Objectives – What you will need to know from this section Study auxin as an example of a plant...
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Transcript of Objectives – What you will need to know from this section Study auxin as an example of a plant...
![Page 1: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/1.jpg)
Objectives – What you will need to know from this section
Study auxin as an example of a plant growth regulator under the headings of :
H 3.5.5 AUXINS
production
initiator
production site(s),
function,
different effects.
![Page 2: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/2.jpg)
Auxins affect virtually every aspect of plant development, and how they respond to environmental stimuli.
AUXINS -- HIGHER LEVEL
phototropism,
geotropism,
cell enlargement and growth,
apical dominance,
root growth,
fruit development,
vascular development,
and senescence [aging].
AUXINS influence includes
![Page 3: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/3.jpg)
Indole-3-acetic acid (IAA) is the most abundant naturally-occurring auxin,
AUXINS
Promote cell enlargement and growth
Are involved in phototropism—stem bends towards light.
Are responsible for apical dominance, where the main bud inhibits the growth of buds lower down stem.
Regulate the differentiation of the vascular tissue (xylem and phloem).
![Page 4: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/4.jpg)
IAA (Indoleacetic acid) is an auxin that is made in the meristems of shoots, buds and root, and in the tips of coleoptiles [of grasses].
![Page 5: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/5.jpg)
Auxin travels backwards from the tip in the vascular tissue and causes cells to elongate (get longer).
This makes the zone of elongation grow and so the tip is pushed further upwards (in shoots) and downwards (in roots).
Movement is by active transport from cell to cell – this requires energy.
![Page 6: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/6.jpg)
Auxins
APICAL DOMINANCE
PHOTOTROPISM
promote cell enlargement and growth,
are involved in phototropism and apical dominance
![Page 7: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/7.jpg)
LEARNING CHECK
• What is an auxin?
• List 4 effects of auxins in a plant.
• List the properties of auxins.
• What does elongation mean?
• What is IAA?
• What is a meristem?
• What is a coleoptile?
![Page 8: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/8.jpg)
A tropism is a plant’s response to a stimulus coming from one direction, e.g. sunlight, gravity.
Phototropism is a growth response of a stem towards light, so that it can receive the maximum amount of light for photosynthesis.
![Page 9: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/9.jpg)
APICAL DOMINANCE
Auxins are responsible for apical dominance, where the main bud inhibits the growth of buds lower down stem.
This photograph shows side buds sprouting when the main stem is cut off [pruned].
![Page 10: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/10.jpg)
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, …
Quicker growth here due to
more hormones
![Page 11: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/11.jpg)
Uses of plant regulators
Fruit is transported green and unripe, and can then be quickly ripened by spraying it with ethene.
A synthetic auxin [2,4-D] is used as a selective weedkiller, making the plants grow too fast.
Artificial auxins are used in rooting powders to stimulate root formation in stem cuttings.
![Page 12: Objectives – What you will need to know from this section Study auxin as an example of a plant growth regulator under the headings of : H 3.5.5 AUXINS.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649f2a5503460f94c43d68/html5/thumbnails/12.jpg)
LEARNING CHECK
• What is phototropism?
• What is apical dominance?
• If you remove the apical bud from a stem, what happens next?
• Give 3 uses of plant growth regulators.