Pollination and Fertilization - Questions & Answers

1. Match the items in Column I with those in Column II

Column I
(i) Feathery stigma hanging out
(ii) Different timings for maturation of anthers and stigma
(iii) Pollination by elephant
(iv) Flowers produce nectar

Column II
Rafflesia
Entomophilous
Wind-pollination
Dichogamy

(i) - Wind-pollination
(ii) - Dichogamy
(iii) - Rafflesia
(iv) - Entomophilous

2. Complete the following statements :

(i) Pollination is the process of transfer of pollen grains from the anther to the stigma.

(ii) The two kinds of pollination are self-pollination and cross-pollination.

(iii) For self-pollination, the flowers need not be large and showy.

(iv) For self-pollination, anther and stigma must mature at the same time.

(v) Self-pollination does not yield new varieties.

(vi) In cross pollination, there is much wastage of pollen.

1. Mention if the following statements are true

(i) Intine is the outer wall of pollen grain.
False

(ii) Pollen tube enters ovule through micropyle.
True

(iii) Zygote gives rise to embryo.
True

(iv) Ovule becomes fruit.
False

(v) Dry sepals may persist in some fruits.
True

1. Choose the correct answer from the options given below :

(i) Exine and intine are the parts of :
(a) Embryo sac
(b) Pollen grain
(c) Stigma
(d) Seed
Answer: (b) Pollen grain

(ii) Which one of the following is one of the characteristics of self-pollinated flowers ?
(a) Flowers are large and showy
(b) Flowers remain closed and do not open
(c) Stigma and anthers mature at the same time
(d) Pollen is produced in very large quantities
Answer: (c) Stigma and anthers mature at the same time

(iii) The kind of pollination in which the pollen of the same flower fall on its stigma is termed as :
(a) Geitonogamy
(b) Autogamy
(c) Homogamy
(d) Allogamy
Answer: (b) Autogamy

(iv) Which of the following conditions favours self-pollination ?
(a) Homogamy
(b) Herkogamy
(c) Dichogamy
(d) None of these
Answer: (a) Homogamy

(v) Pollination by birds is termed as :
(a) Entomophily
(b) Anemophily
(c) Ornithophily
(d) Elephophily
Answer: (c) Ornithophily

(vi) Which of the following is an example of an ornithophilous flower ?
(a) Bougainvillea
(b) Vallisneria
(c) Bignonia
(d) Rafflesia
Answer: (c) Bignonia

(vii) Bright, showy and nectar producing flowers are needed for pollination to occur by :
(a) Wind
(b) Water
(c) Insects
(d) Elephant
Answer: (c) Insects

(viii) The male inflorescence of maize plant is termed as :
(a) Cob
(b) Ear
(c) Tassel
(d) Silk
Answer: (c) Tassel

(ix) Wing and keel petals are found in the flowers of :
(a) Pea plants
(b) Vallisneria
(c) Maize plants
(d) Dahlia
Answer: (a) Pea plants

(x) Which of these does not belong to the embryo sac of a flower ?
(a) Generative nucleus
(b) Antipodal cells
(c) Polar Nuclei
(d) Synergids
Answer: (a) Generative nucleus

(xi) The given figures A and B show ............. and ............. conditions which favour cross-pollination.
(a) Herkogamy and Heterostyly
(b) Heterostyly and Herkogamy
(c) Herkogamy and Homogamy
(d) Heterostyly and Homogamy
Answer: (b) Heterostyly and Herkogamy

(xii) Look at the table given below and identify the kind of pollination that usually occurs in the flowers mentioned.
Flower: Hibiscus (P), Hydrilla (Q), Wheat (R)
(a) P - Entomophily, Q - Hydrophily, R - Anemophily
(b) P - Hydrophily, Q - Elephophily, R - Anemophily
(c) P - Ornithophily, Q - Anemophily, R - Elephophily
(d) P - Ornithophily, Q - Hydrophily, R - Entomophily
Answer: (a) P - Entomophily, Q - Hydrophily, R - Anemophily

1. Given below is the internal structure of an ovule. Read the information below the diagram and fill in the blanks :

Each ovule has one or two protective coverings, the integuments. The integuments leave a small opening called the (a) micropyle at one end. Enclosed by the integuments is the (b) nucellus (a mass of food laden cells), and further inside it, is the embryo sac. Embryo sac contains one (c) egg cell and two (d) synergids at one end. Three (e) antipodal cells are found at the opposite end of the embryo sac.

