Increasing Flower Number in Single-Truss Tomatoes

Flower number in the first truss (inflorescence) of glasshouse tomatoes was increased by growing the seedlings at low temperatures shortly after pricking off. The optimal timing for this treatment varied by only a few days over most of the year. The longest chilling duration (14 days) was most effective, possibly because of variability between plants. In summer flower number could be doubled, but in winter only 30% to 40% increases were obtained. Chilling delayed anthesis by up to ten days, the delay being proportional to the duration of chilling.

Day/night temperatures of either 10°/10° C. or 16°/4° C. during chilling had similar effects on flowering, and resulted in similar delays to growth and anthesis.

The mechanism by which chilling may increase flower number and the distinctions between this process and vernalization are discussed.