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SUB-TOPIC 2: ARRANGEMENT OF REPRODUCTIVE ORGANS IN DIFFERENT PLANTS.
The rattle box (crotalaria retusa) which is a short dicotyledonous shrub flowers are found clustered together (inflorescences) at the end of the branches. Each bisexual flower is butterfly-shaped. The flowers are complete (has all the floral parts) and zygomorphic (bilateral symmetry)
Acanthus
The acanthus, commonly called bear’s breech, is cultivated for its ornamental leaves and bright flowers. The plant is native to southern Europe, preferring rich, well-drained soils and full sunlight.
In the Guinea grass (Panicum maximum) the flowers are wind pollinated unlike crotalaria which is insect pollinated. It is also inflorescence made up of long slender branches with a pair of flowers at intervals along each branch. The flowers are smell and inconspicuous. They are enclosed within a tract to form a spikelet about 4mm long.
Within the spikelet, the lower of the two flowers is made up of three yellow stamen. The upper flower has three stamens and an ovary with two feathery purple-red stigma. Each flower has two tiny structures called lodicules which represent a perianth. Some of the spikelets have protruding stamens whereas others have stigma. The flower is thus protandrous. The flowers with ripe stigma are therefore slightly older than those with ripe stamen. When ripened, the anther burst open releasing lots of tiny blown about by the wind.
Hibiscus Flower
The large, showy flowers of the hibiscus have five petals that range in color from red, orange, and pink to yellow and white. The many varieties of hibiscus grow in warm climates.
EVALUATION
- Draw to show the arrangement of flower of a named insect pollinated plant.
- State three (3) differences between the floral arrangements of and insect pollinated and a wind pollinated plants.
SUB-TOPIC 3: TYPE OF FLOWERS
Flowers can be classified based on the shape of the receptacle and the mode of arrangement of the floral parts on it.
- Hypogynous flower: in this type of flower, the receptacle is in a conical shape. The other floral parts (whorls) are then arranged in concentric rings below the position of the ovary. Such an ovary is said to be superior. An example is Hibiscus.
- Perigynous flower: in this type of flower, the receptacle is cup shaped with the ovary situated in the centre of the cup. The whorls then emerge from the edges of the cup. The ovary is then said to be half inferior. Example is Rose.
- Epigynous flower: the ovary is completely embedded in a fleshy receptacle so that all the other floral parts are above it.
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