'Floral' scent production by Puccinia rust fungi that mimic flowers

Crucifers (Brassicaceae) in 11 genera are often infected by rust fungi in the Puccinia monoica complex. Infection causes a 'pseudoflower' to form that is important for attracting insect visitors that sexually outcross the fungus. 'Pollinator' attraction is accomplished through visual floral mimicry, the presence of a nectar reward and floral fragrances. Here we used gas chromatography and mass spectrometry to identify and quantify fragrance production by these rust fungi on several Arabis hosts, and by co-occurring true flowers that share insect visitors. Fungal pseudoflowers produced distinctive floral fragrances composed primarily of aromatic alcohols, aldehydes and esters. Pseudoflower fragrances were chemically similar to noctuid-moth-pollinated flowers, such as Cestrum nocturnum and Abelia grandiflora , but were very different from host flowers, host vegetation and the flowers of coblooming, nonhost angiosperms. There was variation in the quantity and composition of fragrance profiles from different fungal species as well as within and among hosts. The evolution of scent chemistry is relatively conservative in these fungi and can be most parsimoniously explained in three steps by combining chemical data with a previously determined rDNA ITS sequence-based phylogeny. Pseudoflower scent does not appear to represent a simple modification of host floral or vegetative emissions, nor does it mimic the scent of coblooming flowers. Instead, we suspect that the unique fragrances, beyond their function as pollinator attractants, may be important in reducing gamete loss by reinforcing constancy among foraging insects.     

Physiology of the interaction of angiosperm parasites and their higher plant hosts

Abstract. Interactions between parasitic angiosperms and their hosts occur at the level of seed germination, haustorial development and resource transfer. Chemicals released from the host function as cues for host recognition, and trigger germination as well as haustorial initiation. Transpiration is a key process regulating solute transfer from host to parasite, and some parasitie plants have unusual stomatal characteristics. Although solute transfer is apoplastic, the haustorium appears to play a role in regulating solute composition. Host responses to infection are reviewed, and it is concluded that competition for water and solutes are unlikely to play a major role in determining reductions in host productivity: metabolic incompatability is suggested to be the major cause of this.     

Application of the headspace gas chromatographic technique for continuous monitoring of the acetone-butanol-ethanol fermentation

An automatic, electropneumatic gas sampling system has been coupled to a gas chromatograph in order to monitor the acetone-butanol-ethanol fermentation. During calibration, signal responses for individual aqueous solutions of acetone, butanol and ethanol were linear up to 20 g l^?1, and negligible deviations from linearity were observed in aqueous solvent mixtures. Although dissolved salts in the medium increased individual solvent activity coefficients, these remained constant throughout the fermentation. After calibration, this quantitative gas chromatographic method proved suitable for rapid, continuous, accurate and precise monitoring of the fermentation.     

Multivariate interpretation of the foliar chemical composition of Norway spruce (Picea abies)

Twenty-four chemical elements were analysed by INAA, ICP-AES and CN in needles of Norway spruce (Picea abies (L.) Karst.). Branches were sampled from 54 trees on eight sites in Switzerland and South Germany. From each tree, twigs were sorted into the most recent four or five age classes and their needles analysed separately. All measured concentrations could be considered as log-normally distributed and statistical analyses were, therefore, performed on logarithms. Variance components were estimated by maximum likelihood and compared between elements. Non-essential elements varied more than essential nutrients (Mn was an exception). The sites and the age of the needles were the most important sources of variance. The interaction between site and age, the individual tree, the sampled branch and the residual variance were usually much smaller sources of variance. The effects of the most significant factors – site and age – were further described by principal components and cluster analyses. Mineral elements either increased or decreased with the age of the needles according to their mobility in the phloem. Two different components were identified in the effect of the sites: a geochemical component linked to soil pH and a climate component linked to altitude, temperature and precipitation. Multivariate statistics are discussed as a tool for the interpretation of complex interaction patterns between element concentrations in plants.     

