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291.
Lack of rapid monoterpene turnover in rooted plants: implications for theories of plant chemical defense 总被引:4,自引:0,他引:4
Summary Evidence for the rapid metabolic turnover of leaf monoterpenes is a significant component of theories regarding the evolution and metabolic cost of plant chemical defenses. We re-examined whether monoterpenes are continuously synthesized and lost in intact peppermint plants, and demonstrate that the rapid monoterpene turnover previously observed using detached stems does not occur in intact plants. The apparent artifactual nature of rapid monoterpene turnover in peppermint suggests that a re-evaluation of the rates of metabolic turnover of plant defenses is needed before accurate hypotheses regarding the cost of plant chemical defense can be proposed. 相似文献
292.
293.
RB Marchase 《The Journal of cell biology》1977,75(1):237-257
The preferential adhesion of chick neural retina cells to surfaces of intact optic tecta has been investigated biochemically. The study uses a collection assay in which single cells from either dorsal or ventral halves of neural retain adhere preferentially to ventral or dorsal halves of optic tecta respectively. The data presented support the following conclusions: (a) The adhesion of ventral retina to dorsal tecta seems to depend on proteins located on ventral retina and on terminal β-N-acetylgalactosamine residues on dorsal tecta. (b) The adhesion of dorsal retina to ventral tecta seems to depend on proteins located on ventral tecta and on terminal β- N-acetylgalactosamine residues on dorsal retina. (c) A double gradient model for retinotectal adhesion along the dorsoventral axis is consistent with the data presented. The model utilizes only two complementary molecules. The molecule suggested to be concentrated dorsally in both retina and tectum seems to require terminal β-N-acetylgalactosamine residues for adhesion. Its activity is not affected by protease. A molecule fitting these qualifications, the ganglioside GM(2), could not be detected in a gradient, but lecithin vesicles containing GM(2) adhered preferentially to ventral tectal surfaces. The second molecule, concentrated ventrally in both retina and tectum, is a protein and seems capable of binding terminal β-N- acetylgalactosamine residues. One enzyme, UDP-galactose:GM(2) galactosyltransferase, has been found to be more concentrated in ventral retina than dorsal, but only by 30 percent. 相似文献
294.
Emily K. Croteau Stephen C. Lougheed Pamela G. Krannitz Nancy A. Mahony Brett L. Walker Peter T. Boag 《Conservation Genetics》2007,8(6):1453-1463
Assessing the genetic consequences of habitat fragmentation is a crucial step in conservation planning for species in endangered
habitats. We tested for the impact of natural habitat fragmentation on gene flow and genetic diversity in seven northern breeding
locations of the sagebrush Brewer’s sparrow, Spizella breweri breweri. Genetic analyses using five highly variable DNA microsatellite loci suggested that individuals sampled within a sagebrush
landscape fragmented by natural elements such as coniferous forest, comprise a single genetic population and that gene flow
among them is unimpeded. We posit that juvenile dispersal links seemingly isolated breeding locales of this species, and discuss
implications of our findings for conservation of migratory songbirds in the northern portion of their ranges in light of potential
shifts in distribution due to climate change. 相似文献
295.