Short essay on Pistil of Flower

It is the innermost and the female reproductive whorl of the flower. It is composed of one or more carpels or megasporophylls.

A carpel is simple or monocarpellary when it consists of a single carpel. This condition is the characteristics of family Fabaceae. But when it is made up of more than one carpel it is termed as compound or multi capillary.

Multi carepllary gynoecium may be apocarpous in which each carpel is free from the other or syncarpous when all the carpels are united forming a compound gynoecium. Apocarpous condition is found in Clematis, Ranunculus, etc., while syncarpous condition is seen in most angiosperms such as Brassica, Hibiscus, Datura, etc.

Among multicarepllary conditions, there are five types. This is based on the number of carpels. It may be bicarpellary (e.g., Mussaenda, Coriandrum) with two corpels, tricarpellary (e.g., Allium cepa) with three, tetra capillary (e.g., Datura, Berberis) with four, penta capillary (e.g., Melia, Hibiscus) with five and multi capillary, number of carpels more than five (e.g., Papaver). A typical carpel has three parts – ovary, style and stigma

(a) Ovary:

It is the lowermost swollen part containing one or more egg like bodies known as ovule. After fertilization, ovary transforms into fruit while ovules into seeds. So, ovules are the predecessor of seeds.

The position of the ovary with respect to other floral whorls and classified as superior, semi-inferior and inferior has already been discussed under thalamus.

Chambers in the ovary:

The ovary is only one chambered or unilocular in mono carepllary condition. Thus, in apocarpous ovary each free carpel would be unilocular. In syncarpous ovary, it may be bilocular (e.g., Solunum, Murraya, etc.), trilocular (e.g., Euphorbia, Musa, etc.), tetra ocular (e.g., Ocimum, Salvia, etc.), Pentalocular (e.g., Hibiscus, Geranium etc.) or multi ocular (e.g., Citrus, Melia, etc.)

The ovary contains ovules and the stalk of the ovule that attaches with the carpel is known as placenta.

Arrangement of ovules?

In different flowers the ovules are arranged differently with their placenta in the ovary in a characteristic definite manner which is called placentation. Different types of placentations as mentioned in Table 11.4 are shown in.

(b) Style:

The ovary protrudes to a small or long style. Style connects the ovary below and stigma above. It is usually terminal as it originates from the top of the ovary. In some Stigma (A) Sessile in Sambucus nigra; (B) Bifid in sunflower; (C) Bifid and feathery in rice; (D) Striate and sessile in poppy; (E) Highly branched in Begonia; (F) Funnel shaped in Crocus sativus cases, the ovary apex is deflected and the style appears to orginate from near the base (basal) or from the side (lateral), e.g., Alchemilla and mango.

Style may originate from the central depressed portion of the ovary and such condition is known as gynobasic as seen in the members of family Lamiaceae. The style is usually deciduous, but in some cases it is persistent, e.g., Naravelia, Clematis.

The style of Canna is petaloid. The base of the style may be swollen forming stylopodium as in the members of family Apiaceae. Sometimes, the style may be branched, e.g., members of family Euphorbiaceae.

(c) Stigma:

Stigma is present at the top of the style. Sometimes, when there is no style, the stigma is placed on the top of the ovary (e.g., Sambucus, Berberis, Lotus, etc.). In this case, it is termed as sessile. The stigma is commonly rough or hairy and sticky due to secretions. In China rose, stigmas are separated while it is bifid in Asteraceae.

The number of lobes of stigma may correspond to the number of carpels. Monocarellary flower of family Poaeeae shows exceptions having bifid and feathery stigmas.

The stigma I of Papaver is sessile as well as striate giving star like appearance. The stigma is branched] in Begonia. The three stimgas of Crocus have funneled shaped forms. The different types of stigmas as discussed above are given in.