Question

Structure of pollen graine

Answer 1

$\Huge{\sf Pollen \ Grain \ \colon}$

• Pollen grain is the male gametophyte of the plants belonging to phylum angiospermae.

• Pollen grains are produced in the sporangia of the anther (generally an anther is tetrasporangiate )

• In the pollen grain,the spore mother cells ( diploid in nature ) undergo meiosis to form a tetrad of microspores which are haploid in nature

$\underline{\underline{\sf Outer \ Layer \ \colon}}$

• A typical pollen grain is covered by two layers : the outer exine and the inner intine. The intine is absorptive in nature while the exine is protective in nature

• Exine is made up of a protein called sporopollenin which protects the grain from critical temperatures, enzyme action etc

• In contrast,intine is made up of cellulose and pectose

• In certain regions of exine,it is not surrounded by sporopollenin,these pores are termed as Germ Pores which give rise to the pollen tube

$\underline{\underline{\sf Inner \ Structure \ \colon}}$

• A typical angiospermae pollen grain is two celled

• A generative cell which forms the male gamete

• A vegetative cell which is rich in food and supplies nutrients to the generative cell during development

• About 60 percent of angiosperms, shed pollen grains at two celled stage. However, rest of them shed pollen grains at 3 celled stage; one tube cell (vegetative cell) and two male gametes.