Red Light Effects on Uptake of 14C and 32P into Etiolated Corn Leaf Tissue During Photomorphogenic Leaf Opening.

Red light effects on the uptake of ¹⁴C and of ³²P was studied by observing leaf sections from 8-day-old etiolated coin leaves that were placed on various substrates following a brief exposure to red radiant energy. There was a general increase of ¹⁴C uptake over dark levels into all metabolite fractions that were prepared. This is in contrast with results obtained previously in which leaf samples were first floated on substrate and then irradiated (Mitrakos et al. 1967, Price et al. 1965). The latter tests resulted in a general decrease in sugar and starch as well as ¹⁴C content of all fractions. However, under both types of experimental conditions the red light effect manifested itself as an increase in hexosemonophosphate turnover rate and accumulation of radioactivity in the cell wall polysaccharide fraction. The present data further substantiate the previous work in that they demonstrate the regulatory influence of the hexose pool size on the intermediary metabolism and the manifestation of the phytochrome responses. From the data thus far obtained it cannot be determined as to whether or not phytochrome mediates by controlling phosphorylating activity or through control of specific enzymatic processes that lead to observable cell wall polysaccharide synthesis and leaf unrolling. [ABSTRACT FROM AUTHOR]