Gynoecium: structure - placentation - ovule structure

Structure of Gynoecium

The gynoecium is composed of one or more carpels. The gynoecium may be simple (consisting of one carpel) or complex (consisting of two or more carpels). Compound gynoecium may have loose carpels (Apocarpous), as in “lotus,” “rose,” “magnolia,” etc., or they may be joined with carpels (Syncarpous), as in “Watermelon.” , “zucchini,” “cucumber,” etc
The gynoecium consists of three parts - the stigma, the style, and the ovary. The ovary contains one or more egg-like, oval or semi-round bodies that represent the beginning of the seed, known as ovules. Each egg contains a large oval cell known as the embryonic sac. Sometimes the gynoecium is sterile (Pistillode). The style connects to the ovary, and the connection may be peripheral, lateral, or basal. The basal style arises from a central depression in the middle of a four-lobed ovary, and it appears as if it emerges directly from the base of the ovary, as in the “labial” family. At the top of the style, there is a stigma on which the pollen grains shed, and they grow. if they are pollen grains of the same type, and give rise to the pollen tube that penetrates the pen to reach the ovary, where the fertilization process takes place.
For more information Gynoecium watch the attached video and read the attached reference.

Structure of Ovary

It is inferred from a flower that consists of only one carpel, such as a “pea” flower, a “bean” flower, a “chickpea” flower, etc., that the ovary is a modified leaf. It bents along its middle vein, and its two edges met and merged, forming one room. The fusion area is known as the ventral suture, and the middle vein along which it folds is known as the dorsal suture. On the ventral side, a protrusion of tissue known as the placenta arises, which carries the eggs. The ovary is formed with separate carpels in the previous manner. while the ovary is fused with carpels. the carpels are united by their edges only,. forming a single-chambered ovary, as in “orchids,” “paws,” etc. Or it may fold inward, and its edges meet in the center, forming a multi-chambered ovary with a central axis, as in “Iris,” “Chinese rose,” etc. In gymnosperms, the carpels remain flat, and the ovules develop naked along the open carpel edges. Here the stigma, the pen, and the ovary are absent.
The carpels may be fused either along their length, as in most of Syncarpous Carpels; They may be united in one area only. Some carpels are fused in the ovary area only, such as the carpels of “clove,” “Flax,” and “Plumbago”. Some of them are fused in the ovary and style area, such as the “Cotton” and “China Rose”. Others are fused in the style and stigma area, such as the “ Vinca herbacea” and “Oleander”. Some are fused in the stigma area (and partly the style), as in “Al-Ashar.”
Defining the numbers of carpels in Syncarpous Carpel
In fused carpels, the number of carpels is difficult to determine. To infer the number of carpels in an ovary that is fused with carpels. we determine (1) the number of stigmas or stigmatic lobes. (2) Number of styles. (3) number of ovary lobes. (4) Number of ovarian chambers. (5) number of placentas in the ovary. (6) The number of egg groups in the ovary. In most cases, the number of previous components corresponds to the number of carpels.

Placentation‎

Each ovule -within the ovary - is born by a placenta or arises as a ‎continuation of the floral apex. Often, the placentas occur in distinct ‎lines called lines of placentation. Each ovary of monocarpous and apocarpous ‎gynoecia has a single line of placentation. In syncarpous gynoecia, the placentation line can be ‎regularly spaced along the wall of the ovary (parietal placentation). O near the center of the ovary. In the latter case, separate terms ‎are used depending on whether or not the ovary is divided into ‎separate locules. If the ovary is divided, with the ovules born on a ‎line of placentation at the inner angle of each locule, this is axile ‎placentation. An ovary with free central placentation, on the other ‎hand, consists of a single compartment without septae and the ‎ovules are attached to a central column that arises directly from ‎the floral apex (axis). In some cases a single ovule is attached to ‎the bottom or top of 7 (Plant Placentaion).

Structure of Ovules

The egg is connected to the placenta by a cylindrical stalk known as (1) the funiculus. The point where the egg body connects to its stem or funiculus (2) is known as the funiculus In the inverted egg , the funiculus extends behind the navel along the body of the egg, forming a protrusion known (3) as the raphe. The upper end of the fusion forms the area of contact between the egg envelope and the nucellus, which is known (4) as the chalaza. Surrounding (5) the nucellus - the body of the egg - are two covers called (6) integuments. But in some families with separate corollas, there is only one cover. In parasitic plants, such as: "Sandalwood" and "Laurenthus", the covers are completely absent. At the top of the covers there is a small opening, known as the hilum (7). Finally, in the nucellus, towards the hilar end, there is a large egg cell, known (8) as the embryonic sac, that is, the sac that carries the embryo, and is considered the important part of the egg (Structure of Ovule).

For more information on placentation in the ovary of plant watch the attached video.

References

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/gynoecium