Plant Reproductive Structures - Ovules and Gametophytes

In seed plants, Ovule is the part of the female reproductive organ. It consists of three parts; Integument ( forming its outer layer) Embryo sac ( female gametophyte) and a Nucellus that is the central and largest part of the ovule as a source of nutrients for the embryo and its ploidy is diploid i.e 2n
Nucellus is derived from the apical portion of the ovule primordium of the ovule primordium and function as a megasporangium i.e, the nucellus produces the megasporocyte, which will undergo meiosis to form megaspores that is the reason that nucellus of the ovule is diploid in nature.
So, the nucellus of ovule is diploid.

So, the correct answer is 'Megasporangium'

The
ovule of flowering plants are located inside the gynoecium and are connected to
the placenta which is a parenchymatous tissue via a stalk-like structure called
the funiculus.

A. Female gametes are also called eggs or ovum. They are created during the cellular reproduction process known as meiosis. The resulting gamete cell is a haploid cell.

When in a flower, the internode between the corolla and the androecium is lengthened so as to raise the androecium high up in the air then that internode is called Androphore. It is an extension of the receptacle carrying the androecium and the gynoecium, typical of the caper family. In Passiflora, androphore is lightly differentiated.

When pollen tube enters through the micropyle, the phenomenon is known as porogamy. When pollen tube enters to the embryo sac through the tissue of the chalaza, the phenomenon is known as chalazogamy. When pollen tube enters through the base of a funiculus or the integument, the phenomenon is known as mesogamy. Isogamy is a form of sexual reproduction that involves fusion of gametes of similar size and structure. 

Ovule means 'small egg'. In seed plants, the ovule is the surface that gives rise to and contains the female reproductive cells. It consists of three parts: the integuments form its outer layers, the nucellus and female gametophyte in its center. The female gametophyte specifically termed as megagametophyte is also called the embryo sac in angiosperms.

The mature ovule contains in its central part a region called the nucellus that in turn contains an embryo sac with eight nuclei, each with one set of chromosomes. The two nuclei near the centre are referred to as polar nuclei. In the pines, the female gametophyte develops within the tissues of the nucellus and acquires abundant food reserves. The proembryo forms after a period of free-nuclear division in the zygote, and the tier of cells above the basal four then elongates to form a suspensor which pushes the embryonic group deep into the gametophyte.

Endothecium is defined as the lining of the inner cavity of the anther. It is present as a middle layer. 

The pollen tube ultimately enters an ovule through the micropyle and penetrates one of the sterile cells on either side of the egg ( synergids). These synergids begin to degenerate immediately after pollination. 
Synergids are haploid in nature. Thus, if root cell has 2n = 42, synergids will have n = 21.

The hilum is the point of attachment of funicle with the chalazal end. It is the point where ovule attaches to the base. It is generally present as an eye of the seed as it is present as a scar.

The ovules where micropyle come to lie close to the funiculus due to unilateral growth of the ovule are called anatropous. This is the most common type of ovule in angiosperms where the curvature of the ovule also affects the nucellus so that the later becomes horse shoe-shaped. The ovule is called amphitropous.

When funicle lies at right angle to body of ovule and micropyle, the ovule is called hemianatropous or body of ovule has rotated by $90^{o}$.

The nucellus is a part of the inner structure of the ovule, forming a layer of diploid (sporophytic) cells inside the integuments. It is structurally and functionally equivalent to the megasporangium. In some plants, the diploid tissue of the nucellus gives rise to a seed through a mechanism of asexual reproduction called nucellar embryony.

An ovule is a structure in seed plants that develops into a seed after fertilization. Botanically, it is defined as an integumented megasporangium.

• Campylotropous ovule- This type of ovule is similar to Anatropous ovule but the curvature is less than that of an anatropous ovule. Micropyle is near to the funiculus. Chalaza and micropyle lie in the straight line but hilum is at 90° to the micropyle.

In the ovule or megasporangium, during the process of megasporogenesis, a hypodermal cell functions as a archesporium cell and becomes more prominent because of large size, denser cytoplasm and large nucleus. In tenuinucellate ovules, archesporial cell directly functions as megaspore mother cell while in crassinucellate ovules, archesporial cell divides periclinally to form an outer parietal cell and inner primary sporogenous cell that functions as megaspore mother cell.

•Hemianatropous ovule- The body of ovule is turned through 90° and micropyle and chalaza lie in a straight line but funiculus is at right angle or 90° with both these two.

•Orthotropous ovule is the simplest and primitive type of ovule. In this type of ovule, micropyle, chalaza and funiculus lie in one vertical plane.

The placentas consists an enlarged basal portion which is called as ovary bearing one or more ovules also called as integumented megasporangium.

• Orthotropous ovule - The simplest and primitive type of ovule. In this type of ovule, micropyle, chalaza, and funiculus lie in one vertical plane. Examples: all gymnosperms, Polygonum.

The placenta is attached to the developing seed near hilum. It is the scar located nearthe edge where seed breaks from stalk of funiculus, i.e., connecting the seed with fruitwall and placenta. 

Ovule- The ovule is the structure that gives rise to and contains the female reproductive cells. The ovule is located inside the portion of the flower called the gynoecium.

In flowering plants, the functional megaspore undergoes mitotic divisions to form the female gametophyte, which is known as the embryo sac. The megaspore mother cell and pollen mother cell are earlier precursor stages, not the developmental product of the functional megaspore.

The ovule  develops into seed and ovary develops into fruit and seeds are enclosed within the fruit. Both are result of fertilisation in angiosperm plant. 

In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument(s), forming its outer layer(s), the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its centre.

Those ovules in which the funicle, chalaza and micropyle lie in one straight line are called orthotropous ovules. Example, Urticaceae.

Egg cell is inside the embryo sac in the ovule. The embryo sac is further enclosed by the parenchymatous tissue, nucellus, which provides nutrition to developing embryo. Nucellus is ultimately surrounded by integuments.

In seed plants, the ovule ("small egg") is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument(s) form its outer layer(s), the nucellus (or remnant of the megasporangium), and female gametophyte (formed from haploid megaspore) in its centre. Mature ovules i.e. megasporangia in angiosperms are mainly of five types. The principle of classification is based on the position of the micropyle, chalaza and hilum with regard to one another and also to the placenta.

The ovule is the structure that gives rise to and contains the female reproductive cells. The megaspore is produced inside the nucleus of the ovule. During megasporogenesis, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). After megasporogenesis, the megaspore develops into the female gametophyte (the embryo sac) in a process called megasporogenesis

The carpel is one of the leaflike, seed-bearing structures that constitute the innermost whorl of a flower. The seeds of flowering plants are enclosed inside an ovary which contains ovule. The ovary is part of a flower's female reproductive structure called a carpel. A flower can have one or more carpels. If there are many carpels, they can be separate or fused together. Together, all the carpels are called a gynoecium, or a pistil.

The synergid cell wall forming an extremely thick structure at the micropylar end is called the filiform apparatus. It bears several finger-like projections into the structure of synergid cytoplasm. The function of filiform apparatus is to guide entry of pollen tube and release of sperm cells.