Photoautotrophic Growth of Soybean Cells in Suspension Culture

Abstract

Highly chlorophyllous photomixotrophic callus was visually selected from callus originating from soybean (Glycine max (L.) Merr. var. Corsoy) cotyledon. Suspension cultures initiated from this callus became photoautotrophic under continuous light with an atmosphere of 5% CO(2) (balance air). Dry weight increases of 1000 to 1400% in the 2-week subculture period have been observed. The cellular Chl content ranged from 4.4 to 5.9 micrograms per milligram dry weight which is about 75 to 90% of the Chl content in soybean leaves under equivalent illumination (300 micro-Einsteins per square meter per second).No growth can be observed in the dark in sucrose-lacking medium or in the presence of 0.5 micromolar 3-(3,4-dichlorophenyl)-1,1-dimethylurea, a concentration which does not inhibit heterotrophic growth (on sucrose). Photoautotrophic growth has an absolute requirement for elevated CO(2) concentrations (>1%). During the 14-day subculture period, growth (fresh weight and dry weight) is logarithmic. Photosynthesis quickly increases after day 4, reaching a peak of 83 micromoles CO(2) incorporated per milligram Chl per hour while dark respiration decreases 90% from day 2 to day 6. The pH of the growth medium quickly drops from 7.0 to 4.5 before slowly increasing to 5.0 by day 14. At this pH range and light intensity (200-300 microEinsteins per square meter per second), no O(2) evolution could be detected although at high pH and light intensity O(2) evolution was recorded.

Photosynthetic Carbon Metabolism in Photoautotrophic Cell Suspension Cultures Grown at Low and High CO2

“…Unlike a leaf, however, the majority of photoautotrophic cells require elevated levels of CO2 (1-5%) for growth (1 1, 17), and the successful establishment of a cotton cell line that grows at low CO2 (660 ,uL/L) (32) led us to investigate the differences in photosynthetic carbon metabolism between cotton cells grown at the culture room ambient level of 660 ,gL/L versus 5% CO2. A comparison was also made with two lines of soybean cells that grow at 5% CO2, which have been reported previously (10,22,23 …”

Development of Nitrogen Assimilation Enzymes during Photoautotrophic Growth of Chenopodium rubrum Suspension Cultures

“…1). During the first 14 d of growth, the C. rubrum cell cultures grew with the same doubling time and increased in fresh and dry weight to the same extent as photoautotrophically grown soybean cells (8). Huseman et al (10) have previously reported that photoautotrophic C. rubrum cell cultures, which were grown in continuous light, increased 600% in fresh weight in 14 d and had a Chl content of 0.2 mg g-' fresh weight.…”

“…The medium contained 39.4 mm NO3-, 20.6 mm NH4+, and 1 ;tM MoO4r-with 0.1 Mm 2,4-D, but omitted sucrose and kinetin (9,16 (27). For comparative purposes, the inset to Figure 1 14 d of photoautotrophic growth for C. rubrum and soybean cells (8) (Fig. 1, D (8).…”

“…For comparative purposes, the inset to Figure 1 14 d of photoautotrophic growth for C. rubrum and soybean cells (8) (Fig. 1, D (8).…”

“…In addition, continuous photoautotrophic cultures were demonstrated with spinach and asparagus cell lines (20). Recently, Horn et al (8) developed a photoautotrophic suspension culture ofsoybean cells and established the culture's dependence on a photosynthetic capacity for growth. Photoautotrophic cell cultures could serve as model systems for a variety of physiological and photosynthetic experiments.…”