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

3 DORMANCY IN TILIA PLATYPHYLLOS Results 1. Quantitative changes in the endogenous free gibberellin-like substances during stratification In the course of seed maturation a transformation of free gihberellins into inactive, bound forms can be observed. According to SEMBDNER et al. (1968), in the mature seeds of Phaseolus coccineus only hound gibberellins can be found. Attempts to detect gibberellin activity in dormant seeds of Fraxinus excelsior (KENTZER 1966, SZALAI—NAGY 1968) and Corylus avellana (FRANK­LAND—WAREING 1966) also failed. On the other hand, gibberellin activity could be detected in dormant seeds of Fagus sylvatica (FRANKLAND—WAREING 1966), Acer platanoides (TOMASEWSKA 1976) and apple (SINSKA—LEWAK 1970). On the basis of these contradictory data it is difficult to decide whether the appearance of the free gibberellins is the decisive momentum in the termination of dormancy. Quantitative changes in the endogenous free gibberellin-like substances of T. platyphyllos seeds during stratification are shown in Fig. 1 (A and B). Since the gibberellins show different biological activities in the different tests (REEVE 1974) two kinds of biological tests were used to study the change in the endogenous gibberellin content (lettuce hypocotyl and barley endo­sperm). The barley endosperm is responsive to lower gibberellin concentrations than the lettuce hypocotyl, and is not inhibited by solvent residues which might he contained in the extract; the lettuce hypocotyl test, on the other hand, reacts to a wider range of gibberellins (JONES-—WARNER 1967). As shown by the figures, in the dormant, non-stratified T. platyphyllos seeds free gibberellin-like substances occur in demonstrable quantities. The lettuce hypocotyl test (A) displayed the presence of six kinds of free gibberellin­like substances; four of them showed significant quantitative changes during the stratification. A sudden quantitative increase can he observed from the sixth week of stratification. Similar results were arrived at with examinations made with the barley endosperm test (B), except that in this case the presence of a gibberellin-like substance in the Rf 0.5—0.6 position could not be detected. 2. Quantitative changes in gibberellin conjugates in the butanol soluble fraction during stratification According to the literary data the gibberellin conjugates (gibberellins bound to smaller molecules) show no biological activity in dwarf plant tests (KATSUMI 1971, 1973). However, in the biological tests used in the present work the butanol soluble fraction displayed considerable biological activity. 1* Acta Agronomica Academiae Scientiarum Hungaricae 29, 1980

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