PHOTOSYNTHETIC CARBON METABOLISM OF TRADESCANTIA-FLUMINENSIS AFTER PROLONGED DARK INCUBATION OF LEAVES IN AN ATMOSPHERE OF ARGON OR HYDROGEN

Prolonged residence of spiderwort leaf disks (Tradescantia fluminensis Vell.) in the dark in an anaerobic atmosphere leads to significant de cline of the photosynthetic rate (during exposures of 15-30 min) as co mpared with the variant involving dark preincubation of disks in a nor mal atmosphere. When the time of illumination is increased to 60 min, the rate of CO2 assimilation in argon rises and attains the control le vel. Together with intermediates of the Benson-Calvin cycle, C4 dicarb oxylic acids and amino acids are present among products of assimilatio n of (CO2)-C-14 under light in spiderwort leaves preincubated in the d ark in a normal atmosphere. Anaerobic conditions of dark preincubation produce an increase in relative content of certain amino acids and ap pearance of C-14 in organic acids of the Krebs cycle. During prolonged (60-min) light exposures in an argon atmosphere, pools of the given c ompounds (and 3-phosphoglyceric acid) exceed the control level in abso lute as well as relative values; accumulation of C-14 in malate and ph osphoenolpyruvate approaches the control level; and formation of photo respiratory products and aspartate declines significantly. The regular ity of C-14 accumulation in sugar phosphates and free sugars is virtua lly identical to the nature of changes in the total pool of absorbed ( CO2)-C-14 for each variant of dark incubation. The findings suggest po ssible existence of cooperative interaction between heterotrophic and phototrophic leaf tissues of spiderwort in realization of carbon dioxi de assimilation under light. Such interaction can expand the range of tolerance of the photosynthetic apparatus.