Water/nutrient interactions affecting the productivity of stands of Pinus radiata

The accumulation of above-ground biomass and the seasonal patterns of leaf-area development, foliar nutrient concentrations and tree and soil water-status have been measured for fertilised, irrigated, and control stands of Pinus radiata D. Don growing on a low-productivity site, average annual precipitation of 790 mm, near Canberra in southeastern Australia. In the second growing-season after treatments commenced, projected leaf-area index reached peak values of 7 on the irrigated/fertilised stands compared with approximately 5 on the other stands. Average canopy nitrogen concentration (dry-weight basis) varied across the treatments from 9 to 17 mg g⁻¹. Measurements of soil and tree water-status over a 2-year period indicated that stands which were not irrigated experienced summer droughts of up to 4 months duration.

Annual volume production measured over the 2-year period ranged from 17 to 45 m³ ha⁻¹. The extent to which this variation could be attributed to differences in leaf area, rats of photosynthesis, duration of the period of positive net photosynthesis, and hence growth, was analysed in terms of a process-based model of stand growth dependent on climate and soil water-balance.

Annual canopy net photosynthesis simulated by the model ranged from 18 t carbon ha⁻¹ for the control stand to 38 t ha⁻¹ for the irrigated/fertilised stands. Simulations indicated that 67% of this difference could be attributed to the role of irrigation in extending the period of active growth. The additional leaf area carried by the irrigated/fertilised stands contributed a further 23%, while differences in rates of photosynthesis, related to nitrogen nutrition, explained the remaining 10%.     

Ultrastructure of pits inPinus banksiana lamb

Summary The cross-sectional view of pitting between various cell types inPinus banksiana Lamb. was studied at the ultrastructural level. Cell types inPinus banksiana include longitudinal tracheids, ray tracheids, ray parenchyma cells, buffer cells and epithelial cells. Two common characteristic features of bordered pit-pairs between longitudinal tracheids are an initial pit border and a thickened torus at the center of the pit membrane. The shape and size of the pit border and torus of bordered pit-pairs between two compression wood cells, and between the last-formed latewood longitudinal tracheid and first-formed earlywood longitudinal tracheid were different from those in the earlywood and latewood longitudinal tracheids. The pit border on the ray tracheid side varied in size and shape due to wall dentation. No initial pit border was found on the pit border of the ray tracheid side. The shape of bordered pit-pairs between two ray tracheids varied considerably due to irregularity of the dentate cell wall. The size of bordered pit-pairs in longitudinal tracheids was between 16 m to 20 m, which was twice the diameter of bordered pit-pairs in ray tracheids. Bordered pitpairs at the end wall of two ray tracheids appeared to be the smallest at 5 m, Pit aspiration occurred in the bordered pit-pairs with or without a torus. In the heartwood zone, some half-borders pit-pairs between tracheary and ray parenchyma cells showed an additional secondary wall on the ray parenchyma cell side. Plasmodesmata were found in the half-bordered pit-pairs as well in the simple pit-pairs. Blind pits were observed between a ray tracheid and a longitudinal tracheid. Bordered pit-pairs between two buffer cells were also observed. The possible functions of buffer cells were discussed.Use of transmission electron microscope provided by the Science Instrumentation Lab, Lakehead University and the technical assistance provided by Mr. A. MacKenzie, Director of Science Instrumentation Lab are gratefully appreciated     

Viability and stability of biological control agents on cotton and snap bean seeds

Cotton and snap bean were selected for a multi-year, multi-state regional (south-eastern USA) research project to evaluate the efficacy of both commercial and experimental bacterial and fungal biological control agents for the management of damping-off diseases. The goal for this portion of the project was to determine the viability and stability of biological agents after application to seed. The biological seed treatments used included: (1) Bacillaceae bacteria, (2) non-Bacillaceae bacteria, (3) the fungus Trichoderma and (4) the fungus Beauveria bassiana. Seed assays were conducted to evaluate the following application factors: short-term (< or = 3 months) stability after seed treatment; quality (i.e. isolate purity); compatibility with chemical pesticides and other biocontrol agents; application uniformity between years and plant species. For the bacterial treatments, the Bacillaceae genera (Bacillus and Paenibacillus) maintained the greatest population of bacteria per seed, the best viability over time and the best application uniformity across years and seed type. The non-Bacillaceae genera Burkholderia and Pseudomonas had the least viability and uniformity. Although Beauveria bassiana was only evaluated one year, the seed fungal populations were high and uniform. The seed fungal populations and uniformity for the Trichoderma isolates were more variable, except for the commercial product T-22. However, this product was contaminated with a Streptomyces isolate in both the years that it was evaluated. The study demonstrated that Bacillaceae can be mixed with Trichoderma isolates or with numerous pesticides to provide an integrated pest control/growth enhancement package.     

