Unit 5 Plant Physiological Processes Topic Plant Movements

PLANT MOVEMENTS The movement of higher plants are chiefly in the form of bending,

CONT… A: AUTONOMIC OR SPONTANEOUS MOVEMENTS 1: Movements of locomotion: Movements of the whole

CONT… 3: Variation movements These movements occur due to periodic variations in the turgidity

CONT… A. Phototropism: These curvature movements occur when a plant is provided with artificial

CONT… 2. TACTIC MOVEMENTS Tactic movements are movements of locomotion, which are induced by

CONT… C. Thermotactic The movement of locomotion in response to certain unidirectional temperature stimulus.

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Unit 5: Plant Physiological Processes Topic: Plant Movements B. Ed (Hons) Secondary Semester: III Subject: Biology III Minor Course Title: Plant Physiology and Ecology Represented By: Ms Sidra Younis Department of Education (Planning and Development) Lahore College For Women University, Lahore

PLANT MOVEMENTS The movement of higher plants are chiefly in the form of bending, twisting, and elongation of certain plant parts or organs. Spontaneous movement: There are other plant movements which take place spontaneously, without any external stimuli. These movements are described spontaneous or autonomic movements. Induced movement: Some plant movements are caused in response to certain stimuli and they are said to be induced or plant movement which take place spontaneously, without any irritability and sensitivity of protoplasm. There are the following three types of autonomic movements: §Movements and locomotion §Growth and curvature movement §Variation movements Similarly, paratonic movements also of three kinds: §Tropic movements §Tactic movements §Nastic movements

CONT… A: AUTONOMIC OR SPONTANEOUS MOVEMENTS 1: Movements of locomotion: Movements of the whole plant body or of an organ or of material within the plant cell which occur in responses to inherent factors and are free and spontaneous are said to be movements of locomotion. Examples: cyclosis (streaming of protoplasm), oscillatory movements of Oscillatoria, Motility of zoospores. 2: Growth and curvature movement : These movements are brought about by unequal growth on different sides of an organ. These are of the following two types: A) Nutation : The side of the supporting organ that is in contact of the support grows at a slower rate than the opposite side. This brings about a curvature which helps the supporting organ in spiralling or twinning around the support. B) Nastic : These movements occur due to differences in the rate of growth on the two opposite surfaces of a plant organ. When the movement occurs due to faster growth on the upper surface of the organ, it is said to be epinastic movement and when on the lower surface of the growing organ, it is known as hyponastic movement. Examples: Opening of floral buds and circinately coiled leaves are good examples of nastic movements.

CONT… 3: Variation movements These movements occur due to periodic variations in the turgidity of cells of an organ. The best example is Indian telegraph plant, Desmodium gyrans, where up and down movements of the two lateral leaflets occur in a rhythmic manner. These leaflets periodically drop down and rise up. This happens due to the presence of large thin walled motor cells at the bases of the leaflets. When these cells lose water into neighboring cells, they collapse and the leaflets drop down, and when they regain water, they become turgid and leaflets acquire their upright position. B. PARATONIC OR INDUCED MOVEMENTS 1. TROPIC MOVEMENTS: Growth movements, which occur in response to unidirectional external stimuli & result in positioning of the plant part in the direction of the stimulus, are said to be tropic movements. Depending upon the nature of stimuli, these movements are of following types: A) Phototropism B) Geotropism C) Hydrotropism D) Chemotropism

CONT… A. Phototropism: These curvature movements occur when a plant is provided with artificial or natural light only from one direction. Stems which generally show a curvature toeard the source of light are said to be positively phototropic. Roots which grow away from the source of light are called negatively phototropic. B. Geotropism Growth movements induced by stimulus of gravity are said to be geotropism. Primary roots always grow downward in the direction of gravity and thus are positively geotropic, whereas the main shoots grow upward away from the gravity and are thus negatively geotropic. The secondary lateral roots and shoots show a weaker response to gravity and thus take up a position at an angle to the gravitational stimulus and are called diageotropic. C. Hydrotropism Growth movements in response to unilateral stimulus of water are known as hydrotropism. Roots are positively hydrotropic as they bend towards the source of water. D. Chemotropism This is the movement caused by unilateral stimulus of some chemicals. Movement of pollen tube through the style towards the ovary is an example of chemotropism.

CONT… 2. TACTIC MOVEMENTS Tactic movements are movements of locomotion, which are induced by some unidirectional external stimuli. Their direction is controlled by the direction of the stimulus. Depending upon the nature of stimuli, these movements are of following types: A) Phototactic B) Chemotactic C) Thermotactic A. Phototactic : These tactic movements are in response to unidirectional light. Examples: Free swimming algae, zoospores, gametes when swim towards the diffused light are said to be positively phototactic and when they move away from the strong light, they are called negatively phototactic. B. Chemotactic The unidirectional movements of locomotion in response to certain chemicals is called chemotactic. The movement of antherozoids of bryophytes and pteridophytes towards egg due to chemicals.

CONT… C. Thermotactic The movement of locomotion in response to certain unidirectional temperature stimulus. Examples: Rapid rotational cytoplasmic movement in the leaf of Vallisneria due to increase in temperature and movement of algae form a cloder to a warmer place. 3. NASTIC MOVEMENTS The movement can be due to changes in turgor or changes in growth Depending upon the nature of stimuli, these movements are of following types: A) Nyctinasty B) Chemonasty C) Seismonasty A. Nyctinasty These movement of plant organs occur in response to day and light and thus are also known as sleep movement. Photonastic: If these movement when induced by change in light intensity. Examples: Flowers of Oxalis B. Chemonasty These movement occur in response to some chemical stimulus. C. Seismonasty These movements are in response to shock by a touch stimulus.