Transcript 23.4 Growth and development in plants

23 Growth and development (Extension)
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23.1 Growth and development
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23.2 Growth and development in humans
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23.3 Seed germination
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23.4 Growth and development in plants
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23.5 Measurement of growth
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Mind Map
23.1 Growth and development
23.1 Growth and development
1. What is Growth ?
Size
A permanent increase in
Weight
By
cell division
1
By
cell
elongation
2
2. What is Development ?
Increase in complexity
3
By cell
differentiation
23.1 Growth and development
After fertilisation
Growth
Size &
weight
Zygote
undergoes
mitosis
23.1 Growth and development
Development
Complexity
cells undergo
differentiation
Other cells
Different types of cells
are formed
23.2 Growth and development in humans
&
in
23.2 Growth and development in humans
Growth curve of humans
First two years
after birth,
growth rate is
very fast
birth
age (years)
23.2 Growth and development in humans
Growth curve of humans
Age 3 to 12,
growth rate
slows down
birth
age (years)
23.2 Growth and development in humans
Growth curve of humans
Age 13 to 17,
growth rate is
fast again
birth
age (years)
23.2 Growth and development in humans
Growth curve of humans
Growth rate
stops at
about 20
birth
age (years)
23.2 Growth and development in humans
Relative growth rates of
different parts of the body
Grow rapidly in
the first three
years and then
slow down
head & brain
whole body
reproductive organs
Age (years)
Different parts of
the body grow at
different rates
23.2 Growth and development in humans
Relative growth rates of
different parts of the body
head & brain
whole body
reproductive organs
Age (years)
The last
organs to
develop
and
differentiate
Different parts of
the body grow at
different rates
23.2 Growth and development in humans
Different parts of the body
grow at different rates
2 months
(foetal)
5 months newborn
(foetal)
2 years
6 years
12 years
25 years
23.2 Growth and development in humans
The growth rates of boys and girls
Between ages of
11 & 14
boys
girls
growth rate is
faster in girls
than in boys
After age 14
growth rate is
faster in boys than
in girls
Age (years)
23.3 Seed germination
23.3 Seed germination
When a seed starts to germinate
Fresh mass increases
∵ it absorbs water from the soil
23.3 Seed germination
However, the dry mass of the seed decreases
The stored starch is
broken down into sugar
and is used to
Make new cell walls
Release energy in
respiration
The stored protein is
broken down into amino
acid and is used to
Make new protein
molecules for cell
membrane and cytoplasm
23.3 Seed germination
But…
Once the plumule appears
above the soil
the young leaves appear and
carry out photosynthesis
If the rate of photosynthesis
is faster than that of
respiration
the dry mass increases
23.3 Seed germination
Conditions for
seed germination
Water
Warmth
Oxygen
23.3 Seed germination
Conditions for seed germination
Water
Softens the seed coat
1
2
Activates the enzymes to break
down the stored food
3
Dissolves food
4
Transports dissolved food to the
growing point of embryo
23.3 Seed germination
Conditions for seed germination
Warmth
Enzymes work at a faster rate
at higher temperature
23.3 Seed germination
Conditions for seed germination
Oxygen
Enables seeds to respire
aerobically to supply energy
for growth
23.3 Seed germination
Experiment 23.1
To study seed germination
1. You are given some mung bean seeds. Design and perform
investigations to study the conditions necessary for seed
germination.
2. Bring your proposal to your teacher for perusal.
3. You can carry out the investigation with the permission of
your teacher.
