F. E. Drewes

The effect of a plant-derived smoke extract on the germination of light-sensitive lettuce seed

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°C and shows responsiveness to smoke-derived extracts over a wide concentration range. For some seed lots where the Pfr 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.

Cytokinins in cut carnation flowers. VIII. Uptake, transport and metabolism of benzyladenine and the effect of benzyladenine derivatives on flower longevity.

Summary [8- 14 C]Benzyladenine (BA) was rapidly transported up the stems of cut carnations and accumulated in the receptacles. Although the petals contained a considerable percentage of the total radioactivity taken up by the flower, this radioactivity was diluted by the large overall mass of the petals. Very little radioactivity was present in the petals when expressed on a unit dry weight basis. Metabolism was rapid and ribosylation to ribosylbenzyladenine (BAR) seems to be a major metabolic route. BAR appears to be converted to ribosylbenzyladenine monophosphate (BARMP). By day eight, degradative metabolism to yield adenine dominated. Throughout the 12 days of the experiment interconversion between BA, BAR and BARMP apparently occurred. All three of these compounds had similar effects on flower longevity. They were only effective in maintaining flower quality at 4 × 10 −6 and 4 × 10 −7 M. Apart from glucosyl-3-benzyladenine, which never appeared to be a major metabolic product, the BA-glucosides did not delay flower senescence.

Some chromatographic characteristics of germination stimulants in plant-derived 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.

The search for germination stimulants in plant-derived smoke extracts

Aqueous extracts of plant-derived smoke stimulates seed germination. To isolate the active compound(s), smoke extracts of Passerina vulgaris and Themeda triandra were subjected to bioassay-guided fractionation. Purification steps included liquid-liquid partitioning, semi-preparative HPLC, two TLC systems and analytical HPLC. Each purification step was examined using the lettuce seed germination bioassay. Biologically active fractions were selected for further purification. Active fractions from the last HPLC purification step were analysed by high-resolution GC-MS. Twelve compounds were identified, of which seven were present in both the P. vulgaris and T. triandra extracts. Four of the compounds that were commercially available were tested in the lettuce seed bioassay and were found to be inactive. Waterekstrakte verkry van plantrook stimuleer saadontkieming. Om die aktiewe verbindings in rook te isoleer is rookekstrakte van Passerina vulgaris en Themeda triandra onderwerp aan biotoets-gereguleerde fraksionering. Suiweringstappe het vloeistof-vloeistof partisie, semi-preparatiewe HPLC, twee TLC stelsels en analitiese HPLC ingesluit. Elke stap is ondersoek met die slaaisaad-biotoets. Biologies-aktiewe fraksies het verdere suiwering ondergaan. Aktiewe fraksies van die laaste HPLC stap is onderwerp aan hoe resolusie GC-MS. Twaalf verbindings is geidentifiseer waarvan sewe in beide die P. vulgaris en T. triandra ekstrakte gevind is. Vier van hierdie verbindings wat kommersieel bekom kan word was onaktief in die slaaisaad-biotoets.

The biological activity of cytokinin derivatives in the soybean callus bioassay

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 O-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.

Effect of seaweed concentrate on growth and development of the marigold Tagetes patula

The seaweed concentrate Kelpak, made fromEcklonia maxima, and applied as a foliar spray or a root drench at transplanting, improved both the vegetative and reproductive growth of marigolds. Of particular significance is that the overall production of seeds (fruits) was increased by as much as 50% in some instances. Very low concentrations of seaweed concentrate were not always effective, while the higher dosages decreased vegetative growth.

Initiation of and solasodine production in hairy root cultures of Solanum mauritianum Scop.

Initiation and establishment of hairy root cultures from leaf or seedling hypocotyl explants of Solanum mauritianum Scop., using six strains of Agrobacterium rhizogenes was attempted. Success was only achieved following hypocotyl inoculation with strain LBA 9402. Transformation frequency was very low, with only one instance out of a possible 90 being recorded. Resultant hairy root cultures grew rapidly and could be maintained using a Murashige and Skoog (1962) medium supplemented with 0.1 g L−1myo-inositol and 3% sucrose, either as a solid or liquid culture. Under these conditions, the roots had a solasodine content of 126 μg g−1 DW. Lower levels of solasodine and decreased root growth rates were recorded when the medium strength was reduced by half or 3% glucose substituted for the 3% sucrose.

The stability and metabolism of benzyladenine glucosides in soybean callus

Summary Using cytokinin dependent soybean callus the 3-, 7- and 9-glucosides of BA were investigated with respect to biological activity and metabolic stability. [3G]BA was the most, and the [7G]BA the least active in the soybean callus bioassay. This order was also established with respect to the rates of metabolism, and is apparently the reason for the differential rates of cell division observed with the three BA-glucosides investigated. The rapid metabolism of [3G]BA resulted in the release of a biologically active compound that had a similar retention time to that of BA. As this hydrolysis and release of BA resulted in substantially better growth it provides further circumstantial evidence that the free base is the active cytokinin. Although all three glucosides have N-C bonds, [3G]BA is hydrolyzed more readily by acid. In addition it can be enzymatically hydrolyzed by R-glucosidase. We propose that the term «storage» compound must be applied more rigorously with respect to cytokinin glucosides. In the case of [7G]BA and [9G]BA this term is clearly inappropriate and the terms «detoxification, inactivation» and/or «bound» seem more correct. As [3G]BA can be utilized readily and appears to serve as a ready source of BA (slow release compound) following application to plant tissues the use of the term «storage» compound appears in order. From the present results it would not seem as if there is reversible sequestration between BA and [3G]BA. During the 24 h of the experiment [7G]BA and [9G]BA but not [3G]BA were formed following BA application to soybean callus.

Accumulation of Cyanidin-3-glucoside in Callus and Cell Cultures of Oxalis reclinata

Summary Callus formation from stem internode segments of Oxalis reclinata was initiated in vitro with 5 mg L −1 NAA (α-naphthaleneacetic acid) and 0.5 mg L −1 BA [6-(benzylamino)purine]. With the onset of organogenesis, a red-pigmented callus developed. A stable red callus line was subsequently isolated from this tissue whereafter cell cultures were initiated. Both callus and cell cultures produced cyanidin-3-glucoside at 25°C in the light as the major pigment. At 10°C in the light, extensive organogenesis was promoted, with a concurrent reduction in anthocyanin production.

Cytokinins in cut carnation flowers. IX. Transport and metabolism of iso-pentenyladenine and the effect of its derivatives on flower longevity

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. [3H]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 [3H]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.