Development of the Tapetum in Pinus banksiana Preceding Sporogenesis

Early in sporangial ontogeny, the cells destined to become thesporogenous and tapetal tissue differentiate in a strikinglysimilar manner. The first conspicuous step in development isa contraction of the protoplasts, beginning at the centre ofthe microsporangium and moving radially to its periphery. Similardevelopment of the two groups of cells ceases as the callosewall is formed around the meiocytes. At this point the originalwalls investing the tapetal cells become gelatinous, and lipidsynthesis commences within the contracted protoplasts. The bulkof this lipid is secreted from the cells, and becomes lodgedin the loculus, either as globules in the expanded radial andinner cell walls, or as a continuous layer on the inside ofthe middle lamella separating the loculus from the wall of themicrosporangium. This lipoidal layer forms the basement of aperitapetal membrane, believed to serve as a container for thefluid in which the young sporogenous cells are immersed. Examination of protein levels and ribosome numbers in the tapetalcells reveals that protein synthesis proceeds at an increasingrate throughout the development preceding meiosis, but apparentlyceases as the pollen mother cells become enveloped in callose.     

Bluetongue epidemiology in the Caribbean region: serological and entomological findings from a pilot sentinel system in Trinidad and Tobago

When monitored by the agar gel immunodiffusion test for antibody to bluetongue viruses, a sentinel flock of twenty-five lambs remained seropositive through the year, whereas in a sentinel herd of twenty calves only two individuals seroconverted and these became negative again within 2 months. A light trap operated with the calf herd yielded high numbers of Culicoides insignis Lutz (over 18,000 per trap night) along with C. filariferus Hoffman, C. pusillus Lutz, C. leopoldi Ortiz, C. foxi Ortiz, C. limai Barretto, C. diabolicus Hoffman and C. guyanensis Floch and Abonnenc. Culicoides were trapped at the sheep station which had housed the lambs 3 years following the sentinel study. No virus was isolated from pools of C. insignis, C. filariferus and C. pusillus. Six other species were collected in insufficient numbers to warrant attempted virus isolations.     

Two Stages in the Redifferentiation of Amyloplasts in the Microspores of Lilium

The first stage in the redifferentiation of plastids in themeiocytes of Lilium occurs late in meiotic prophase and involvesthe formation of an association between particles and membranouscisterna. The distribution of carbohydrate within this associationhas been examined cytochemically, and the particles are demonstratedto contain a high proportion of carbohydrate. The osmiophilicglobules of the stroma also react with the cytochemical probefor carbohydrate, indicating that they must, at least in part,be composed of glycolipid. Structure within the organelles remainsunchanging until the break-up of the tetrad, when elements ofthe membrane—particle association expand to fill the stroma.Electron microscopic evidence suggests that the particles formthe nuclei of the starch grains which then swiftly develop.It is proposed that the association represents the limit ofdifferentiation possible in the tetrad of microspores, and thatthe callosic special wall restricts the availability of materialsfrom the thecal fluid required for full development of the amyloplast.The association should thus be more correctly termed the proamyloidbody. Amyloplasts, Lilium, pollen development, proplastids     

Effect of growing media and their constituents on fungus gnat, Bradysia sp, nr, coprophila （Lintner） adults

This study was conducted to determine the attractiveness of two growing media, commonly utilized in greenhouses, to fungus gnat, Bradysia sp. nr. coprophila adults. The constituents of the most attractive growing medium tested were determined by gas chromatography analysis using a steam-distillation procedure. We found that fungus gnat adults were more attracted to the growing medium, SB300 Universal Professional Growing Mix, which contains composted bark, than to another growing medium （Sunshine LC1 Mix） and their components when tested in a series of laboratory experiments using multiple-choice experimental arenas. A higher percentage of fungus gnat adults were attracted to moist SB300 （92%） than SB300 growing medium that had been oven dried （8%）. In addition, fungus gnat adults preferred SB300 although they had been reared on Sunshine LC1 Mix. When comparing the SB300 fresh from the bag to growing medium that had been pasteurized and moistened with water, gas chromatographic-mass spectroscopic data showed there were declines in several terpenoid constituents as well as an increase in fatty acids and cyclosulfur. The results of this study indicate that B. sp. nr. coprophila adults prefer certain growing media, which may assist greenhouse producers in managing fungus gnats in crop production systems.