ACTA AGRONOMICA TOMUS 29. (A MTA AGRÁRTUDOMÁNYI KÖZLEMÉNYEI, 1980)

1980 / 1-2. szám - M. NAGY: Dormancy in fruits of Tilia platyphyllos Scop. IV. Changes in the endogenous gibberellin content during stratification

Acta Agronomica Academiae Scientiarum Hungaricae, Tomus 29 (1—2), pp. 1—11 (1980) DORMANCY IN FRUITS OF TILIA PLATYPHYLLOS SCOP IV. CHANGES IN THE ENDOGENOUS GIBBERELLIN CONTENT DURING STRATIFICATION By M. NAGY JÓZSEF ATTILA UNIVERSITY, DEPARTMENT OF PLANT PHYSIOLOGY, SZEGED Quantitative changes in various forms of gibberellin occurring in Tilia platy-phyllos seeds during stratification were studied using the lettuce hypocotyl and barley endosperm tests. From dormant, non-stratified seeds various forms of gibberellin, including free gibberellin-like substances, were detected, which suggests that it is the right level, rather than the presence, of free gibberellins that is required to break dormancy and start germination. A sudden increase in the quantity of ethyl-acetate soluble free gibberellin-like substances is observed from the sixth week of stratification. During stratification considerable biological activity takes place in the butanol soluble fraction containing gibberellin conjugates, probably as a result of non-specific glucosid­ase activity. The identical Rf-values found for the gibberellin-like substances obtained after the hydrolysis of the butanol soluble fraction, and for those of the ethyl acetate fraction indicate a genetic relationship between the gibberellin conjugates and the free gibberellins. In the TCA-insoluble fraction, which contains gibberellins bound to macro­molecules, a low degree of biological activity was found, but only one of the active spots showed a quantitative change. CCC treatment during stratification does not inhibit germination in seeds, which points to the fact that the quantitative increase in free gibberellin-like substances is mostly due to a release from the bound forms rather than to de novo synthesis. Introduction Of all the physiological effects of gibberellin its ability to break dormancy and stimulate germination is the best known. In many species the stratification requirement can be successfully re­placed by exogenous GA3 treatment (AMEN 1968, JUNTTILA 1970, Ross— BRADBEER 1971, KOPCEWICZ—PORAZINSKI 1973, BASKIN—BASKIN 1970,1974). These findings justified the examination of changes in the endogenous gib­berellin level during stratification, in the course of which some authors (FRANKLAND—WAREING 1962, 1966, Ross—BRADBEER 1968, KENTZER 1966) pointed out that the endogenous gibberellin content of the seeds increased during the stratification, suggesting a relationship between the increase in gibberellin content and the termination of dormancy. In earlier investigations with Tilia platyphyllos seeds we too found the endogenous free gibberellins to increase during stratification, but we did not succeed in replacing the stratification by exogenous GA3 (NAGY—SZALAI 1973, SZALAI—NAGY 1974). Naturally this does not mean that the gibberellins are of Acta Agronomica Academiae Scientiarum Hungaricae 29, 1980 1

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