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Title: Stimulus reception in plants - GCSE level
Description: Sensitivity, tropism, darwin's theory, Boysen-Jensen theory, Paal theory, Went theory, and the chemical auxin and how it works.
Description: Sensitivity, tropism, darwin's theory, Boysen-Jensen theory, Paal theory, Went theory, and the chemical auxin and how it works.
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Stimulus Reception in Plants
Sensitivity: the ability to detect changes in the internal/external environment and
respond to them
...
They can be positive (towards) or negative (away)
...
g
...
(coleoptiles: surrounds and protects the apical meristem and
young leaves)
Darwin: coleoptiles are phototropic, they bend towards light
...
If the tip is cut off, no bending occurs
...
1 | P a g e
Boysen-Jensen: if the tips are placed on gelatine blocks, bending occurs
...
Therefore the signal is a chemical substance which passes through permeable
materials
...
If it is placed on the
opposite side of light, no bending occurs
...
Paal: if coleoptile tips are cut off and placed in light, then placed back off-centred,
the bending occurs towards the opposite side of the tip
...
Went: If agar with the chemical is placed on one side, bending occurs towards the
other side
...
The chemical is auxin – ‘indol-3-acetic acid’ (IAA)
Synthesised in the shoot apical meristem and growing leaves
...
It moves by diffusion
...
They cannot burst as the cell wall die to
cellulose is elastic
...
Auxins stimulate the secretion of H+ out of the cells into the cell wall
...
This allows stretching
...
3 | P a g e
Title: Stimulus reception in plants - GCSE level
Description: Sensitivity, tropism, darwin's theory, Boysen-Jensen theory, Paal theory, Went theory, and the chemical auxin and how it works.
Description: Sensitivity, tropism, darwin's theory, Boysen-Jensen theory, Paal theory, Went theory, and the chemical auxin and how it works.