II.Non-Vascular plants (Bryophytes)

Primitive form-  Riccia and Marchantia

comprises of thalloid-  attached to substratum through unicellular, unbranched rhizoids

Rhizoids-branched, multicellular in Funaria

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Blue light depolarizes membrane of hypocotyl cells and inhibits of growth rate.

This membrane depolarization is caused by the activation of anion channels, which facilitates the efflux of anions such as chloride.

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an anion channel blocker, NPPB (5-nitro-2-[4-phenylbutylamino]- benzoate), prevents the blue light–dependent membrane depolarization and decreases the inhibitory effect of blue light on hypocotyl elongation.

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Phototropins (phots) are involved in directing organ, chloroplast, and nuclear movements, solar tracking, and stomatal opening

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In Mougeotia, the photoreceptors regulating chloroplast movement consist of a fusion between phytochrome and a phototropin known as neochrome, and show typical bilin binding as well as red/far-red reversibility.

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Mougeotia appears to have evolved the ability to exploit red light as a signal to induce a response (chloroplast movement) that is typically mediated by blue light.

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phot1 is the primary phototropic receptor mediates phototropism in response to low and high fluence rates of blue light. 

phot2 mediates phototropism in response to high light intensities