Fig. 4

Effects of exogenous organic substances on respiratory and photosynthetic rates in nutrient-deficient cells. Organic substrates were added to culture at 0 h in the flat-plate culture. a Respiratory oxygen consumption rate (respiratory rate) dependent on sugar concentration. b Respiratory rate with addition of organic substances at 200 mM. Leucine, aspartic acid, and glutamic acid were added to the culture at 100 mM for their low aqueous solubility. Respiratory rate dependent on concentration of acetic acid, propionic acid, and formic acid (c), glyoxylic acid (d), and l-lactic acid, pyruvate, and d-lactic acid (e). Photosynthetic oxygen evolution rate dependent on concentration of glucose and glycerol (f) and pyruvate and l-lactic acid (g). Each value is an average ± standard deviation of triplicates