NEET Biology Notes Morphology of Flowering Plants Gynoecium
Gynoecium
Gynoecium
It consists of one or more carpels. Each carpel consists of ovary, style and stigma. Ovary contains ovules.
Style may be terminal (i.e. upright, arises on tip of ovary), lateral (i.e. arises from one lateral side on an ovary,
e.g. mango, strawberry) or gynobasic (i.e. arises directly from centre of ovary or from thalamus,
e.g. Ocimum and Salvia).
Gynoecium may be either monocarpellary (having single carpel, e.g. pea) bicarpellary (having two carpels, e.g. Funaria), tricarpellary (having three carpels,
e.g. Stellaria), tetracarpellary (having four carpels, e.g. Rhamnaceae), pentacarpellary (having five carpels, e.g. Melia) of multicarpellary (having many carpels, e.g. Papaver). In mustard [Brassica campestris), the carpel is unilocular (one chambered) but a false septum, called replum is present due to which carpel seems to be bicarpellary.
In Cucurbita (pumpkin), the carpel is unilocular but there are three false placenta, which grow inwardly and meet at the centre and then bend downwardly.
This leads a false tri-chambered or tri-locular situation. In apocarpous condition, carpels remain free from each other, e.g. Ranunculus, Aconitum, Clematis (Magnoliaceae), in contrast syncarpus is condition where carpels are fused, e.g. mustard (Cruciferae), China rose (Malvaceae).
Placentation
The mode of arrangement or distribution of placentae and ovules within ovary is called placentation. Based on the position on thalamus, ovary may be superior, semi-superior or inferior.
Position of Ovary on Thalamus
On the basis of position ovary is grouped into three categories, which are described below:
- Superior ovary Here, the ovary occupies the highest (superior) and central position on the thalamus, while the other floral whorls like androecium, petals and sepals are arised successively below it. Flowers containing superior ovary are called hypogynous flowers, e.g. Citrus, rose, butter cup, Stellaria, etc.
- Semi-superior or semi-inferior ovary This situation arises due to slight growth in the margins of thalamus. It leads to a disc-shaped thalamus as is seen in pea or cup-shaped thalamus e.g. rose. Flowers with this type of ovary are called superior flowers. In these flowers, the position of ovary on the thalamus is same with that of other floral whorls (androecium), sepals and petal
- Inferior ovary In this, the marginal growth of the thalamus has completed and it completely covers the ovary. Here, the position of ovary is inferior (lowermost), while the other whorls of flower like sepals, petals and androecium grow successively above the ovary.
- Flowers containing inferior ovary are called inferior flowers, e.g. coriander, carrot, apple, sunflower, Cucurbita, guava, etc.
