A. D. Bayley

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.

Somatic Embryogenesis in Pinus patula

Softwood species make up about 50 % of the plantation area in South Africa, of which Pinus patula is the most important, occupying approximately half of this (Department of Water Affairs and Forestry, 1998). Introduced from Mexico, this species is deployed in commercial plantations over a range of sites in the summer rainfall regions of the country, typically characterized by a minimum of 800 mm MAP, located above an altitude of 1200 m and MAT less than 18°C (Morris and Pallett, 2000). Under these conditions, yields of 22 m ha y can be expected from the best quality sites (Evans, 1999), while mean annual increments (MAI) of about 17 m ha y are derived from lower productivity sites (Pallett, 2000). The timber products derived from softwood species include saw timber, pulp and paper among others (Department of Water Affairs and Forestry, 2001).

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.

The in vitro metabolism of [8-14C]benzyladenine by excised organs of tomato plants

The metabolic fate of [8-14C]benzyladenine applied to the excised organs of tomato (Lycopersicon esculentum Mill. cv. Heinz 1370) was investigated after 2 and 6 h of feeding. Although the roots were the most effective at uptake of the cytokinin the leaves metabolised it the most efficiently. The predominant metabolite in all of the tissues was an unknown compound which did not have a retention time corresponding with any of the standards used. The roots contained the most extensive range of metabolites which included the unknown metabolite and compounds co-eluting with adenine, and the riboside, nucleotide and 9-glucoside of benzyladenine. The 9-glucoside was detected only in the root material. The stem yielded the highest levels of radioactivity at the retention times of benzyladenosine-5′-monophosphate and benzyladenosine. The radioactivity associated with these two cytokinins was transient in the leaf extract. This organ ultimately yielded radioactivity only at the retention times of the unknown metabolite and adenine. Since only the roots and leaves contained relatively large peaks of radioactivity at the elution volume of adenine it seems that degradative metabolism was more predominant in these organs than in the stem.

Fate of benzyladenine metabolites extracted from tomato shoots in biological systems

The metabolism of radioactive metabolites of BA, obtained from tomato shoots, and purified by chromatographic techniques, was studied in rootless tomato shoots and soybean callus. There is apparently a great deal of interconversion between BA, BAR and BARMP. From the present results it is not possible to determine whether BARMP is formed directly from BA or whether BAR serves as an intermediate in its production. Irrespective of the metabolite applied, the principal metabolite formed in all instances had a retention time of 51 min following HPLC separation. This metabolite was itself not metabolized to any great extent by either tomato shoots or soybean callus. In contrast to tomato shoots this metabolite was not formed when a radioactive metabolite tentatively identified as BAR, was applied to soybean callus.

A comparison of two extraction procedures for the recovery of cytokinin nucleotides.

Summary While it is contended in the literature that alcoholic extraction of plant material could result in excessive breakdown of cytokinin nucleotides no support for this could be obtained in this investigation. The recovery rate of DHZMP was similar when using Bieleskis solution and 80 % ethanol for the extraction of this molecule when added to soybean callus. The latter procedure is more rapid and allows material to be quickly processed by HPLC with a minimum of prior purification.

Cytokinins and mango flower malformation III. The metabolism of [3H]iso-pentenyladenine and [8-14C]zeatin by Fusarium moniliforme

Abstract Cultures of Fusarium moniliforme metabolized both trans -zeatin and iso -pentenyladenine rapidly but did not accumulate the applied compound, or the metabolites formed, in the hyphae. Whether these molecules enter the fungus at all is not known. The fungal cultures interconverted zeatin and iso -pentenyladenine and ribosylated these compounds. They did not produce radioactive metabolites that co-chromatographed with glucosyl-O-zeatin or dihydrozeatin derivatives. The significance of the interconversion of cytokinins, or lack thereof, within the fungus is discussed in relation to the etiology of mango flower malformation.

Tissue culture of Schizobasis intricata, a medicinal plant

Bulb formation was initiated on bulb scale explants of Schizobasis intricata Bak., using Murashige and Skoog’s medium supplemented with auxins and cytokinins. A combination of 2 mg l −1 benzyladenine and 2 mg l −1 naphthalene acetic acid induced the best shooting response, with an average of 14.1 shoots being initiated per explant. In addition, shoot-producing callus developed. Concentrations of 0.5 and 1 mg l −1 naphthalene acetic acid induced between 5 and 8 roots per bulb in 5 weeks, as opposed to less than 2 in the controls. Hardening-off of the rooted plants was very successfull.

Hypoxis spp.: Micropropagation and In Vitro Production of Hypoxoside

Species of the genus Hypoxis L. are used for herbal remedies throughout the world. In Asia use is made of H. aurea (Lewis and Elvin-Lewis 1977), while in the West Indies H. decumbens and H. scuronera are collected for curing tumors of the testicles (Hartwell 1967). Utilization of this genus is, however, most frequent on the African continent, where species such as H. rooperi are extensively employed in folk medicine (Watt and Breyer-Brandwijk 1962). The merit of these folk medicines has been recognized by the scientific, medical, and commercial communities. This has resulted in attempts to isolate the medicinally active agents, to determine their range of application, to propagate the plants, and to produce the required chemicals by suspension culture.

Propagation of Gasteria croucheri Bak. from shoot producing callus

Leaf explants of Gasteria croucheri Bak. cultured on a modified Murashige and Skoog medium supplemented with 8.8 × 10-6M (2 mgl-1) benzyladenine and 2.7 × 10-5M (5 mgl-1) α-naphthalene acetic acid yielded a callus which produced adventitious shoots. This callus could be maintained on a medium with 1.9 × 10-5M (4 mgl-1) kinetin only and continued to produce shoots which could be rooted on a hormone free medium. Plantlets could be readily acclimatized.