Morphometric changes in Asterionella formosa colonies under phosphate and silicate limitation1

Abstract

Steady state ponulations of Asterionella formosa show a marked dependence of the number of cells per colony on growth rate under both phosphate and silicate limitation. At high steady state growth rates the cells per colony average 8. Under phosphate limitation, the number of cells per colony decreases with decreasing steady state growth rate in a linear manner to less than 2 cells colony−1 at very low growth rates. Under silicate limitation, the number of cells per colony increases with decreasing steady state growth rate in an approximately exponential manner to over 20 cells colony−1 at very low growth rates.