2. Most of the plants are fixed at a place and only a part of them move
Plant movement can be categorized into
1. Movement of locomotion
2. Movement of curvature
3. Hygroscopic movement
Plant movement
Movement of variation
Movement of growth
3. 1. Movement of locomotion
Movement of plant body from on place to another.
Categorized in two types
a. Autonomic movement of locomotion
• Movement is not influenced by external stimuli
• It is further of three types
i. Ciliary movement
• Takes place due to cilia or flagella.
e.g, Chlamydomonas, Volvox, Euglena, Antherozoides of fern, etc.
Plant movement
4. ii. Amoeboid movement
• Takes place due to Pseudopodia.
e.g, slime mould
iii. Cyclosis
Movement of cytoplasm around vacuole
e.g, many plants
Plant movement
5. b. Paratonic movement of locomotion
• Movement is exhibited by external stimuli. It is also called tactic movement or
taxis.
It is further of following types
i. Phototaxis: stimulus is light e.g. zoospore and gametes of certain algae like
Chlamydomonas, Volvox
ii. Chemostaxis: stimulus is chemical e.g. Antherozoids in bryophytes and
pteridophytes
iii. Thermotaxis: stimulus is temperature e.g. movement of Chlamydomonas from
cold to warm water and also from hot to warm water
iv. Rheotaxis: stimulus is water current
Plant movement
6. 2. Movement of Curvature
• Higher plants cannot move from on place to another
• Movements are restricted only to the bending or curvature of some organ/parts of
plant
• Categorized in two types
a. Movement of variation
b. Movement of growth
Plant movement
7. a. Movement of variation
• Movement is temporary
• Plant part bends or moves in various direction and again goes back to same
position
• may be caused due to Shrinking and swelling of cells
E.g. Telegraph plant (Desmodium gyrans)
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Plant movement
8. a. Movement of variation
i. Autonomic (not stimulated by external factor)
• Not stimulated by external factors. E.g. telegraph plant (Desmodium)
• In this plant, two lateral leaflets move up and down periodically.
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Plant movement
9. ii. Paratonic (stimulated by external factor) (Nastic movement)
a. Nyctinastic movement
• Leaves or flowers exhibit different positions in day or night.
• E.g. leaf of oxalis.
• May be thermonastic as well. E.g. Crocus flower open in high temperature and
close in lower temperature
b. Seismonatic movement
• Stimulated by touch or shock
• e.g. Mimosa pudica
Plant movement
11. 2. Movement of Curvature
b. Movement of growth
• Growth of plant parts in particular manner directs them to curve in a particular
direction
i. Autonomic movement of growth
ii. Paratonic movement of growth
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Plant movement
12. i. Autonomic movement of growth
• Growth movement not directed by external stimulus.
a. Hyponastic and epinastic movements
• If more growth takes place in lower side of organ, they curve upward, and this is
called hyponastic.
• If more growth takes part in upper side, organs curve downward and this is called
epinasty
e.g., hyponasty and epinasty in young and mature fern leaves.
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Plant movement
13. b. Nutational movement
• Growth of stem apices in zigzag
c. Circumnutational movement
• Growth may occur in rotational way
in the apices of some plants
Plant movement
14. ii. Paratonic movement of growth
• Growth movement directed by external stimulus and called as tropical movement .
The phenomenon is called tropism
a. Geotropism
• In response to gravity
Positive geotropism: root
Negative geotropism: stem
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Plant movement
15. b. Phototropism
• In response to light
c. Chemotropism
• In response to stimulus of chemicals.
e.g. pollen and fungal hyphae
d. Thigmotropism
• In response to touch or contact.
e.g. growth of tendrils in contact with solid object
e. Hydrotropism
• In response to water stimulus.
e.g. growth of young roots
Plant movement
16. f. Thermotropism
• In response to temperature
e.g. in winter when the leaves of rhododendrons curl downward in extremely cold
weather
g. Aerotropism
• In response to stimulus of air
e.g. Mangrove tree
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Plant movement
17. 3. Hygroscopic movement
• Found in dead parts of plants.
• Occurs either due to loss of or gain of water
e.g. elaters in bryophytes, peristome teeth in moss capsule
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Plant movement
18. Seed germination
Germination is process by which the embryo in the seed becomes activated and
begins to grow into a new seedling
Plant growth
19. Process of seed germination
Plant growth
Imbibition Seed coat ruptures Absorption of water
Respiration starts
GA activates
Stimulates the
synthesis of enzymes
Metabolizes the
stored food
Radicle emerges to
form primary root
and absorbs
underground water
Shoot starts
growing up
Lastly cells of seeds become
metabolically active, elongate and
divide to form seedling
20. Types of seed germination
1. Epigeal germination
Hypocotyl elongates rapidly pushing the cotyledon above the soil
e.g. Bean, cotton, papaya
Plant growth
21. Types of seed germination
2. Hypogeal germination
Epicotyl elongates rapidly and cotyledons remain below the soil
e.g. maize, rice grain, pea
Plant growth
22. Factors affecting seed germination
1. External factors
a. Water: water activates the enzymes which digest complex reserve foods of seed.
