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Afrikaanse Inligting
Protea Flowers versus Protea Flowerheads
The
classification of plants is based largely on the shape of flowers and the protea
flower must rank as one of the easiest to identify.
The secret is to ensure that you are looking at a flower, and not the flowerhead - which is composed of many flowers together with some colourful bracts. It is a feature of southern African proteas, together with daisies, that the flowers are grouped into large heads which many mistake for flowers.
Unlike the majority of flowering plants, protea flowers do not have separate sepals and petals. Instead, there is only one set of four perianth segments (called tepals). This is most unusual and is an important diagnostic feature. In the bud these segments abutt one another, but never overlap. As the bud opens the four tepals separate and curl back to expose the style (the stalk of the female organs). The manner in which the tepals separate, and how much of the lower portions remain fused to form a tube are characteristics of the different genera.
The male organs (anthers) of proteas are also distinctive. The anthers do not have long stalks (filaments), but are joined directly to near the top of the tepals. Unlike most other plants, the anthers shed their pollen onto the topmost portion of the style just before the flowers open. Because the style presents the pollen in a position suitable for placing onto any visitor, the top-most portion of the style is called the pollen-presenter. The presence of a pollen-presenter is another diagnostic feature for proteas. In order to ensure adequate transfer of pollen to pollinators, the pollen-presenter is often elaborately shaped.
The female organs of protea flowers are similar to other flowers, consisting of the stigma, style and ovary. The ovary is superior (not enveloped by or fused with the tepals) and contains 1 ovule in all southern African species. The style is a long thin stalk, modified at the tip to form a pollen-presenter. The stigma is a tiny groove, situated at the top of the pollen-presenter, and is dry and seldom sticky.
Four minute floral nectaries may be situated at the base of the ovary, between the ovary and the tepal bases. These secrete nectar to attract pollinators. These always alternate with the tepals, and may be all that remains of the petals. Below each flower is the floral bract, situated either adjacent to stalkless flowers or on the flower stalk.
The ovary develops into the small dry fruit, each containing 1 seed. The fruit is often incorrectly considered a seed.
The situation is more complicated in those genera which have sexes separated onto different plants, because female features are absent in male flowers and vice versa. However, all the Proteaceous features are still prominent.
Other features characteristic of the Protea Family are that none of its members are herbaceous - all are woody shrubs or trees, although some have underground stems or sprawl on the ground. The wood of proteas is also characteristic, having long medullary rays which give it a "silky" appearance. The leaves are sclerophyllous - hard and leathery, snapping rather than folding over when bent - and are either entire or dissected into needle-like lobes.
In the southern African proteas the manner in which flowers are grouped into flower-heads allows the ready recognition of different genera.
Tony Rebelo
Have a look at Examples of Flowers and Flowerheads for the Proteaceae Genera.
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