Division Rates of Salt Marsh Diatoms in Relation to Salinity and Cell Size

Fourteen species of motile pennate diatoms obtained from a Georgia salt marsh were cultured under uniform conditions (19°—20°C, 16,000—23,000 lux) in soil—water medium at salinities between 1 and 68 %. All species grew well over at least the range of 10 to 30%; several species grew well over the entire salinity range. At 20 % the division rate was either maximal or close to maximal. Diatom preconditioned to particular salinities in general divided at the same rate as those not preconditioned. Maximum rates for the 14 species ranged from 0.6 to 3.2 divisions/day. These maximum rates had highly significant correlations with both the logarithm of the cell volume and the square root of cell area/cell volume. Least squares regressions were computed for these relationships with volume expressed in μ 3 and area in μ 2 . Maximum number of divisions per day = 3.75 — 0.7 (log volume) =—0.01 + 1.64 (area/volume)½