Pollination and Fertilization

A is False and R is True.

Reason — Autogamy is self-pollination, while allogamy is cross-pollination.
Self-pollination includes: Autogamy: Within same flower and Geitonogamy: In different flowers on the same plant.

Both A and R are True.

Reason — Herkogamy refers to the presence of a physical barrier between the anthers and stigma in a bisexual flower. This adaptation prevents self-pollination.
In Pansy, the stigma is covered by a hood-like structure, making it a good example of herkogamy.

Both A and R are False.

Reason — Entomophilous flowers are pollinated by insects. They are usually brightly coloured, scented, and often produce nectar to attract insects.
Entomophily involves insects as pollinators.

A is False and R is True.

Reason — One of the two male gametes fuses with the two polar nuclei, this fusion forms the triploid endosperm nucleus. The other male gamete fuses with the egg cell to form the zygote.
The large central cell in the embryo sac contains two polar nuclei. One male gamete fuses with these two to form the endosperm, a process called triple fusion (2 polar nuclei + 1 male gamete).

Both A and R are True.

Reason — Emasculation is the process of removing anthers from a young flower to prevent self-pollination.
It is an important step in artificial hybridization, where the emasculated flowers are manually pollinated with pollen from a selected plant to develop desired varieties.

(a) Difference between Autogamy and Geitonogamy:

(b) Difference between Homogamy and Dichogamy:

(c) Difference between Protandry and Protogyny:

(d) Difference between Entomophilous and Anemophilous flowers:

(e) Difference between advantages of self and cross-pollination:

1. Long and feathery stigma — Help to trap pollen grains in wind-pollination.

2. Brightly coloured petals — Attracting insects for cross-pollination.

3. Smooth and light pollen — Easily carried by wind to enable cross-pollination.

4. Protruding and easily movable anthers — Even slightest wind can move them.

5. Fragrant nectar — Attracting insects for pollination.

Advantages of cross-pollination:

1. The offspring are healthier.

2. The seeds produced are abundant and viable.

3. New varieties may be produced by cross-pollinating two different varieties of the same species.

Disadvantages of cross-pollination:

1. Pollination is not always certain.

2. The pollen has to be produced in large quantity.

3. The process is uneconomical for the plant because the flowers have to be large, coloured, scented and have to produce nectar for attracting pollinating agents.

Pollen grain

Reason — The outer wall of the pollen grain is known as exine and the inner wall is known as intine.

Stigma and anthers mature at the same time

Reason — Homogamy i.e., maturation of stigma and anthers at the same time is necessary for self-pollination.

Autogamy

Reason — Autogamy refers to pollination in which the pollen grain is transferred from anther to stigma of the same flower.

Homogamy

Reason — In homogamy anther and stigma of a flower mature at same time, favouring self pollination.

Ornithophily

Reason — Ornithophily refers to pollination where pollinating agent are birds.

Bignonia

Reason — Bignonia flower is pollinated by birds.

Insects

Reason — Bright, showy and nectar producing flowers attract insects.

Tassel

Reason — Tassel is the male inflorescence of maize plant.

Pea plants

Reason — Wing and keel petals of pea plant help in pollination by insects.

Generative nucleus

Reason — Embryo sac contains one egg cell, two synergids, three antipodal cells, one large central cell. Generative nucleus is present in pollen grain.

Atul and Anaya

Reason — Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of a flower on a different plant. Adaptations for cross pollination are: -
Herkogamy – Physical barrier between anther and stigma.
Heterostyly – Styles and stamens of different lengths in flowers.
Unisexuality – Male and female flowers on different plants.
Dichogamy – Anthers and stigma mature at different times.

P — Entomophily, Q — Hydrophily, R — Anemophily

Reason — Flower of Hibiscus are large, colorful and scented which attracts insects, hence pollination is by insects (Entomophily).
Hydra is an aquatic plant so pollination happens via water (Hydrophily).
Flower of wheat are small, non-showy hence pollens are carried by wind (Anemophily).

1. Pollination is the process of transfer of pollen grains.
2. The two kinds of pollination are self pollination and cross pollination.
3. For self-pollination, the flowers need not be fragrant and showy.
4. For self-pollination, anther and stigma must mature at the same time.
5. Self-pollination does not yield new varieties.
6. In cross pollination, there is much wastage of pollen grains .

