Page 21 - Biology - XII

(a) Dusting pollens on a slide (b) Pollen grains of China rose
from stamens of China rose with a drop of nutrient medium

Pollen grain
Pollen tube Gametes

Pollen tube
Intine

Gametes Tube nucleus Tube nucleus Exine

(c) Germinated pollen (d) Germinated pollen (e) Trinucleate pollen of
(a section view) China rose (a section view)

Fig. 4.1: Germination of pollen grains and a section view

Observations
1. Some pollen grains will germinate and develop pollen tube. These pollen grains are said as viable
pollen grains.
2. Some pollen grains may not show the development of pollen tube. These pollens did not germinate.
They are called as non-viable pollen grains.

Conclusion
Viable pollen grains germinate in nutrient medium.

Precautions

1. Use clean and dry slide for dusting pollens on it.
2. Use two-three drops of nutrient medium.

VIVA VOCE

Q1. From where does pollen tube extend out of pollen?
Ans. Germ pore
Q2. What is the source of pollens?
Ans. Stamens with mature anther lobes.

Q3. The nutrient medium for pollen germination has
Ans. (i) sucrose (ii) potassium nitrate (iii) magnesium sulphate (iv) distilled water
Q4. Can pollens of one species germinate on any other species stigma?
Ans. No, it germinates on the stigma of the same species.

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