Explanted cotyledons from cineraria 'Jester Pink' seeds were cultured in vitro on a modified Murashige-Skoog medium containing (in mu M): 13.5 NAA, 13.5 2,4-D, 4.4 BAP, 13.5 NAA + 4.4 BAP, 13.5 2,4-D + 4.4 BAP or no plant growth regulators (control). Photographs were taken at 7-day intervals for 35 days to follow the embryogenic/organogenic development of the explanted cotyledons. Calorespirometric (metabolic heat rate, R-q and respiration rate, R-CD2) measurements were made in triplicate on the cultured cotyledons at the same interval as the photographs. Results showed a close correlation between the embryogenic/organogenic response of the tissues and R-q values. Cotyledons on a medium containing 2,4-D + BAP had the highest R-q values while those cotyledons that failed to develop or those of control, that suffered deterioration, had the lowest. This work showed that calorespirometric data may be useful in estimating early responses of tissues/organs in vitro embryogenic/organogenic culture systems. (C) 2006 Elsevier B.V. All rights reserved.