QUANTITATIVE CHANGES OF ENDOGENOUS GROWTH SUBSTANCES IN OLIVE SEEDS SUBJECTED TO LOW TEMPERATURE FOR BREAKING THEIR DORMANCY

The cis-ABA conc. was three times as high in the endosperm of non-chilled seeds as that in the embryo (165 and 45 ng/g d.wt. respectively but it dropped sharply in the endosperm when the seeds had been chilled at 10°C for 1 wk., and remained at a low level during the rest of the chilling period. The cis-ABA conc. in the embryo decreased from 64.5 to 0 ng/g d.wt. as the duration of chilling increased from 2 to 4 wks. The cis-ABA content of embryos taken from seeds subjected to 20° or 25°C for 4 wks was relatively high (56 and 68 ng/g d.wt. respectively).

The conc. of GA-like substances in the ethyl acetate fraction, of both, embryos and endosperms, was generaly low; only a sharp peak in conc. was observed in embryos taken from seeds which had been subjected to 10°C for 3 wks. In nearly all cases the GA-like activity appeared at the same Rf with GA₇ (Rf.0.7) in paper chromatograms developed in isopropanol-water (60 15 V/V).

The IAA conc. in the endosperm fluctuated between 1.6 and 24 ng/g d.wt. during the 4 wks of chilling; in the embryo, after a decrease from 14.7 to 0 during the first two weeks, it rose to 36.5 ng/g d.wt. after 4 wks at 10°C. A significant increase of the IAA conc. was observed in both tissues when the seeds, after 4 wks at 10° were transferred to 20°C for 3 days.

A positive relation seems to exist between the GA and IAA levels in the embryo on the one hand and the duration of chilling and germination capacity on the other. This relation was negative in the case of cis-ABA.

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