EFFECTS OF TEMPERATURE REGIMES ON TOMATO SEEDLING DEVELOPMENT

To investigate effects of temperatures in the preceding developmental stage on the following developmental stage, `Sunny' tomatoes were seeded in the greenhouse at six dates and three temperature levels. Plants were rotated among temperature levels so that all plants received approximately the same temperature accumulation at the time of field transplanting. Developmental stages defined were: emergence, 1st, 2nd, 3rd, 4th, 5th, and 6th leaf appearance. Temperature and solar radiation were recorded hourly. Results indicated a significant effect of temperature in the preceding stage on the following stage. Coefficients of variation (CV) in growing degree days (GDD) calculated from the 1st to the ith stage were significantly smaller than those calculated from the (i-1)th to ith stage. When Ri, defined as the reciprocal of the number of days from the 1st to the ith stage, was regressed to Ri-1 and the daily average temperature was regressed from the (i-1)th to the ith stage, all coefficients of Ri-1 were significant at the 1% level. This model was superior to one in which Ri was regressed to the daily average temperature from the 1st to the ith stage.