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Sensory Reception in Plants

Sensory Reception in Plants. Learning objectives:. What is a tropism? How does a tropism increase an organism’s chances of survival? How do plants respond to change? What are plant growth factors?. A tropism is a growth movement of a part of a plant in response to a directional stimulus.

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Sensory Reception in Plants

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  1. Sensory Reception in Plants

  2. Learning objectives: • What is a tropism? • How does a tropism increase an organism’s chances of survival? • How do plants respond to change? • What are plant growth factors?

  3. A tropism is a growth movement of a part of a plant in response to a directional stimulus. Response to light is called phototropism. Response to gravity is called geotropism. Response to water is called hydrotropism. Responses can be towards (positive) or away from (negative). Tropisms:

  4. How does this response help a plant to survive?

  5. How does this response help a plant to survive?

  6. Questions: Name the tropism involved in each response: • Shoots growing towards light? • Roots growing towards gravity? • Shoots growing away from gravity? • Roots growing away from light? • Roots growing towards water?

  7. What are the missing words? Tropism is how plants respond to their environment. When sunlight is the stimulus this is known as ______tropism. Positive phototropism is where the plant grows _______the light. This happens at the _____tip. ________ phototropism is where the plant grows away from the______, this happens at the_____. When gravity is the stimulus this is known as ______tropism. ________Geotropism is where the plant grows in the direction of_______. This happens at the roots. Negative ___tropism is where the plant grows opposing gravity, this happens at the _____tips.

  8. Plant Growth Factors: • Plants respond to these stimuli through the use of hormones or plant growth factors. • They exert their influence by affecting growth. • They are made by cells. • They have effects close to the tissues that produce them.

  9. Plant Hormones What is controlled by hormones in plants? Growth – roots and shoots, seed germination, leaf fall, disease resistance, fruit formation and ripening, flowering time, bud formation.

  10. Control of Tropisms by IAA • Auxins are a group of the hormones used by plants for growth – you need to know about indoleacetic acid (IAA). • IAA is produced in the cells at the shoot tip. • Light will cause IAA to gather on the shaded side of the shoot. • IAA in the shoots causes cell elongation. • This results in one side of the shoot elongating faster than the other – uneven growth causes bending. • At the root, high concentration of IAA inhibits growth, small concentration promotes growth.

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