1. False
   Corrected Statement — Exine is the outer wall of pollen grain.
2. True
3. True
4. False
   Corrected Statement — Ovule becomes seed.
5. True

1. The process of pollination affected by birds is known as Ornithophily.

2. The process of pollination affected by elephants is known as Elephophily.

3. The process of pollination affected by men through artificial modes is referred to as Artificial pollination.

1. Pollination is the process of transfer of pollen grain from the anther to stigma.
2. Herkogamy is the condition of flower favouring cross pollination, in which a structural barrier around the stigma prevents self pollination.
3. Cleistogamy is a condition favouring self pollination, in which the flower remains closed even at maturity of anther and stigma.
4. Emasculation is the process of removal of anther in young flower for ensuring artificial pollination.
5. The process of fusion or union of the nuclei of male and female gametes is called fertilisation.

1. Ovules — Ovules become the seed post fertilization.
2. Calyx — After fertilization, the calyx sheds or falls off or remains intact in a shriveled and dried form.
3. Petals — Post fertilization, the petals shed and fall.
4. Stamens — Once fertilization takes place, the stamens fall off.

Contrivances in flowers which favour cross-pollination:

1. Unisexuality

2. Different timings of maturation of androecium and gynoecium

3. Self-sterility

4. Structural barriers

(a) The process is Cross-Pollination. It is defined as the transfer of pollen grains from the anthers of one flower to stigma of another flower of a different plant of the same species.

(b) Allogamy

(c) Oxalis, Hibiscus

(d) Advantage — The offsprings are healthier and can adapt to environmental changes.
Disadvantage — The pollination is not always certain because some pollinating agent is always needed which may or may not be available at the proper time.

(e) Insects, Wind

(a) The parts labelled 1, 2, 3, 4 and 5 are:

• 1 → Exine
• 2 → Intine
• 3 → Pollen tube
• 4 → Tube nucleus
• 5 → Generative nucleus

(b) Germination of the pollen grain takes place only after it falls on the stigma of the same plant species. The pollen grain is stimulated to germinate due to the secretion of sugars by the stigma.

(c) The function of part '4' (tube nucleus) is to direct the growth of the pollen tube towards the ovary.

(d) During germination of the pollen grain, part '5' (generative nucleus) present at the tip of the pollen tube divides into two sperm nuclei. The pollen tube enters one of the synergids and releases its two sperm nuclei. Of these, one sperm nucleus enters the egg cell and fuses with its nucleus, while the other sperm nucleus moves towards the two polar nuclei in the central cell and fuses with them.

(a) The parts labelled 1, 2, 3, 4, 5 and 6 are:

• 1 → Style
• 2 → Pollen tube
• 3 → Polar nuclei
• 4 → Embryo sac
• 5 → Antipodal cells
• 6 → Micropyle

(b) After fertilization, the ovary enlarges to form the fruit and the ovarian wall forms the fruit wall. The ovule becomes the seed.

(c) Synergid cells are two small, specialized cells found in the embryo sac adjacent to the egg cells in the female gametophyte of a flowering plant. It nourishes the ovum and plays an important role in guiding the pollen tube. These structures are key for cessation of pollen tube growth and in the release of the sperm cells.

(d) Pollen grain is transferred to the stigma during pollination. Germination of pollen grain takes place only if it falls on the stigma. After germination, the pollen tube grows through the stigma and reaches the ovary for the fertilization of the egg cell.

(a) Diadelphous

(b) The standard (1), the wings (2) and the keel (formed by fusion of 2 petals).

(c) Entomophily (pollination by insects). The flowers pollinated by insects are brightly coloured and produce nectar.

Each ovule has one or two protective coverings, the integuments. The integuments leave a small opening called the Micropyle at one end. Enclosed by the integuments is the Nucellus (a mass of food laden cells), and further inside it, is the embryo sac. Embryo sac contains one Egg cell and two Synergids at one end. Three Antipodal cells are found at the opposite end of embryo sac.

1. butterflies
2. wind
3. water

1. Transfer of pollen grains from anthers to stigma of the same flower is called autogamy.
2. Different timings for maturation of gynoecium and androecium, is called dichogamy.
3. Vallisneria is a water-pollinated flower.

(a) Seed - Ovule
(b) Fruit - Ovary wall
(c) Fruit wall - Ovary wall (Pericarp)

1. Bisexual flower

2. Inflorescence

3. Self-pollination/Autogamy

4. Dichogamy

5. Heterostyly

6. Entomophily

7. Ornithophily