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POLLINATION by Wayne Handlos   (Photos by Wayne Handlos)

1.   2.   3.   4.

1.Sepals           2.Sepals/petals       3.Stamens          4.Stigma

5.  6.   7.

            5. & 6. Pollen grains on stigma lobe                7. Seed with coiled tip

The flower’s various parts have different functions. The sepals are generally regarded

as protective structures – enclosing the other floral parts, hiding or camouflaging the

developing flower because of their green color, as well as protecting these more delicate

structures from drying out.

The petals, when they expand and are finally exposed, are usually colored to some degree

or other. In the geranium family, lavender-pinkish flowers would seem to be most common;

white, cream or ivory are found among many of the species, while red (though it is the most

frequently seen color amongst the common bedding geraniums) is relatively rare amongst

the species. Lavender, pink and white are colors that bees see easily – while red is not

recognized by most bees, it is attractive to birds and some butterflies. Blue is not found

among the flowers of Pelargonium species, though blue and bluish flowers are found in a

number of species and cultivars of the related genus Geranium. Again the blue wavelengths

of light are readily seen by most bees.

So, what are the bees, birds and butterflies doing in the flowers? After seeing a flower, the

bee, bird or butterfly regularly goes in search of food usually nectar (a source of sugar) or pollen

(which contains various nutrients including oils and protein).

The pollen, as noted, is produced by the stamens – specifically within the anthers. Nectar,

in Pelargonium flowers, is produced in a nectar tube within the hypanthium which is the

fused bases of sepals, petals, and stamens.

When a bee, bird or butterfly is moving around in or on the flower, pollen may be picked up on the insect’s

body and can be transferred to the sticky surface of the stigma of the same flower (self-pollination) or a different

flower (cross-pollination).

When the pollen grains touch the stigma, they send out a tube which grows down the style and ultimately reaches

the ovary containing the ovules or potential seeds. If all these steps are successful a nucleus from the pollen tube

unites with a nucleus in an egg cell in an ovule. The fusion of the male nucleus (from the pollen grain) with a female

nucleus (in an egg cell in an ovule) results in an incipient new individual called a zygote. Upon further development

the zygote grows into a small plant held within a seed. The small plant consists of two simple leaves (it’s a dicot), a

shoot apex, a short stem and a root.

When an ovary is mature in a Pelargonium flower, it may contain five seeds, each with a twisted "tail" and some

feathery hairs. The ovary breaks apart and the seeds are released. In Pelargonium, the seed leaves (also called

cotyledons) are often green and the little plant is ready to grow as soon as water enters the seed. In nature, this may

not happen for years – but if you open the seed coat the embryonic plants is ready to begin growth immediately.



 

 

© 2017, Central Coast Geranium Society (CCGS )