Effect of thiourea on the ionic content and dark fixation of CO2 in embryonic axes of Cicer arietinum seeds

During the first 12 h of germination of Cicer arietinum L. (cv. Castellans) seeds, K⁺ is first lost into the surrounding medium and is later reabsorbed. Thiourea accelerates this reabsorption. Since there is an increase in the mobilization of K⁺ in response to thiourea, a greater accumulation of malate due to the carboxylation of phosphoenolpyruvic acid takes place as compared with that occurring in water. The subapical zone of the radicle accumulates the greatest amounts of water, K⁺ and malate. The variation in the "in vitro" activity of phosphoenolpyruvate carboxylase does not explain the difference in malate in response to the different treatments, consequently there must be chemical changes in the cytoplasm which favour this carboxylation "in vivo". These results show that thiourea accelerates the mobilization of K⁺ and stimulates the dark fixation of CO₂ in embryonic axes of Cicer arietinum.