A possible virus cryptic in carnation

Small isometric virus-like particles were found in low concentration in apparently healthy carnations of the Mediterranean, miniature and Chinese type but not in eleven Sim cultivars tested. Most carnations containing these particles were from Italy but some were from France and the USA. The particles were not transmitted by grafting or by mechanical inoculation but were seed-transmitted to a large proportion of seedlings. Antisera to partially purified particles were obtained. The particles did not react with antisera to twenty-eight isometric plant viruses or virus-like particles but were serologically related to similar particles found in carnations in England, Holland and Israel. When negatively stained, the particles were isometric with a diameter of about 29 nm and a rounded rather than angular profile, but without clear substructure; some particles were penetrated by the stain. The particles remained intact in neutral sodium phosphotungstate. After isopycnic centrifugation in CsCl solution, preparations of particles formed a main band of mean density 1.377 g/ml and other fainter bands that varied in intensity and position in different preparations. In thin sections of carnations, no virus-like particles or cytological abnormalities were observed.     

Utilization of adenine and guanine as nitrogen sources by Chlamydomonas reinhardtii cells

Chlamydomonas reinhardtü Dangeard, adenine or guanine can be used as the sole nitrogen source for growth by means of an inducible system which is repressed by ammonia. Cells grown on either adenine or guanine were able to take up both purines, although the adenine uptake rate was always about 40% of the guanine uptake rate. Both adenine and guanine were taken up by an inducible system(s) exhibiting hyperbolic kinetics with identical apparent A, values of 3-2 mmol m^?3 for adenine and 3-2mmol m^?3 for guanine. Adenine and guanine utilization depended on pH, with similar optimal pH values of 7·3 and 7·4, respectively. Adenine and guanine each acted as a competitive inhibitor of the other's uptake, and their utilization was also inhibited by hypoxanthine, xanthine and urate. Inhibition of adenine uptake by guanine and hypoxanthine was competitive, with A′, values of 5·5 and 1. 6 mmol m^?3 respectively. Guanine uptake was also inhibited competitively by adenine (K₁= 1·3mmol m^?3) and hypoxanthine (K₁= 3. 3 mmol m^?3). Utilization of both adenine and guanine was inhibited by cyanide, azide, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, 2,4-dinitrophenol and carbonylcyanide m-chlorophenylhydrazone, and was also sensitive to p-hydroxymercuribenzoate and N-ethyl-maleimide. On the basis of these results, taken together, the possibility that adenine and guanine are translocated into Chlamydomonas by a common system is discussed.     

Reconciling the optimal and empirical approaches to modelling stomatal conductance

Models of vegetation function are widely used to predict the effects of climate change on carbon, water and nutrient cycles of terrestrial ecosystems, and their feedbacks to climate. Stomatal conductance, the process that governs plant water use and carbon uptake, is fundamental to such models. In this paper, we reconcile two long‐standing theories of stomatal conductance. The empirical approach, which is most commonly used in vegetation models, is phenomenological, based on experimental observations of stomatal behaviour in response to environmental conditions. The optimal approach is based on the theoretical argument that stomata should act to minimize the amount of water used per unit carbon gained. We reconcile these two approaches by showing that the theory of optimal stomatal conductance can be used to derive a model of stomatal conductance that is closely analogous to the empirical models. Consequently, we obtain a unified stomatal model which has a similar form to existing empirical models, but which now provides a theoretical interpretation for model parameter values. The key model parameter, g₁, is predicted to increase with growth temperature and with the marginal water cost of carbon gain. The new model is fitted to a range of datasets ranging from tropical to boreal trees. The parameter g₁ is shown to vary with growth temperature, as predicted, and also with plant functional type. The model is shown to correctly capture responses of stomatal conductance to changing atmospheric CO₂, and thus can be used to test for stomatal acclimation to elevated CO₂. The reconciliation of the optimal and empirical approaches to modelling stomatal conductance is important for global change biology because it provides a simple theoretical framework for analyzing, and simulating, the coupling between carbon and water cycles under environmental change.     

Bacterial rhamnolipids are novel MAMPs conferring resistance to Botrytis cinerea in grapevine

Rhamnolipids produced by the bacteria Pseudomonas aeruginosa are known as very efficient biosurfactant molecules. They are used for a wide range of industrial applications, especially in food, cosmetics and pharmaceutical formulations as well as in bioremediation of pollutants. In this paper, the role of rhamnolipids as novel molecules triggering defence responses and protection against the fungus Botrytis cinerea in grapevine is presented. The effect of rhamnolipids was assessed in grapevine using cell suspension cultures and vitro-plantlets. Ca²⁺ influx, mitogen-activated protein kinase activation and reactive oxygen species production form part of early signalling events leading from perception of rhamnolipids to the induction of plant defences that include expression of a wide range of defence genes and a hypersensitive response (HR)-like response. In addition, rhamnolipids potentiated defence responses induced by the chitosan elicitor and by the culture filtrate of B. cinerea . We also demonstrated that rhamnolipids have direct antifungal properties by inhibiting spore germination and mycelium growth of B. cinerea . Ultimately, rhamnolipids efficiently protected grapevine against the fungus. We propose that rhamnolipids are acting as microbe-associated molecular patterns (MAMPs) in grapevine and that the combination of rhamnolipid effects could participate in grapevine protection against grey mould disease.     

