Edelstein, M., Dept of Vegetable Crops, Agricultural Research Organization, Newe Ya'ar Research Center, P.O. Box 90000, Haifa, 31900, Israel
Ben Tal, Y., Dept of Ornamental Horticulture, ARO, Volcani Center, P. O. Box 6, Bet Dagan, 50-250, Israel
Wodner, M., Dept of Ornamental Horticulture, ARO, Volcani Center, P. O. Box 6, Bet Dagan, 50-250, Israel
Kigel, J., Dept of Agricultural Botany, Hebrew Univ. of Jerusalem, Faculty of Agriculture, Rehovot, 76100, Israel

The effect of the plant growth retardants ancymidol. mefluidide and uniconazole on germination of two melon accessions differing in their ability to germinate at 14°C was examined. The accessions were the cold sensitive Noy Yizre'el and the cold tolerant Persia 202. The three growth retardants were able to delay the germination of intact Noy Yizre'el seeds, but did not affect that of intact Persia 202 seeds. On the other hand germination of decoated seeds of both accessions was unaffected by these inhibitors at normal oxygen concentration, but was inhibited at 5% oxygen. When gibberellin‐like activity was measured by a dwarf rice biological assay following HPLC fractionation, it was found that seeds of Persia 202 contained much more gibberellin‐like activity than Noy Yizre'el seeds. Among the extracted compounds several endogenous gibberellins were identified by combined gas chromatography‐mass spectrometry (GC‐MS). They included GA4, GA20, GA1 and GA3 in Noy Yizre'el and GA34, GA20, GA1 and GA8 in Persia 202. It is suggested that the better germination of intact Persia 202 seeds, compared to Noy Yizre'el seeds at low temperature and low oxygen concentration, is due to a higher endogenous level of GA and a better seed coat permeability to oxygen. Copyright © 1995, Wiley Blackwell. All rights reserved