Plant Growth and Movements


   
 
Influence of Quality of Light on Flowering
Green colour of the visible spectrum is ineffective in inducing flowering whereas blue colour induces poor flowering. The wavelength 580 nm to 680 nm in the red portion of the spectrum has been found to be most effective for inducing flowering.
 
Flowering is a phytochrome mediated process. It occurs in 2 possible forms. The form which absorbs red light (660 nm) is PR and the form which absorbs far red light is termed PFR. PR stimulates flowering while PFR inhibits it. The two forms are easily interconvertible.
 
 
The red light and far red light exposures showed that in flowering also the last exposure determines the response.
 
 
Perception of Light Stimulus
The site of perception of light is the green leaves. This is evident from the fact that a plant from which all leaves have been removed fails to flower even when exposed to proper light conditions. In experiments with xanthium, a SDP, flowering occurred even when one eighth of a leaf was exposed to short days.
 
 
 
     
   
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