Reproduction of Sunflower

Flowers are borne on a fairly standard Asteraceae capitulum of 700-8,000 individual florets. Disk flowers are perfect; ray flowers are sterile with a rudimentary pistil. Disk flowers within a single capitultum open centripetally for a period of 5-10 days or more; each capitulum may have, depending on timing, a central portion of unopened buds, surrounded by a ring of florets with exposed stamens, another ring of florets with exposed stigmas, and finally a ring of pollinated florets. On the morning of anthesis of an individual floret, the sta mens elongate and shed pollen inward. Later that day, the style elongates and by the following morning presents a receptive stigma above the stamens with pollen brushed upward by stigma hairs. At this stage pollination of the stigma occurs. Removal of fertile flower parts at various stages, insect pollination, self-incompatibility, and male sterility alter the above pollination outline and can be used in breeding programs. Pollen can be moved physically from one flower to another, but movement of the large spiny grains by wind cannot occur farther than a few feet.

Traditional cultivars have been maintained as open pollinating populations, but more recent breeding approaches have involved hybrids dependent on male sterility/restorer systems introduced from wild Helianthus species.

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