NCERT Class 12 Biology: Chapter –2 Sexual Reproduction in Flowering Plants Part 7

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Question 4:

Does self-incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.

Answer:

The Self-incompatibility imposes restrictions on autogamy.

Self-incompatibility is a genetic mechanism that prevents self-pollination (i.e., pollination from same flower or other flowers of same plant) from fertilizing the ovules. This is done by inhibiting pollen germination or pollen tube growth in the pistil.

The restrictions are imposed as continued self-pollination leads to inbreeding depression. And to prevent such type of depression self-incompatibility is used.

In Self-incompatible plants self-pollination (i.e., pollination from same flower or other flowers of same plant) doesn’t occur. So in such case cross-pollination particularly xenogamy takes place.

That is transfer of pollen grains from anther to the stigma of a different plant.

Question 5:

In the given diagram, write the names of parts shown with lines.

- This Diagram, Write the Names of Parts Shown with Lines

Write the Names of Parts Shown with Lines

- This Diagram, Write the Names of Parts Shown with Lines

Answer:

write the names of parts shown with lines

Write the Names of Parts Shown with Lines

write the names of parts shown with lines

This is longitudinal section of embryo of grass which is monocot in nature.

Embryos of monocotyledons possess only one cotyledon. In the grass family the cotyledon is called scutellum that is situated towards one side (lateral) of the embryonic axis. At its lower end, the embryonal axis has the radical and root cap enclosed in a sheath called Coleorrhiza. The portion of the embryonal axis above the level of attachment of scutellum is the epicotyl. Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure, the coleoptile.

Question 6:

What is polyembryony and how can it be commercially exploited?

Answer:

Presence of more than one embryo in a seed is known as polyembryony.

It can be commercially exploited in many ways, out of which few are listed below:

i. It helps in plant breeding

ii. It helps in horticulture

iii. Plantlets obtained from these embryos are virus free and more vigorous, resulting in high productivity.

iv. All these embryos can be isolated and grown on embryo culture to produce clones.

Question 7:

Are parthenocarpy and apomixis different phenomena? Discuss their benefits.

Hint: Yes, they are different. Parthenocarpy leads to development of seedless fruits. Apomixis leads to embryo development.

Answer:

Are Parthenocarpy and Apomixis Different Phenomena
Are parthenocarpy and apomixis different phenomena

Parthenocarpy

Apomixis

Parthenocarpy is development of a fruit without prior fertilization. Here fruits are seedless.

Apomixis development of a seeds without prior fertilization. Apomixis is a form of asexual reproduction that mimics sexual reproduction. Apomixis avoids the processes of meiosis and fertilization, leading to embryo development.

This can be used to commercially produce seedless fruits like grapes, banana, etc.

This can be used to commercially produce hybridized plants. This is possible as isolation is not needed.

These are very useful in juice

They are used to produce uniform root-stock and virus free varieties.

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