ISHS Acta Horticulturae 177: IV International Symposium on Flower Bulbs
CRITERIA RELATED TO PRECOOLING OF TULIP BULBS CV.APELDOORN AT 5°C |
| Authors: | F.T. Heidema, G. Grevers, N. Gorin, C.T.C.v. Hulst, J.M. Franssen |
| Abstract:
Based on trials in 1981, 1982 and 1983 the following tentative criteria are proposed for detecting whether dry bulbs (12–13 cm circumference) have been exposed to 5°C: the starch content of freeze-dried anthers should exceed 10% and the specific activity of -amylase in anthers extracts should be below 0.16 (arbitrary unit per mg protein). Data from a recent trial (1984) corroborated the proposed indicators. However, these critaria could not be used to determine how long the bulbs had been exposed to 5°C. During the 12 weeks of cold treatment development of anthers, expressed as fresh or dry weight, was a linear function of time; but, as the slope and Y-intercept of the lines differed from one year to another, this criterion was discarded as an indicator of the duration of cold treatment. The ratio of two bands obtained by liquid chromatography of acetone extracts from shoots shows no significant trend as a function of duration of cold treatment. The osmotic potential of shoots was not included in our model because it decreased linearly during treatment but after one week of simulated transport it increased to a level that would indicate a treatment of only 6 weeks. | |
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