Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

The life of a Plant
• Radicle Emergence and Root Growth
Anatomy [structure and function]
Quiescent zone
Tropisms:
-Positive gravitropism
-Negative gravitropism
• Trees were the first natural flowering plant
...

• Get inhibition thing going on in the seed and bud then you get the emergence
of a radicle which is the first thing that happens under normal
circumstances- absolutely crucial in terms of survivability of the seed in
the long run in terms of water uptake to the plant
...
Not long after
that you’ll begin to see emergence of secondary leaves and all of this is
occurring in the root prior to the development of anything significant
above the soil
...

• You see different stages of development in the root and thus gives you an
idea of the various active zones that exists in the root
...
Down below within the root cap, you begin to see various
zones that are visible
...
Cells hanging out of the side of the root cap
are known as cell sloughing
...

• The root has to push down through the soil and is bound to get damaged
...

• Mucilage- mucilage secretion out of these root caps is like an oil that makes it
easier and acts as a lubricant for the cells to penetrate through the soil
...
The cells below are
shorter
...

• As the root grows there are regions where elongation occurs- have an
increase in the volume of cells due to elongation that pushes the root cap
down into the soil
...
Cellular division occurs in the small cells near the
tip below the elongation zone
...
This is of functional interest in terms of the
developmental biology point of view
...
Looking at
positional roles- where a cell in each location within the root cap have
different roles associated with them
...

• What kind of experimental technique would you use to determine cell division?
Can either look at it and wait for cell division to occur
...
Can then visualize the
radioactivity caused by thymidine
...
Black space in
between the dividing cells where cells haven’t divided is known as
the quiescent zone where cells do not divide
...

[Refer to the picture below]

• These cells do not do anything except very very rarely
...
One cell may retain quiescence and the
other cell may divide constantly [ around 30-40 cell divisions] and will
depending on the position be an epidermal, xylem, phloem cell for the
survival of the germinating seed
...
The chances of you being
mutated is less if you’re quiescent
...
This is a way to
protect your DNA and is important for survival and protects the cells from
DNA mutation and thus the chances of that occurring is significantly
lower
...

The daughter cell either above or below the quiescent zone can either
undergo elongation up top or aid in the root cap down below
...
Cells carry out their function
depending on where they are
...
Sort of concept that is used to describe this is
tropisms- growth directions
...
Positive is associated with the root going towards
gravity and negative is the one going against gravity
...

• Phototropism - growth towards light and negative means going away from
light
...

• How does a root sense gravity so that it knows its growing downwardsdifferent experiments conducted to study this aspect
...
Intact root cap grows downwards- remove half of the tip and it
grows side ways- the root cap inhibits cell elongation within the root
...
The root cap then appears to be influencing
cell division in terms of elongation
...
Normally the
root would grow down- block communication between elongation and
root cap zone by adding a myco-cylinder- nothing can move or diffuse
between them and thus see an increase in elongation which means that
the root cap typically sends an inhibitory signal that causes the root to
grow side ways
...

Question for the test/exam:
What is a quiescent zone and why do plants have them?
a) Quiescence minimizes the possibility of DNA mutations
...

c) Where cell division occurs
...

e) Quiescent cells are the top layer of the root cap

---