Carbon Fluxes in Leaf Blades of Barley

S ummary Gas exchange, mass of carbohydrates, and turnover of carbohydrates, have been followed diurnally in barley leaf blades. Mature second leaf blades store sucrose, which occurs in at least two types of pool which turn over at different rates. Over a light‐dark cycle, photosynthesis, sucrose synthesis and translocation all show appreciable changes in rate but are not obviously related; nor is the rate of translocation a function of the total concentration of sucrose in the leaf. In the dark, starch mobilization starts immediately and that of sucrose increases, maintaining the mean rate of translocation in the dark at 77 % of that in the light. Fructans are turned over but show little diurnal variability in mass.