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If the roots of a plant always grow downwards due to geotropism, then the growth of pollen tubes towards ovules is due to ________.
phototropism
geotropism
hydrotropism
chemotropism
chemotropism
The growth of a pollen tube towards the ovule is known as chemotropism. This is a directional growth movement of a plant part in response to a chemical stimulus.
The growth of a pollen tube towards the ovule is known as chemotropism. This is a directional growth movement of a plant part in response to a chemical stimulus.
Think of it like a tracking device following a scent trail to reach a destination; the pollen tube 'smells' the chemical cues released by the ovule to find its way.
CHEM-o: 'CHEM' stands for Chemical stimuli, 'o' reminds you of Ovules.
During fertilization in angiosperms, the stigma secretes chemical substances (sugars and nutrients) that trigger the pollen grain to germinate. The growing pollen tube senses these chemical gradients produced by the synergid cells within the ovule, directing its growth towards the micropyle to ensure successful fertilization.
Chemotropism is a type of nastic or tropic movement where growth is directed by a chemical gradient.
Positive chemotropism occurs when growth is towards the chemical source.
The pollen tube growth is a classic example of positive chemotropism in plants.
Ensures precise delivery of male gametes to the female egg cell.
Maximizes the chances of successful sexual reproduction in flowering plants.
Fertilization in angiosperms
Hyphal tip growth in certain fungi towards nutrients
Geotropism (or gravitropism) involves growth in response to gravity (roots are positively geotropic).
Phototropism involves growth in response to light (shoots are positively phototropic).
Hydrotropism involves growth in response to water (roots are positively hydrotropic).
D is correct тАФ the growth of pollen tubes towards the ovules is a classic example of chemotropism, triggered by chemical signals.
Always differentiate between 'tropic' (directional growth) and 'nastic' (non-directional) movements; chemotropism is specifically directional growth towards a chemical.
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