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from several sources, including mineralized soil organic matter, symbiotically fixed N, and N incorporated into Research on the effects of N and B applications on soybean [Glyplant tissue. Demand for seed N is highest from the R5 cine max (L.) Merr.] yield is limited. Experiments were conducted kg ha Ϫ1 applied from seedling emergence to R1 in-Holland Rd., Suffolk, VA 23437; and M.M. Alley, Dep. of Crop and creased yields by 720 kg ha Ϫ1 , averaged across all treat-

Since fat accumulation takes place in many algae as a response to exhaustion of the nitrogen supply, it has been suggested that this may provide a means of enhancing the potential food value of algae. To test this possibility, chemostatic continuous cultures of Chlorella sorokiniana and Qocystis polymorpha were subjected to successive reductions in influent nitrogen. As cellular nitrogen content decreased from about 10 to 4%, oxygen evolution, carbon dioxide uptake, chlorophyll content, and tissue production were drastically reduced, but total lipid content was essentially unchanged. Caloric values and C, H, and N analyses suggested a moderate increase in carbohydrate content, but gas chromatographic analyses revealed no significant qualitative or quantitative changes in the fatty acid fraction. In batch-cultured cells, nitrogen could be reduced to 3% of dry weight, causing a concomitant increase in total fatty acids and pronounced changes in the composition of the fatty acid fraction. These results suggest that cellular nitrogen must fall to approximately 3 % of

Total fatty acid, total sterol, fatty acids of specific lipid classes, and unsaturated fatty acids produced inNitzschia closterium were compared qualitatively and quantitatively as a function of changes in light intensity. Increased levels of total fatty acids were observed in cells grown at high light intensity when compared to cells grown at low light intensity. However, the percentage of unsaturated fatty acid decreased under high light conditions. Fatty acid analysis of triglyceride and 1,3 diglyceride fractions indicated an increase in levels of fatty acid at high light intensity when compared to low light intensity, while levels of polar lipid fatty acids increased at low light intensity. These analyses can be taken to indicate an increase in triglyceride and diglyceride at high light and a decrease in polar lipid at high light. Levels of free fatty acids did not differ significantly with light intensity. The levels of total sterol also were unaffected by changes in light intensity. However, levels of sterol isolated as free sterol and sterol associated in a yet unknown manner in the polar lipid fraction varied with changes in light intensity. Levels of polar lipid sterol increased at high light intensity compared to low light intensity, while the opposite was true for free sterol. The greatest percentage of total sterol was found in the polar lipid class regardless of light intensity.

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