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pollination services

    Sunflower

Below is an extract from a pollination research paper prepared by the Rural Industries Research and Development Corporation (RIRDC).  To download the document, simply click on the image on the left of this screen.

Most sunflower cultivars are self-incompatible meaning that for successful pollination, pollen must come from another plant.  However, if pollen from a floret is transferred to the receptive stigma of another flower on the same head then seed will set.  When self-pollination (within the same head) occurs, seed set is usually low, the seed undersized, and oil content and germination are reduced.  McGregor (1976) also found that selfed seed sprouts more slowly, and production is lower than plants derived from crossed seed.

Several studies comparing seed yield and weight in sunflower heads exposed to bees and heads bagged to exclude bees have demonstrated the importance of bee pollination in the sunflower industry (Degrandi-Hoffman and Chambers 2006; Krause and Wilson 1981; Langridge and Goodman 1974).  Degrandi-Hoffman and Chambers (2006) found a significantly greater seed set and seed weight in flower heads that were exposed to bees compared to those that were not.  Krause and Wilson (1981) also found greater seed numbers and weight in exposed heads but no significant differences in oil content between bagged and unbagged heads.  An earlier study by Langridge and Goodman (1974) in northern Victoria found that plots to which bees had access produced in excess of 60% more seed than plots from which bees were excluded.  Seeds set per cm2 of flower head, the percentage germination and the oil content of seed from plots serviced by bees were also significantly greater than from plots without bees (Langridge and Goodman 1974).

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