The action spectrum is the electromagnetic radiation, or light, that plants use for photosynthesis and the subsequent photochemical and biochemical reactions critical to plant growth. In 1972, KJ McCree published an influential paper describing the different action spectra for 22 plant species.

Who described the action spectra?

Withrow et al. (1957) constructed the action spectrum in Figure 6 by determining the energy fluence necessary to potentiate 8° of straightening, converting to photon fluence, and plotting the reciprocal of that photon fluence as a function of wavelength.

What does action spectrum indicate?

An action spectrum indicates which wavelengths of irradiation are most effective in eliciting a response. An action spectrum is constructed because it allows a comparison with absorption spectra of known pigments and thus an insight into the nature of the photoreceptor involved.