Seasonal Changes in Growth Promoters and Inhibitors in Buds of Apricot1

Abstract

Spur buds of apricot were sampled at intervals from late July, 1968, until bloom in 1969, and from 1 month after bloom until the end of September. The samples were freeze-dried and then extracted with 80% methanol. The extracts were partitioned into 4 phases: water, neutral ethyl acetate, acidic ether, and acidic butanol, and then bioassayed for auxins, inhibitors and gibberellins. Although an inhibitor and gibberellin-like activity were present in the extracts, no consistent auxin-type activity was found. The end of rest was correlated with a decrease in the level of inhibitor and gibberellin-like activity, with the inhibitor increasing again towards anthesis. The onset of rest in May, 1969, was correlated with a decrease in inhibitor and increase in gibberellin-like activity. The inhibitor was present in scales and floral parts of buds, while gibberellin-like activity was confined mainly to the floral parts.

The Relation of Endogenous Abscisic Acid to the Dwarfing Capability of East Malling Apple Rootstocks1

“…From results with other clones, EM XVIa, having only slight dwarfing ability, should be expected to have even less inhibitory activity than EM I. Using the extraction method of Ramsay and Martin (15), the EM XVIa root extract was slightly less inhibitory at Rf 0.7 than that of EM I roots (Fig. 3).…”

“…The final lengths of sections were measured by enlarging their shadows 10 times with a photographic enlarger. In all wheat bioassays results are expressed as growth (increment in the length of coleoptile sections) as percent of controls (15). Where possible, the confidence (conf) limits at.5% level (t0.o5o Sx) for the controls were calculated according to the method of Snedecor and Cochran (20).…”

The Role of Bud Scales in the Dormancy of Apples

“…The passage of temperate zone deciduous trees into and out of dormancy and rest generally is attributed to phytohormones, including both growth promoters and inhibitors (4,13,14,17,20,24,25). Correlations between rest intensity and inhibitor levels, particularly ABA, have been found, but ABA is not always effective in prolonging dormancy; nor are high ABA levels always required for deep rest (7,9,14,17,20,22,25).…”

“…The inhibitor level in Prunus scales during the dormant period does not seem to vary as much as in the primordia (6 , 17). Levels of growth promoters in Prunus bud scales are too low to measure (17).…”