Pollen Deposition Rate Effects on Seed Set in Meadowfoam
Meadowfoam (Limnanthes alba Hartweg ex Benth. cv. Mermaid) is an entomophilous, winter-annuai oilseed crop that typically produces an average of only two out of five potential seeds per flower. This study was conducted to determine whether improved pollination enhances seed set of this new crop. In the field, 1, 6, and 11 honey bee (Apis mellifera L.) visits per flower resulted in 1.6, 2.3, and 3.3 seeds per flower, respectively. In later pollen deposition studies, one and six honey bee visits per flower deposited an average of 15 and 43 pollen grains per five stigmatic papillae (FSP) per flower, respectively, in 1988, and 22 and 47 pollen grains per FSP, respectively, in 1989. Hand-applied pollen deposition treatments were studied in a greenhouse to investigate the cause of these flowervisitation responses. Seeds per flower increased linearly (b = 0.086) in the range of 5 to 25 pollen grains deposited per receptive FSP. Seed set was 4.1 seeds (out of five potential seeds per flower) with 25 pollen grains per FSP. Although the greenhouse results cannot be directly extrapolated to the field, these data suggest that multiple honey bee visits to meadowfoam flowers are required for maximum pollination and seed set to occur.
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