Soluble sugar changes in etiolated corn leaf tissue as influenced by red-light treatment

Summary

Etiolated corn leaf tissue floated on tap water and irradiated with red light (10 minutes) exhibits changes in monosaccharide content during an 18 hour dark period that follows the light treatment. After 4 hours of darkness, the light effect manifests itself primarily as decrease in glucose and fructose levels, whereas after 18 hours, only a sizeable decrease in fructose level is observed.

If the tissue is floated on glucose solution for 2 hours prior to the 10 minute exposure to light, the sucrose and starch content of the leaf sample is appreciably increased without any accumulation of “free” glucose. During the dark period on tap water following the red light exposure a greatly increased disappearance of sucrose is apparent, and the light response appears only as sucrose loss during the early hours. After feeding, the 18 hour dark responses are influenced by the presence of the high levels of sucrose and increased starch content. This increase in substrate levels is associated with a general enhancement of the light responses.

If the leaf sample is supplied with glucose-C¹⁴ and the same experimental procedures followed, the earlier reported losses of total soluble sugars content attributable to the light stimulation of the photomorphogenic processes are clearly substantiated. Decrease in radioactivity of the extractable soluble sugars is accompanied by an increase in C¹⁴ content of the tissue residue. The residue, therefore, contains such compounds as are representative of the fate of the photomorphogenically-induced utilization of the carbohydrates.