Adventitious in vitro plantlet formation from immature floral stems of Crinum macowanii

Adventitious shoots and plantlets were regenerated in vitro from floral stem explants of Crinum macowanii (Bak.) (bush lily). The length (age) of the floral stem as well as the orientation and position of the explant disc in the floral stem were the most important factors affecting shoot regeneration. The highest number of shoots were regenerated when immature floral stems of 70–100 mm were used as starting material, using the middle or basal parts of the stem, and orientating the discs with their proximal ends on the medium. Combinations of kinetin (4.65 M) and either indoleacetic acid (0.57 M) or naphthaleneacetic acid (0.54 M), or a combination of benzyladenine (4.44 M) and 2,4-dichlorophenoxyacetic acid (0.45 M) resulted in the highest numbers of shoots being regenerated. Although a slight degree of callus formation was noticed on the cut-edges of the discs, shoot formation did not occur via callus, but directly from the floral stem epidermis. Unrooted shoots were rooted on MS-medium containing 0.17 M sucrose.Abbreviations BA benzyladenine - IAA indoleacetic acid - IBA indolebutyric acid - NAA naphthaleneacetic acid - 2,4-d 2,4 dichlorophenoxyacetic acid     

Antifungal cinnamic acid derivatives from Persian leek (Allium ampeloprasum Subsp. Persicum)

A cinnamic imidate, (1Z,2E)-methyl 3-(-p-hydroxy-m-methoxyphenyl)-N-(-p-hydroxyphenethyl) acrylimidate, named persicoimidate (1), has been isolated and characterized from bulbs and seeds of Persian leek, Allium ampeloprasum Subsp. Persicum. Two cinnamic acid derivatives, N-feruloyl tyramine (2) and N-caffeoyl tyramine (3) were isolated from bulbs and seeds. Compound 2 has been previously reported from garlic and leek, while compound 3 is described in Allium plants for the first time. The chemical structures of the isolated compounds have been elucidated unambiguously by spectroscopic methods, including 2D NMR and MS. The isolated compounds were evaluated for their antifungal activity against four fungal pathogens, the soil-borne pathogen Penicillium italicum, the air-borne pathogens Aspergillus niger and Botrytis cinerea, and the antagonistic fungi Trichoderma harzianum to evaluate the possible involvement of such compounds in resistance to pathogen attack.     

Patterns of geophyte diversity and storage organ size in the winter-rainfall region of southern Africa

The winter‐rainfall region of southern Africa, covered largely by the fynbos and succulent karoo biomes, harbours the world's greatest concentration of geophyte species. Species diversity is greatest in the south‐west, where more than 500 species co‐occur in one quarter‐degree square; in the south‐east the values are generally around 100, and in the arid north‐west, always less than 50 (more often less than 10). In at least three species‐rich genera (Moraea, Eriospermum and Oxalis), the size of storage organs (bulbs, corms, tubers) varies inversely, with the largest average values occurring in the species‐poorer areas — both in the north‐western, and in the south‐eastern parts of the region. This negative correlation between average storage organ size and species diversity is, however, only observed at relatively large spatial scales, which suggests that there is no direct relationship between storage organ size and species diversity. More likely, both these measures are driven by winter rainfall amount and reliability, both of which peak in the south‐western Cape. We suggest that reliable winter rainfall makes large storage organs unnecessary and depresses extinction rates, thus leading to the accumulation of species.     

Bud regeneration from inflorescence explants for rapid propagation of geophytes in vitro

