Carbohydrate Metabolism of Avocado. II. Formation of Sugars during Short Periods of Photosynthesis

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Abstract
A kinetic study of C14o2 assimilation in avocado leaf disks during periods of 10 seconds to 16 minutes revealed that mannoheptulose phosphate was labeled concurrently with hexose phosphates and sedoheptulose phosphate. Activity appeared very early in the free ketoses, fructose, sedoheptulose, mannoheptulose and ribulose. Mannoheptulose and sucrose continued to accumulate activity at a linear rate over a long period of time but the pools for the other ketoses appeared to saturate very early. A mechanism is proposed for the accumulation of mannoheptulose based on 1) a ketose phosphate phosphatase acting upon the early products of photosynthesis to give rise to free fructose, sedoheptulose and mannoheptulose, and, 2) a kinase specific for the fructose and sedoheptulose configuration which returns these sugars, but not mannoheptulose, into active metabolism.