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Hormonal-Response
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Uploaded: 7 years ago
Category: Biology
Type: Lecture Notes
Tags: growth, causes, plants, seedless, phototropism, geotropism, auxins, collect, elongation, ripening, source, inhibits, control, towards, shoot
growth
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Filename: Hormonal-Response.docx
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Transcript
Hormonal response and co-ordination in humans
Endocrine and exocrine glands
Exocrine:
Glands whose secretions pass through a series of ducts ultimately to the exterior of the body.
Eg: Salivary glands
Prostrate gland
Sweat glands
Portion of Pancreas that secretes bile into the duodenum (Islets of Langerhands are ENDOcrine)
Endocrine:
Glands whose secretions pass through the blood stream to the target organs.
Eg: Islets of Langerhans (in Pancreas)
Pituitary gland
Hypothalamus
Liver
Stomach and intestines
481965029654500Adrenaline (An ENDOcrine hormone):
Brain senses stress or danger
Brain sends electric signals to the adrenal glands
Adrenal glands secrete adrenaline into the bloodstream
Results of adrenaline:
Increase in metabolic activity, releasing more energy to cope with the situation
Causes liver to break down glycogen into glucose to provide energy for higher metabolic activity
Effects of adrenaline:
Faster heart beat
Breathing rate increases
Pupils dilate
Blood diverted from the gut to muscles
Chemical co-ordination in Plants
Auxins
One of five plant growth hormones
Made in cells that are dividing (Behind the tip of the root and the shoot)
Auxins diffuse into nearby cells:
Shoot - Causes growth and elongation
Root - Slows down growth and inhibits elongation
Tropisms
Growth movements made by plants in response to a stimulus
Stimuli include: Gravity, light, temperature, water, chemicals, touch
39433509969500Geotropism
Positive geotropism (In the root):
Growth TOWARDS gravity.
Negative geotropism (In the shoot):
Growth AWAY FROM gravity.
Auxins are responsible for the growth pattern
Positive geotropism: Auxins collect at the lower side of the root and inhibits the cell elongation. This causes the downward curve of the root (radicle).
Negative geotropism: Auxins collect at the lower side of the shoot and causes growth and elongation. This causes the upward curve of the shoot (plumule).
364807511938000
Phototropism
Positive phototropism (In the shoot):
Growth TOWARDS the light.
Negative phototropism (In the root):
Growth AWAY FROM the light.
Auxins move away from a source of light and are responsible for the growth pattern:
Positive phototropism: Auxins collect in the dimmer side of the shoot and cause those cells to elongate. This causes the curve of the stem (radicle) towards the source of light.
Negative phototropism: Auxins collect in the dimmer side of the root and inhibit the cell elongation. This causes the curve of the root (plumule) away from the source light (the soil).
Synthetic plant growth substances
Definition:
Artificial substances which are made to control and regulate plant growth by imitating natural plant growth substances.
Several uses:
Weedkillers
Production of seedless fruits
Control of frit ripening
Rooting of cuttings
Micropropagation of plants
Weedkillers
Sprayed onto weeds to encourage rapid, uncontrolled growth which eventually cause those plants to die.
This type of weedkiller is selective and effects on certain plants.
Eg: Broad-leaved plants amongst crops of cereals (narrow-leaved)
Weeds on lawns
Undergrowth in tree plantations
Production of seedless fruits
Some fruits develop without fetilization (and therefore without seeds)
This development is called parthenocarpy.
Synthetic auxins are added to some plants to induce the production of seedless fruits.
Gibberellins have a similar effect on other plants.
Used to grow seedless grapes and increase their size before harvesting
Control of fruit ripening
The control of fruit ripening can increase the profitability for farmers and resellers.
Auxins are used to prevent potatoes from sprouting buds.
Gibberellins are used to slow down the ripening of grapefruit.
Ethene gas can stimulate the ripening of fruit.
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