2. State of the chief pollinating agent against the corresponding plant by choosing from those given in brackets.

(a) Dahlia butterflies (Crow, butterflies, mosquito).
(b) Maize wind (Bees, locusts, rain, wind).
(c) Vallisneria water (Wind, water, ants, rabbits).

3. Fill in the blanks with suitable words.

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

4. Name the parts of the ovary which give rise to :
(a) Seed Ovule
(b) Fruit Ovary
(c) Fruit wall Ovary wall (Pericarp)

5. Give one word/term for the following :
(a) A flower containing both male and female parts
Bisexual flower
(b) Arrangement of flowers on a twig/stem
Inflorescence
(c) When pollen grains of a flower reach the stigma of the same flower.
Self-pollination (Autogamy)
(d) When maturation time of reproductive parts in a flower is different.
Dichogamy
(e) When stigma and anthers do not grow up to the same height, what favours only cross pollination?
Heterostyly
(f) Pollination of flowers by insects.
Entomophily
(g) Pollination of flowers by birds.
Ornithophily

6. Match the items in Column A with those in Column B.

Column A
(a) Generative nucleus
(b) Germ pore
(c) Exine
(d) Secondary nucleus
(e) Integument
(f) Egg nucleus

Column B
(i) Pollen tube
(ii) Endosperm nucleus
(iii) Testa
(iv) Fertilization
(v) Male nuclei
(vi) Rough

(a) - (v)
(b) - (i)
(c) - (vi)
(d) - (ii)
(e) - (iii)
(f) - (iv)

1. Explain briefly the following terms :
(a) Ornithophily.
It is the pollination of flowers by birds. For example, Bignonia and Canna.
(b) Elephophily.
It is the pollination facilitated by elephants, found in extremely large ground-level flowers like Rafflesia where pollen grains stick to the elephant's feet.
(c) Artificial pollination.
It is a standard practice where humans manually transfer pollen of a desired variety to the stigma of a flower to evolve new varieties, often involving emasculation and bagging.

2. Define :
(a) Pollination
Pollination is the process of transfer of pollen grains from the anther to the stigma of a flower.
(b) Herkogamy
It is a condition where mechanical or structural barriers in some flowers prevent the pollen from reaching the stigma of the same flower, favouring cross-pollination.
(c) Cleistogamy
It is a condition where certain bisexual flowers do not open even at maturity, ensuring self-pollination as reproductive structures remain hidden.
(d) Emasculation
It is the process of removal of anthers in young flowers by plant breeders during artificial crossing.
(e) Fertilization
Fertilization is the union or fusion of the nuclei of male and female gametes.

3. What happens to the following after fertilization?
(a) Ovules
They change into the seeds.
(b) Calyx
It may either fall off or remain intact in a dried and shrivelled form (like in apple) or persist as green attached leaves (like in brinjal).
(c) Petals
They wither and generally fall off.
(d) Stamens
They wither and generally fall off.

4. Mention any two contrivances in flowers which favour cross-pollination.
1. Unisexuality (flowers are exclusively male or female).
2. Dichogamy (different timings of maturation of androecium and gynoecium).

