Gynoecium also refers as “Carpel” or “Pistil” which primarily consist of three structures, namely stigma, style and ovary. It is the female reproductive part of the flower which carries the female gametes or ovules within an ovary. On the base of the gynoecium, pedicle or thalamus is present which provides support to the female reproductive part and the other parts as well. To the thalamus, an ovary is attached, which appears as a whorl, and it gives rise to the formation of egg cells after the fertilization process.
An ovary contains one or multiple chambers and also bears one or more ovules attached to the placenta. After double fertilization, an ovary develops into a fruit and the wall of an ovary forms a fruit tissue refers as “Pericarp”.
Ovary protrudes into a long, slender, filamentous structure refers as “Style” which connects the stigma to the ovary. Style acts as a transmitting track where it helps in the passage of pollen grains from the stigma to the ovary. On top of style, sticky stigma is present, which traps the pollen grains and allow it to enter inside the ovary to carry out the process of fertilization.
Content: Gynoecium
Definition of Gynoecium
A gynoecium can define as the term for the female reproductive structure of flower, which consists of three structures like stigma, style and ovary, and collectively refers as “Carpel”. A carpel can define as the unit of the gynoecium, which is usually the modified leaf structure. Gynoecium refers as the female reproductive unit because it bears ovule which on fusion with the pollen grain (Male gamete) forms the egg cells.
Types
A gynoecium can be of three types:
- Monocarpous
- Apocarpous
- Syncarpous
When a gynoecium consists of a single carpel, then it refers as “Monocarpous” or “Unicarpellate gynoecium”.
Examples: Avocado, peach etc.
When a gynoecium consists of multiple and distinct carpels, then it refers as “Apocarpous” or “Chloricarpous gynoecium”.
Examples: Strawberry, buttercup, michelia etc.
When a gynoecium consists of multiple and fused carpels, it refers as “Syncarpous gynoecium”.
Examples: Tulip, china rose etc.
Gynoecium Structure
The gynoecium is the innermost whorl of a typical flower which mainly bears three parts, namely, stigma, style and ovary.
Stigma
It is a topmost part of the female reproductive unit of a flower, which remains exposed to the air and other elements. A stigma commonly also refers to as the “Head of pistil”. The surface of the stigma can be sticky, hairy, smooth, rough etc. Due to its viscous nature, it can easily catch the pollen grains of the male productive system or “Androecium”.
A stigma provides a platform for the attachment of the pollen grains. Thus, it plays a crucial role by promoting the process of “Pollination”. Stigma can show a wide range of shapes from simple to lobed, feathery, funnel-shaped, branched etc.
Stigma is composed of stigmatic tissue and a single-layered elongated papillary cell. The elongated papillary cells also refer as “Stigmatic papillae” which acts as a receptor for the attachment of pollen grains. Thus it performs the following functions like:
- Pollen adhesion
- Recognition of pollen grains
- Germination of the pollen grains
- Begins the process of fertilization
- Prevents entry of the pollen grains from the different plant’s species
Stigma also consists of a tissue, enriched with extracellular polysaccharide matrix refers as the “Transmitting tissue”. The transmitting tissue assists the growing pollen tube present towards an ovule.
Based on location, when a stigma is directly present on the top of the ovary, then it is termed as Sessile stigma.
Examples: Sambucus, Berberit, Lotus etc.
A stigma remains free or separated in the syncarpous gynoecium. Sometimes, stigma can be lobed, bilobed/bifid (Compositae family), trifid etc. Some are branched like the begonia species, and few are funnel-shaped like crocus species.
Style
It is a stalk-like and a filamentous structure which acts as the joining element between stigma and an ovary. When pollen falls onto the stigma, it starts travelling down through the structure refers as style. A style originates from the basal whorl, i.e. Ovary.
When style originates from the central base of the ovary, it refers as “Gynobasic”. Sometimes, these present at the right angle to an ovary axis. In a few flowers, the base of the style is slightly swollen and refers as “Stylopodium” which generally seen in the members belong to the family of Umbelliferae.
A style is sometimes branched and free, like in the members of the family Euphorbiaceae. It acts as a “Transmitting track” made of transmitting tissue where the pollen tubes grow.
Ovary
It is the most crucial part of the gynoecium which contains the female gametes refers to as “Ovule”. If a gynoecium, lacks the part of the ovary, then it is meant to be sterile or parthenogenic. A pollen grain travels down from the style to the ovary and fuses with the ovule or megasporangia, to bring about the process of fertilization.
It encloses and protects the megasporangia that carry the megaspores. Ovary also provides nourishment to the developing ovule through the placental wall.
Classification of Ovary
An ovary can classify into the following three types, with respect to its position in the flower.
Superior ovary: This kind of ovary is present above the attachment of the other flower parts. A flower consists of superior ovary refers as “Hypogynous flower”.
Example: Mustard
Inferior ovary: This kind of ovary is present below the insertion of the other flower parts. A flower comprises of inferior ovary refers as “Epigynous flower”.
Example: Coriandrum
Semi inferior ovary: This kind of ovary is present between the insertion of the other flower parts. A flower comprises of semi-inferior ovary refers as “Perigynous flower”.
Example: Pea
According to the number of chambers or locules, an ovary can classify into the following types:
Unilocular: In this type, an ovary consists of a single chamber. Example: Pea
Bilocular: In this type, an ovary consists of two locules. Example: Petunia
Trilocular: In this type, an ovary consists of three locules. Example: Asphodelus
Tetralocular: In this type, an ovary consists of four chambers. Example: Ocimum
Pentalocular: In this type, an ovary comprises five locules. Example: Shoe-flower
Ovules also refer as “Megasporangium” that is located innermost to the ovary and destined to grow into a seed upon fertilization. Ovule attaches to the placenta by the funicle. When an ovule gets lacks a funicle and gets directly connected to the placenta, then refer as “Sessile”. An ovule composes of the nucellus tissue, which encloses by the two integuments (inner and outer).