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1.
Autotrophic nutrition plays an important role in adult Tridachiacrispata in the western Atlantic Ocean and results from an endosymbioticassociation between the sacoglossan and the kleptoplastids ofChlorophyta. A series of living specimens 7-80 mm in length was studied inthe laboratory. After a body length of 10 mm has been attained,the parapodial lobes of the two sides meet and fuse. Microscopicexamination of faecal strings of specimens undergoing this transitionrevealed that algal remains were produced only by juvenilesless than 13 mm long. Larger specimens defaecated only rarelyand the diminutive faecal strings contained no recognizablealgal debris. This transition probably parallels the physiologicaltransition between juvenile heterotrophic nutrition and adultautotrophic nutrition. Microscopic examination of the radulae of transitional specimensshowed no diminution of the size, number or morphology of theteeth. This indicates that in an emergency heterotrophic nutritionmay be resumed. Growth rates of Tridachia were measured in the laboratory, withand without light and the provision of algal foods. Unfed animalslost weight rather rapidly in captivity, whereas those fed uponsuitable algae (Halimeda discoidea, Caulerpa verticillata, C.racemosa and Chaetomorpha sp) did not.Caulerpa sertularioideswas suitable for food for a limited time, but proved toxic afterabout a week. Of the other species tested, Caulerpa verticillatawas the least suitable, while Halimeda, Chaetomorpha and Caulerparacemosa were the best. Ironically, C. verticillata was theonly one of the algal species tested which is known to be takenin the natural diet in Floridean waters. These experiments confirmedthat heterotrophic feeding will be resumed in Tridachia if theculture-conditions do not favour autotrophic nutrition.  相似文献   
2.
An account is given of the elysiid sacoglossans collected ondiving expeditions to the eastern Mediterranean shores of Yugoslaviaand Greece during the period 1978–1986, supplemented bymaterial collected around Naples and some preserved specimensfrom other Mediterranean localities. In all, 6 species of Elysiaand 1 of Bosellia were investigated, including one new to science,E. gordanae from the Yugoslav Istrian Peninsula. The enigmaticElysia translucens Pruvot-Fol, 1957 was found in the easternbasin for the first time. The presence of the Bermudan, CanaryIslands and Jamaican E. flava Verrill, 1901 was confirmed inthe Greek Ionian and Aegean Seas, as well as in the Gulf ofCorinth. The geographical ranges of the other species were extendedby these collections from the eastern basin. The 7 elysiid specieswere illustrated from life and the radulae compared; great differencesin the size, shape and denticulation of the teeth of the differentspecies were evident (Received 8 May 1987;  相似文献   
3.
Eamus, D., Thompson, W., Cairney, J. W. G. and Jennings, D.H. 1985. Internal structure and hydraulic conductivity of basidiomycetetranslocating organs.–J. exp. Bot. 36: 1110–1116. The presence in rhizomorphs of Armillaria mellea and cords ofPhallus impudicus of wide diameter hyphae (5–20 {diaeresis}m),which run for considerable distances along these linear organs,has been demonstrated. The longitudinal hydraulic conductivityof these organs has been determined experimentally and similarvalues were obtained when the hydraulic conductivity was calculatedtheoretically on the basis that the vessel hyphae were the solechannel for water movement along these organs. The experimentaldata have been discussed in relation to other data for long-distancetranslocation in basidiomycete linear organs. It is concludedthat the vessel hyphae are the main channels for turgor-driventranslocation. Key words: -Basidiomycete fungi, translocation, hydraulic conductivity  相似文献   
4.
Tracer amounts of atmospheric [13N]-Iabelled ammonia gas, wereabsorbed by leaves of Lupinus albus and Helianthus annuus inboth the light and the dark. Exogenous [13N]-ammonia was onlyabsorbed in the dark when the feeding occurred shortly aftera period of illumination and the tissue was not depleted ofits carbohydrate reserves (e.g. starch). Incorporation of the[13N]-ammonia appeared to occur via the leaf glutamine synthetase/glutamatesynthase (GS/GOGAT) cycle since 2.0 mol m–3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of 11CO2 was not affected by this treatment Therate of movement of [13N]-assimilates in the petiole of attachedleaves of Helianthus and Lupinus was similar to that of the11Cl-photo assimilates. Export of both [13N] and [11C]-Iabelledassimilates from the leaf and movement in the petiole in boththe light and the dark was inhibited by source leaf anoxia (i.e.nitrogen gas). Translocation was re-established at the samerate when the feed leaf was exposed to gas containing more than2% O2 which permitted dark respiration to proceed. After aninitial feeding of either 11CO2 or [13N]-ammonia at ambient(21%) O2 exposure of the source leaf to 2% O2, or 50% O2 didnot alter the rates of translocation, indicating that changesin photosynthetic activity in the source leaf due to photorespiratoryactivity need not markedly alter, at least during the shortperiod, the loading and translocation of either [11C ] or [13N]-labelledleaf products. Key words: Translocation, CO2, NH3, Leaves, Helianthus annuus, Lupinus albus  相似文献   
5.
THOMPSON  P. A. 《Annals of botany》1970,34(2):427-449
Comparisons were made between the germination responses to temperatureof species of Caryophyllaceae collected in the wild from differentparts of Europe. Species occurring predominantly in the Mediterraneanzone were compared with those distributed in the deciduous woodlandzone of central and southern Europe; steppeland and grasslandareas of eastern Europe, and in the Taiga and Tundra of northernEurope. The geo-botanical distributions of different specieswere reflected in their germination responses. Species fromthe Mediterranean germinated over a range with a mean of 4.5to 24.2 °C; those from deciduous woodland over the range11.8 to 30.0 °C; those from steppelands over the range 6.0to 30.0 °C. There was little uniformity in the northernEuropean species. The significance of the results is discussedin relation to the distribution of different species, the variationwithin a species, and the climatic components of the variousgeo-botanical zones.  相似文献   
6.
