2. Plant movement
• The movement of higher
plants are chiefly in the
form of bending, twisting,
and elongation of certain
plant parts or organs, e.g.
• Tropic movements向性运动
• Nastic movements感性运动
• Tactic movements倾性运动
4. Tropic movements
• Greek τρόπος, tropos, "a turning"
• Tropic movements are growth
movements, which occur in response
to unidirectional external stimuli and
result in positioning of the plant part
in the direction of the stimulus.
• Positive tropism: the movement is
towards the direction of stimuli
• Negative tropism: the movement is
away from the direction of stimuli
5. Quiz
• Tropisms _____.
A. are due to differential growth
B. are responses to multidirectional stimuli
C. both A and B
6. Quiz
• Plant growth toward a stimulus is called a _____ tropism.
• positive
• negative
7. Bending of the plant body
• The bending of a specific part of the
plant body is due to the uneven growth
in the elongation zone.
• The plant will bend to the opposite side
of the longer cells.
8. Auxin生长素
• from Greek auxein ‘to increase’ + -in
• Auxins are a class of plant hormones
that induces plant growth and
development.
• Auxin promotes growth in plants by
increasing the plasticity of plant cell
walls.
• Auxins are produced in the stem,
buds, and root tips, and the embryo
in the seeds.
• Plant natural auxin is called indole-3-
acetic acid (IAA).
stem
9. Quiz
• Auxin promotes growth in plants by
A. stimulating the uptake of water by seeds.
B. increasing the plasticity of plant cell walls.
C. causing elongation of stems.
D. increasing the rate of photosynthesis.
E. promoting root tip growth.
10. Transportation of auxin
• Auxin molecules is
transported with active
transport.
• The distribution of IAA
transport protein in the
stem is asymmetrical,
causing a directional
(polar) transport 极性运输
from the apical end to the
basal end.
• Auxin can be transported
horizontally only at the
shoot and root tip (zone
of cell division).
12. Effects of auxin concentration of plant growth
• Different parts of the plants
have different sensitivity
to auxin.
• The optimum
concentration for the
growth of the roots is much
lower than that of the
buds.
• High concentration of
auxin will inhibits
development of roots.
13. Quiz: Draw the placements of auxin in the
shoot and root.
14. Type of trophic movement
• Phototropism向光性: shoot grows towards the light
• Geotropism / gravitropism向地性: roots grows towards the centre of
gravity
• Hydrotropism向水性: roots grows towards moisture
• Thigmotropism向触性: shoot grows towards direction of contact
• Chemotropism向化性: root grows towards the fertilizers or cytokinins
• Rheotropism向流性: root grows towards the water flow
• Aerotropism向空气性: root grows towards the oxygenated area
15. Quiz
• A movement in response to touch is known as _____.
A. phototropism
B. thigmotropism
C. gravitropism
17. Phototropism
• Phototropism is the growth of
an organism which responds to
a light stimulus.
• Shoots exhibits positive
phototropism.
• Roots exhibits negative
phototropism (but more
affected by positive
gravitropism).
20. Quiz
• Plants bend toward the light so as to promote photosynthesis. This
occurs because auxin is transported to the _____ , causing the cells
on this side to elongate.
A. shady side of the shoot
B. sunny side of the shoot
C. shady side of the root
D. sunny side of the root
23. Quiz
• A mica plate is inserted into the shoot tips of four plant younglings.
The direction of the light is different in each case. After a period of
time, the growth of the shoot tips are:
A BA
A：Straigth B：Turn right
C
C：Turn right
24. Quiz
• Youngling Y will turn ________.
A. left B. right
C. downwards D. no bending
D
25. Clinostat植物旋转器
• A clinostat is a device which
uses rotation to negate the
effects of direction of
stimulate source.
26.
27.
28. Quiz
• A young shooting is left inside a dark box with a side window. Fix light
source enter the box from this window. The box and the plant
together are place on a clinostat to rotate horizontally in the
frequency of 15 minutes per turn. After one week, the plants will
grow into _______.
小
窗
光
源
小
窗
光
源
小
窗
光
源
小
窗
光
源
A B C D
B
29. Quiz
• If the vase is fixed by the opaque box is rotated evenly on the
clinostat, then the plants will grow into _______.
小
窗
光
源
小
窗
光
源
小
窗
光
源
小
窗
光
源
A B C D
C
30. Action spectrum
of phototropism
• Phototropism is
mostly due to
reaction towards
light of shorter
wavelength, i.e.
blue-purple light.
31. Light for
photosynthesis
• Chlorophyll a
prefer blue and
red light.
• Blue light contain
most energy
compare to red
light.
• Hence
phototropism is
more sensitive to
blue light.
33. Geotropism
• Geotropism is the growth of the
parts of plants in response to the
force of gravity.
• Roots show positive geotropism.
• Stems show negative geotropism.
35. Statoliths平衡石detect gravity
• Greek stásis “standing” +
líthos “stone”
• Plants sense gravity
through statoliths found in
specialized starch
parenchyma cell, the
statocytes平衡细胞.
• Statoliths are dense
amyloplasts淀粉体,
organelles that generally
synthesize and store
starch.
