Chapter 33: Plant Responses Objectives. Explain the term: growth regulation. Define the following terms: tropisms, phototropism, geotropism, thigmotropism, hydrotropism, chemotropism. Name examples of phototropism & geotropism. Define the term: growth regulator.
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Explain the term: growth regulation.
Define the following terms: tropisms, phototropism, geotropism, thigmotropism, hydrotropism, chemotropism.
Name examples of phototropism & geotropism.
Define the term: growth regulator.
Outline the transport of regulators via the vascular system.
Explain the term: Growth Promoter.
Explain the term: Growth Inhibitor
Name 4 methods of anatomical/chemical adaptations that protect plants.
State 2 examples of the use of plant regulators.
Mandatory Activity :Effects of I.A.A. Growth Regulators on Plants
A stimulus is anything that causes a response in an organism, A stimulus is anything that causes a response in an organism,
or in any of its parts.
A response is the activity of a cell or organism to a stimulus.
Plant responses involve growth and changes in growth due to a stimulus
Plant adapt to new situations by
modifying their growth, by means of
chemicals called growth regulators [hormones].
Growth is the increase in the number, size and volume of cells.
A hormone is a chemical produced in one part of an organism, transported to other tissues where it has its effect.
Plant growth regulators [hormones] are chemicals that interact with one another to control a particular development or response.
A tropism is a plant’s response to a stimulus coming from onedirection, e.g. sunlight, gravity.
Geotropism is the growth of a plant in response to gravity—itallows the root to get the water and nutrients it needs fromthe soil, and raises the leaves up into the light forphotosynthesis.
Hydrotropism is the response of roots to water – they willgrow towards it.
Growth shut down for winter
Plant growth regulators
promote cell enlargement and growth,
are involvedin phototropism and apical dominance
In shoots, light causes auxin to move down the shaded part of the stem, causing the shoot to grow towards the sunlight. This is called PHOTOTROPISM.
Artificial auxins can also be used to kill weeds, stimulate root formation in cuttings, …
3. In autumn, trees recycle all the nutrients they can out of the leaves for storage in phloem tissue. The red pigments of autumn serve as a kind of botanical sunscreen, a defence mechanism against sun damage that could interfere with the storage process and cause a leaf to drop before the tree was done with it.
Heat-shock proteins [stress proteins] are created when cells are exposed to higher temperatures or to other kinds of environmental stress, such as UV light. Their activities are part of a cell's repair system and allow the plant to tolerate extra heat, light, etc. for a limited period, and resume normal cellular activities when the stress ends.
They protect themselves against:
Plants can adapt themselves for protection in two ways:
Plants can grow and regenerate throughout their life.
They can produce new roots, stems, leaves.
To investigate the effect of IAA concentration on plant tissues.
1. Different concentrations of IAA are prepared.
2. Seeds are grown in petridishes with different
concentrations of IAA.
3. Changes in length of seedlings shoots and roots are recorded.
At low concentrations the roots grow larger and
shoots stay short.
At higher concentrations the shoots grow larger and
roots stay short.