ISHS Acta Horticulturae 430: VII International Symposium on Flowerbulbs
INDUCING FREEZING TOLERANCE IN NARCISSUS BULBS BY GROWTH RETARDANTS |
| Authors: | V. Cohen, A. Borochov, S. Philosoph-Hadas |
| Abstract:
Transient exposure to below-freezing temperatures, during growth or post-harvest, damages many ornamental geophytes. The aim of this work was to investigate means for hardening narcissus (N. tazetta, cv. Ziva) bulbs to freezing stress. Several techniques were used to evaluate bulb viability. The increase in electrolyte leakage and visible injuries in the in-bulb inflorescence were positively correlated with the freezing stress effects on plant growth and flowering. Injuries were observed following exposure to -2°C for more than 6 h. Attempts to reduce sensitivity of the bulbs to low temperatures through hardening at +2°C for several weeks were unsuccessful. However, a single soil drench with paclobutrazol or uniconazole resulted in production of daughter bulbs that were not injured by freezing at -2°C for 12 h, as judged by electrolyte leakage and growth measurements. This bulb hardening was accompanied by modifications in membrane enzymes and solute uptake activities. We therefore assume that changes in membrane properties are to a large extent involved in the hardening process. | |
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