● They are seen as a deposition of `color{Violet}"yellowish powdery substance"` on the opened anthers of Hibiscus and other flowers.
● The pollen grains from `color{Violet}"different species"` show a `color{Violet}"variety of architecture"` – sizes, shapes, colours, designs.
● Pollen grains are generally `color{Violet}"spherical"` measuring about `color{Violet}"25-50 micrometers"` in diameter.
● It has a prominent `color{Violet}"two-layered wall"`.
`star` `color{Brown}"Exine"`:
● The `color{Violet}"hard"` outer layer called the `color{Violet}"exine"` is made up of `color{Violet}"Sporopollenin"` which is one of the most `color{Violet}"resistant organic material"` known.
● It can withstand `color{Violet}"high temperatures"` and strong `color{Violet}"acids and alkali"`.
● `color{Violet}"No enzyme"` that degrades sporopollenin is so far known.
● Pollen grain exine has `color{Violet}"prominent apertures"` called `color{Violet}"germ pores"` where sporopollenin is absent.
● Pollen grains are well preserved as `color{Violet}"fossils"` because of the presence of `color{Violet}"sporopollenin"`.
● The exine exhibits a fascinating array of `color{Violet}"patterns and designs"`.
`star` `color{Brown}"Intine"`:
● The `color{Violet}"inner wall"` of the pollen grain is called the `color{Violet}"intine"`.
● The cytoplasm of pollen grain is surrounded by a `color{Violet}"plasma membrane"`.
`star` `color{Brown}"Cells within Pollen Grains"`:
● When the pollen grain is `color{Violet}"mature"` it contains two cells, the `color{Violet}"vegetative cell"` and `color{Violet}"generative cell"`.
● The vegetative cell is `color{Violet}"bigger"`, has `color{Violet}"abundant food reserve"` and a large `color{Violet}"irregularly shaped"` nucleus.
● The generative cell is `color{Violet}"small and floats"` in the cytoplasm of the vegetative cell.
● It is `color{Violet}"spindle shaped"` with `color{Violet}"dense cytoplasm"` and a nucleus.
● In over `color{Violet}"60 per cent"` of angiosperms, pollen grains are shed at this `color{Violet}"2-celled stage"`.
● In the remaining species, the generative cell `color{Violet}"divides mitotically"` to give rise to the two male gametes before pollen grains are shed (`color{Violet}"3-celled stage"`).
● They are seen as a deposition of `color{Violet}"yellowish powdery substance"` on the opened anthers of Hibiscus and other flowers.
● The pollen grains from `color{Violet}"different species"` show a `color{Violet}"variety of architecture"` – sizes, shapes, colours, designs.
● Pollen grains are generally `color{Violet}"spherical"` measuring about `color{Violet}"25-50 micrometers"` in diameter.
● It has a prominent `color{Violet}"two-layered wall"`.
`star` `color{Brown}"Exine"`:
● The `color{Violet}"hard"` outer layer called the `color{Violet}"exine"` is made up of `color{Violet}"Sporopollenin"` which is one of the most `color{Violet}"resistant organic material"` known.
● It can withstand `color{Violet}"high temperatures"` and strong `color{Violet}"acids and alkali"`.
● `color{Violet}"No enzyme"` that degrades sporopollenin is so far known.
● Pollen grain exine has `color{Violet}"prominent apertures"` called `color{Violet}"germ pores"` where sporopollenin is absent.
● Pollen grains are well preserved as `color{Violet}"fossils"` because of the presence of `color{Violet}"sporopollenin"`.
● The exine exhibits a fascinating array of `color{Violet}"patterns and designs"`.
`star` `color{Brown}"Intine"`:
● The `color{Violet}"inner wall"` of the pollen grain is called the `color{Violet}"intine"`.
● The cytoplasm of pollen grain is surrounded by a `color{Violet}"plasma membrane"`.
`star` `color{Brown}"Cells within Pollen Grains"`:
● When the pollen grain is `color{Violet}"mature"` it contains two cells, the `color{Violet}"vegetative cell"` and `color{Violet}"generative cell"`.
● The vegetative cell is `color{Violet}"bigger"`, has `color{Violet}"abundant food reserve"` and a large `color{Violet}"irregularly shaped"` nucleus.
● The generative cell is `color{Violet}"small and floats"` in the cytoplasm of the vegetative cell.
● It is `color{Violet}"spindle shaped"` with `color{Violet}"dense cytoplasm"` and a nucleus.
● In over `color{Violet}"60 per cent"` of angiosperms, pollen grains are shed at this `color{Violet}"2-celled stage"`.
● In the remaining species, the generative cell `color{Violet}"divides mitotically"` to give rise to the two male gametes before pollen grains are shed (`color{Violet}"3-celled stage"`).