growth response of plants n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Growth Response of Plants PowerPoint Presentation
Download Presentation
Growth Response of Plants

Loading in 2 Seconds...

play fullscreen
1 / 39

Growth Response of Plants - PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on

Growth Response of Plants. Prepared by Ms W.S.Kwan. Plants have no nervous system. Can plants detect stimulus? Can plants response?. Tropism (Tropic Movement). A directional growth movement made by a part of a stationary plant in response to unilateral stimulus. stimulus. gravity.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Growth Response of Plants' - marc


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
growth response of plants

Growth Response of Plants

Prepared by Ms W.S.Kwan

slide3

Tropism (Tropic Movement)

A directional growth movement made by a part of a stationary plant in response to unilateral stimulus

types of tropism

stimulus

gravity

unilateral light

water

tropism

Types of Tropism

geotropism

phototropism

hydrotropism

geotropism
Geotropism
  • Geotropism is the growth movement (growth response) shown by a plant part in response to gravity
slide6

Investigation 17.1

To show Geotropism in Seedlings

to show geotropism in seedlings
To show Geotropism in Seedlings

Why is it necessary to leave the apparatus in darkness ?

Ans: To avoid any stimulus from light.

to show geotropism in seedlings1
To show Geotropism in Seedlings

What has happened to the radicles and plumules ?

Ans: The radicles grow downwards, while the plumules grow upwards.

to show geotropism in seedlings2
To show Geotropism in Seedlings

Do the radicles show positive geotropism (towards gravity) or negative geotropism (away from gravity)?

Ans:Positive geotropism.

slide10

What advantage do the seedlings have by showing such geotropism ?

Ans: Roots grow downwards deep into the soil to provide a firm anchorage underground and absorb water and mineral salts in the soil.

slide11

Importance of Geotropism(Roots grow towards gravity)

  • provide firm anchorage for roots
  • ensure the plant can get adequate supply of water & mineral salts
clinostat
Clinostat
  • for control experiments
  • contains a cork disc which can be set to rotate in a vertical or horizontal plane by a motor
  • Cancel out the effect of unilateral stimulus
  • to make factors uniform (evenly distributed)
slide13

Investigation 17.2

To show the effect of Gravity by using a Clinostat

slide14

plastic cover lined with moist blotting paper

X

in complete darkness

Y

What is the purpose of marking the radicles at equal intervals ?

Ans:To find out which region of the radicle grows faster.

slide15

plastic cover lined with moist blotting paper

seedling in X

X

in complete darkness

seedling in Y

Y

Does the direction of growth of the seedlings in clinostat X change ?

Ans: The radicle of the seedlings in clinostat X bends downwards in response to the pull of gravity.

slide16

plastic cover lined with moist blotting paper

seedling in X

X

in complete darkness

seedling in Y

Y

Does the direction of growth of the seedlings in clinostat Y change ? Why ?

Ans: Since every side of the radicle of the seedling in clinostat Y is acted on by gravity, the radicle will grow straight horizontally.

slide17

plastic cover lined with moist blotting paper

seedling in X

X

in complete darkness

seedling in Y

Y

What is the purpose of setting up clinostat Y ?

Ans: Serve as a control for comparison.

phototropism
Phototropism
  • Phototropism is the growth movement (growth response) shown by a plant part in response to light.
slide20

Investigation 17.3

To show Phototropism in Shoots

slide21

A

B

C

unilateral light

unilateral light

light-proof box

clinostat

in complete darkness

What is the effect of the clinostat on the shoot of plant B ?

Ans:The revolving clinostat cancel out the effect of unilateral stimulus (light) on the shoot of plant B.

slide22

A

B

C

unilateral light

unilateral light

light-proof box

clinostat

in complete darkness

What has happened to the shoots of plants A and B ?

Ans: The shoots in pot A respond by growing towards the light source.

The shoot in pot B do not show any curvature but grow vertically upwards.

slide23

A

B

C

unilateral light

unilateral light

light-proof box

clinostat

in complete darkness

What has happened to the shoot of plant C ?

Ans:the shoots in pot C grow vertically upwards with slender and longer nodes(elongated), and carries smaller leaves which are yellow in colour (etiolated).

slide24

A

B

C

unilateral light

unilateral light

light-proof box

clinostat

in complete darkness

What is the significance of phototropism to plants ?

Ans:This tropism ensures that a plant gets enough light energy for photosynthesis.

slide25

Importance of Phototropism(Shoots grow towards light source)

  • enables leaves to be in a position to receive maximum sunlight for photosynthesis
hydrotropism
Hydrotropism
  • Hydrotropism is the growth movement (growth response) shown by a plant part in response to water.
slide27

Importance of Hydrotropism(Roots grow towards water supply)

ensures that a plant gets

  • enough water as a raw material for photosynthesis &
  • enough mineral salts to maintain normal growth
types of tropism1

stimulus

gravity

unilateral light

water

tropism

response

Types of Tropism

geotropism

phototropism

hydrotropism

no response

negative

shoot

positive

root

negative

positive

positive

slide31

cut & replaced tip

few days later

decapitated

Experiments on Oat Coleoptiles

dark box

no growth

grows

Conclusions :

The tip is responsible for the growth

slide32

unilateral

light

few days later

black covers

Experiments on Oat Coleoptiles

Conclusion :

The tips are sensitive to light.

(responsible for the detection of light)

slide33

agar plate

fewdayslater

Experiments on Oat Coleoptiles

dark box

Conclusions :

The tip must have produced a diffusible chemical substance which stimulates growth

slide34

mica

plate

Experiments on Oat Coleoptiles

bending directions

bending directions

Can the explanation still work ?

the tip is put aside

Explanation of results :

The side with the tip has a higher concentration of that particular chemical, the growth rate is faster than the other side.

auxins
Auxins
  • commonest plant hormones
    • produced by shoottip
    • regulate growth & other physiological processes in plants
    • promote growth by inducing cell elongation & cell division.
effect of auxin on plant parts

shoot

high

conc.

low

conc.

root

auxin concentration

plant growth

high conc.

low conc.

shoot

root

Effect of auxin on Plant Parts

positive

growth

Growth of

plant

auxin

concentration

negative

growth

Positive (promote)

no effect

Negative (inhibit)

Positive (promote)

phototropism in shoot
Phototropism in Shoot
  • The shoot tip produces auxins which diffuse downward
  • The auxins diffuse to the shaded side due to the presence of unilateral light
  • High auxin concentration stimulates growth in shoot
  • The shaded side grows faster than the lighted side
  • The shoot bends towards the light
geotropism in root
Geotropism in Root
  • The auxins diffuse to the lower side due to gravity
  • High auxin concentration inhibits growth in root
  • The lower side of root grows slower than the upper side
  • The root bends downward