1. Distinguish between the following pairs :
(a) Autogamy and Geitonogamy
Autogamy is the transfer of pollen grains from the anthers to the stigma of the same flower. Geitonogamy is the transfer of pollen grains from the anther to the stigma of another flower on the same plant.
(b) Homogamy and Dichogamy
Homogamy is the condition where the anther and stigma of a bisexual flower mature at the same time to ensure self-pollination. Dichogamy is when the anthers and stigma of the same flower mature at different times, favouring cross-pollination.
(c) Protandry and Protogyny
Protandry is when the anthers of the flower mature earlier than the stigma. Protogyny is when the stigma of the flower matures earlier than the anthers.
(d) Entomophilous and Anemophilous flowers
Entomophilous flowers are insect-pollinated, usually large, brightly coloured, scented, and produce nectar. Anemophilous flowers are wind-pollinated, usually small, dull-coloured, lack scent and nectar, and produce abundant light, dry pollen.
(e) Advantages of self and cross-pollination
Advantages of self-pollination include that it is a much surer process, preserves parental characters indefinitely, and is highly economical for the plant. Advantages of cross-pollination include healthier offspring, production of abundant and viable seeds, and the creation of entirely new varieties.

2. What are the advantages of the following in the flower to the plant concerned ?
(a) Long and feathery stigma
They hang out of the flower to easily trap lightweight pollen grains carried by the wind.
(b) Brightly coloured petals
They attract insects to the flower to facilitate cross-pollination.
(c) Smooth and light pollen
They can be easily carried away over long distances by the wind.
(d) Protruding and easily movable anthers
They allow the slightest wind to move them (versatile anthers), shaking loose and blowing away the pollen.
(e) Fragrant nectar
It acts as food for insects, attracting them to visit the flower and thereby transferring pollen.

3. Describe the advantages and disadvantages of cross-pollination to the plant.
Advantages: The offspring produced are much healthier. The seeds produced are abundant and highly viable. It allows for the production of new varieties through genetic intermixing.
Disadvantages: It is not always certain as it depends on external pollinating agents. There is a massive wastage of pollen as it must be produced in large quantities. The process is uneconomical because the plant must invest large amounts of energy and material into growing large, colourful, scented, and nectar-producing flowers.

4. What is the function of the pollen tube ? Explain it with the help of a diagram.
The function of the pollen tube is to safely transport the two male gametes (sperm nuclei) from the germinating pollen grain on the stigma, down through the tissues of the style, and into the embryo sac of the ovule through the micropyle to carry out double fertilization. (Please refer to diagram Fig. 5.6 in the textbook showing the path of the pollen tube).

1. The figure shown below represents a process in flowers. Study the same and answer the following questions.
(a) Name and define the process.
Cross-pollination. It is the transfer of pollen grains from the anthers of a flower of one plant to the stigma of a flower of another plant of the same species.
(b) Write the technical term of the above mentioned process.
Allogamy.
(c) Give two examples of plants in which this process occurs.
Hibiscus and Apple (or Papaya, Oxalis).
(d) Write one advantage and one disadvantage of the process shown.
Advantage: The offsprings produced are healthier. Disadvantage: It is not always certain as it requires an external pollinating agent.
(e) Name two agents that participate in this process.
Wind and Insects.

2. Given alongside is a diagrammatic sketch of the sectional view of a germinating pollen grain. Study the same and then answer the questions that follow :
(a) Name the parts labelled 1, 2, 3, 4 and 5
1. Exine, 2. Intine, 3. Pollen tube, 4. Tube nucleus, 5. Generative nucleus (Sperm nuclei).
(b) Where does the germination of the pollen grain takes place and how ?
It takes place on the stigma of a flower of the same species. The stigma secretes sugars that stimulate the pollen grain to grow a pollen tube through a pore in the exine.
(c) What is the function of the part labelled '4'?
The tube nucleus directs the growth of the pollen tube all the way down the style toward the ovary and then disintegrates.
(d) What happens to the part labelled '5' during the process ?
The generative nucleus divides into two male gametes (sperm nuclei) as it travels down the pollen tube.

