What are geotropic, thigmotropic and chemotropic movements?
What are geotropic, thigmotropic and chemotropic movements?
Geotropic movements:
(a) It is a response of a plant induced by gravity. This response is also known as gravitropism.
(b) Roots of a plant grow downwards towards the gravity, exhibiting positive geotropism.
(c) Stems grow upwards away from gravity and are exhibiting negative geotropism.
(d) Leaves are transversely geotropic as they select their positions at 900 to the center of gravity.
Thigmotropic movements:
(a) It is a response of plants that occurs due to contact with a nearby surface, foreign body.
(b) It is most conspicuous in tendrils and twiners.
(c) For example, the tendrils of a pea plant coil around nearby support and help the plant in climbing and so said to be positively thigmotropic.
Chemotropic movement:
(a) It is a response of a plant or a part of it induced by chemicals.
(b) For example, the growth of pollen tubes through stigma and style towards the embryo sac occurs with the stimulus of chemical substances.
(c) For example; Fungus is positively chemotropic as the growth of fungal hyphae towards sugars and peptones.
(d) These movements are present in all plants and not restricted to specialized plants or plant parts.
(e) e.g., Phototropism: When a plants organ curves due to unilateral light stimulus it is called phototropism. Some parts of the plant e.g., the stem moves toward the light and thus are positively phototropic.
Geotropic movements:
(a) It is a response of a plant induced by gravity. This response is also known as gravitropism.
(b) Roots of a plant grow downwards towards the gravity, exhibiting positive geotropism.
(c) Stems grow upwards away from gravity and are exhibiting negative geotropism.
(d) Leaves are transversely geotropic as they select their positions at 900 to the center of gravity.
Thigmotropic movements:
(a) It is a response of plants that occurs due to contact with a nearby surface, foreign body.
(b) It is most conspicuous in tendrils and twiners.
(c) For example, the tendrils of a pea plant coil around nearby support and help the plant in climbing and so said to be positively thigmotropic.
Chemotropic movement:
(a) It is a response of a plant or a part of it induced by chemicals.
(b) For example, the growth of pollen tubes through stigma and style towards the embryo sac occurs with the stimulus of chemical substances.
(c) For example; Fungus is positively chemotropic as the growth of fungal hyphae towards sugars and peptones.
(d) These movements are present in all plants and not restricted to specialized plants or plant parts.
(e) e.g., Phototropism: When a plants organ curves due to unilateral light stimulus it is called phototropism. Some parts of the plant e.g., the stem moves toward the light and thus are positively phototropic.
