The Theory of Brown Dwarfs and Extrasolar Giant Planets

Straddling the traditional realms of the planets and the stars, objects below the edge of the main sequence have such unique properties, and are being discovered in such quantities, that one can rightly claim that a new field at the interface of planetary science and and astronomy is being born. In this review, we explore the essential elements of the theory of brown dwarfs and giant planets, as well as of the new spectroscopic classes L and T. To this end, we describe their evolution, spectra, atmospheric compositions, chemistry, physics, and nuclear phases and explain the basic systematics of substellar-mass objects across three orders of magnitude in both mass and age and a factor of 30 in effective temperature. Moreover, we discuss the distinctive features of those extrasolar giant planets that are irradiated by a central primary, in particular their reflection spectra, albedos, and transits. Aspects of the latest theory of Jupiter and Saturn are also presented. Throughout, we highlight the effects of condensates, clouds, molecular abundances, and molecular/atomic opacities in brown dwarf and giant planet atmospheres and summarize the resulting spectral diagnostics. Where possible, the theory is put in its current observational context.Comment: 67 pages (including 36 figures), RMP RevTeX LaTeX, accepted for publication in the Reviews of Modern Physics. 30 figures are color. Most of the figures are in GIF format to reduce the overall size. The full version with figures can also be found at: http://jupiter.as.arizona.edu/~burrows/papers/rm

Bacterial wilt of common bean: effect of seedborne inoculum on disease incidence and seedling vigour

Bacterial wilt of common bean caused by Curtobacterium flaccumfaciens pv. flaccumfaciens is a seedborne disease. The seeds of great northern cultivar US 1140 infected by the yellow variant of the pathogen showed symptoms of yellow discolouration on the white seed coat. In this study, the great northern bean seeds, cultivar US 1140, from the dockage of 2001 crops grown in Alberta were sorted into four categories according to the degree of yellow discolouration on the seed coat: apparently healthy or white seeds (0%), slight infection (25-50%), moderate infection (51-75%) and severe infection (76-100% yellow discolouration). Results of testing of these seed samples showed that bacterial population in the seeds, seedling emergence, plant height and incidence and severity of bacterial wilt were significantly (P<0.05) affected by the degree of discolouration of the seed coat. A greater seed coat discolouration was associated with a higher bacterial population of the seed, which resulted in a higher incidence of bacterial wilt and poorer growth of seedlings. Examination of 14-day-old seedlings originating from discolored seeds revealed that the pathogen was systemically distributed throughout the entire seedling if plants showed wilt symptoms. Although some of the 14-day-old seedlings derived from seeds with yellow discolouration remained symptomless, the bacterial pathogen was detectable in such seedlings regardless of differences in the extent of discolouration of seed coat. However, the bacterial pathogen was not detected in the 14-day-old seedlings originating from the seeds with 0% yellow discolouration of the seed coat

Control of apothecia of Sclerotinia sclerotiorum by soil amendment with S-H mixture or Perlka (R) in bean, canola and wheat fields

Ascospores of Sclerotinia sclerotiorum produced from apothecia are the primary source of inoculum for causing diseases such as white mold of common bean, pod rot of pea, stem blight of canola and head rot of sunflower and safflower in the Canadian prairies. A field study was conducted for 4 years to determine efficacy of control of production of apothecia from carpogenically germinated sclerotia of S. sclerotiorum by soil amendment with Pertka((R)) (calcium cyanamide) and S-H mixture (a formulated compound). Results of the 4-year experiments showed that amendment of soil with Perlka((R)) at low (30 g/m(2)) or high (60 g/m(2)) rate was effective in reducing carpogenic germination of sclerotia and production of apothecia under the canopy of host crops (common bean and canola) and a non-host crop (wheat). In the experiments of 1988, for example, the numbers of apothecia produced in the treatments of Perlka((R))-low rate (30 g/m(2)), Perlka((R))-high rate (60 g/m(2)) and untreated control were 42, 46, and 182 apothecia/plot (m(2)), respectively, for bean; 89, 42, and 318 apothecia/plot (m(2)), respectively, for canola; and 146, 143, and 412 apothecia/plot (m(2)), respectively, for wheat. However, soil amendment of S-H mixture at low (30 g/m(2)) or high (60 g/m(2)) rate was ineffective in reducing carpogenic germination of sclerotia and production of apothecia for all the 4 years of testing in all three crops. The ineffectiveness of S-H mixture and the practicality of Perlka((R)) for control of Sclerotinia diseases of crops grown under Canadian prairie conditions are discussed. (c) 2005 Elsevier Ltd. All rights reserved