Self-incompatibility
It is the third device to prevent inbreeding. It is a genetic phenomenon of preventing the pollen from fertilising ovules of the same flower by inhibiting pollen germination or pollen tube growth in the pistil.

1. Chasmogamous flowers are the bisexual, open flowers with exposed anthers and stigma. 
2. Cross-pollination cannot occur in cleistogamous flowers because they remain in bud throughout their life and form seeds via self-pollination.

X-Meiosis (reduction division), A-Mitosis
B-Mitosis, C-Mitosis,
D-Cells reorganised as polar nuclei, antipodals and egg apparatus.

Bottle gourd is unisexual plant and only plant with female reproductive plant can bear fruits.

Mango has only one ovule (apocarpous ovary) while orange has many ovule (syncarpous ovary)

Parthenocarpy.

One

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

(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.

(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) Development of Pollen grain:
   - Microsporocytes undergo mitotic divisions to increase the number of functional microspore mother cells.
   - Each microspore mother cell undergoes meiosis to form a microspore tetrad.
   - All the four microspores remain enclosed in a common wall.
   - They start separating from each other.
   - The nucleus undergoes a mitotic division resulting in the formation of a large vegetative cell and a small generative cell.
   - The spore develops a wall of two layers the outer- exine and inner intine.
   - At this stage, the pollen grains are liberated; but in some cereals the generative cell undergoes mitosis and the pollen grain is 3-celled, at the time of liberation.
(b) Mature Pollen Grain:
   - A mature pollen grain has a protective covering of two layers.
   - The outer is thick, sculptured variously and is made of sporopollenin; this layer is called exine.
   - The inner layer, called intine is thin and is made of cellulose.
   - A mature pollen grain is two celled with a large vegetative cell and a small generative cell floating in the cytoplasm of the vegetative cell.
   - The pollen grains of dicot plants have three germ pores while those of monocots have one.

(a) Development of Pollen grain:
   - Microsporocytes undergo mitotic divisions to increase the number of functional microspore mother cells.
   - Each microspore mother cell undergoes meiosis to form a microspore tetrad.
   - All the four microspores remain enclosed in a common wall.
   - They start separating from each other.
   - The nucleus undergoes a mitotic division resulting in the formation of a large vegetative cell and a small generative cell.
   - The spore develops a wall of two layers the outer- exine and inner intine.
   - At this stage, the pollen grains are liberated; but in some cereals the generative cell undergoes mitosis and the pollen grain is 3-celled, at the time of liberation.
(b) Mature Pollen Grain:
   - A mature pollen grain has a protective covering of two layers.
   - The outer is thick, sculptured variously and is made of sporopollenin; this layer is called exine.
   - The inner layer, called intine is thin and is made of cellulose.
   - A mature pollen grain is two celled with a large vegetative cell and a small generative cell floating in the cytoplasm of the vegetative cell.
   - The pollen grains of dicot plants have three germ pores while those of monocots have one.

(i) The zygote starts dividing only after a certain amount of endosperm is formed as an adaptation to provide assured nutrition to the developing embryo; hence we can say it remains dormant for some time.
(ii) In groundnut, the developing embryo utilises the endosperm completely. There is no residual endosperm in the seed and so the seed is exalbuminous. In castor, the endosperm is not completely used up by the developing embryo, there is some amount of endosperm left in the seeds and the seeds are albuminous.
(iii) The micropyle facilitates the entry of water- and oxygen into the seed during germination.
(iv) The loss of water (up to 10-15% of weight) reduces the metabolic activity and seeds can enter a state of dormancy during unfavorable environment.
(v) Since, the thalamus (part other than ovary) contributes to fruit formation, these fruits are called false fruits and not true fruits.