Photosynthetic enhancement spectra in higher plants

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Abstract
Enhancement spectra for photosynthesis of intact leaves of higher plants were investigated by means of the rate of CO2 absorption under atmospheric conditions. Enhancement spectra for photosystem (system)II measured with a reference beam of 700 nm had two pronounced peaks at about 480 and 650 nm and lower humps at 540–600 nm in all of the nine species tested. By the use of a rice mutant which lacks chlorophyll b, it was revealed that the 650-nm peak and the middle humps in the spectrum can be attributed mostly to chlorophyll b absorption, whereas the 480-nm peak must be due to the absorption of carotenoids and chlorophyll b. Enhancement for system I in wheat had a peak at about 715 nm, and the maximum was much higher than that of the enhancement for system II. Enhancement between a red and a farred light for wheat was much greater for the farred light than for the red light in the presence of an excess amount of the other light. These results demonstrate that the enhancement phenomenon in higher plants is essentially the same as that in green algae.