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Chapter: Introduction to Botany: The Origin of Flowering

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Pollination - Origin of Flowering

Pollination could be of two types: self- and cross-pollination. Cross-pollination can happen in both abiotic and biotic ways.

Pollination

 

Pollination could be of two types: self- and cross-pollination. Cross-pollination can happen in both abiotic and biotic ways. Abiotic would be represented by gravity, wind, or water; biotic would be performed by agents like insects, birds, bats, or in some cases tree mammals like possums. Wind-pollination is seen as being wasteful and unintelligent due to the fact that the plant needs to produce so much more pollen without any precise targeting.

 

Adaptation to the particular pollination agent results in different pollination syndromes. For example, cup-shaped flowers are usually pollinated with mas-sive animals like beetles and even bats. Funnel-shaped flowers as well as labiate flowers (with lips), are adapted to flies and bees. Flowers with long spurs attract butterflies and birds (like hummingbirds or sugarbirds).

 

Self-pollination often exists like a “plan B”, in case cross-pollination is, for some reason, impossible. Sometimes, self-pollinated flowers even do not open; these flowers are called cleistogamous.

 

If pollination needs to be avoided, apomixis will prevent it. Apomixis requires reproductive organs, but there is no fertilization. One type of apomixis is apospory when an embryo develops from the maternal diploid tissue, but does not go through the meiosis stage. In this process, asexual reproduction will have be-come vegetative. Another type of apomixis would be apogamy (parthenogene-sis) when embryo develops from an unfertilized gamete after diploidization has occurred. Here, vegetative reproduction evolved from sexual reproduction.

 

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