Pollination and Major Agent
* Pollination is a process through which pollen shed from the anther is transferred to the stigma of the pistil.
* When pollination takes place within the same flower or between flowers of the same plant, it is known as self – pollination.
* In autogamy, pollen is transferred from the anther of a flower to the stigma of the same flower.
* In geitonomy, the second type of self – pollination, the pollen is transferred from the anther to one flower to the stigma of another flower on the same plant.
* Cross – pollination or xenogamy involves the transfer of pollen grain from a flower of one plant to the stigma of a flower of another plant.
* Pollinating agents are either abiotic or biotic.
* Biotic pollinators include bees, moths, butterflies, birds and bats.
* Abiotic factors such as wind also aid in pollination.
* Out Breeding Devices and Pollen – Pistil Interaction
* Continuous self – pollination or inbreeding throughout successive generations leads to inbreeding depression.
* Inbreeding depression, a condition characterised by a decrease in genetic vigour and vitality, manifests itself in form undesirable traits such as reduced pollen output and decreased seed production.
Various out breeding devices include:
* Dichogamy
* Herkogamy
* Self – Incompatibility
* Pollen – Prepotency
* Unsexuality
* Self – incompatibility is a genetic mechanism that prevents both autogamy and gritonogamy.
* All events – from pollen deposition on the stigma until pollen tube enter the ovule – are together referred to as pollen – pistil interaction
* Pollen – pistil interaction is mediated by the release of chemical substances.
* Artificial hybridisation is a crop improvement programme to produce commercially superior crops with desirable traits such as insect resistance.
* Emasculation and bagging are two techniques followed in artificial hybridisation.