3. Given below is a diagrammatic representation of the process of fertilization. Study the same and then answer the questions that follow :
(a) Name the parts labelled 1, 2, 3, 4, 5 and 6.
1. Pollen tube, 2. Style, 3. Ovary, 4. Micropyle, 5. Polar nuclei, 6. Synergids.
(b) What happens to (i) Ovary (ii) Ovule after fertilization ?
(i) The ovary changes into the fruit. (ii) The ovule changes into the seed.
(c) What is the function of the synergids ?
They help guide the pollen tube to the egg cell; the pollen tube enters one of the synergids to release its sperm nuclei, after which the synergids degenerate.
(d) What part does the stigma play in the process of fertilization ?
The stigma provides a sticky landing surface for the pollen grains and secretes sugars to stimulate pollen tube germination.

4. Shivam dissected a flower of sweet pea and removed all the petals. He observed the reproductive parts of the flower (both male and female), arranged in a specific manner as shown in the diagram given below.
(a) Mention the kind of arrangement of the stamens as shown in the figure.
The stamens are enclosed within the keel petal and form a staminal tube (consisting of 9 fused stamens and 1 free stamen).
(b) What are the three kinds of petals that Shivam removed from the flower ? Name them.
Standard petal, Wing petals, and Keel petals.
(c) Name the kind of pollination (on the basis of pollinating agent) with one specific feature of the flower which favours it.
Entomophily (Insect pollination). Specific feature: Large, conspicuous and brightly coloured petals that attract insects like bees.

(Choose the answer based on the codes given below.)
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

(i) Assertion (A) : Autogamy and allogamy are the two kinds of self-pollination.
Reason (R) : Self-pollination occurs within the same flower or two flowers of the same plant.
Answer: (d) A is false but R is true.

(ii) Assertion (A) : Herkogamous flowers favour cross-pollination as these flowers have a structural barrier between the male and female reproductive parts.
Reason (R) : Pansy is an example of a herkogamous flower which has a hood covering the stigma.
Answer: (b) Both A and R are true but R is not the correct explanation of A.

(iii) Assertion (A) : Entomophilous flowers are brightly coloured and often scented.
Reason (R) : The pollinating agents of entomophilous flowers are insects which usually get attracted towards the bright colours or scents of the flowers.
Answer: (a) Both A and R are true and R is the correct explanation of A.

(iv) Assertion (A) : One polar nucleus fuses with two sperm nuclei of a flower and develop into an endosperm during the process of fertilization.
Reason (R) : The large central cell of the embryo sac contains two polar nuclei, which fuse with one male nucleus. This process is termed as 'triple fusion'.
Answer: (d) A is false but R is true.

(v) Assertion (A) : The process of removal of anthers in young flowers is termed as 'emasculation'.
Reason (R) : Emasculation is mainly performed during artificial pollination to produce the desired variety of the plants.
Answer: (b) Both A and R are true but R is not the correct explanation of A.

1. Shaista is working on her school project about plant reproduction. Her teacher Mrs. Aggrawal gave her the task of investigating pollination in pea flower, a common garden plant. Shaista is curious to know how pollination in pea flower and maize flower differs from each other.
(a) Is pollination a necessary event before fertilization for the reproduction in plants ? Explain.
Yes, pollination is a crucial prerequisite because plants are immobile, and the male gametes enclosed in pollen grains must first be physically transported to the female reproductive structure (stigma) in order to eventually travel down to the ovule for fertilization.
(b) What are the pollinating agents for pea and maize flowers respectively ?
Pea flower: Insects (Bees). Maize flower: Wind.
(c) Write scientific terms for the kind of pollination found in pea flower and maize flower on the basis of pollinating agents.
Pea flower: Entomophily. Maize flower: Anemophily.
(d) Mention the technical term for the specific condition of stamens in pea flower.
Staminal tube (enclosed within the keel).
(e) What are the two advantages of cross-pollination?
1. The offsprings produced are healthier and better adapted to environmental changes.
2. Entirely new varieties can be produced due to genetic intermixing.