Formation of Aerenchyma and the Processes of Plant Ventilation in Relation to Soil Flooding and Submergence

Abstract: Enhanced development of gas-spaces beyond that due to the partial cell separation normally found in ground parenchymas and their derivatives creates tissue commonly termed "aerenchyma". Aerenchyma can substantially reduce internal impedance to transport of oxygen, nitrogen and various metabolically generated gases such as carbon dioxide and ethylene, especially between roots and shoots. Such transport lessens the risk of asphyxiation under soil flooding or more complete plant submergence, and promotes radial oxygen loss from roots leading to oxidative detoxification of the rhizo-sphere. Aerenchyma can also increase methane loss from waterlogged sediments via plants to the atmosphere. This review of the formation and functioning of aerenchyma particularly emphasises research findings since 1992 and highlights prospects for the future. Regarding formation, attention is drawn to how little is known of the regulation and processes that create schizogenous aerenchyma with its complex cell arrangements and differential cell to cell adhesion. More progress has been made in understanding lysigenous aerenchyma development. The review highlights recent work on the processes that sense oxygen deficiency and ethylene signals, subsequent transduction processes which initiate cell death, and steps in protoplast and wall degeneration that create the intercellular voids. Similarities between the programmed cell death and its causes in animals and the predictable patterns of cell death that create lysigenous aerenchyma are explored. Recent findings concerning function are addressed in terms of the diffusion aeration of roots, rhizosphere oxygenation and sediment biogeochemistry, photosynthesis and ventilation, pressurised gas-flows and greenhouse gas emissions and aspects of ventilation related to secondary thickening.     

Dietary and metabolite effects on trivalent chromium retention and distribution in rats

The purpose of this study was to determine if diet or various metabolites alter chromium (Cr) uptake and distribution in rats. Radioactively labeled Cr was detected within 15 min of oral administration to rats, and the total amount retained remained relatively constant from 1 to 24 h. Dietary Cr intake did not alter Cr retention or distribution. The majority of the Cr was retained in the carcass. However, when the amount of labeled Cr was expressed per gram of tissue, the highest amounts of Cr were found in the kidneys, spleen, and pancreas. Pharmacological doses of insulin, epinephrine, glucagon, and dibutyryladenosine-3’ −5’ cyclic monophosphate, prostaglandins A₁, A₂, B₁, B₂, E₁, E₂, F_1α, and F_2α did not significantly influence Cr retention. Glucose, sucrose, nicotinic acid, glutathione, and other metabolites administered orally in conjunction with labeled Cr also did not significantly alter Cr retention. These data indicate that most nutrients and metabolites do not alter Cr retention and distribution. The regulation of Cr homeostasis appears to be at the level of excretion.     

The physical-chemical limnology of a desert reservoir

The physical-chemical limnology of a desert lake in central Arizona was investigated from February 1971–July 1973. The reservoir was found to be a warm-monomictic, eutrophic lake which exhibited pronounced thermal stratification during the summer months. Surface water temperatures ranged from a minimum of ca. 9 C in January to a maximum near 30 C in July–August. Chemically the lake may be described as a hard water lake of moderately high alkalinity and salinity. The concentration of the principal ions was affected significantly by precipitation run-off. The primary nutrients N and P were subject to considerable seasonal variability, being influenced most by precipitation and phytoplankton abundance. Trace element concentrations were low and showed comparatively little fluctuation during the study.     

Incorporation of trace elements from environment into the hair structure

A model describing the incorporation of trace elements from environment into the hair structure is presented. Model predictions for radial and longitudinal concentration profiles are given. Comparison with elemental data is satisfactory.     

Recovery of photosynthesis from water stress in Eucalyptus pauciflora—a process in two stages

Abstract. Seedlings of Eucalyptus pauciflora Sieb. ex. Spreng. were stressed by withholding water. They were then rewatered, and the time course of recovery of photosynthesis was followed. Recovery always followed a distinct bi-phasic pattern. A first, rapid, stage of recovery commenced between 5 and 60 min after rewatering and was completed by between 30 min and four h after rewatering. Recovery in this stage always involved concurrent increases in stomatal conductance and the leaf's capacity to assimilate CO₂ at any intercellular partial pressure of CO₂ [ A(p_i) relationship]. This stage of rapid recovery was followed either by a constant or gradually declining rate of photosynthesis for the remainder of the light period. In plants kept to a normal diurnal cycle, a second stage of recovery occurred and was completed during the night following rewatering. In this second stage of recovery, the A(P_i) relationship recovered to 90–100% of prestress values. In contrast, the recovery of stomatal conductance was not complete by the first day after rewatering. In darkness, complete recovery of the A(p_i) relationship required as little as five h. If plants were kept in continuous high light, then between six and 16 h elapsed after rewatering before the second stage of recovery commenced. After this lag, almost complete recovery of the A(p_i) relationship was possible. These results indicate that water stress has two independent and parallel effects on the mesophyll capacity for photosynthesis. The first may be simply reversible when the plant is rewatered, while the second may involve damage to the photosynthetic machinery that requires protein synthesis for its reversal.