POLLEN GRAIN
Study of Pollen is called Palynology.
Typical shape- Spherical
Size- 25-50 um (in diameter)
Pollen grain represents the male gametophyte i.e. it carries the male gametes to the female reproductive parts in Gymnosperms and Angiosperms.
STRUCTURE OF POLLEN
1. POLLEN WALL
Pollen has a prominent two-layered wall i.e. Exine and Intine.
EXINE
Outermost protective layer of the pollen
Hard and thick layer
Discontinuous layer as exine has prominent apertures called Germ Pores
Exine exhibits fascinating array of patterns and designs
Made up of Sporopollenin (most resistant organic material known)
INTINE
Thin and elastic layer
Continuous layer
Made up of cellulose and pectin
2. CELLS
A mature pollen consist of two cells i.e. Vegetative cell and Generative cell
VEGETATIVE CELL
Large in size
Nucleus is large and irregularly shaped
Contains abundant food reserve
Fn- Helps in development of pollen tube
GENERATIVE CELL
Small in size
Floats in the cytoplasm of vegetative cell
Nucleus is Spindle shaped
Contains dense cytoplasm
Fn- Divides by mitosis to form two non-motile male gametes.
ADVANTAGES OF POLLEN
TO PLANTS
Carries male gametes to the female sex organ for fertilisation.
Enabled the higher plants (Gymnosperms and Angiosperms) to grow in a wide range of terrestrial habitat as pollen eliminated the dependence on water for fertilisation.
to HUMANS
Pollen are rich in nutrients and are used as food supplements.
Pollen consumption increases the performances of athletes and race horses.
Pollen can be preserved using liquid Nitrogen for future use (Cryopreservation)
DISADVANTAGES OF POLLEN
Pollen are small in size so can be inhaled during breathing.
Pollen of many species causes severe allergies and bronchial afflictions in some people.