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 Many insects may consume pollen or nectar without bring about pollination. Such floral visitors are referred
aspollen/nectar robbers.

Outbreeding Devices:

 Majority of the flowering plants produce hermaphrodite flower and undergo autogamy.
 Continuous autogamy or self-pollination results in inbreeding depression.
 Flowering plants have developed many devices to avoid self pollination and to encourage cross-
pollination. Such devices are called Outbreeding devices.
o Pollen released and stigma receptivity is not synchronized.
o Spatial separation of anthers and stigmas
o Anther and stigma are placed at different positions.
o Self incompatibility.
o Production of unisexual flowers.

Pollen pistil Interaction:

 All the events – from pollen deposition on the stigma until pollen tubes enter the ovule – are
together referred aspollen-pistil interaction.
 Pollination does not guarantee the transfer of the right type of pollen grain to the right type of
stigma.
 The pistil has the ability to recognize the pollen whether it is compatible or incompatible.
 If it is right type the stigma allow the pollen to germinate.
 If it is wrong type the stigma rejects the pollen, preventing germination.
 The ability of the pistil to recognize the pollen by continuous dialogue mediated by chemical
like Boron, Inositol and sucrose level.
 Following compatible pollination, the pollen grain produce pollen tube through one of the germ
pore.
 Content of the pollen grain move into the pollen tube.
 Pollen tube grows through the tissues of the stigma and style and reaches the ovary.
 If the pollen grain is in 2-celled stage the generative cell divides and forms two male gametes
inside the pollen tube.
 If the pollen grain is in 3- cell stage the pollen tube carry two male gametes from the beginning.
 Pollen tube enters into the ovule through micropyle and then into the embryo sac through synergids
guided by filiform apparatus.

Artificial hybridization:

 One of the major approaches of crop improvement programme.
 Only desired pollen grain used for pollination.
 Stigma is protected from contamination (from unwanted pollen grain).
 Removal of anthers from the flower bud before the anther dehisces is called emasculation.
 Emasculated flowers covered by bag generally made up of butter paper, to prevent contamination
of its stigma with unwanted pollen. This step is called bagging.
 If the female flower is unisexual there is no need of emasculation.