The Nonessentiality of Boron for Chlorella1 2

SUMMARY With growth rate as the criterion, the responses of several species and strains of Chlorella to boron were investigated. The algae were Chlorella vannielii Shihira and Krauss, C. emersonii Shihira and Krauss, C. protothecoides var. mannophila Shihira and Krauss, and C. vulgaris Beijerinck, Columbia strain. There was no evidence of a boron requirement for any of the four strains of algae. In contrast with most higher plants, for which a few parts of boron per million are usually toxic, 50 to 100 ppm of B, depending on the alga, toxic required for a statistically significant (5% level) reduction in growth rate.