Relationship Between the Duration of the Mitotic Cycle, the Rate of Cell Production and the Rate of Growth of <i>Pisum</i> Roots at Different Temperatures

Abstract

Seedling of Pisum sativum (var. Alaska) were cultured at 10°, 15°, 20°, and 25°C in the dark for several days. During this time length measurements were made on the root and the rate of growth determined. For three successive days samples were removed from each group and the mitotic index determined. The total number of cells in the terminal 2mm segment was estimated at day zero. Previous experiments, performed after the seedlings were maintained at a given temperature for three days, provided information concerning the minimum mitotic cycle time of root meristem cells (Van't Hof and Sparrow 1963b). These three sets of data provided the necessary information for investigating the relationship between the duration of the mitotic cycle, the rate of cell production and the rate of root growth at different temperatures. The analyses showed: 1) that the rate of root growth was primarily dependent on the rate of cell production which, in turn, was dependent on the duration of the mitotic cycle, 2) that the rates of root growth and cell production are functions of temperature differing in sensitivity to temperature change and in the maximum temperature limit, 3) that the rates of growth and cell production are interconvertible when the conversion factor for a given temperature is known and 4) the number of proliferating cells in the meristem can be calculated.