LONG-TERM TEMPERATURE INTEGRATION OF TOMATO - GROWTH AND DEVELOPMENT UNDER ALTERNATING TEMPERATURE REGIMES

The effects of alternating temperature regimes on the growth and development of tomato (Lycopersicon esculentum) cultivar 'Counter' were investigated in a glasshouse experiment. The plants received low- and high-temperature regimes alternating every 3, 6 or 12 days. During each cycle of 6, 12 and 24 days, respectively, the temperature sum was the same as that for a control kept constant at a moderate temperature. Two temperature amplitudes (difference between high and low temperature level), viz. 3 and 6°C were applied. Only the combination of 6°C amplitude and 24-day cycle was excluded. The treatments started 10 days before (young plants) or 10 days after (old plants) anthesis of the first truss. The experiment was carried out in spring. The development rate was dependent on the actual temperature. The developmental stage achieved depended on the temperature sum received, only temperature alternation with a 6°C amplitude inhibited development of the young plants slightly. Also the plant length increase was reduced only for the young plants at the 6°C temperature amplitude treatments. For the old plants, none of the treatments reduced growth (fresh weight increase). With the young plant, only a 6°C temperature amplitude combined with a 12-day integration period reduced total growth with respect to the control. Tomato proved to have a great ability to integrate (compensate within a certain period) temperature. Because it results in a greater flexibility in control priorities, this ability is an important means to optimize other growth factors of the glasshouse environment and to use energy more efficiently. © 1990.