Abstract
Haploid callus cells of tobacco (Nicotiana tabacum) were grown photoautotrophically on a solid agar medium in the absence of sucrose in Petri plates in an atmosphere of 1% or 3% CO2 in air. The averages of dry weight increases for four to five consecutive passages were 2.3- to 3.6-fold per 3-week passage for different subclones. Photosynthetic 14CO2 assimilation was maximum at about 1% CO2 with half-maximal rates obtained at 0.2% CO2. At saturating CO2 concentration the average rate of CO2 fixation was about 5 μmole per gram fresh weight per hour or about 125 μmole per mg of chlorophyll per hour.
The existence of an active photorespiratory system in these tissues was established in a number of independent ways. The photosynthetic rate in 0.18% CO2 was inhibited 38 to 50% in 100% O2 compared with 21% O2. Glycolate accumulated at a constant rate in the presence of 5 mm α-hydroxy-2-pyridinemethanesulfonic acid for 20 minutes in light. This rate was rapid relative to the photosynthetic rate. Glycolate synthesis was three times faster in autotrophic than in heterotrophic cells. [1-14C]Glycolate was rapidly metabolized and the products included 14CO2, [14C]glycine, and [14C]serine, thus demonstrating an active glycolate pathway. Photorespiration was demonstrated directly by measurement of an O2-dependent release of 14CO2 in the light from callus that fixed 14CO2 for about 22 hours. Autotrophic growth in 60% O2 and 0.03% CO2 was slowed and ceased entirely after two or three passages, while heterotrophic growth was unaffected by 60% O2 in the atmosphere.
The method of growing autotrophic callus which has an active photorespiratory system should facilitate the selection and analysis of photosynthetic mutants in which photorespiration is regulated.
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Selected References
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- Berlyn M. B., Zelitch I. Photoautotrophic growth and photosynthesis in tobacco callus cells. Plant Physiol. 1975 Dec;56(6):752–756. doi: 10.1104/pp.56.6.752. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kennedy R. A. Photorespiration in c(3) and c(4) plant tissue cultures: significance of kranz anatomy to low photorespiration in c(4) plants. Plant Physiol. 1976 Oct;58(4):573–575. doi: 10.1104/pp.58.4.573. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Oliver D. J., Zelitch I. Increasing photosynthesis by inhibiting photorespiration with glyoxylate. Science. 1977 Jun 24;196(4297):1450–1451. doi: 10.1126/science.867040. [DOI] [PubMed] [Google Scholar]
- Zelitch I., Day P. R. The effect on net photosynthesis of pedigree selection for low and high rates of photorespiration in tobacco. Plant Physiol. 1973 Jul;52(1):33–37. doi: 10.1104/pp.52.1.33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zelitch I., Day P. R. Variation in photorespiration. The effect of genetic differences in photorespiration on net photosynthesis in tobacco. Plant Physiol. 1968 Nov;43(11):1838–1844. doi: 10.1104/pp.43.11.1838. [DOI] [PMC free article] [PubMed] [Google Scholar]