RESPONSES TO SUCROSE AND GLUTAMINE BY SOYBEAN EMBRYOS GROWN IN-VITRO

Immature soybean (Glycine,nax [L.] Merr. cv. Ransom) embryos were grow n in vitro in the presence of different concentrations of sucrose and glutamine to examine how availability of carbohydrate and nitrogen aff ects dry matter accumulation and embryo composition. Embryos were tran sferred to fresh medium every 4 days to maintain sucrose and glutamine concentrations of the culture medium. In all experiments, accumulatio n of dry matter and protein content increased when the sucrose concent ration of the culture medium was increased from 1.5 to 150 mil; howeve r, a relatively greater enhancement of dry matter than of protein accu mulation resulted in a lower protein concentration at 150 than at 1.5 mM sucrose. Both content and concentration of protein were increased b y the increases in glutamine supply to concentrations exceeding 68% pr otein at 120 mM glutamine. In combination with 150 mM sucrose, however , oil increased as glutamine supply was increased from 0.6 to 6 mM and then decreased as glutamine supply was increased from 6 to 120 mM. Va rying the concentration of sucrose available during seed development a lso affected embryo composition. Decreased availability of sucrose dur ing either the early or late portion of the culture period resulted in lower accumulation of dry matter as well as oil. Protein concentratio n was actually higher for embryos transferred from 150 to 1.5 mM sucro se than for those remaining in 150 mM throughout the culture period; h owever, the greater percentage of protein was due to a decrease in acc umulation of dry weight. In addition, embryo composition was affected by altering the availability of glutamine during culture, indicating t hat variation in the level of nitrogen assimilate delivered during see d development can change embryo composition. Decreasing the glutamine concentration of the medium lowered both protein and oil content. In c ontrast, increasing the glutamine concentration of the medium from 0.6 to 6 mM 8 days after initiation of culture increased the protein cont ent and concentration of the embryo while oil content was not affected .