Environmental Factors Affecting Growth and Chlorophyll Synthesis in Euglena. I. Physical and Chemical. II. The Effectiveness of the Spectrum for Chlorophyll Synthesis.

SUMMARY. Light ⇌ dark reactions in the algal flagellate, Euglena gracilis, were studied. When cultures are aged, dark‐adapted, or subjected to elevated temperatures, analysis of absorption spectra indicates the magnesium is removed from the chlorophyll molecule and the chlorophyll is transformed to pheophytin. It also appears from chemical analyses, that the dark‐adapted and heat‐treated organisms are similar. The kinetics in terms of activation‐energy for growth and chlorophyll synthesis can be evaluated by their effective response to temperature. The action spectrum for greening indicates that in Euglena protochlorophyll is probably the light‐acceptor, as has been found for higher plants.