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Root Temperature and Carbohydrate Status of Young Cotton Plants¹

Tests were conducted to determine the effects of root temperature on carbohydrate status of leaves, epicotyls, hypocotyls, and roots of young cotton plants when the tops remained warm. Glucose, fructose, and sucrose were separated by paper chromatography and estimated colorimetrically. Reducing sugars, total sugars, and starch were also estimated by standard colorimetric tests.

Low root temperatures caused rapid increases in sugar contents of all plant parts. Hypocotyls contained the most sucrose, whereas epicotyls contained the most glucose, fructose, and total sugars. Roots contained the lowest concentrations of glucose and fructose.

Low root temperatures also increased the starch contents of leaves, epicotyls, and hypocotyls, except that a root temperature of 10 C caused wilting and a very low starch content of leaves. Roots contained very little starch.

Since starch as well as sugars accumulated at low root temperatures, the accumulations of sugars were not likely caused by starch breakdown, except in wilted leaves on plants whose roots were chilled at 10 C. On the basis of other reports, the effects of temperature on respiration rate and rate of conversion of sugars to other compounds appear to be more probable causes of the observed carbohydrate accumulations.

Key Words: Fructose • glucose • moisture stress • paper chromatography • starch • sucrose

² Plant Physiologist and Plant Pathologist, Crops Research Division, and Department of Botany and Plant Pathology, Oklahoma State University, Stillwater, Okla. 74074.

Received for publication May 26, 1967.