CONTROL AND CO-ORDINATION IN PLANTS :

All living things respond to environmental stimuli.  Plants also respond to stimuli with the help of chemical compounds secreted by the cells. Plants being living organisms, exhibit some movements.

TYPES OF MOVEMENTS :

1. GROWTH DEPENDENT MOVEMENT

2. GROWTH INDEPENDENT MOVEMENT

GROWTH DEPENDENT MOVEMENT :These are also called as tropic movements. Tropic movements are the movements which occur in the direction of the stimulus.

• The shoot of the plant responds towards light i.e towards sunlight.   This movement is called as phototropic movement.

• The shoot of the plant responds toward water and also toward gravity. these movements are called as Hydro-tropic movement and Gravitropic movement.

• Chemo-tropism is the movement of the plant in response to certain chemicals.

GROWTH INDEPENDENT MOVEMENT: These are also called as nastic responses.  These are exactly the movement of plant parts.

       • These movements are independent of growth.  
       • Plant cells must change their shape for this movement to happen. 
       • The movement in plants occurs in the direction opposite to the stimulus.

• Plants hormones are responsible for the growth independent movements.

Plant hormones

• Plants have various hormones, which help to coordinate growth, development and response to the environment.  Hormones are the chemical compounds released by stimulated cells. Hormones diffuse all around the cell.  Different hormones secreted by the plant are auxins, gibberellins, cytokinins, absscisic acid.

       • Auxins are the hormones synthesised at the tip of the stem.  These help the plant in  growth by cell elongation.

       • Gibberellins are hormones that help in the growth of the stem, seed germination, bolting, and flowering.

       • Cytokinins are hormones present in the areas of rapid cell division, such as fruits and seeds. They also promote the opening of the stomata.

• Abscissic acid is a hormone that inhibits the growth in various parts.  It is also responsible for the closure of stomata.