Control of greening in cultured plant cells.

Plant cell suspension cultures were used to study environmental factors that affected culture growth, greening and photosynthesis. Most experiments were conducted with cultures of Spinacia oleracea but some experiments involved Chenopodium giganteum or Atropa belladonna. Light (continuous white, 1.4 x 103 ergs.cm-2. sec-1 reflected irradiance) was demonstrated to be necessary for culture growth and greening in the absence of the organic growth factors of the medium. Cultures would grow in the dark in the presence of the organic growth factors (pages 67-86). Gas phase components were found to control growth and greening of lighted suspension cultures. (1) Reducing O2 from 21 to 5% AP promoted greening in conditions that prevented O2-limitation of growth. (2) Increasing CO2 from 5 to 10% inhibited culture growth and to a lesser extent greening. (3) Increasing C2H4 from 1 to 12 vpm caused a gradual parallel inhibition of culture growth and greening. Two sequential 336 h passages in 12 vpm C2H4 were toxic, resulting in cell death and chlorosis (pages 151-222). S, oleracea suspension cultures would grow and green in a salts plus sucrose (10 g 1-1) medium, based on that described by Murashige and Skoog (1964). 1-NAA (10-6M) applied in this medium promoted C2H4 production and chlorosis. Sucrose at any concentration between 0 and 20 g 1-1 inhibited greening, which was not overcome by glucose (20 g 1-1) substitution. Copper sulphate (10-6 M) was implicated as being involved in the protection mechanism against O2-toxicity (pages 87-150). Growth and greening of S, oleracea 1 to 5 1 cultures was inhibited by sparging, in contrast with rapidly stirred (vortex) gassed 1.5 1 cultures. The photosynthesis of S. oleracea cultures in certain cases equalled respiration rate (in terms of O2 exchange). Photosynthetic competence was related to chloroplast pigments content, the latter declining on subculture and reaching maximum values in early stationary phase of batch culture growth. Completely photo-autotrophic growth was not demonstrated.