In plant seeds, the photoreceptor phytochrome is responsible for the process termed photomorphogenesis<span>. This occurs when a seed initially situated in an environment of complete darkness is exposed to light. A brief exposure to electromagnetic radiation, particularly that whose wavelength is within the red and far-red lights, results in the activation of the photorecepter phytochrome within the seed. This in turn sends a signal through the signal transduction pathway into the nucleus, and triggers hundreds of genes responsible for growth and development</span>
It is bright-field...............
Because bacteria mutates that's why we have a new flu vaccine every year , because strains of DNA in the bacteria change all the time.