Melanin Standard Method: Particle Description

Melanin isolated from the ink sac of Sepia officinalis (Sepia melanin) has been proposed as a standard for natural eumelanin. There are no standard methods for the isolation, purification, and storage of melanins. Mild methods designed to preserve the native composition and structure of melanin are needed. The specific aim of the present work, using Sepia melanin, was to develop a mild and generally applicable protocol for the isolation and purification of melanins. It is well established that melanin polymers contain a large number of free carboxylic acid residues. These anionic residues are responsible for the cation exchange properties observed for melanins. Heating melanins with hydrochloric acid at reflux has been demonstrated to lead to extensive decarboxylation. Indeed, heat alone has been shown to cause decarboxylation, and care must be exercised to avoid such conditions. By analogy with cation exchange resins, melanins should be isolated and named according to the associated counterion (e.g., Sepia melanin—K⁺ form). The method reported here avoided extremes in pH and temperature, and was designed to yield melanin in the K⁺ form. Physical disaggregation of particulate melanin using a wet milling step was also found to facilitate removal of significant quantities of adsorbed protein. The following physical parameters were used to monitor the purification and to characterize the resultant melanin: pH, conductance, particle size, and diffuse reflectance spectroscopy.     

Environmental and socio‐economic factors related to urban bird communities

Urban fauna communities may be strongly influenced by environmental and socio‐economic factors, but the relative importance of these factors is poorly known. Most research on urban fauna has been conducted in large cities and it is unclear if the patterns found in these locations coincide with those from smaller human settlements. We examined the relative importance of environmental and socio‐economic factors in explaining variation in urban bird communities across 72 neighbourhoods in 18 regional towns in south‐eastern Australia. Native bird species richness varied from 6 to 32 across neighbourhoods and was higher in neighbourhoods with more nectar‐rich plants. Variation in bird species diversity across neighbourhoods was also strongly positively related to the density of nectar‐rich plants, but was higher also in neighbourhoods with higher socio‐economic status (reflecting higher levels of disposal income, education and home ownership). The density of native birds across neighbourhoods per season varied from 1 to 15 birds per hectare and was lower in neighbourhoods with a greater cover of impervious surfaces. The density of exotic birds (introduced to Australia) per season also varied across neighbourhoods (0–13 birds per hectare) and was lower in neighbourhoods with more nectar‐rich plants and higher in neighbourhoods with greater impervious surface cover. Our results demonstrated that the vegetation characteristics of household gardens, along streetscapes and in urban parklands had a strong influence on the richness and diversity of urban bird communities. The density of native and exotic birds varied primarily in response to changes in the built environment (measured through impervious surface cover). Socio‐economic factors had relatively little direct influence on urban birds, but neighbourhood socio‐economics may influence bird communities indirectly through the positive relationship between socio‐economic status and vegetation cover recorded in our study area.     

Influence of Summer and Autumn Nutrition on Body Condition and Reproduction in Lactating Mule Deer

ABSTRACT Recent work suggests that availability and quality of forage in late summer and early autumn, a time when female ungulates face multiple energetic demands, is critical to reproduction in wild ungulates. Therefore, we examined direct links between nutritional quality of diets, body condition, and reproduction of lactating mule deer. Using captive mule deer, we tested the hypothesis that females consuming diets with lower digestible energy (DE; kJ/g) would have lower DE intake rates (DEI; MJ/day), have less body fat and muscle, have later estrus cycles, and have lower pregnancy and twinning rates. Deer fed lower DE diets had lower DEI during summer and autumn. In turn, deer with lower DEI, regardless of diet DE, had lower body mass, body fat, and muscle thickness. When nutritional quality of diets began to decline earlier in the summer, relationships between food quality, DEI, and body condition were stronger. Although DEI did not influence estrus date for deer that became pregnant before 21 December, deer with lower DEI had a lower probability of becoming pregnant and had a lower probability of producing twins. Measures of body condition in October (i.e., body mass, body fat, and muscle depth) predicted pregnancy and twinning rates in mule deer. Serum concentration of hormones leptin and Insulin Growth Factor 1 were not good predictors of body condition or reproduction. These findings suggest that managers concerned with productivity of mule deer populations should consider focusing on assessing and improving quality of forage available in summer and autumn.