Constant, fluctuating and effective temperature and seed longevity:: a tomato (Lycopersicon esculentum Mill.) exemplar

Tomato seeds with a moisture content of 16.4 % were stored hermetically at one of five constant temperatures (10, 20, 30, 40, 50 degreesC) or in one of nine alternating temperature (24 h/24 h) regimes (10/30, 10/40, 10/50, 20/30, 20/40, 20/50, 30/40, 30/50, 40/50 degreesC) for up to 224 d. In each regime, seed survival conformed to cumulative negative normal distributions and all 14 survival curves could be constrained to a common origin. Estimates of the constants C-H and C-Q of the viability equation determined at constant temperatures were 0.0346 (s.e. 0.0058) and 0.000401 (s.e. 0.000096), respectively. The effective temperature for seed survival of each alternating temperature regime was always much higher than the mean. Tomato seeds were also stored hermetically at 15.9 % moisture content at 40 degreesC for 0, 7, 14, 21 or 28 d before transfer to 50 degreesC. This investigation showed that the standard deviation of the subsequent survival curves at 50 degreesC was unaffected by the duration of previous storage at 40 degreesC. The results of both investigations were consistent with the hypothesis that loss in probit viability is solely a function of the current storage environment, with no effect of change in temperature per se. The application of the viability equation to seed survival in fluctuating environments was validated against independent observations for rice in uncontrolled storage conditions. (C) 2001 Annals of Botany Company.