Factors affecting the response of tulips to gibberellin |
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Authors: | Gordon R Hanks |
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Institution: | Glasshouse Crops Research Institute, Littlehampton, West Sussex BN17 6LP Gt. Britain |
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Abstract: | Gibberellic acid (GA3) treatment of forced tulip crops has potential for producing faster growth to anthesis in the glasshouse, for reducing losses due to floral bud blasting, and for reducing the duration of cold storage needed to obtain satisfactory flowers. Using partly and fully cooled direct-forced tulips, cultivar ‘Apeldoorn’, several factors (relevant to the definition of GA3 treatments) were studied. Experiments confirmed the previously recorded effects of gibberellins in tulips: GA3 injections reduced the duration of the glasshouse period, enhanced flower survival and flower length, and reduced stem length at flowering.Following bulb storage at temperatures from ?2 to 20°C, GA3 reduced the glasshouse period by 15–25% and increased flower length, compared to controls, irrespective of storage temperature. Stem length was also reduced by GA3, this effect being greater following a storage temperature of 5°C or lower. When GA3 was applied during the period of 17°C-storage which precedes cool storage, or during or after storage at 5°C, it was found that treatments during or at the end of cool storage were more effective in producing the characteristic effects of GA3 than were pre-cooling applications. In partly cooled bulbs (but not fully cooled ones), the GA3-induced earliness of flowering was about doubled when GA3 injections were given repeatedly at 2-week intervals throughout storage. The responses to GA3 injections were found to be unmodified by early-lifting and heat-treatment (for earlier forcing), by delaying the start of 5°C storage (for later forcing), by glasshouse temperature (16 and 18°C), and by shading treatments; there was little effect of bulb size. |
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Keywords: | bulb forcing cold requirement flowering gibberellin |
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