Poor or extra supply affect the seed germination adversely.
b. Temperature: seed fails to germinate at very low and very high temperature. The
optimum temperature is 25-35 C for most species.
c. Oxygen: Deficiency of oxygen affect the seed as germinating seeds respire
vigorously.
Plant growth
23. Factors affecting seed germination
1. External factors
d. Light: Some seeds require light (photoblastic seeds) to germinate. E.g Betula sp.
e. Soil: influenced by soil conditions such as water holding capacity, mineral
composition and aeration of the soil.
2. Internal factors
a. Maturity of embryo
b. Viability of seeds
c. Seed dormancy
Plant growth
24. Seed dormancy
A resting period in the life of plant during which growth slows or appears to stop is
called dormancy.
Seed dormancy: state or the condition in which seeds are prevented from
germinating even under favourable environmental conditions. Seeds should be
viable
Plant growth
25. Seed dormancy
Factors responsible for seed dormancy
a. Seed coat: thick and hard coat
b. Immature embryos: Some seeds are shed before maturation of embryo and thus
are fit to germinate. Such seeds do not germinate until embryo maturation.
c. Germination inhibitors: ammonia, parasorbic acid, etc can inhibit germination.
d. Period after ripening: Some seeds require after ripening period
e. Specific light requirements: Some seeds need specific light wavelenghth for
germination.
Plant growth
26. Seed dormancy
Types of seed dormancy
a. Innate dormancy
• It is the condition in which seeds do not germinate even after supplying all the
necessary conditions suitable for seedling growth.
• May be due to immature embryo
b. Enforced dormancy
• Caused due to environmental restraints such as moisture, oxygen, light,
temperature.
Plant growth
27. Seed dormancy
Types of seed dormancy
c. Induced dormancy
• Occurs when seeds have imbibed water but have been placed under extremely
unfavorable conditions for germination.
Plant growth
28. Seed dormancy
Methods of breaking seed dormancy
a. Scarification
• Cutting or chipping of hard seed
Coat- mechanical method
• Use of organic solvent to remove
Waxy or fatty compounds
Plant growth
29. Seed dormancy
Methods of breaking seed dormancy
b. Impaction
• Shaking of seeds to remove plug on micropyle.
c. Stratification
• Seeds are exposed to well aerated, moist condition under low temperature for
weeks to months.
Plant growth
30. Seed dormancy
Methods of breaking seed dormancy
d. Alternating temperature
• Alternation of high and low temperature promote germination
e. Light
• Exposure to red light can break dormancy
Plant growth
31. Photoperiodism
• phenomenon of physiological changes occurring plants in response to relative
length of day and night
• In some plants, flowering depends on exposure and the duration of light.
• The photoperiod required to induce flowering is called critical day length
Plant growth
32. Photoperiodism
Classification of plants on the basis of their photoperiodic response
1. Short day plants
• Require a short critical day length for flowering.
• Flower in the late summer or early winter
• E.g. tobacco, soybean, rice
Plant growth
33. Photoperiodism
Classification of plants on the basis of their photoperiodic response
2. Long day plants
• Require a long critical day length for flowering.
• Flower in the late winter or early summer
• E.g. wheat, barley, radish, spinach
Plant growth
34. Photoperiodism
Classification of plants on the basis of their photoperiodic response
3. Day neutral plants
• Do not require specific photoperiod
• E.g. potato, tomato
Plant growth
35. Vernalization
• The cold treatment to a plant bud seedling in order to fulfill specific low-
temperature requirement for accelerating flowering
• Method of inducing flowering in plants by treatment of their seeds at very low
temperature
Plant growth
37. Importance of Vernalization
• Shortens juvenile or vegetative period and brings early flowering
• Make plants resistance to cold and diseases
• Increase yield
• Applicable to tropical plants like wheat, rice, etc
Plant growth
38. Senescence
• The last stage in the development of a plant leading to slow and orderly process
of death of organs/organism
• Genetically programmed by plants
• Consequence of ageing
• Maintains plant fitness by getting rid of inefficient old organs and by recycling the
Nitrogen
Plant growth
39. Types of Senescence
1. Monocarpic or whole-body senescence
• Occurs in annual plants
• Whole plant is affected and dies
2. Top senescence
• Senescence of aerial shoot
• Occurs in perennial herbs
Plant growth
40. Types of Senescence
3. Deciduous or seasonal senescence
• Takes place in woody deciduous
• Senescence occurs in all leaves simultaneously
• Stem and root remain unaffected
4. Progressive senescence
• Senescence of leaves from base to top as
plant grows
Plant growth
41. Significance of Senescence
• Helps in recovery of inorganic and organic nutrients committed to the organ
• Helps to get rid of inefficient leaves
• Helps in fruit dissemination
Plant growth