AGEING OF HYDROLYSED IRON (III) SOLUTIONS1

Three 0.01m Fe(ClO₄)₃ Solutions of R= 0, 1, and 2, respectively, were studied over a period of 8 months, where R is referred to the HCO₃^?/Fe³⁺ mole ratio in preparation. The R= 0 solution was initially light yellow and clear but rapidly changed to a dense cloudy Suspension after a 9-day induction period. Hydrolysed species rapidly grew from <10 nm to >650 nm. Particles of intermediate size were not observed during the entire period of study. Settleable FeOOH precipi-tate was first observed in 5 weeks with 23 per cent of its iron noted as precipitate at the end of 5 months. The R= 1 and R= 2 Solutions were reddish-brown of low turbidity. Rapid hydrolysis and polymerization were observed immediately after preparation. The hydrolysed species gradually grew in size during ageing and no settleable FeOOH precipitate was observed for at least two years. A hypo-thesis based on Lamb and Jacques's model of Fe³⁺ hydrolysis is proposed to interpret the reactions taking place in these three Solutions. In the R= 0 solution, the initial number of nuclei for condensation is low, whereas the poten-tial supply of Fe(OH)₃ is abundant. In the R= 1 and R= 2 Solutions the number of nuclei initially formed is high, whereas a limited amount of mono-meric Fe(OH)₃ is available for condensation. The initial number of nuclei relative to the concentration of monomeric species is the key factor that governs the appearance and properties of these Solutions.     

Electrothermal control of weed beet and bolting sugar beet

The proportion of weed beet and bolting beet in sugar beet crops is increasing, and as much as 24% of beet acreage may now be badly infested. Mechanical and chemical methods of control are being developed, but neither is completely satisfactory. The use of electricity has recently been suggested as a means of control and is investigated in this paper. It is found that high voltages around 5 kV rms can physically destroy annual beet in pots in under 20 sec. Maximum currents vary according to the plant size and range from 0·5 to I A rms for bolters 1-1·4 m high. It is not necessary to completely burn the plant in two to kill it and various ways of minimizing the treatment for speed and energy economy are suggested. Field trials using hand-held electrodes to apply the electric currents to annual beet growing amongst a crop showed that much larger powers (up to 20 kW) were necessary to kill the plants. A tractor-driven system was constructed producing 8kV rms which enabled it to cover 6 rows and travel at speeds up to 16 km/h and it removed 75% of the bolting and weed beet. La lutte électro-thermique contre les betteraves sauvages el les montées dans les betteraves sucrières. La proportion des ressemis et des montées dans les cultures de betteraves à sucre est en augmentation et jusqu'à 14%, des surfaces cultivées en betteraves peuvent maintenant être fortement infestées. Des procédés mécaniques et chimiques de lutte ont été proposés, mais aucun n'est pleinement satisfaisant. L'emploi de l'électricité a été récemment suggéré comme moyen de lutte el il est examiné dans cette publication. II a été constaté que des voltages élevés. autour de 5 k Veff. peuvent détruire physiquenient des betteraves de I'année. cultivées en pots, en moins de 20 sec. Les courant maximaux varient selon la talle de la plante et s'échelonnent entre 0,5 et 1 A_eff, pour des plantes montées de I m à 1,40m de haut.II n'est pas nécessaire de brûler complètement la planie pour la tuer et divers procédés économisant sur la vitesse et l'énergie sont suggérés pour alléger le traitement. Des essais du champ utilisant des électrodes manipulées à la main, pour appliquer les courants électriques aux betteraves annuelles poussant dans une culture, ont montré que des puissances élevées (jusqu'à 20 kW) étaient nécessaires pour tuer les plantes. Un dispositif tiré par un tracteur a été construit produisant 8K V_eff lequel permet decouvrir 6 rangs et travaille à des vitesses atteignant 1.6 km/h; il élimine 75%, des montées et des betteraves sauvages. Elekrothermische Bekämpfung von Unkrautrüben und Zukerrübenschossern Der Anteil von Unkraut- und Schossrüben in Zuckerrüben ist ansteigend und derzeit sind 14% der Rübenfläche damit stark verseucht. Zu ihrer Bekämpfung werden mechanische und chemische Verfahren entwickelt, aber keines ist befriedigend. In dieser Arbeit wird über Untersuchungen zur neuerdings vorgeschlagenen Anwendung von Elektrizität berichtet. Unter hohen Spannungen von durchschnittlich 5 kV werden annuelle Rüben, die zu diesem Zweck in Gefässen kultiviert wurden, in weniger als 20 Sekunden zerstört. Die maximalen Stromstärken bewegen sich hierbei. Abhängig von der Pflanzengrösse, zwischen durchschnittlich 0.5 bis I A. wenn die Schossrüben 1 bis 1,4 m hoch sind. Um die Pflanze abzutöten ist es nicht nötig, sie völlig zu verbrennen. Es werden verschiedene Vorschläge zur Reduktion des Aufwandes bezüglich Fahrgeschwindigkeit und Energie gemacht. In Feldversuchen, in denen mit manuell bedienten Elektroden annuelle Rüben in einer Kultur behandelt wurden, zeigte sich, dass weit höhere Leistungen (bis zu 20 kW) notwendig waren, um die Pflanzen zu töten. Es wurde ein traktorbetriebenes Gerät konstruiert. das durchschnittlich 8 kV produziert und mit dem 6 Reihen mit einer Fahrgeschwindigkeit bis zu 1.6 km/Stunde bebandelt werden können. Mit diesem Gerät konnten 75%, der Schossrüben und Unkrautrüben beseitigt warden.     

