Solution :

(i)
The transfer of pollen grains from the anther to the stigma of the same flower or of different flower is termed as pollination.
Depending upon the source of pollen grains, pollination is of following types:
(i) Self-Pollination Pollens from the anther of a flower are transferred to stigma of same flower.
(ii) Cross-pollination Pollens from the anther of one plant are transferred to the stigma of another plant. Cross-pollination produces better offsprings with many desired characters. So, nature prefers cross-pollination over self-pollination.
(ii)

Solution :

Plants require some adaptations to fulfil the needs for self-pollination which are as follows :

(i) Bisexuality (Hermaphroditism) Self-pollination can take place only in bisexual flowers (those bear both stamens and carpels).
(ii) Homogamy In this method, both the anthers and the stigma of bisexual flowers mature at the same time, e.g. Mirabilis.
(iii) Cleistogamy In some plants, flowers never open up and the anthers dehisce inside the closed flowers to ensure self-pollination. Thus, there is no chance of cross-pollination in cleistogamous flowers, e.g. Oxalis, Viola, etc

Solution :

Plants require some adaptations to fulfil the needs for cross-pollination which are as follows :
(i) Unisexuality - In this, separate male and female flowers born on same or different plants, e.g. papaya, palm.
(ii) Self-sterility or Incompatibility - In this condition, the pollen grains of a flower fail to germinate on the stigma of the same flower, e.g. potato, tobacco.
(iii) Dichogamy - In some bisexual flowers, the anther and stigma do not mature at the same time. It is of two kinds:
(a) Protandrous or Protandry - The anthers mature earlier than the stigma, e.g. sunflower, sweet pea, Jasminum, etc.
(b) Protogynous or Protogyny - The stigma matures earlier than the anthers, e.g. Magnolia, custard, apple, peepal, rose, etc.
(iv) Heterostyly - Some flowers has style and anthers at different heights. Either the style is very long or anthers are at more height so that selfpollination becomes impossible. This condition is known as heterostyly, e.g. Oxalis, Primula.
(v) Herkogamy - In such condition, flower possesses certain structural barrier which does not allow self-pollination. For example, in pansy flower, a hood covering the stigma acts as a mechanical barrier.

Solution :

Solution :

Solution :

Ovule is a small structure present in the ovary. It has following characteristic features:
(i) It is attached to the placenta by a stalk called funicle.
(ii) Hilum is a junction between ovule and funicle.
(iii) Each ovule has one or two protective envelops called integuments.
(iv) Micropyle is an opening present at the tip, where integument is absent.
(v) The integuments enclose a mass of cells called the nucellus. Nucellus have food reserves.
(vi) Embryo sac or female gametophyte is located in the nucellus. The embryo sac contains the following structures:
• A female gamete called egg towards the micropyle.
• Two polar nuclei which fuse to form the secondary nucleus in the centre.
• Two synergids.
• Three antipodal cells

Solution :

Pollen grains have following characteristic features:
(i) Unicellular and spherical
(ii) Outer hard layer exine is made up of sporopollenin
(iii) Germ pore is present on exine, where sporopollenin is absent. The pollen tube emerges out during germination through it.
(iv) The inner wall intine is made up of cellulose and pectin.
(v) Pollen grain has two nuclei called tube nucleus and generative nucleus.
(vi) Once pollen grains deposit on stigma, they absorb sugar and water from the surface of stigma and swell up.
(vii) A mature pollen grain contains two cells:
• vegetative cell in pollen grain (bigger), which contains food reserves
• generative cell (small), which floats on the cytoplasm of vegetative cell

Solution :

(i) One male gamete unites with egg forming embryo. The process is called fertilisation or syngamy.
(ii) Another male gamete unites with two polar nuclei resulting in the formation of endosperm by triple fusion to form triploid Primary Endosperm Nucleus (PEN).
(iii) The process of fusion of one of the male gametes with egg nucleus and the other sperm fuses with the two polar nuclei together is called double fertilisation.

Solution :

Post-fertilisation changes in floral parts are as follows:
(i) Sepals fall down or persist in few.
(ii) Petals, stamen, stigma and style fall down.
(iii) Ovary changes into fruit, ovary wall forms pericarp.
(iv) Ovules become seeds.
(v) Synergids and antipodal cells degenerate.
(vi) Central cell becomes endosperm. May persist or get consumed.
(vii) Outer integument forms seed coat.
- A fruit is defined as ripened or mature ovary. Fruits contain one or more seeds.
- The mature ovule after fertilisation is known as seed. The seed is covered from outside by hard and protective seed coat.

Solution :

• A–Filiform apparatus
• B–Synergids
• C–Egg cell
• D–Central cell
• E–Polar nuclei
• F–Antipodal cell