Bulbs, corms and other subterranean storage organs are commonly used as explant source material for the establishment of geophytes in vitro. The inflorescence stalk was found to be a good alternative source of explants to overcome explant contamination originating from underground storage organs. Inflorescence explants of Allium, Dichelostemma, Eucrosia, Gladiolus, Haemanthus, Hyacinthus, Narcissus, Nerine and Ornithogalum were used to establish cultures in vitro. The regeneration potential of the inflorescence was compared with regeneration from bulb twin scales or from apical buds isolated from corms. Gladiolus (Iridaceae) explants isolated from the floral stem just below the expanding florets, still enclosed in the bracts, were highly regenerative in the presence of naphthalene acetic acid (NAA) and kinetin. In the presence of 2,4-dichlorophenoxyacetic acid and benzyl aminopurine (BA) in the medium, explants isolated from the tissue at the junction between the peduncle and the pedicels of a young Nerine (Amaryllidaceae) inflorescence regenerated several buds. The scapes of young unemerged inflorescences taken from sprouting bulbs of Narcissus (Amaryllidaceae), following a 15 °C storage treatment, regenerated buds in the presence of NAA, BA, elevated phosphate and adenine sulfate in the medium. The number of buds regenerated depended on the location on the scape from which the explant was isolated, and on the duration of the 15°C treatment. In Allium (Alliaceae), capitulum tissue between the flower pedicels regenerated buds. Explants excised from the peduncle, as well as the pedicel-peduncle junction of Dichelostemma (Alliaceae), Ornithogalum, Hyacinthus (Hyacinthaceae) and Eucrosia (Amaryllidaceae) regenerated several buds in each type of explant. In the case of Haemanthus (Amaryllidaceae), pedicel-peduncle junction explants regenerated buds only when excised from inner whorl florets. Propagation protocols and the potential use of expediently isolated inflorescence explants for efficient micropropagation of geophytes are discussed. Received: 1 September 1999 / Revision received: 13 December 1999 / Accepted: 13 December 1999     

Alkaloids from Narcissus angustifolius subsp. transcarpathicus (Amaryllidaceae)

Seven alkaloids have been isolated from fresh bulbs of Narcissus angustifolius subsp. transcarpathicus (Amaryllidaceae). Nangustine, reported here for the first time, is the first 5,11-methanomorphanthridine alkaloid with a C-3/C-4 substitution. The structure and stereochemistry of this new alkaloid, as well as those previously known, have been determined by physical and spectroscopic methods. Spectroscopic data of pancracine have been completed. The in vitro assay activity against the parasitic protozoa Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani and Plasmodium falciparum was carried out with the compounds nangustine and pancracine.     

The development of dormancy in bulblets of Lilium speciosum generated in vitro. II. The effect of temperature

Upon harvest, lily ( Lilium speciosum Thunb. cv. Rubrum) bulblets generated in vitro under standard conditions (11 weeks at 20°C) were dormant and needed a cold treatment prior to planting. During culture in vitro at 20°C, the bulblets proceeded through three phases: (1) at first they were non–viable and non-dormant (up to 5 weeks), (2) then viable and non-dormant (5–9 weeks) and (3) finally viable and dormant (from 9 weeks onwards). At 15°C, the bulblets became viable but did not develop dormancy, even after protracted culture. The results suggest that the development of dormancy depends upon an accumulation of'heat units'occurring at temperatures higher than 15°0. At 25°C, the succession of the three phases occurred more rapidly than at 20°C and heat units were accumulated more rapidly. During the third period, the chilling requirement increased showing that heat units continued to be accumulated during this period.
Dormancy connotes an arrest of growth. In lily bulblets, however, the number of scales continued to increase after the induction of dormancy at 20 or 25°C. Many of the scales initiated before the onset of dormancy were formed by swelling of a petiole, whereas, after the onset of dormancy, all scales were formed directly from a primordium. We conclude that the development of dormancy corresponds to a switch in the development of the primordium. Thus, after the induction of dormancy the primordium lost the ability to become a leaf and always developed into a scale.     

Alkaloids from Nerine filifolia

The novel compounds N-demethylbelladine, 6alpha-methoxybuphanidrine and filifoline, in addition to five known alkaloids, and phenol have been isolated from fresh bulbs of Nerine filifolia (Amaryllidaceae). The structure and stereochemistry of the compounds were determined by physical and spectroscopic methods, including 1D and 2D NMR and mass spectroscopic techniques. An unusual circular dichroism response from filifoline has required a semi-synthetic derivatisation strategy towards key C-11endo analogues of the beta-crinane representative ambelline in which the nature of substituents was observed to have a profound effect on molecular ellipticity. Filifoline was not cytotoxic to myoblast (L6) cells and exhibited no anti-protozoal activity in an in vitro screen against four different parasitic protozoa.