POLLEN DEPOSITION BY BOMBUS-TERRESTRIS L, BETWEEN MALE-FERTILE AND MALE-STERILE PLANTS IN VICIA-FABA L

We have studied pollen transfer by Bombus terrestris from a male-fertile line (D-27) to a male-sterile line (INRA Ad 23) of Viola faba. Studies on visitation sequences were conducted with single workers visiting caged plants. The average pollen production was 24 200 +/- 2 000 grains per flower, and the pollen carried on the head and thorax of a worker after visiting 10 male-fertile flowers ranged between 1 620 +/- 300 and 6 300 +/- 400 grains. Of 21 workers, only 11 foraged on male-sterile flowers. The total amount of pollen deposited on stigmas by a single worker was on average 55 grains. A total of 67% visited flowers received no grains at all on the stigma. The size of non-null stigma loads ranged from 1 to 152 grains, but frequency of small deposits (1-10 grains) was high (78%). Runs varied greatly in visitation sequence length and pollen deposition patterns on successively visited flowers, which were not always monotonically decreasing. Statistical analysis by Monte-Carlo tests has provided a good method for studying sequences.