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phototropins control the movement of chloroplasts

these responses serve to enhance the photosynthetic

Phototropins, like photoreceptor pigments associated with mammalian vision, comprise many amino acids (900–1000) that form the main structure of the protein (the apoprotein) to which an accessory chemical cofactor is bound that can absorb light and impart color (the chromophore)

a small fraction of the receptor pool is rapidly internalized (within minutes) upon blue light irradiation

Phototropins are typically associated with the plasma membrane

However, the biological significance

As light passes through the stem, it becomes progressively diffracted, thereby generating a gradient of phototropin activation across the organ, with the highest level of activity occurring on the irradiated side

In some plant species, including the fern Adiantum capillus-veneris, phototropism and chloroplast movement are induced by red light as well as blue.

novel

The presence of such a hybrid photoreceptor is proposed to enhance light sensitivity and aid the prevalence of species such as ferns in low light conditions