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What movement in plants causes a tendril to circle and cling to an object?
Tropic movement
Turgor movement
Nastic movement
Locomotary movement
Tropic movement
The movement of a tendril circling and clinging to an object is known as thigmotropism, which is a specific type of tropic movement. It occurs when a plant organ responds to the stimulus of touch by growing towards or away from it.
The movement of a tendril circling and clinging to an object is known as thigmotropism, which is a specific type of tropic movement. It occurs when a plant organ responds to the stimulus of touch by growing towards or away from it.
Think of it like a climber using their arm to grab onto a ladder; the part of the arm facing the ladder pulls in while the outer muscle stretches, wrapping the arm securely around the rung.
T-T-T: Thigmotropism is Touch-based Tropism.
Differential┬аGrowth┬аRate=╬ФLengthnearтАЛ╬ФLengthfarтАЛтАЛ тАФ representing the ratio of growth between sides
When a tendril comes into contact with a support, the concentration of the plant hormone auxin changes across the stem. The side of the tendril in contact with the support experiences slower growth, while the side away from the support grows faster due to higher auxin concentration. This differential growth causes the tendril to coil around the object, providing structural support to the plant.
Thigmotropism is a directional growth response triggered by mechanical stimulation.
Auxin redistribution is the primary chemical driver of differential growth in climbing plants.
Tropic movements are permanent, growth-related, and directional.
Nastic movements are non-directional and often reversible (e.g., Mimosa pudica folding).
Allows weak-stemmed plants to reach sunlight without investing energy in thick, woody tissues.
Dependent on the presence of external support structures.
Pea plants (Pisum sativum) using tendrils to climb fences.
Grapevines clinging to trellises for vertical expansion.
| Feature | Tropic movement | Nastic movement |
|---|---|---|
Directionality | Dependent on stimulus | Independent of stimulus |
Auxins are produced in the shoot tips and are crucial for gravitropism, phototropism, and thigmotropism.
Option B (Turgor movement) refers to changes in cell volume due to water pressure, common in rapid leaf-closing responses like those in the 'touch-me-not' plant.
Option C (Nastic movement) is non-directional, meaning the direction of response is fixed regardless of the stimulus direction.
Option D (Locomotary movement) refers to the displacement of the entire organism, which does not apply to sessile plants.
A is correct тАФ The movement of a tendril is a directed growth response to contact known as thigmotropism, which is classified as a tropic movement.
Always distinguish between Tropic (growth-dependent, directional) and Nastic (turgor-dependent, non-directional) movements for biology exam questions.
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