A simple and rapid bioassay using seeds of Lactuca sativa L. Grand Rapids has been developed for the detection of germination-enhancing compound(s) in plant-derived smoke extracts. This light-sensitive species germinates within 24 h in the dark at 20 or 25 O C and shows responsiveness to smoke-derived extracts over a wide concentration range. For some seed lots where the Pf,. level is high and germination in the dark is unacceptably high, a brief (10 min) exposure to far-red light, one hour after the start of imbibition in the dark, is necessary to clearly demonstrate biological activity in the smoke extracts.

Plant-derived smoke extracts stimulate the germination of many different seeds. the present report explains steps to determine some of the chemical characteristics of the compounds concerned. Grand Rapids lettuce seeds were used as a bioassay because smoke-derived extracts overcome their light-sensitivity. The active compounds were partitioned into ethyl acetate, separated by various TLC systems and fractionated by reverse phase HPLC. They are stable surviving a series of chromatographic steps and are very active biologically. In order to ascertain their chemical properties it was necessary to use a range of dilutions after each isolation step. It would appear that similar types of compounds are present in smoke extracts derived from different plant material.

Of the four 2iP derivatives applied to cut carnations 2iP, IPA and IPAMP delayed the rate of flower senescence but did not delay longevity . 2iP9G was the least effective . ['H]2iP was rapidly transported to all flower components . The receptacular tissue apparently plays a major role in the distribution of the applied cytokinin to the rest of the flower parts . Over and above possible interconversion between 2iP, IPA and IPAMP the applied [' H]2iP was also converted to 2iP9G, Ade, Ado, tZ and DHZ . The presence of Ade indicates the involvement of cytokinin oxidase-type enzymes while the presence of tZ and DHZ indicates a degree of hydroxylation . These latter steps may contribute to the efficiency of 2iP in the system .

No abstract

The effect of 28 natural and synthetic cytokinins, including cytokinin nucleotides, the growth of soybean cotyledonary callus was investigated . Generally the nucleosides and nucleotides gave a slightly better response than their respective free bases. The differences in response were, however, not significant and there is a distinct possibility that rapid interconversions between these three types of cytokinin occur within the tissue . The 0-glucosides of Z and ZR were the most active . Glucosylation in the 3, 7 and 9 positions reduced activity . In the case of BA-derivatives the order of activity of the N-glucosides was 3G > 9G > 7G . Since iso-pentenyl derivatives had little activity they may be very difficult to detect using the soybean callus bioassay .Abbreviations . Z = zeatin ; DHZ = dihydrozeatin; IP = iso-pentenyladenine ; BA = benzyladenine ; K = Kinetin; R = riboside ; MP = monophosphate; OG = 0-glucoside ; 3G = 3-glucoside ; 7G = 7-glucoside; 9G = 9-glucoside ; GC-MS = gas chromatography -mass spectrometry .