Question

why plants grown in light have short hypocotyl

Answer 1

COP1, a protein thought to repress plant photomorphogenesis in the dark, is nuclear in the dark and cytoplasmic in the light. It may lie on the light signal transduction pathway and may be inactivated intracellularly by light.


Plants use light as a source of both energy and information about their environment. One of the ways they use the information is to adjust their development to suit prevailing light conditions. Perhaps the most striking example of this plasticity comes from dicotyledonous seedlings, which adopt different developmental programs when grown in light or darkness. Light-grown seedlings undergo photomorphogenesis, developing short hypocotyls, open and expanded cotyledons, and photo-synthetically active chloroplasts; many mRNAs are also specifically induced by light. Dark-grown seedlings, by contrast, follow skotomorphogenesis, developing elongated hypocotyls, closed and unexpanded cotyledons, and non-photosynthetic etioplasts.