Experiments demonstrated that bud necrosis in tulip bulbs is caused by mites that penetrate the flower bud during storage. This penetration is only possible if the buds, which are normally closed, are open at their tips. Such buds were found after administration of ethylene (3 ppm) during storage at 20~ shortly after lifting and in 'Red Champion' also after storage at higher temperatures (20 to 23 ~ in ethylene-free atmospheres. Open buds, caused by ethylene, resulted from unequal growth inhibition of the young leaves and stamens. The difference in sensitivity of both organs to ethylene decreased during storage. Later on, the growth inhibition of stamens and leaves became equal, and the buds remained closed. Then ethylene caused blasting of the flower buds. Open buds in 'Red Champion', caused by higher storage temperatures, resulted from aberrant differentiation of the tips of the young leaves.
Ethylene in concentrations as low as 0.05 ppm inhibited the elongation growth of the main generative bud within tulip bulbs during storage after lifting. The sooner the ethylene was administered after lifting and the higher the storage temperature, the higher the concentration of ethylene needed to obtain the same degree of inhibition. Fifty percent inhibition was found at concentrations between 0.05 and 10 ppm.Stamens within the buds were inhibited to a degree which was generally lower compared with the leaves; the largest differences were found at 13~ whereas at 23~ the degree of inhibition was nearly equal.Open buds (which result from unequal growth of stamens and young leaves and are the prerequisite of bud necrosis) were induced by exposure to ethylene in concentrations as low as 0.1 ppm. This phenomenon occurred in bulbs exposed to ethylene for 6 weeks at 17 ~ shortly after lifting; at other temperatures and later exposure times, higher concentrations were needed to obtain the effect.During storage after exposure to ethylene, growth resumed and the degree of bud deformation mostly decreased; in bulbs that had been treated later, an increase was found when the ethylene concentration had been higher than 1 ppm.After planting, shoots emerging from ethylene-treated bulbs were shorter, basal internodes of the stem were shorter if the concentration was 1 ppm or higher, and the width of leaves was reduced after early exposure.
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