Brandle, J. E., Starratt, A. N. and Gijzen, M. 1998. Stevia rebaudiana: Its agricultural, biological, and chemical properties. Can. J. Plant Sci. 78: 527-536. Stevia rebaudiana is a member of the Compositae, native to Paraguay. It produces a number of high-potency low-calorie sweeteners in its leaf tissue. The sweeteners are diterpene glycosides and range between 30 and 320 times sweeter than sugar. Increasing consumer interest in natural food ingredients means that products like stevia sweeteners will be subject to increasing demand. Such demand will need to be supported by a modern mechanised production system. The purpose of this review is to summarize the existing agricultural, chemical and biochemical literature to provide a baseline for new research.Key words: Stevia, diterpene, steviol glycoside, sweeteners Brandle, J. E., Starratt, A. N. et Gijzen, M. 1998. Stevia rebaudiana : qualités agricoles, biologiques et chimiques. Can. J. Plant Sci. 78: 527-536. Stevia rebaudiana, plante originaire du Paraguay, appartient à la famille des Composées. Il produit dans les tissus foliaires un certain nombre d'agents édulcorants puissants mais hypocaloriques. Ces produits, des glycosides diterpéniques sont de 30 à 320 fois plus sucrés que le sucre. Compte tenu de l'intérêt croissant du consommateur pour les ingrédients alimentaires naturels, la demande de produits comme les édulcorants du stevia ne pourra qu'aller en croissant, mais il faudra que cette demande soit étayée par un système moderne de production mécanisée. Voulue comme une base pour les recherches futures, cette mise au point vise à compulser la bibliographie actuelle de cette espèce sur les plans tant agricoles que chimiques et biochimiques.

For several millennia, stem extracts of Ephedra (Ephedraceae, Gnetales) have been used as folk medicines in both the Old and New World. Some species were used in treatments of questionable efficacy for venereal disease in North America during the last century. Many Eurasian species produce phenylethylamine alkaloids, mostly ephedrine and pseudoephedrine, that interact with adrenergic receptors in the mammalian sympathetic nervous system. Asian Ephedra have been used recently in the clandestine manufacture of a street drug, methamphetamine. Although ephedrine alkaloids are not detectable in New World species of Ephedra, together with Asian species they contain other nitrogen-containing secondary metabolites with known neuropharmacological activity. Many mesic and particularly xeric species worldwide accumulate substantial amounts of quinoline-2-carboxylic acids, or kynurenates, in their aerial parts. Many species of Ephedra accumulate cyclopropyl amino acid analogues of glutamate and proline in their stems and roots, and particularly in the seed endosperm. Mesic species synthesize substantial amounts of three L-2-(carboxycyclopropyl)glycine stereomers rarely seen in nature. A cyclopropyl analogue of proline with known antimicrobial activity, cis-3,4-methanoproline, is found in large amounts in the stems and seeds of many Ephedra species. The ability to synthesize cyclopropyl amino acids may be an ancestral feature in the taxon. The natural function in the taxon of these three groups of secondary compounds remains to be established.

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Abstract-The persistence of the xenoestrogenic compound 4-nonylphenol in agricultural, noncultivated temperate, and Arctic soils was assessed in laboratory microcosm incubations. At 30ЊC, [ring-U-14 C]4-nonylphenol was rapidly mineralized without a lag in six soils tested. A sandy loam agricultural soil was chosen for more detailed study. The 4-nonylphenol mineralization did not occur in autoclaved soil. The response of 4-nonylphenol mineralization to variation in temperature and moisture content was consistent with an aerobic biological mechanism of degradation. Mineralization of [ring-U-14 C]4-nonylphenol was rapid in the concentration range of 1 to 250 mg/kg soil. Sludge solids did not inhibit 4-nonylphenol mineralization, although sewage sludge at high concentrations was inhibitory, apparently because of high biological oxygen demand. Gas chromatographic-mass spectrometric analyses of extracts prepared from soil incubated with commercial nonylphenol indicated that all detectable isomers were degraded. In summary, these results indicate that microorganisms that can metabolize 4-nonylphenol are found in a wide variety of soils, including two originating from the Canadian Far North, which presumably have not been exposed anthropogenically to this chemical. We conclude that 4-nonylphenol should be generally biodegradable in well-aerated arable soils.

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Pseudomonas syringae pv. tomato produces the chlorosis-inducing phytotoxin coronatine. Five of 3700 (0.13%) kanamycin-resistant mutants generated by random Tn5 mutagenesis were unable to synthesize this toxin. Clone pEC18, isolated from a cosmid pLAFR1 library of wild-type P. syringae pv. tomato DC3000 genomic DNA, complemented four of the mutants. Restriction enzyme analysis of pEC18 and corresponding clones from the four mutants indicated that the Tn5 insertion sites of these four mutants spanned a 19-kb region of DC3000 genomic DNA. Complementation tests with subclones of pEC18 confirmed the relative locations of the Tn5 insertions. Because pEC18 did not complement all five mutants or confer the ability to produce toxin on nonproducing P. syringae pathovars, sequences outside this cloned region must also be involved in toxin synthesis. As demonstrated by Southern blot analysis, this cloned region was not on the 68-kb indigenous plasmid of DC3000. The only P. syringae pathovars with DNA homologous to sequences within the coronatine gene cluster were the coronatine producers P. syringae pv. tomato, P. syringae pv. atropurpurea, and P. syringae pv. glycinea. Since the hybridization patterns of these toxin producers were identical, this locus is highly conserved and appears crucial to the synthesis of coronatine.Key words: coronatine, phytotoxin mutants, Pseudomonas syringae pv. tomato.

Coronatine was detected in culture filtrates of 12 out of 19 pathogenic strains of Pseudomonas glycinea examined, but not in culture filtrates of strains of P. phaseolicola, P. syringae, or P. tabaci. A reversed-phase high-performance liquid chromatographic procedure was developed for coronatine quantitation. Generally, coronatine production by strains in culture correlated with their ability to induce systemic symptoms (chlorosis and stunting) in inoculated soybean plants. Application of purified preparations of coronatine to unifoliate leaves of soybean plants resulted in localized chlorosis, development of chlorosis in subsequently developing trifoliate leaves, and stunting of plant growth, similar to symptoms induced by infection. Coronatine was demonstrated in soybean leaves infected with P. glycinea but was not detected in healthy leaves. The results indicate that coronatine can play an important role in the development of symptoms of bacterial blight of soybean, but the demonstration that some pathogenic strains do not produce coronatine indicates that it may not be essential for pathogenicity.