As plants are fixed to the ground, they cannot move bodily

but their protoplasm is sensitive to certain external

factors act as stimuli such as heat, light, gravity,

chemicals, electricity etc.

Movements may be classified into two main groups.

1. Autonomic or Spontaneous.

2. Paratonic or Induced.

Spontaneous Movements. It is the movements of creation

organs of plants without the influence of any external

stimuli e.g. movement of protoplasm and cilia, brisk

movement of many desmids movement of protoplasm and cilia,

brisk movement of many desmids etc..

This type of movements may be of two kinds.

(a)Movement of variation:- These movement are due to

variation in turgity of cell. This movement is exhibited by

pulsation.

This kind of movement is seen in Indian telegraph plant.

(b)Movement of growth:- This si movement of growing regions

die to unequal growth of organs on different sides. This

kind is seen in some creepers and trailers and this type of

movement is very slow.

Induced Movement:-This is movement of plant organ are

induced by some external stimuls. These induced movements

are of following kinds

(a)taxes

(b)tropisms

(c)nasties

(a)Taxes:-Taxic movements are the movements of free organs

or entire free organism induced by external sources at

temperature light and chemical substance. Cillated bodies as

Zoospores and antherozoids show this kind of movement. These

bodies either show positive or negative movement by the

stimulus.

(b)Tropism:- In this type of movement the organ concerned

moves either towards the source of the stimulus or away from

it. These movements are also influenced by external stimulus

as contact gravity and moisture. These movements are of

following kinds according to nature of stimulus.

(c)Haptotropism:-This moment is induced by contact with

foreign body. Climbers, Tendils and twinning stems show

this kind of movement, when climbers or tendrils some in

contact with any support, the opposite side of contact

continues to grow while the growth of contacted side is

checked. This opposite side continues to grow while the

growth of contacted side is checked. This opposite side

continue to grow until it coil around the object. Some

climbers climb clockwise some move anticlockwise.

(d)Phototropism:- These movements of plant organs are due to

influence of light. Some organs of plants are attracted by

light and grow towards it as shoots. These are positively

heliotropic or positively phototropic but some orgems e.g.

roots grow away form light are known to be negatively

phototropic or negatively heliotropic. Dorsiventral leaves

are said to be Diaheliotropic these grow at tight angles

to the direction of light so their upper surface is only

exposed to light.

(e) Geotropism:-This kind of plant movement is due to

influence of forced gravity. The roots shows positive

geotropism but stem show negative geotropism.

(f)Moisture:-This movement of plant organs is due to

moisture and is known as hydrotropism. Roots show a great

tendency to grow towards the source of moisture and these

are therefore known as positively hydrotropism.

(g)Nasties or Nastic Movements:- Nasties or nastic movements

are movements dorsiventral or like petals, leaves induced by

external stimuli as contact light, and temperature. These

movements not like tropic movements, as in these directions

of movements is not determined by direction of stimulus.

Two the of movements are found under these which are as follows

(h)Scismonasty:-This type of movement is so called as this

is brought about by some mechanical stimuli as contact with

a foreign body; drops of rain etc.

Examples of plants which show this kind of movements are

sensitive plant, Neptunia

Nyctinasty:-This type of movement is due to alternation of

day and night i.e. light and darkness. Leaves are mostly

affected by this kind of movement. Lequminous plants show

this kind of movements.