Biology Class 12 NCERT Solutions: Chapter 2 Sexual Reproduction in Flowering Plants Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 13 Differentiate between:

(a) Hypocotyl and epicotyl;

(b) Coleoptile and coleorhiza;

(c) Integument and testa;

(d) Perisperm and pericarp.

Answer:

(a) Hypocotyl and epicotyl

Table of Hypocotyl V/S Epicotyl
HypocotylEpicotyl
1.The portion of the embryonal axis which lies below the cotyledon in a dicot embryo is known as the hypocotyl.The portion of the embryonal axis which lies above the cotyledon in a dicot embryo is known as the epicotyl.
2.It terminates with the radicle.It terminates with the plumule.

(b) Coleoptile and coleorhiza

Table of Coleoptile V/S Coleorhiza
ColeoptileColeorhiza
It is a conical protective sheath that encloses the plumule in a monocot seed.It is an undifferentiated sheath that encloses the radicle and the root cap in a monocot seed.

(c) Integument and testa

Table of Integument V/S Testa
IntegumentTesta
It is the outermost covering of an ovule. It provides protection to it.It is the outermost covering of a seed.

(d) Perisperm and pericarp.

Table of Perisperm V/S Pericarp
PerispermPericarp
It is the residual nucellus which persists. It is present in some seeds such as beet and black pepperIt is the ripened wall of a fruit, which develops from the wall of an ovary.

Q. 14 Why is apple called a false fruit? Which part (s) of the flower forms the fruit?

Answer:

  • Fruits derived from the ovary and other accessory floral parts are called false fruits.
  • On the contrary, true fruits are those fruits which develop from the ovary, but do not consist of the thalamus or any other floral part.
  • In an apple, the fleshy receptacle forms the main edible part. Hence, it is a false fruit.
Apple Flower

Q. 15 What is meant by emasculation? When and why does a plant breeder employ this technique?

Answer:

  • Emasculation is the process of removing anthers from bisexual flowers without affecting the female reproductive part (pistil) , which is used in various plant hybridization techniques.
  • Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain.
  • To remove the anthers, the flowers are covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only.
  • Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.
  • If the female parent bears bisexual flowers, removal of anthers from the flower bud before the anther dehisces using a pair of forceps is necessary
  • This step is called emasculation. In crossing experiments, it is necessary that only desired pollen grains are used for pollination and stigma is protected contamination (from unwanted pollen) . This is achieved by emasculation and bagging

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