Many large mammals, including humans and K selected individuals – Type I curve 

Many birds, small mammals, reptiles and some annual plants – Type II curve 

Many fish and marine invertebrates, r selected individuals - Type III curve

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#XL - R Botany

Effect of light is Photomorphogenesis

 A decrease in the rate of stem elongation

The beginning of apical-hook straightening

The initiation of the synthesis of pigments

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#XL - R Botany

TLS Online TPP Program

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#XL - R Botany

Phytochromes are photoreceptors that absorb red and far-red light most strongly (600–750 nm)

they also absorb blue light (350-500 nm) and UV-A radiation (320–400 nm).

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The amount of light is referred to as the fluence, which is defined as the total number of photons impinging on a unit surface area. Total fluence = fluence rate × the length of time

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#XL - R Botany

Bacterial phytochrome-like proteins (BphPs) regulate the biosynthesis of the photosynthetic apparatus in Rhodopseudomonas

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#XL - R Botany

In dark-grown or etiolated plants, phytochrome is present in a red light–absorbing form, referred to as Pr. Pr, which to the human eye is blue, is converted by red light to a far-red light–absorbing form called Pfr, which is blue-green.