1. Apomixis is a form of asexual reproduction that mimics sexual reproduction and seeds are formed without fertilisation.
2. Apomictic embryos are genetically identical to the female parent.
3. If hybrid seeds can be made apomictic, the desirable characters can be maintained in the progeny.
4. It is often associated with polyembrony.

Parthenocarpy.

One

There is an adaptation in angiospermic plants to provide assured nutrition to the developing embryo. Most zygotes divide only after certain amount of endosperm is formed. Therefore, zygote remains dormant for sometime in a fertilised ovule.

1. Male gametophyte - In the Anther (microsporangia) and later on the stigma and style.
2. Female gametophyte - inside the ovule.

Tapetum is the innermost layer of the microsporangium. It produces the exine layer of the pollen grains, which is composed of the sporopollenin, the most resistant organic material. During microsporogenesis, the cells of tapetum produce various enzymes, hormones, amino acids and other nutritious materials required for the development of pollen grains.

Triple fusion:
It is  the process of fusion of three nuclei, two polar nuclei (fuse to form a diploid secondary nucleus) and a male gamete.
It occurs in the central cell of the embryo sac of the ovule of angiosperms.
Then nuclei involved are two polar nuclei and a male gamete.

(a) (i) In the mature embryo sac of an angiosperm, two polar nuclei in the central cell fuse to form a diploid secondary nucleus.
(ii) During fertilisation, one of the male gametes fuses with the secondary nucleus to form a triploid primary endosperm nucleus (PEN); the central cell is now called primary endosperm cell (PEC).
(iii) Since, three nuclei triple fusion.
(b)(i) The primary endosperm nucleus of the primary endosperm cell undergoes repeated mitotic divisions, to give rise to a number of free nuclei; at this stage, the endosperm is called free nuclear endosperm.
(ii) Subsequently, cell wall formation starts from the periphery and the endosperm becomes cellular.
(iii) The water in the tender coconut represents the nuclear endosperm, while the white kernel represents the cellular endosperm.

(i) In coconut, endosperm formation is of nuclear type. The primary endosperm nucleus undergoes repeated nuclear division without cell wall formation.
(ii) Tender coconut is an endosperm. It is rich in nutrients like fats, proteins, carbohydrates, minerals, vitamins, etc. Hence, it is considered as a healthy source of nutrition.
(iii) Pea seeds are non-endospermic, while castor seeds are endospermic.

(i)

(ii)

(iii)

(iv)

1. The ovule is attached to the placenta by a short stalk called funiculus.
2. The junction between the funiculus and the ovule, is called hilum.
3. The primordium of the ovule grows into a mass of cells, forming the nucellus, the main body of the ovule.
4. It becomes surrounded by two protective envelopes called integuments, which leave a small opening called micropyle, at the tip of the ovule.
5. The basal part of the ovule (opposite to the micropyle) is called chalaza. Cells of the nucellus are rich in reserve food materials.
6. There is a single embryo sac/female gametophyte in the nucellus; it has developed from a megaspore.
7. The embryo sac contains the following cells:
(i) Three antipodal cells at the chalazal end.
(ii) Three cells at the micropylar end, forming egg apparatus, which consists of two synergids and a female gamete.
(iii) Two nuclei in the central cell, called polar nuclei, which fuse to form a diploid secondary nucleus.

Meiosis occurs during sporogenesis.
The structure formed at the end are microspores and megaspores respectively.

(a) Syngamy
Syngamy refers to the fusion of a male gamete with the female gamete in the embryo sac to form a diploid zygote.
Triple fusion
Triple fusion refers to the fusion of a male gamete with the secondary nucleus (formed by fusion of two haploid polar nuclei) to form the triploid primary endosperm nucleus.
(b) Embryo development
Th'e zygote undergoes mitotic divisions during embryogeny.
The first division is transverse and results in a basal cell and a terminal cell; the basal cell forms the suspensor while the terminal cell forms the embryo proper.
It first, forms a filamentous proembryo, which later forms in sequence a globular embryo, heart-shaped embryo and then a mature embryo.

(a) Differences: 

(b) Pollen-Pistil Interaction.
The stigma/pistil has the ability to recognise the right type of pollen, i.e. the compatible pollen of the same species and rejects the wrong type of pollen grains.
It is the result of interaction between the chemical components of the pollen and those of stigma. - A compatible pollen grain starts its germination on the stigma.
The intine grows out through one of the germ pores as a protuberance.
The contents of the pollen move into this tube, i.e. the tube nucleus (nucleus of the vegetative cell) and the generative cell (or the two male gametes in those species where pollen is liberated in the three-celled stage).
The pollen tube grows through the tissues of stigma and style and enters the ovule through micropyle.
It enters the embryo sac through the filiform apparatus of one of the synergids to liberate the male gametes.
The events from the deposition of pollen on the stigma till the pollen tube enters the ovule, are collectively referred to as pollen-pistil interaction.

(a) Megasporangium
(b) (i) G. Funicle
(ii) B. Nucellus
(iii) E. Outer integument
(iv) A. Chalaza
(v)  C. Embryo sac.

(a) Similarity
(i) Both are multicarpellary.
Difference
(i) A. Papaver is syncarpous - all the carpels have fused together.
(ii) B. Michelia is apocarpous - the carpels are free.
(b) Ovary, style and stigma are the three parts of a pistil.

(a) (i) Pollen grains of cereals (rice, wheat, etc.) lose viability within 30 minutes after release.
(ii) Pollen grains of members of Leguminosae, Rosaceae and Solanaceae remain viable for many months.
(b) Humidity and temperature.

(b) Placenta is a ridge of tissue in the inner wall of the ovary bearing one or more ovules and the manner of distribution of the placenta within the ovary is called placentation

(b) Both assertion and reason are true but reason is not the correct explanation of assertion

(b) Mostly all the four spores within a tetrad are completely isolated from one another and from the spores in other tetrads of the locule. Usually the microspores separate from one another shortly after meiosis. However, in some plants the spores tend to remain together in tetrads for longer period and develop into compound pollen grains. In many members of Orchidaceae and Asclepiadaceae all the microspores in a sporangium remains together to form what is called a pollinium.

(b) Both assertion and reason are true but reason is not the correct explanation of assertion.

(d) Perisperm is unused nucellus in the seed. It is often non-functional for seed. Pericarp is the covering of fruit that develops from ovary wall. It is protective covering and also helps in dispersal and nutrition.