[Mechanism of dwarfing effect of tomato (Solanum lycopersicon) seedlings induced by cold-shock treatment under high temperature stress].

To explore the dwarfing mechanism of tomato seedlings induced by cold-shock treatment followed by high temperature, tomato seedlings were subjected to cold-shock treatment once a day at 8:00 with temperature of 5, 10 and 15 °C for 10, 20 and 30 min, respectively, and ethylene production rate was measured. Plant height, ethylene production and gibberellin (GA3) content of the seedlings treated with T10 °C D10 min (cold-shock with 10 °C for 10 min), coupled with utilization of growth regulators, were also evaluated. The results showed that the release of ethylene was increased with the decrease of cold-shock temperature and extension of treatment time. The cold-shock treatment of 5 °C and 30 min had the highest ethylene production rate of 60.3 nL h-1 . g-1, which was 6.5 times of the control. None of ethephon (ETH), silver thiosulphate (STS), GA, or paclobutrazol (PP333) could completely block high ethylene production induced by cold-shock treatment. Tomato seedlings with cold-shock treatment (T10 °C D10 min ) resulted in reduction in GA3 content by 38.1% compared with the value of control (130.6 µg . g-1). Neither ethephon nor STS had significant effect on the dwarfing induced by cold-shock. However, GA3 weakened the dwarfing effect induced by cold-shock treatment (T10 °C D10 min), while PP333 greatly enhanced it. The dwarfing effect by cold-shock treatment of T10 °C D10 min was equivalent to that of application of 4.0 mg . L-1 PP333 based on the seedling height as an evaluation indicator. It was concluded that cold-shock treatment stimulated shoot ethylene production and blocked GA3 synthesis. GA3 played a vital role in dwarfing effect on tomato seedling induced by cold-shock treatment. Cold-shock with 10 °C and duration of 10 min could promote the growth of tomato seedlings with shorter stem and higher dry mass accumulation.