Quantitative Analysis of Intercellularly-Transported Photoassimilates inChara corallina

Abstract

Using a thin-layer chromatographic technique, we have identified the photoassimilates that are transported intercellularly from branchlets to internodes in Chara corallina. An internode-branchlet complex having a primary apex was used in these experiments. After feeding 1 mol m^⊟3 NaH¹⁴CO₃ to a branchlet for 10 min, the ¹⁴C-labelled photoassimilates (¹⁴C-photoassimilates) found in the sol endoplasm of the branchlet were composed of sucrose, amino acids, malate, and sugarphosphates. The composition of the ¹⁴C-photoassimilates transported from the source branchlet to the sink internode in 10 min was the same as that in the sol endoplasm of the source branchlet. From the proportion of each ¹⁴C-photoassimilate in both the source branchlet and the sink internode, it was deduced that the main photoassimilates involved in the intercellular transport were sucrose and amino acids. We found previously that polar transport of photoassimilates occurs from a branchlet to an internode with an apex. Determination of the amount of sucrose, amino acids, glucose-6-phosphate, and malate in both branchlet and internode with or without an apex revealed that there were gradients in the concentrations of sucrose, serine, and glutamic acid between the sol endoplasm of the two cells. The levels were higher in the branchlet and lower in the internode and the gradients decreased when the apex was detached. Therefore, it is concluded that sucrose and these amino acids are the compounds involved in the polar intercellular transport.