ISHS Acta Horticulturae 109: III International Symposium on Flower Bulbs
PARTLY COOLED TULIPS: RESPONSE TO GA3 AND OTHER GIBBERELLINS |
| Authors: | Gordon R. Hanks, A.R. Rees |
| Abstract:
Bulbs of tulip cvs. 'Apeldoorn' and 'Paul Richter' which had received two-thirds of their full cold requirement at 5°C were used to investigate the responses of partly cooled tulips to gibberellins. Gibberellins were given as standardized, 1 ml injections directly into the bulb, prior to planting at the end of cold treatments. In cv. 'Apeldoorn', increasing amounts of GA3 (0. 1 – 10. 0 mg per bulb) gave progressively earlier flowering. 1 mg GA4/7 was as effective in this respect as 10 mg GA3, both treatments giving 33 d earliness. These treatments also increased final first internode length, but earlier flowering was always associated with shorter overall stem length. The effects of such treatments on cv. 'Paul Richter' were relatively small. Standard, 1 mg GA3 injections were also effective when given after planting. When applied at planting time the depth of injection was important: relatively superficial injections were less effective than deeper ones. Greater effects were obtained with injections repeated every two weeks. Using standard 0. 5 mg injections of various GAs, the order of effectiveness in giving earlier flowering was: GA7 > GA4 > GA1 > GA9 > GA13 > GA5 >> GA3. | |
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