Day-length and Hæmatin Compounds in Plants

Abstract

IT has been shown that day-length regulates the chlorophyll content of many plants^1–3 and that this is a true photoperiodic phenomenon⁴. In leguminous plants, day-length controls both the chlorophyll content and the number and efficiency of the root nodules^5,6. It seems that, in this case, both the synthesis of hæmoglobin in the nodules and the synthesis of chlorophyll in the leaves are depressed by short day-length. Moreover, there are indications that in some plants (tobacco, for example), the ratio between the quantity of chlorophyll and the quantity of total hæmatin in the leaves remains constant over a wide range of concentrations (Davenport, H., personal communication).