germination of a pollen grain occurs in flowers.
germination of a pollen grain occurs in flowers.
where does germination of a pollen grain occur?
flowers
another germination event during the life cycle of gymnosperms and flowering plants is the germination of a pollen grain after pollination. like seeds, pollen grains are severely dehydrated before being released to facilitate their dispersal from one plant to another. they consist of a protective coat containing several cells (up to 8 in gymnosperms, 2-3 in flowering plants). one of these cells is a tube cell. once the pollen grain lands on the stigma of a receptive flower (or a female cone in gymnosperms), it takes up water and germinates. pollen germination is facilitated by hydration on the stigma, as well as by the structure and physiology of the stigma and style. pollen can also be induced to germinate "in vitro" (in a petri dish or test tube).
germination
pollen germination has three stages; hydration, activation and pollen tube emergence. the pollen grain is severely dehydrated so that its mass is reduced enabling it to be more easily transported from flower to flower. germination only takes place after rehydration, ensuring that premature germination does not take place in the anther. hydration allows the plasma membrane of the pollen grain to reform into its normal bilayer organization providing an effective osmotic membrane. activation involves the development of actin filaments throughout the cytoplasm of the cell, which eventually become concentrated at the point from which the pollen tube will emerge. hydration and activation continue as the pollen tube begins to grow.
pollination