Soybean cell enlargement oscillates with a temperature-compensated period length of ca. 24 min

Rate of enlargement of epidermal cells from soybean, when measured at inter vals of 1 min using a light microscope equipped with a video measurement sy stem, oscillated with a period length of about 24 min. This oscillation par allels the 24-min periodicity observed for the oxidation of NADH by the ext ernal plasma membrane NADH oxidase. The increase in length was not only non -linear, but intervals of rapid increase in area alternated with intervals of rapid decrease in area. The length of the period was temperature compens ated, and was approximately the same when measured at 14, 24 and 34 degrees C even though the rate of cell enlargement varied over this same range of t emperatures. These observations represent the first demonstration of an osc illatory growth behavior correlated with a biochemical activity where the p eriod length of both is independent of temperature (temperature compensated ) as is the hallmark of clock-related biological phenomena.