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Geotropism:
The movement of a plant in response to gravity is known as geotropism.
Example:
Root of a plant.
In general,
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Positive and Negative Geotropism
Some halophytes like Rhizophora have negatively geotropic roots. These roots turn \(180°\) upright for respiration.
Negatively geotropic roots of Rhizophora & Avicenna - Mangrove forest
Hydrotropism:
The movement of a plant or a part of the plant towards water is known as hydrotropism.
Plants showing hydrotropism
Example:
The root of a plant:
When a plant develops from a seed, the root of the growing plant tends to move towards the area of water. This is due to hydrotropism.
Thigmotropism:
The movement of a plant part due to touch is known as thigmotropism.
Climbing vines:
As we have studied in our lower classes, vines are examples of climbers that cannot grow without support. When a part of these climbers (tendrils) come in contact with the support, it starts to grow at a faster rate than the other parts, thus moving towards the direction of the stimulus.
Tendrils showing Thigmotropism
Chemotropism:
The movement of a part of a plant in response to chemicals is known as chemotropism.
Example:
The growth of the pollen tube in response to the sugar content found in the stigma.
Pollen tube formation in the stigma
Reference:
http://lifeofplant.blogspot.com/2011/03/nastic-movements.html https://commons.wikimedia.org/wiki/File:Pneumatophores.svg https://www.flickr.com/photos/34806414@N00/441496011/in/photolist-F1Moc-HeYJE-WCfNm-3KdUuS-42Zuvn-48f7Cy-4bAMjc-4bAMQT-4bEP2u-4ff1TC-4Aw6r5-4BPTMn-4FL2V9-547JQx-5FbkLt-5FbkUt-5LZ6ZC-6boRWi-6gm7Ue-6qoFmv-6xE5MK-6yt5Vd-6U1oxM-bJrwPg-93SEx3-e5NgH9-bJrwQV-9fqz6a-ckednC-ifPrGS-7Mt6oD-eedEx3-ee3DEu-eedDwU-ee4bN5-edXw7M-ee4e1f-edXzb2-ee4iDN-ee4hGy-7X3TLU-ee48sE-edXhLz-edX6X8-edX4EP-ee3Ph3-9KVS6W-ee3Ny7-edXoaz-edWYUr-9nmvp3
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