ROLE OF ENDOGENOUS GIBBERELLINS IN GERMINATION OF MELON (CUCUMIS-MELO) SEEDS

The effect of the plant growth retardants ancymidol, mefluidide and un iconazole on germination of two melon accessions differing in their ab ility to germinate at 14 degrees C was examined. The accessions were t he cold sensitive Noy Yizre'el and the cold tolerant Persia 202. The t hree growth retardants were able to delay the germination of intact No y 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 wa s 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 ac tivity than Noy Yizre'el seeds. Among the extracted compounds several endogenous gibberellins were identified by combined gas chromatography -mass spectrometry (GC-MS). They included GA(4), GA(20), GA(1) and GA( 3) in Noy Yizre'el and GA(34), GA(20), GA(1) and GA(8) 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 con centration, is due to a higher endogenous level of GA and a better see d coat permeability to oxygen.