write the types of plant movement? explain it.
Answers
ANSWERS:-
Plants different type of movement these are categorised into:-
1. Hygroscopic movement
2. Vital movement
1. HYGROSCOPIC MOVEMENT:-
Such type of movement is observed in Dead part of plant. It is observed due to loss or gain of water.
Ex = curling of peristome teeth in moss. Spore dispersal in pteris.
2. VITAL MOVEMENT:-
It involves vital parts of plant. It is of two types:-
A. Movement of locomotion:- the movement is observed due to internal and external stimuli.
B. Movement of curvature:- it is largrer
movement which occurs due to growth and change in turgidity of cells.
Ex:- indian telegraph plant.
Explanation:
there are two types of plant movements such that
: nastic movements
Type # 1. Seismonastic Movements:
These movements are brought about by mechanical stimuli such as contact with a foreign body, fast wind and rain drops etc. Seismonastic movements are seen in stigmas, stamens and leaves of many plants. For instance, movements of leaf lets in Mimosa pudica , Biophytum sensitivum and Neptunia, etc.
Type # 2. Photonastic Movements:
These movements are induced by fluctuations in the intensity of light Such movements are exhibited by flowers of several plants. Many flowers open with the increasing illumination of the day and close up with the decrease in light intensity. Flowers of Cestrum nocturnum open at night, and close up with the dawn of the day.
Type # 3. Thermonastic Movements:
Such movements are brought about by changes in temperature. Many of the flower movements are thermonastic. Such flowers open with a rise and close with a drop in temperature. Sometimes thermonastic movements are associated with photonastic movements. In both types of responses the mechanism may be either differential growth, or changes in turgor on upper and lower sides of the petiole, leaf blade, or perianth part.
Type # 4. Nyctinastic Movements:
These movements are commonly called ‘sleeping movements’. Some authors have classified such movements under the category of photonastic or thermonastic movements. These movements are induced by alternation of day and night. The leaves of some plants like Enterobium (Fig. 7.15), clover and oxalis, growing approximately horizontal during the day, begin to droop and close toward evening and do not rise again until the next morning.
2,. tropic movements
The six types are: (1) Thigmotropism (Haptotropism) (2) Phototropism (3) Geotropism (4) Thermotropism (5) Chemotropism and (6) Hydrotropism.
Type # 1. Thigmotropism (Haptotropism):
Growth movements made by plants in response to contact with a solid object are called thigmotropism. These are curvature movements and are most apparently seen in tendrils and twiners. In most plants the curvatures of the tendrils which follow contact with a support are mostly the result of increased growth on the side opposite the stimulus
Type # 2. Phototropism:
This kind of movement is induced by light. Not all plants and not all parts respond in the same way to this stimulus. In general, the stem mostly grows and turns towards the source of light, while the roots away from it. The leaves, however, take up such a position in which the broad surface of the blade is at right angles to the light rays. A stem is, therefore, said to be positively phototropic, a root negatively phototropic, and a leaf transversely phototropic or diaphotropic. Phototropism is also known as heliotropism.
Type # 3. Geotropism:
Any reaction to the stimulus of earth’s gravity is called geotropism. The effects of gravity on plants are not like those of light and temperature because it is both continuous in action and constant in strength. Primary roots and certain other portions of the root system tend to grow directly toward the centre of gravity and hence called positively geotropic.
Stem mostly grows away from the centre of gravity and is thus negatively geotropic. However, stems in prostrate plants have lost their negative geotropism and even develop into root stock or tubers which behave exactly like roots. Most of the leaves take up their positions at right angles to the centre of gravity and are, therefore, called transversely geotropic or diageotropic. Geotropism is of three types: orthogeotropism (e.g. primary root), plageotropism (e.g., secondary roots) and diageocropism (movement of tertiary roots