Plant Movement | CEE Academy

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MOVEMENT

▢ Definition: Living plants → positional change due to environmental/endogenous causes

▢ Cause: Sensitivity / irritability of protoplasm

▢ Level:

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Whole organism
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Organ level
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Cellular level

▢ Cellular Example: Cyclosis = cytoplasmic streaming; cytoplasm flows like river inside living cell

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STIMULUS & RESPONSE

▢ Stimulus: External environmental change → reaction in plant/organ

▢ Threshold Intensity: Minimum stimulus intensity → response induction

▢ Response: Visible change/reaction of plant/organ due to stimulus

▢ Reaction Time / Presentation Time: Interval: stimulus presentation → actual response development

▢ Stimulus-Based Movement:

Table 1: Nature of Stimulus

Type	Cause	Also Called
Autonomous	Internal stimulus	Spontaneous
Paratonic	External stimulus	Induced

▢ Stimuli Prefixes:

Table 1: Stimulus → Prefix

Stimulus	Prefix
Light	Photo
Temperature	Thermo
Water	Hydro
Chemical	Chemo
Water current	Rheo
Gravity	Geo
Touch / Contact	Thigmo / Hapto
Shock	Seismo

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HYGROSCOPIC MOVEMENT

▢ Occurrence:

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Bryophytes
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Pteridophytes

▢ Examples:

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Twisting movement of elater
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Sporangial wall of fern

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TYPES OF MOVEMENT

Table 1: Major Types

Feature	Movement of Locomotion	Movement of Curvature
Common In	Lower plants	Higher plants
Change	Position of whole body	Position of body parts only
Main Types	Autonomic + Paratonic	Movement of variation + Movement of growth

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Movement of locomotion

▢ Autonomic / Self Movement:

Table 1: Autonomic Locomotory Movements

Type	Mechanism	Examples
Amoeboid	Pseudopodia-like structure	Synchytrium / slime mould
Ciliary	Cilia / flagella	Chlamydomonas, Volvox
Cyclosis / Streaming	Protoplasmic streaming	Chloroplast movement in Elodea

▢ Cyclosis Types:

Table 1: Cyclosis

Type	Movement Direction	Example
Rotation	Clockwise OR anticlockwise; single direction	Leaf of Hydrilla, Vallisneria
Circular	Clockwise + anticlockwise; all possible directions	Staminal hairs of Tradescantia

▢ Paratonic / Induced Movement:

❖ Name: Tactic / Taxis movement

Table 1: Tactic Movements

Type	Stimulus	Key Points	Examples
Phototactic	Light	Movement: dark → diffused light; intense light ↔ diffused light	Zoospores of Chlamydomonas, Volvox
Thermotactic	Temperature	Cold water ↔ warm water	Chlamydomonas, bacteria
Chemotactic	Chemical, e.g., malic acid	Antherozoid movement: antheridium → archegonium	Bryophytes, pteridophytes
Rheotactic	Water current	Movement due to water current	Aquatic algae

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Movement of curvature

▢ Movement of Variation:

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Change in position without growth
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Mostly turgor/osmotic change

▢ Movement of Growth:

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Change in position due to growth
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Growth differential → curvature

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Movement of Variation

▢ Autonomic:

❖ Example: Leaves of Desmodium gyrans = Indian telegraph plant

❖ Key Point: Lateral leaflets → continuous up-down movement

▢ Paratonic / Induced / Nastic Movement:

Table 1: Nastic Movements

Type	Stimulus	Key Point	Examples
Photonasty	Light	Response to light intensity	Head of sunflower → helionasty
Thermonasty	Temperature	Flowering/opening at higher temperature	Tulip, crocus flower
Nyctinasty / Sleep movement	Light + temperature	↓ light intensity → sleep movement of leaves	Oxalis + Albizzia: open day, close night; Oenothera: open night, close day
Seismonasty / Osmotic / Turgor movement	Shock / touch	Water loss from pulvinus + pulvinules → drooping	Leaves of Mimosa pudica
Thigmonasty / Haptonasty	Touch / contact	Touch-induced movement	Insectivorous plants; hairs of Drosera

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Movement of Growth

▢ Autonomic Growth Movement:

Table 1: Autonomic Growth Movements

Type	Growth Pattern	Movement	Examples
Hyponasty	More growth of lower surface / abaxial side	Part moves upward	Closed flower petal; young fern leaf / circinately coiled leaf
Epinasty	More growth of upper surface / adaxial side	Part moves downward	Opening of flower; erect fern leaf / mature frond
Nutational movement	Alternate growth on either surface	Zig-zag / forward curvature	Zig-zag shoot apex; forward growth of branches

Hyponasty + epinasty → common in bifacial structures: leaf, sepal, petal

▢ Paratonic Growth Movement:

❖ Also Called: Tropic movement; process = tropism

Table 1: Tropic Movements

Type	Stimulus	Positive Response	Negative Response	Examples / Notes
Phototropic	Light	Shoots	Roots	Differential hormonal effect; auxin accumulates on shaded side; coleoptile bends toward light due to greater elongation on shaded side
Geotropic	Gravity	Roots	Shoots	Main root = +ve geotropic; main shoot = -ve geotropic
Hydrotropic	Water	Roots	Shoots	Important for young roots
Thigmotropic / Haptotropic	Touch / contact	Contact side response		Tendrils bending on support; haustoria in Cuscuta
Chemotropic	Chemical, e.g., malic acid	Growth toward chemical source		Pollen tube growth toward embryo sac

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Geotropism Types

Table 1: Types of Geotropic Growth

Type	Growth Direction vs Gravity	Examples
Orthogeotropic	Parallel to gravity	Main roots → +ve orthogeotropic; main shoot → -ve orthogeotropic
Diageotropic	Right angle to gravity	Tertiary root; rhizome; prostrate plants; leaves
Plagiogeotropic		Secondary/lateral roots → +ve plagiogeotropic; stem branches → -ve plagiogeotropic
Apogeotropic / Ageotropic	No effect of gravity	Respiratory roots/pneumatophores of mangroves; coralloid root of Cycas

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INSTRUMENTS & SPECIAL TROPISMS

▢ Clinostat: Instrument → eliminates effect of gravity on plant

▢ Traumatotropism: Movement induced by injury

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READ & DIGEST

▢ Bulliform Cells:

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Grass leaves → folding + unfolding
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Specialized bulliform cells
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Bulliform cells → turgor movements

▢ Nastic vs Tropic: Nastic movements = non-directional; tropic movements = directional

▢ Scototropic Movement: Induced by night

▢ Xerochasy: Peristome teeth of moss

▢ Earthworm: Moves down soil → +ve geotropism

▢ Telotaxis: Honey bee drawn toward flower

19Plant Movement