Download Plant Hormones / Growth Substances

Certain minerals are needed for healthy plant growth:
Nitrates
needed to make amino acids (and so proteins)
without nitrates, the plant would have stunted growth and yellow leaves
Phosphates needed for photosynthesis and respiration
without phosphates, the plant would have poor root growth and the leaves
would be younger and purple
Potassium
needed for enzymes in photosynthesis and respiration
without potassium, the plant would have yellow leaves with dead spots.
Plant Hormones / Growth Substances
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Promote:
o Growth
o Leaf Fall
o Flowering
Break dormancy in seeds
Inhibit growth of buds
Stimulate root formation
Bring about fruit ripening
Plant growth substances are produced in one part of the plant and are spread to other parts
through the phloem or from cell to cell.
Animal Hormones
Plant Growth Substance
Chemical
Chemical
Effects organs elsewhere
Effects organs elsewhere
Bring about long term growth effects
Bring about long term growth effects
Produced in ductless glands
Produced in cells
Released in the blood
Not released in blood – by diffusion instead
Plant Growth Substances
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chemicals produced in one part of the plant, which diffuses to cells of another
part of the plant and bring about actions such as cell division, fruit ripening,
cell elongation and leaf falling.
Auxins are ‘hormones’ that control the growth of the tips of roots and shoots:
Shoots:
auxins promote growth in shoots.
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Roots:
bend towards the light (i.e. more auxins on the shady side)
bend away from gravity (i.e. more auxins on the lower side)
auxins inhibit growth in roots
bend towards gravity (i.e. more auxins on lower side)
towards moisture (i.e. more auxins where more moisture is present)
How this can be used
1.
Weed killer: selective weed killers attack broad-leaved plants and others attack
grass.
2.
Fruit ripening / production:
Sprayed on fruit to make them ripen or to stop the fruit from falling
Spray flower to stimulate fruit formation (seedless fruits)
3.
Rooting power
cut shoot
dip end in rooting hormone powder
place / plant in moist soil
hormone stimulates growth of roots from shoot
o form of asexual reproduction
o genetically identical to parent (from which shoot is cut)
o same colour flower as parent