15 March 2014

#107 Reproduction in plants - agents of pollination

Reproduction in flowering plants may occur both sexually or asexually.

Pollination can take place with the help of agentswind or insects.

Pollination:  transfer of pollen grains from the male part of the plant (anther) to the female part (stigma).  

Pollen grains. 

Structural adaptations

Common misconceptions

Students often get confused between pollination and seed dispersal. When animals such as insects carry pollen, they aid pollination. When animal carry seeds, they aid seed dispersal. 

Growth of pollen tube and the process of fertilization

Figure below shows a section through a single carpel. 

If pollen grains are of the same species as the flower they land on, they may germinate. Germination is triggered by a sugary solution on the stigma, an involves the growth of a pollen tube from the pollen grain. 

The pollen tube contains the male nucleus, which is needed to fertilise the ovule inside the ovary. The pollen tube grows down the style, through the ovary wall, and through the micropyle of the ovule. 

Fertilisation is the fusion of the male nucleus with the female nucleus. If the ovary contains a lot of ovules, each will need to be fertilised by a different pollen nucleus.

Video: Flower Reproduction

Video: Sexual Reproduction in Flowering Plants

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