Rates of photosynthetic gas exchange in suspensions of synchronized algal cells have been reported not to remain constant with time but to undergo fluctuations whose direction, extent, and timing depend on the developmental status of cells as well as on the external conditions during and prior to observations (SoaoKIN 1960 a, b, and e; 1961 a, b, and e). Basically, younger cells and cells of intermediate developmental stages possess a higher capacity for photosynthesis than cells of later developmental stages. Photosynthesis is but one indicator of the level of metabolic activity of eells. Another indicator of this activity is sy~thesis of organic matter. Observations reported in this communication were made with the purpose of studying changes in synthetic capacity of cells in regard to the composition of the suspending fluid and to the developmental status of cells. 3laterial and methods Observations were made on syzlchronized suspensions of the high-temperature green alga, ChloreUa 7-11-05 (SO~OKL~ 1959). Cells were growi1 at 39~ and light intensity of 2,800 foot-candles (coot-white fluorescent lamps) in a medium containing the following compounds (in grams per liter): KN03, 1.44; KH2PO 4, 1.31; MgSQ 9 7H20, 0.5. The concentration of minor elements (in ppm) was: Ca, 5; Fe, 2; Mn, Zn, and B, 0.5; Cu, 0.04; 5'[o, 0.02; Co and V, 0.01. Fe, Mn, Zn, Cu, and Co were used as compounds chelated by ethylenediaminetetraacetie acid (EDTA). The p~ of the medium was 6.0. Test tubes with inner dimensions of 16 X 150 ram, used as growth vessels, were fitted with cotton plugs, through which cotton-plugged bubbling tubes were passe4 to supply the cultures with a 4 per cent C02 in air mixture (SoRo~zIN and KR~vss 1958).
Synchronization of cells was achieved by an intermittent light:dark regime. Cell suspensions were grown diurnally for 9 hours in light, then they were transferred for 15 hours into darkness. Liberation of daughter cells from the mother cell wall usually took place soon after transferring cell suspensions into the dark. Cells were prevented from growing as long as they were kept in darkness. After 3 or 4 cycles of this regimen, ~n algal population contained, at the end of a dark period, up to 99 per cent of the cells as small autospores. As soon as the cells were transferred