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Plant responses

Plant responses. Why do plants need to respond to their environment?. Tropisms Directional growth responses of plants Phototropism Geotropism Chemotropism Thigmotropism. Apical meristem of a shoot

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Plant responses

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  1. Plant responses Why do plants need to respond to their environment?

  2. Tropisms Directional growth responses of plants Phototropism Geotropism Chemotropism Thigmotropism

  3. Apical meristem of a shoot Apical meristem of the apical bud adds new tissue to the stem tip. This increases the length of the stem. (a) Shoot apical meristem (b) Leaf primordial (c) Axillary bud primordium (d) leaf (e) Stem tissue

  4. Tropsims Shoots – positive phototropism – negative geotropism Roots – negative phototropism – positive geotropism Auxins are a class of plant growth hormones which promote cell elongation

  5. " when seedlings are freely exposed to a lateral light some influence is transmitted from the upper to the lower part, causing the latter to bend".

  6. This suggests the growth promoting substance is chemical and moving down the shaded side.

  7. Again these Boysen-Jensen experiments add confirmation that the growth promoting substance is chemical in nature

  8. Plant hormones and leaf shedding • Senescing = Leaves age and turn brown • Abscission = Leaves fall off

  9. Leaf senescence Fall in Auxin production Ethene production increases Cells in the abscission zone become more sensitive to Ethene The production of the enzyme Cellulase increases. Cell walls in the abscission zone are digested, causing leaf loss

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