ON PIGMENT CHANGES AND GROWTH IN THE BLUE-GREEN ALGA, PLECTONEMA NOSTOCORUM BORNET EX GOMONT

¹ Botany Department, Cornell University, Ithaca, New York

1. Spectrographic analyses of cultures of Plectonema nostocorum are reported, which demonstrate that the nitrogen-containing pigments disappear in the living alga when nitrogen becomes depleted in the culture medium.

2. Re-greening of cultures upon the addition of nitrogen is rapid and can serve to separate the process of pigment synthesis from other processes of growth.

3. Extraction and measurement of the carotenoid pigments at any stage in growth under controlled conditions is considered a reliable index of growth.