Effect of yohimbine on xylazine-induced hypoinsulinemia and hyperglycemia in mares

Serum insulin and plasma glucose concentrations were determined in 8 mares. Four IV treatments were studied: xylazine (1.1 mg/kg of body weight); yohimbine (0.125 mg/kg); yohimbine (0.125 mg/kg) followed 5 minutes later by xylazine (1.1 mg/kg); and 5 ml of isotonic saline solution as a control. Blood samples were collected before (time 0) and at 5, 15, 30, 60, 120, and 180 minutes after drug administration. Serum insulin concentration decreased and plasma glucose concentration increased in mares given xylazine. Plasma glucose concentration was unchanged in control mares and in mares given yohimbine or yohimbine followed by xylazine. Serum insulin concentration was unchanged in mares given saline solution, but transiently increased in mares given yohimbine alone. Treatment with yohimbine prevented xylazine-induced hypoinsulinemia and hyperglycemia.     

Decoupling from international food safety standards: how small-scale indigenous farmers cope with conflicting institutions to ensure market participation

Although inclusion in formal value chains extends the prospect of improving the livelihoods of rural small-scale producers, such a step is often contingent on compliance with internationally-promoted food safety standards. Limited research has addressed the challenges this represents for small rural producers who, grounded in culturally-embedded food safety conceptions, face difficulties in complying. We address this gap here through a multiple case study involving four public school feeding programs that source meals from local rural providers in the Bolivian Altiplan. Institutional logics theory is used to describe public food safety regulations and to compare them to food safety conceptions in the local indigenous Aymara rural setting. We identify a value-based conflict that leads to non-compliance of formal food safety rules that jeopardizes the participation of small farmers in the market. These include: (1) partial adoption of formal rules; (2) selective adoption of convenient rules; and (3) ceremonial adoption to avoid compliance. Decoupling strategies allow local actors to largely disregard the formal food safety regulations while accommodating traditional cultural practices and continuing to access the market. However, these practices put the long-term sustainability of the farmers’ participation in potentially favorable opportunities at risk.     

Injectable anesthetics and anesthetic adjuncts

The purpose of this article is to review the use of selected anesthetics and anesthetic adjuncts in horses. Emphasis is placed on the pharmacologic bases of their use.