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Sexual Reproduction in Flowering Plants

Q1. What is apomixis and polyembryony?

Ans: The phenomenon of asexual reproduction that imitates sexual reproduction by the formation of seed without fertilization is called apomixis or agamospermy.

The occurrence of more than one embryo in a seed is called polyembryony, e.g., orange.


Q2. What is emasculation?

Ans: The process of removal of anther from bisexual flowers without affecting the pistil is called emasculation.


Q3. Mention any five features of insect pollinated flowers.

Ans:

  1. The form of pollination in which insects distribute pollens is called entomophily.

  2. Flowers are large, sticky and brightly coloured.

  3. They have honey and nectar glands, which are highly fragrant to attract insects.

  4. The pollen grain surface is sticky due to exine layer and stigma is sticky due to mucilaginous secretion.

  5. The flowers offer floral rewards like nectar and pollen grains for pollination to insects.

  6. In some species, floral rewards provide safe place to lay eggs, e.g., Amorphophallus.

  7. The flower sometimes secretes foul odour to attract insects like flies and beetles.


Q4. Mention two strategies evolved to prevent self-pollination (autogamy) in flowers.

Ans:

  1. Unisexuality: Male and female flowers are present on different plants.

  2. Dichogamy: The condition in which the stamens and stigma of a bisexual flower mature at different times.

  3. Protandry: This is the condition where anthers mature earlier than the stigma and release pollens.

  4. Protogyny: This is the condition where the stigma matures earlier than the anther.

  5. Self-sterility or self-incompatibility: It is a genetic mechanism that prevents self-pollination.

  6. Chasmogamous flowers: These are open flowers with exposed stamens and stigma which facilitate cross-pollination.


Q5. Differentiate between perisperm and pericarp.

Ans:

Perisperm:

  1. It represents the persistent nucellus in the seed.

  2. It is a part that belongs to seed.

  3. It is usually dry.

Pericarp:

  1. It represents the fruit wall formed by the ovarian wall.

  2. It is a part of fruit.

  3. It can be dry or fleshy.


Q6. Describe the structure of pollen grains.

Ans:

  1. They develop from Pollen Mother Cell by meiotic division.

  2. They represent the male gametophyte.

  3. Pollen grains are generally spherical in structure.

  4. They possess two prominent layered walls - outer exine and inner intine.

  5. The exine is a hard layer made of sporopollenin which is one of the most resistant organic material present in nature.

  6. The inner thin layer of intine is made up of cellulose and pectin.