Environmental Control of Flowering in Barley (Hordeum vulgare). III. Analysis of Potential Vernalization Responses, and Methods of Screening Germplasm for Sensitivity to Photoperiod and Temperature

Three genotypes of barley were subjected to 18 potentially vernalizingpre-treatments, comprising constant temperatures of 1, 5 or9 °C in factorial combination with photoperiods of 8 or16 h d^–1 for 10, 30 or 60 d^–1. These pre-treatedseeds or seedlings, together with non-pre-treated seeds as controls,were then transferred to each of four growing-on regimes, namelyday/night temperatures of 18/5 °C or 24/3 °C in factorialcombination with photoperiods of 11 or 16 h d^–1. The timesfrom sowing to awn emergence were recorded. The warmer growing-onregime (mean 19 °C) was not supra-optimal in long days,but in short days it considerably delayed awn emergence in allthree genotypes. In cv. Athenais there was no specific responseto the potentially vernalizing pre-trcatments: the rate of progresstowards awn emergence could be treated as a linear functionof the integrated responses to temperature and photoperiod actingindependently throughout development. In addition to these responses,cv. Gerbel B and the land-race Arabi Abiad also responded tolow-temperature vernalization and the response became saturatedduring the longer-duration pre-treatments. In Arabi Abiad, therate at which vernalization occurred, and the period requiredto saturate the response, were not greatly influenced by differencein pre-treatment temperature between 1 and 9 °C. In contrast,in Gerbel B the cooler the temperature of pre-treatment thegreater the saturated response to vernalization, the greaterthe effect of each day of pre-treatment, and the shorter theperiod required to saturate the response. Models of the photothennaland vernalization responses were combined in a single entitywhich described the influence of environment on rate of development.Simple germplasm-screening techniques are proposed for genotypecharacterization so that the phenotypic flowering response canbe estimated for any environment Hordeum vulgare L., barley, flowering, phtoperiodism, vernalization, photothennal time, germplasm screening     

Reevaluation of the systematic position of Scenella

Specimens originally illustrated from Lower Cambrian rocks of the Sierra Morena in Badajoz and Sevilla Provinces, southwestern Spain are supplemented by new material from another locality and are described as Scenella morenensis n. sp. Although Scenella was originally considered to be a patelliform gastropod, for three decades now the genus has been classified as a monoplacophoran. The type species of Scenella, S. reticulata Billings, does not show any paired muscles scars, nor does this new species; such scars are indicative of the Monoplacophora. This new species of Scenella does exhibit features which suggest assignment to the chondrophorine coelenterates. If so, Scenella cannot represent the ancestral form of mollusk.     

The germination and emergence of seeds of winter oilseed rape stored and sown in admixture with pelleted methiocarb

The possibility that pellets of the molluscicide Draza (a.i. methiocarb) might reduce field emergence of seeds of winter oilseed rape (Brassica napus, cv. Jet Neuf) when sown admixed, laboratory germination when stored admixed, or field emergence when both stored and sown admixed was the subject of three separate investigations. Admixture at sowing did not influence the emergence of five seed lots (P > 0·05). Neither did admixture influence loss in germination or change in moisture content during 2 months' storage of one lot in four different regimes (P > 0·05). Field emergence following 2 months' storage in paper bags was not influenced by admixture (P > 0·05), whereas a 12% reduction in field emergence resulting from storage in admixture within polyethylene bags was detected (P < 0·05). Thus short-term storage within paper sacks of winter oilseed rape seeds in admixture with slug pellets containing methiocarb did not damage the seeds. The emergence of five seed lots differed considerably within and between field sowings. Tentative advice on the calculation of sowing rates for different seed lots of winter oilseed rape is provided to account for this variation.     

Epidemiology of bluetongue in Central America and the Caribbean: initial entomological findings

Abstract. Forty-four species of Culicoides (Diptera: Ceratopogonidae) were caught in insect light traps during the first 2 years of studies on the epidemiology of bluetongue virus in the Caribbean and Central America. Traps were operated near sentinel ruminants which were bled monthly for serologic evaluation and then virus isolation. More than 570,000 individuals were identified. Culicoides insignis Lutz accounted for 90% of the catch, C.filarifer Hoffman/C.ocumarensis Ortiz 5%, C.furens Poey 3% and C.pusillus Lutz 2%. Other species accounted for less than 1% of the total catch. Sentinel ruminants became seropositive when C.insignis populations were high at many study sites. At a few sites C.pusillus and C.filarifer I C.ocumarensis were predominant or were present in large numbers during seroconversions of sentinels. Virus isolations were obtained from sentinel ruminants during times when these same species were present in large populations.     

Sites of Synthesis of Chloroplast Proteins

The antibiotic lincomycin, which specifically inhibits protein synthesis on chloroplast ribosomes, has been used to investigate further the inference from genetic studies that chloroplasts are not autonomous units.     

A Comparison of the Quantitative Effects of Seed Moisture Content and Temperature on the Accumulation of Chromosome Damage and Loss of Seed Viability in Lettuce

The rate of accumulation of cells containing chromosome aberrationsin lettuce (Lactuca sativa L.) seeds is a positive functionof temperature and moisture content. It may be described byan equation similar to that for loss of seed viability. Therelative effect of temperature on the rates of loss of viabilityand accumulation of chromosome aberrations is the same. In contrast,the relative effect of moisture on the rate of loss of viabilityis greater than that for the rate of accumulation of aberrations.Hence considerably more chromosome damage accumulates beforedeath in drier lettuce seeds. Lactuca sativa, lettuce, seed storage, seed viability, seed longevity, chromosomal aberrations temperature, moisture content