36. Sedimentation of statoliths
• The statoliths
are denser than
the cytoplasm
and can
sediment
according to the
gravity vector.
37. Reposition of auxin carriers
• The statoliths are enmeshed in a
web of actin and it is thought
that their sedimentation
transmits the gravitropic signal
by triggering the release Ca2+ by
the smooth endoplasmic
reticulum.
• The auxin efflux carriers
reorient to redistribute the
auxin.
40. Quiz
• Curving away from light is called _____.
• A) positive phototropism
• B) positive thigmotropism
• C) negative gravitropism
• D) negative phototropism
41. Quiz
• If the root cap is removed, the plant root still responds to gravity.
• A) True
• B) False
42. Quiz
• In response to stimulation by gravity, auxin _____ the growth of root
cells causing the cells of the upper surface to elongate more quickly.
• A) stimulates
• B) inhibits
43. Quiz
• Sketch the distribution of
auxins in the stem and roots.
• Explain why the direction of
the growth is different.
44. Clinostat: spin horizontally
• The rotation creates centrifugal
force向心力.
• The gravity is still in effect.
• The roots will growth towards to
combination direction of both
the centrifugal force and
gravitational force.
• The shoots will grow towards the
direction of centre of centrifugal
force.
45. Quiz
• A vase of youngling is place of a clinostat that spins horizontally in
even seed. The light source is on the left. After a period of time, the
shoot and roots will grow towards ________.
A. Shoot ↖, root ↘ B. Shoot ↖, root ↙
C. Shoot ↗, root ↘ D. Shoot ↗, root ↙
D
light source
46. • No net direction of gravitational
pull.
• Root and stem grows horizontally.
Clinostat: spin vertically
(plant placed horizontally)
47. Quiz
• Does the direction of growth of the seedlings in clinostats X and Y
change? Why?
48. Conclusion
• Auxin is produced in shoot and root tips.
• Auxin is transposed to the dark side and towards the gravity.
• Plants sense gravity through statoliths
Shoot Root
Auxin Stimulate growth Inhibit growth
Phototropism Positive Negative
Geotropism Negative Positive
50. Nastic movement
• Greek ναστός "pressed"
• Nastic movement is a non-directional
respond to stimuli.
• Growth may not be involved in nastic
movement.
• The movement is generally due to changes
in turgor and is generally reversible.
• suffix "-nasty":
• Thermonasty感温性运动: response to temperature
• Nyctinasty感夜性运动: movements at night or in
the dark
• Thigmonasty/seismonasty/haptonasty感震性运动:
response to contact
• Hydronasty: response to water
52. Nyctinasty: Sleeping movement
• Nyctinasty is the
circadian rhythmic
nastic movement of
higher plants in
response to the onset of
darkness.
• Examples are the closing
of the petals of a flower
at dusk and the sleep
movements of the
leaves of many legumes.
53. Pulvinus叶褥 facilitates nyctinastic movement
• Pulvinus (pl. palvini) is a thickening at the
base of the petiole叶柄 or petiolule小叶柄.
• Pulvinar movement is caused by changes in
turgor pressure leading to a contraction or
expansion of the parenchyma tissue薄壁细胞
of the pulvinus.
54. Process of Nyctinasty
• During the day the palvinus
cells are turgid.
• During the night, cells on
the lower side of the
palvinus lost water.
• The petioles bend
downwards and the petal
closes.
57. Thigmonasty
• Thigmonasty is the nastic response of a
plant or fungus to touch or vibration.
• The closing movement of many species in
the leguminous subfamily Mimosoideae
such as Mimosa pudica
• The prey-catching movement of active
carnivorous plants such as Dionaea.
58. Mechanism of
closing
• Similar to nyctinasty
• A lost of turgidity in one
side of the palvinus leads
to closing of leaflets.
60. Hydronasty
• Hydronasty is the nastic response of a
plant or fungus to atmospheric
humidity.
• The turgor movement膨胀运动:
movement due to change in turgidity.
• stomata movement
• leaf rolling
• spore dispersal
• The hygroscopic movement吸湿运动:
movement due to desiccation干燥 and
the cell walls dry and shrink.
• spore dispersal in ferns and bryophytes
苔藓植物
61. Turgor movement: stomata movement
• Stomata open when the guard cells
are swollen
• Stomata close when the guard cells
are shrunken
62. Turgor movement: leaf rolling
• Xerophyte旱生植物 leaves
rolls during dry season
when turgidity decrease
70. Tactic movements倾性运动
• Tactic movements are movements of locomotion,
which are induced by some unidirectional external
stimuli.
• Their direction is controlled by the direction of the
stimulus.
• Generally occurs in small, simple, unicellular
organisms.
• E.g. movement of unicellular algae and euglena眼
虫 towards light stimuli with flagellum
• Depending upon the nature of stimuli, these
movements are of following types:-
• Phototactic: light
• Chemotactic: chemicals
• Thermotactic: temperature
72. Conclusion
• Nastic movement is a non-directional respond to stimuli.
• Growth may not be involved in nastic movement.
• The movement is generally due to changes in turgor and is generally
reversible.
• Tactic movements are movements of locomotion, which are induced
by some unidirectional external stimuli.
• Tactic movement occurs in small, simple, unicellular organisms.
