A COMPARATIVE STUDY OF BICARBONATE INHIBITION OF ROOT GROWTH IN CALCICOLE AND CALCIFUGE GRASSES

S ummary A study has been made of the effects of bicarbonate on the root growth of a number of calcicole and calcifuge grasses. Differential effects of bicarbonate concentrations likely to be encountered in a calcareous soil solution (0–10 m‐equiv./litre) were found between the species. In general the root growth of calcifuge species was more strongly inhibited than was the root growth of calcicoles. Using the technique of colchicine‐induced metaphase accumulation the mitotic index of the roots of the bicarbonate‐inhibited calcifuge Deschampsia flexuosa was measured and the effects of bicarbonate were then studied. No effect of bicarbonate on cell division was detected and it was concluded that the inhibitory effect of bicarbonate was mainly on cell elongation. Using H 14 CO 3 it was found that the maximum rates of dark‐fixation occur in those zones of cell elongation where the main inhibition of growth takes place.