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The life of a higher plant
Shoot Biology
• dicot/monocot
• tropisms [+ve phototropism; -ve gravitropism]
• structure/function
• Budding structure associated with it- have outer scales- inhibition associated
with it during break of dormancy
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• Populus balsamifera is a common tree
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Phototropism when the coleoptile pushes
out of the soil
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If you
rely on cells that reside in the meristematic region- you want to protect
them and so the buds represent a protective layer to the shoot
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The
single apical cell will not divide as much as the cells underneath
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• With the gymnosperms- instead of a single apical cells the becomes a shoot
you have a apical cell cluster and is now becoming multicellular
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• There is an additional level of complexity associated with this and is shown in
the angiosperm diagram
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The cells are aligned in some kind of layer [1-3 layers]
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You have a tunica and a corpus associated
with the shoot meristem
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Microtubules are used to hold two nuclei
apart that generates 2 daughter cells
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Usually you
have diploid cells 2n, but with colchicine, it will generate cells that are 4n,
6n or even 8n
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So each layer arises from a progenitor of cells that have some

functional architecture associated with the shoot meristems
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In a mutated form, the
knotted ene is expressed constitutively and is thus expressed in high
concentrations
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Question for the test:
What happens when you add colchicine?
a) cells become triploid
b) disrupts microtubule function
c) disrupts actin function
d) inhibits karyokinesis (nuclei division/sep in a dividing cell)
e) a and b
f) b and c
g) b and d —> answer
h) c and d
*might see something to do with tunica or corpus or quiescent zone in the
exam
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The inner leaves are
the youngest and the outer is the oldest
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• The leaf primordia are going to be the newest one in the middle, the others
spread around- can see a pattern that arises as a helical form
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• Shoot meristem is where all the activity is going on
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• Each of the branches in a monocot come from an inner primordia
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All the
cell division is occurring in the soil
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