1.The relation between light intensity and the ratio light activity: dark activity of NADP+-dependent glyceraldehyde-3-phosphate-dehydrogenase (as a measure of the increase in activity caused by light) is expressed by a saturation curve. It is therefore similar to the curve expressing the relationship between light intensity and photosynthesis.2.Very high light intensities not only diminish the degree of enzyme activation by light, but reduce the enzyme activity below the dark value.3.The increase of enzyme activity is effected not only by red (maximum intensity 671 nm) but also by blue (450 nm) and green (525 nm) light. At the same quantum density blue light is more effective than green and red, which have the same effect. At the same light intensity green light shows the smallest effect, while blue light has the greatest effect.4.It is assumed that chlorophyll is the responsible receptor pigment involved in the increase in activity of the NADP+-dependent glyceraldehyde-3-phosphate-dehydrogenase caused by light.
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