Effects of Glyphosate on Metabolism of Phenolic Compounds

Light enhanced the inhibiting effect of root-fed glyphosate (5 × 10^?4M) on dry weight accumulation of soybean [Glycine max. (L.) Merr.] seedling axes. Inhibition of growth by light was greatest in hypocotyls, whereas by glyphosate it was greatest in roots. A synergistic effect of light and glyphosate on stimulation of phenylalanine ammonia-Iyase (PAL, E.C. 4.3.1.5) activity was also demonstrated. In continuous white light PAL activity increased linearly for 4 days in axes of seedlings exposed to glyphosate. Evidence of phytochrome involvement in the light effect was shown. The stimulatory effect of glyphosate on PAL activity was greater in roots than in hypocotyls. Soluble hydroxyphenolic compound levels were reduced by glyphosate but were increased by light on a per axis basis. On a fresh weight basis, hydroxyphenolics were more concentrated in glyphosate-treated than in control tissues in the light. When compared to other amino acids, disproportionate decreases in free pools of phenylalanine and tyrosine occurred in axes of seedlings treated with glyphosate and light. The effect of light on all measured parameters was mainly in the hypocotyl, while that of glyphosate was primarily in the root. In the light, glyphosate caused increases in levels of glutamine and other amino acids that may be the result of amination reactions, protecting from excess ammonia generated by enhanced PAL activity. These results suggest that PAL has a strong influence on its substrate levels in this system and/or that glyphosate inhibits synthesis of aromatic amino acids.     

GENETIC RELATIONSHIPS BETWEEN ONE BRITISH AND SEVERAL NORTH AMERICAN POPULATIONS OF CREPIDULA FORNICATA BASED ON ALLOZYME STUDIES (GASTROPODA: CALYPTRAEIDAE)

Crepidula fornicata(Linné) was introduced into Britainand Europe with oysters early in this century. The source populationswere probably from Long Island Sound of the Northwestern Atlantic,U.S.A. In order to determine the genetic similarity of the introducedand native populations, starch-gel electrophoresis was performedon 6 native populations from Maine to Long Island Sound. Theseresults were compared with those for one population from Portsmouth,England. The degree of similarity among New England sites was not relatedto the geographical distance between sites. There were no clinesin gene frequencies. The year-to-year variation at one sitewas often larger than variation between sites. Ail Nei's D valueswere very small, compared with those between species, rangingfrom 0.003 to 0.016 for New England samples. The English populationhad Nei's D values of 0.002 to 0.012 from the New England samples,and hence was not divergent. At no locus was the Portsmouthpopulation significantly different in gene frequencies fromall the new England samples. Genetic distances between speciesof Crepidula are usually in the range of 1.0–2.0. Thedifferences between New England sites can be attributed to samplingerror or to local variation in gene frequency caused by variationin source of recruitment. The species is unified by its planktoniclarvae and a fairly uniform habitat within New England. Heterozygosity and other measures of genetic variation werelower for the Portsmouth population than for any of the NewEngland samples. The absence of some alleles in the Portsmouthpopulation could be due in part to sampling error associatedwith small sample size or the loss of some rare alleles fromthe population. (Received 8 March 1984;