SYNOPSIS. Glauconema trihymene n. g., n. sp., a marine hymenostome ciliate, is described from the Virginia coast. Morphologic studies were made on specimens treated with the Chatton-Lwoff silver impregnation technic and on animals observed with the phase microscope. Particular attention is given to the buccal ciliature and its importance to generic assignment in the order Hymenostomatida.  相似文献   
7.
Carbon Dioxide Effects on Carbohydrate Status and Partitioning in Rice   总被引:6,自引:0,他引:6  
The atmospheric carbon dioxide (CO2) concentration has beenrising and is predicted to reach double the present concentrationsometime during the next century. The objective of this investigationwas to determine the long-term effects of different CO2 concentrationson carbohydrate status and partitioning in rice (Oryza sativaL cv. IR-30). Rice plants were grown season-long in outdoor,naturally sunlit, environmentally controlled growth chamberswith CO2 concentrations of 160, 250, 330, 500, 660, and 900µmolCO2 mol1 air. In leaf blades, the priority between the partitioningof carbon into storage carbohydrates or into export changedwith developmental stage and CO2 concentration. During vegetativegrowth, leaf sucrose and starch concentrations increased withincreasing CO2 concentration but tended to level off above 500µmolmol–1 CO2. Similarly, photosynthesis also increased withCO2 concentrations up to 500µmol mol–1 and thenreached a plateau at higher concentrations. The ratio of starchto sucrose concentration was positively correlated with theCO2 concentration. At maturity, increasing CO2 concentrationresulted in an increase in total non-structural carbohydrate(TNC) concentration in leaf blades, leaf sheaths and culms.Carbohydrates that were stored in vegetative plant parts beforeheading made a smaller contribution to grain dry weight at CO2concentrations below 330µmol mol–1 than for treatmentsat concentrations above ambient Increasing CO2 concentrationhad no effect on the carbohydrate concentration in the grainat maturity Key words: CO2 enrichment, starch, sucrose  相似文献   
8.
As a first step towards transferring a tetracycline (Tc)-inducible gene expression system to tomato, we have transformed tomato plants with the Tn10-encoded tet repressor gene (tetR). Homozygous transformed plants with high expression of tetR mRNA show a deleterious phenotype, having reduced shoot dry weights and leaf chlorophyll content, an even more marked reduction in root dry weight and leaf size, and altered photosynthetic physiology. It appears that TetR protein exerts its toxicity only when expressed beyond a threshold level and by interacting with a process that is non-limiting under slow growth conditions. The deleterious phenotype was almost completely reversed by the application of 1 mg dm?3 Tc to plants grown in sand. The possiblity is discussed that TetR causes these symptoms by binding to a specific DNA sequence functioning as a Tet operator. The effect of Tc on growth and physiology in wild-type plants grown in sand or rockwool is described. Tc at 0.1 mg cm?3 had no effect. Tc at 1 mg dm?3 caused a small reduction in root growth, while 5 and 20 mg dm?3 Tc caused large reductions in growth and photosynthetic parameters.  相似文献   
9.
The effects of elevated atmospheric CO2 concentration on plant-fungi and plant-insect interactions were studied in an emergent marsh in the Chesapeake Bay. Stands of the C3 sedge Scirpus olneyi Grey, and the C4 grass Spartina patens (Ait.) Muhl. have been exposed to elevated atmospheric CO2 concentrations during each growing season since 1987. In August 1991 the severities of fungal infections and insect infestations were quantified. Shoot nitrogen concentration ([N]) and water content (WC) were determined. In elevated concentrations of atmospheric CO2, 32% fewer S. olneyi plants were infested by insects, and there was a 37% reduction in the severity of a pathogenic fungal infection, compared with plants grown in ambient CO2 concentrations. S. olneyi also had reduced [N], which correlated positively with the severities of fungal infections and insect infestations. Conversely, S. patens had increased WC but unchanged [N] in elevated concentrations of atmospheric CO2 and the severity of fungal infection increased. Elevated atmospheric CO2 concentration increased or decreased the severity of fungal infection depending on at least two interacting factors, [N] and WC; but it did not change the number of plants that were infected with fungi. In contrast, the major results for insects were that the number of plants infected with insects decreased, and that the amount of tissue that each insect ate also decreased.  相似文献   
10.
The large-scale inoculation of selected beneficial ectomycorrhizal fungi in forest nurseries has generated renewed interest in the ecology of these symbiotic fungi. However, information on the dissemination and persistence of introduced symbionts is scarce due to the limitation of the current identification methods. To identify ectomycorrhizal fungi on single root tips, we investigated the polymorphism of the PCR-amplified ribosomal DNA intergenic spacer (IGS) from a wide range of ectomycorrhizal fungi. To investigate the reliability of this molecular approach in large-scale surveys, the dissemination and persistence on Douglas fir seedlings of the introduced Laccaria bicolor S238N were assessed in a forest nursery in the Massif Central (France). Several hundred ectomycorrhizas and fruiting bodies were sampled from plots where control and L. bicolor inoculated-Douglas fir seedlings were grown for 1.5 years. PCR typing of mycorrhizas indicated that trees inoculated with L. bicolor S238N remained exclusively colonized by that isolate (or sexually derived isolates) for the entire test period. In contrast, control seedlings were infected by indigenous isolates of Laccaria laccata and Thelephora terrestris. The molecular evidence for the persistence of the introduced mycobiont despite the competition from indigenous isolates of the same species provides further illustration of the potential of exotic species for large-scale microbial application.  相似文献   
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