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First 10 minutes
Sort folders
Core Practicals
Marked and self assessed work
Independent study
Complete any unfinished booklets (its says this on
the front the booklet)
If everything is completed then you should
complete Qs… from the I A-level paper.
Due Wednesday 23rd November
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Exercise books
WWW
 Notes are excellent
 Majority of students are making additional annotations
EBI
 More annotations needed during lesson (see Louise and Molly’s book)
 Highlight key terms and words
 Make synoptic links where possible
 Date, title work
Specifics from last few lessons
 Dynamic equilibrium – values may vary within a narrow range but overall kept constant
 Indicate the example of peptide and steroid hormone
 Answer quick questions from Topic 9 – in purple pen.
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C/W
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Chemical Control in Plants
• Understand that chemical control in plants is brought about by plant
growth substances such as auxins, cytokinins and gibberellins.
• Know that auxin has several effects, including cell elongation,
suppression of lateral buds (apical dominance) and promoting root
growth.
• Understand that plant growth substances often interact with each
other as shown by the antagonistic actions of cytokinin and auxin on
apical dominance.
Engage – Discuss with your partner and make a list
of the stimuli that you think plants are sensitive to
and respond to
•
Understand the principles of mammalian hormone production by endocrine
glands and their mode of action involving receptors on target cells.
Chemical control in plants
Plants are sensitive to
Light – direction, intensity
Temperature
Gravity
Water
Touch
Chemicals
Directional growth responses are known as tropisms!
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How plants grow
Do we know
what
assimilation
means?
Growth is a permanent increase in the size of an
organism or some part of it.
Cell division and the assimilation of new material
within the cells that result from the division,
followed by expansion.
Main areas of cell division in plants are known as
the meristems – where might key areas of
growth be?
Regions of cell division and cell elongation are
particularly sensitive to ???.
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C/W
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Checkpoint
• Understand that chemical control in plants is brought
about by plant growth substances such as auxins,
cytokinins and gibberellins.
• Know that auxin has several effects, including cell
elongation, suppression of lateral buds (apical
dominance) and promoting root growth.
• Understand that plant growth substances often interact
with each other as shown by the antagonistic actions of
cytokinin and auxin on apical dominance.
•
Understand that chemical control in plants is brought about by plant growth substances
such as auxins, cytokinins and gibberellins.
Auxins – indoleacetic acid (IAA)
Effective in very low concentrations
Movement involves active transport and calcium ions
Involved in apical dominance – supress growth of
lateral shoots
Low concentrations promote root growth
Response to auxin depends on concentration and
region on plant
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Your task – In your own words, using labelled
diagrams describe how auxin causes growth in shoot
when responding to light
 IAA made in tip of shoot
 Diffuses into zone of elongation
 IAA binds to receptors and causes
H+ to be pumped in cell wall
spaces.
 Causes cellulose to become more
flexible
 Water moves in via osmosis
 Cells stretch and expand
 Enzyme is eventually inhibited and
cellulose becomes more rigid
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Know that auxin has several effects, including cell elongation,
suppression of lateral buds (apical dominance) and promoting root
growth.
Auxin and root growth
 At higher concentrations,
auxin actually inhibits growth.
Explain in your
own words how
Auxin acts at the
root?
 This is an example of positive
gravitotropism.
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Seed Germination – Seeds might save
the world!!!
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Giberellins
Elongation of growing cells
Growth of fruit
Breaking dormancy in seeds
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C/W
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Checkpoint
• Understand that chemical control in plants is brought
about by plant growth substances such as auxins,
cytokinins and gibberellins.
• Know that auxin has several effects, including cell
elongation, suppression of lateral buds (apical
dominance) and promoting root growth.
• Understand that plant growth substances often interact
with each other as shown by the antagonistic actions of
cytokinin and auxin on apical dominance.
Giberellin and seeds
A. In the presence of water, it stimulates the production of
amylase (converts starch into maltose), allowing for the formation
of ATP (via glucose)
B. Gibberellin (or gibberellic acid) is necessary for seed
germination
C. The energy produced in the embryo - as a result of the action
of gibberellin - is used to facilitate germination
D. Gibberellin also causes stem elongation by promoting both cell
elongation and cell division
E. The glucose produced may also be used to synthesis cellulose for cell wall formation
Put the statements in order
on your white boards
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• Understand that chemical control in plants is brought about by plant growth substances
such as auxins, cytokinins and gibberellins.
Giberellin and seeds
B.Gibberellin (or gibberellic acid) is necessary for
seed germination
A. In the presence of water, it stimulates the
production of amylase (converts starch into
maltose), allowing for the formation of ATP (via
glucose)
C. The energy produced in the embryo - as a result
of the action of gibberellin - is used to facilitate
germination
E. The glucose produced may also be used to
synthesis cellulose - for cell wall formation
D. Gibberellin also causes stem elongation by
promoting both cell elongation and cell division
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Breaking seed dormancy
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Cytokinins
Understand that plant growth substances often
interact with each other as shown by the
antagonistic actions of cytokinin and auxin on
apical dominance.
Growth regulators that promote cell division in
the apical meristems and the cambium
through interactions with auxins. (Synergy)
They promote lateral bud development, which
can overcome apical dominance if the
leading shoot is removed or damaged.
(Antagonistic)
Cytokinins work synergistically with ethene in
abscission of leaves, flowers and fruits.
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C/W
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Checkpoint
• Understand that chemical control in plants is brought
about by plant growth substances such as auxins,
cytokinins and gibberellins.
• Know that auxin has several effects, including cell
elongation, suppression of lateral buds (apical
dominance) and promoting root growth.
• Understand that plant growth substances often interact
with each other as shown by the antagonistic actions of
cytokinin and auxin on apical dominance.
Questions
1.List as many of the different environmental
stimuli that elicit a response in plants as
you can. For each, try to explain why it is
important for the plant to respond to that
stimulus.
2.Growth in animals usually stops at a
certain stage. The meristems of plants,
where growth occurs, remain active
throughout the life of the plant. Explain
why this difference is important in the way
the organisms respond to stimuli.
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Key Terms
 Tropisms – Plant growth responses to environmental cues.
 Auxins – Plant hormones that act as a powerful growth stimulants and are
involved in apical dominance, stem and root growth, and tropic responses to
unilateral light.
 Giberellins – Plant hormones that act as growth regulators, particularly in the
internodes of stems by stimulating elongation of the growing cells; they also
promote the growth of fruit and are involved in breaking dormancy in seeds
and in germination.
 Cytokinins – Plant hormones that promote cell division in the apical meristems
and the cambium through interactions with auxins. They promote lateral bud
development, which can overcome apical dominance, they work
synergistically with ethene in the abscission of leaves, flowers and fruits.
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Now complete the Giberellin Exam
Question
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Mark Scheme
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Mark scheme
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Mark scheme
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This relates to the following
specification point:
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