SECRETION IN MALE-STERILE CYBRID OF WINTER RAPESEED (BRASSICA-NAPUS L)

Floral nectar secretions of 5 male sterile cybrids of winter rapeseed (25, 58, 77, 85, 118) and the Darmor variety were compared after pipette collection and analysis of their sugar composition using high pressure liquid chromatography. The influence of various parameters was studied. Regarding the effect of time of collection (fig 1, table I): the nectar secretions at 8 am were more abundant (mean of 60%) and less concentrated (almost-equal-to 1/3) than those at 2 pm; the relative concentrations of each sugar (glucose, fructose) were similar at 8 am and 2 pm and close to 50%. Compared to Darmor, cybrids produced less nectar (50% less for 27, 58, 85 and 90% less for 77 and 118). Regarding the effect of the day of collection (fig 2, table II): on average, the secretions were more abundant on May 3rd than on April 15th (23% more). Independently of the day, Darmor secreted more than the cybrids (65-95% more). The dry matter (19.3-22.4 mg/100-mu-l) and the mean concentrations of each sugar (almost-equal-to 50%) were similar every day. Regarding the combined effect of the day and location (fig 3, tables III, IV): for every day location, secretions were similar within cybrids and lower than that in Darmor (54-58% less). Amounts secreted (2-4-mu-l on average) and total sugar amounts (almost-equal-to 15-40 mg/100-mu-l) differed according to day and location, whereas the relative concentrations of each sugar remained constant. Thus, although large fluctuations might occur in the amounts of nectar, the glucidic composition of the nectars appeared to remain constant in each cybrid and favorable for entomophilous pollination.