Flowering hormone gibberellins

Can we say anything more precise about the function of gibberellins in flower formation Most plant biologists feel that flower formation is controlled by specific, hormone-like substances, so-called flower hormones. Attempts at ex-... 

Thus, gibberellins can substitute for either the effect of cold or the long day as shown in point 2 but seldom both at the same time. Usually the short day cannot be replaced by gibberellins. We can also exclude with certainty the possibility that the gibberellins might be identical with the much sought after flowering hormone. The reasons for this are ... 

Abscisin II is a plant hormone which accelerates (in interaction with other factors) the abscission of young fruit of cotton. It can accelerate leaf senescence and abscission, inhibit flowering, and induce dormancy. It has no activity as an auxin or a gibberellin but counteracts the action of these hormones. Abscisin II was isolated from the acid fraction of an acetone extract by chromatographic procedures guided by an abscission bioassay. Its structure was determined from elemental analysis, mass spectrum, and infrared, ultraviolet, and nuclear magnetic resonance spectra. Comparisons of these with relevant spectra of isophorone and sorbic acid derivatives confirmed that abscisin II is 3-methyl-5-(1-hydroxy-4-oxo-2, 6, 6-trimethyl-2-cyclohexen-l-yl)-c s, trans-2, 4-pen-tadienoic acid. This carbon skeleton is shown to be unique among the known sesquiterpenes. 

O. have been shown to inhibit flowering, promote vegetative growth and control organ development in plant tissue culture. Effective concentrations of O. are 100-1000-fold lower than those of other plant hormones, such as auxins, cytokinins and gibberellins. 

Tompsett PB, Fletcher AM (1979) Promotion of flowering on mature Picea sitchensis by gibberellin and environmental treatments. The influence of timing and hormonal concentration. Physiol Plant 45 112-116... 

Suttle JC, Zeevaart JAD (1979) Stem growth, flower formation, and endogenous gibberellins in a normal and a dwarf strain of Silene armeria. Planta (Berl) 145 175-180 Torrey JG (1976) Root hormones and plant growth. Annu Rev Plant Physiol 27 435-459 Vince-Prue D (1975) Photoperiodism in plants. McGraw-Hill, London Wareing PF, Saunders PF (1971) Hormones and dormancy. Annu Rev Plant Physiol 22 261-288... 

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