EXPERIMENTAL HYBRIDS IN EPILOBIUM (INCLUDING SECT. ZAUSCHNERIA) SPECIES WITH N = 15 (ONAGRACEAE)

Experimental hybrids involving the three diploid subspecies of Epilobium sect. Zauschneria formed 15 bivalents at meiotic metaphase I, as did experimental hybrids between the three other species of Epilobium (comprising sect. Cordylophorum) with n = 15. The gametic chromosome number of E. suffruticosum Nutt., n = 15, and its relationship to the other two species are reported for the first time. Although we have not obtained hybrids between the species of these two sections, their morphological similarities are impressive and they are surely closely related.     

Glutamate transport driven by an electrochemical gradient of sodium ions in Escherichia coli.

The role of Na+ in glutamate transport was studied in Escherichia coli B, strain 29-78, which possesses a very high activity of glutamate transport (L. Frank and I. Hopkins, J. Bacteriol., 1969). Energy-depleted cells were exposed to radioactive glutamate in the presence of a sodium gradient, a membrane potential, or both. One hundred- to 200-fold accumulation of the amino acid was attained in the presence of both electrical and chemical driving forces for the sodium ion. Somewhat lower accumulation values were obtained when either chemical or electrical driving forces were applied separately. A chemical driving force was produced by the addition of external Na+ to Na+-free cells. A membrane potential was established by a diffusion potential either of H+ in the presence of carbonyl cyanide p-trifluoromethoxyphenylhydrazone or of SCN-. These results support the hypothesis of a Na+-glutamate cotransport. Na+-driven glutamate transport was also observed in wild-type E. coli B but not in a strain of K-12.