4. What conclusion can you draw after the experiment?
23.4 Growth and development in plants
&
in
23.4 Growth and development in plants
Growth &
development
at root tips
phloem
xylem
region of
root hairs
region of cell
differentiation
region of cell
elongation
region of cell
division
protects the root
as it grows
through the soil
root cap
23.4 Growth and development in plants
Growth & development at root tips
Cell undergoes
mitosis to produce
small new cells
Growing point
23.4 Growth and development in plants
Growth & development at root tips
Vacuolation helps the
roots to push their way
down into the soil
Cells absorb water &
expand / elongate
Growing point
23.4 Growth and development in plants
Growth & development at root tips
The cell wall
becomes
thickened &
Region of
differentiation
the cells
differentiate
into
specialised
tissues e.g.
cortex, xylem,
phloem &
cambium
23.4 Growth and development in plants
Growth & development at root tips
Growing point
Root cap
23.4 Growth and development in plants
Growth & development at shoot tips
Growing point
(apical meristem)
Shoots grow in a way similar to the roots
23.4 Growth and development in plants
Experiment 23.2
To study the growth of young seedlings
1. Germinate some broad bean seeds by planting them in
moist peat with their radicle pockets positioned deliberately
so that their radicles will emerge and grow directly
downwards. Leave them until their radicles (young roots)
have grown to about 3cm long.
2. Choose 3 broad bean seedlings with straight radicles. Rinse
the seedlings and blot their radicles thoroughly with tissue
paper.
23.4 Growth and development in plants
Experiment 23.2
To study the growth of young seedlings
3. Using Indian ink, mark the terminal 2 cm of the radicles at
2 mm intervals.
4. Carefully place the broad bean seedlings in a beaker or
glass jar as shown below.
thread (used to mark the
wire radicle with Indian ink)
blotting paper
(or newspaper)
glass jar
broad bean
seedling
water
23.4 Growth and development in plants
Experiment 23.2
To study the growth of young seedlings
5. Leave the seedlings for several days. Examine them again.
thread (used to mark the
wire radicle with Indian ink)
blotting paper
(or newspaper)
glass jar
broad bean
seedling
water
23.4 Growth and development in plants
Experiment 23.2
To study the growth of young seedlings
plumule
Question 1:
Do all parts of the radicle grow?
Answer:
Growth occurs only in the
regions just behind the tip. No
growth occurs in the very tip as
it is covered by the root cap.
radicle
23.4 Growth and development in plants
Experiment 23.2
To study the growth of young seedlings
plumule
Question 2:
Which region shows the
greatest growth rate?
Answer:
The region of maximum
growth is the region of
elongation which is located
immediately behind the tip.
radicle
23.4 Growth and development in plants
23.4 Growth and development in plants
Food
reserves are
used for
respiration &
no food
formation
because of
no leaf
Thus, it
shows a
negative
growth
germination
Time (weeks)
23.4 Growth and development in plants
Once the green leaves
undergo photosynthesis &
the rate of photosynthesis is
higher than that of respiration
It shows a
positive
growth
germination
Time (weeks)
23.4 Growth and development in plants
Due to dispersal
of fruits & seeds
After 20 weeks,
there is a sudden
decrease in dry
mass
Finally the
plant dies
germination
Time (weeks)
23.4 Growth and development in plants
Only the
food
reserves
are used
germination
Rate of
photosynthesis is
higher than that
of respiration
Dispersal of
fruits & seeds
& finally the
plant dies
Time (weeks)
Summary
23.5 Measurement of growth
23.5 Measurement of growth
Size
Fresh
mass
Dry
mass
23.5 Measurement of growth
Size
e.g. height, length,
surface area and volume
Advantages
Disadvantage
Quick & easy to
carry out
Does not take into account of
growth in other dimensions
Does not damage
the organisms
23.5 Measurement of growth
Fresh
mass
Total mass of an organism
including the water content
inside its body
Advantages
Disadvantages
A quick and
simple way
May kill the large plant because
it is necessary to uproot it
Usually does no harm
to the organism
The result will vary
depending on the amount
of water taken in or lost
23.5 Measurement of growth
Dry
mass
Advantage
The most
accurate
method
Total mass of an organism
excluding water
Disadvantages
The organism is
killed
Have to use a
large number of
organisms
A time-consuming
method
Impossible for
large organisms
Mind Map
Growth
Development
increase in
complexity
permanent
increase in
processes
include
measurements
include
by
differentiation
1. size
1. cell division
1. size
produce
2. weight
2. cell elongation
by vacuolation
in plants
by
mitosis
2. fresh mass
3. dry mass
different kinds
of cells