To understand the growth and flowering responses when ancymidol and gibberellic acid (GA₃) w-as treated tp plants from cooled bulbs, following experiments were conducted in a nonheated greenhouse.
When 50ppm ancymidol was drenched in soil, flowering was not delayed in ´Merry Widow´, but delayed in ´Oxford´. Totzl plant height ((lowering stalk) was reduced by 25 or 50 ppm ancymidol treatment only in `Oxford´. Although it was not significant, plant height was increased when 5 ppm ancymidol was soil drenched to ´Oxford´.
When ancymidol was drenched in soil, two or four weeks after planting, flowering was delayed by 50 ppm at 4 weeks after planting, not when treated at 2 weeks after planting. However, plant height was greatly reduced when 25 or 50 ppm ancymidol was soil drenched either 2 weeks or 4 weeks after planting in ´Apeldoorn´, ´General Eisenhower´, and ´President Kennedy´.
The growth retarding effect by ancymidol treatment was completely reversed by GA₃ treatment in `Golden Apeldoorn´ and `Red Matador´. ´Red Matador´ cultivar flowered by treatment even though they did not receive sufficient cold treatment.
From these results, ancymidol can reduce plant height effectively when soil drenched within 4 weeks from bulb planting. Further GA₃ treatment can reverse the growth retarding effect of ancymidol and also substitute a non-sufficient cold treatment effect in tulip.
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