Aspects of the adsorption and degradation of isoproturon in a heavy clay soil

Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (<3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.     

On predicting the presence of birds in Eucalyptus forest types

We examine the relationship between the number of bird species and environment within 500 000 ha of eucalypt forests in south-eastern New South Wales, Australia. Birds were surveyed at 39 sites within 31 eucalypt communities, which were, in turn, scored by altitude, temperature, rainfall, basal areas of trees and levels of the nutrients nitrogen, phosphorus, potassium and magnesium in the eucalypt foliage.

Ninety bird species were recorded. Numbers per site, averaged over the whole sample period, ranged between 20 and 38 over all surveys, 24 and 42 in ‘summer’ (October to March) when migrant species were present, and 13 and 38 in ‘winter’ (April to September). A forward stepwise Poisson regression model was used to fit bird species richness to the environmental variables. Over all surveys and in ‘summer’, foliar magnesium and tree basal area (including the basal area of dead trees) were significantly (positive) correlated with the number of bird species. In ‘winter’ the correlations were with altitude and temperature (both negative), presumably the result of emigration of species that avoid cold weather, and tree basal area (positive).

The positive association of number of species over all surveys and in ‘summer’ with tree basal area, including dead trees, and foliar magnesium may index the level of forest maturity and productivity.

Forest management directed solely to timber production reduces the basal area and the number of dead trees and may thereby reduce bird species richness permanently.

A methodology is offered, based on the relationship between the physical environment and the more productive eucalypt communities, for determining forest areas containing the most species of birds.     

Effects of Brans from Specialty Sorghum Varieties on In Vitro Starch Digestibility of Soft and Hard Sorghum Endosperm Porridges

Brans of specialty sorghum varieties (high tannin, black, and black with tannin) were used to investigate the effects of sorghum phenolic compounds on starch digestibility of soft and hard sorghum endosperm porridges. Endosperms of varieties with the highest and lowest grain hardness index were mixed with brans of specialty sorghum varieties in the ratio of 85:15 and cooked into porridges with distilled water using a Rapid Visco Analyzer. Brans of condensed tannin containing sorghum varieties (high‐tannin and black with tannin sorghums) significantly (P < 0.05) decreased starch digestibility and estimated glycemic index (EGI) and increased resistant starch (RS) content of endosperm porridges. However, the addition of phenolic‐rich tannin‐free (mostly anthocyanins) black sorghum bran significantly (P < 0.05) increased starch digestibility and EGI but did not affect RS content of endosperm porridges. The disparate effects with black bran may, in part, result from its larger particle size and different bran structure compared with other sorghum varieties evaluated. Thus, our study showed that not only presence of phenolic compounds in the brans but also structural differences of specialty sorghum brans can have significant effects on starch digestibility.     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

DROUGHT STRESS: Soil Water Availability Alters the Inter‐ and Intra‐Cultivar Competition of Three Spring Wheat Cultivars Bred in Different Eras

Competition for water generates a classic aspect of the tragedy of the commons, the ‘race for fish’, where crops must allocate more resource to acquisition of the limiting resource than is optimal for crop yield allocation. A pot experiment using a simple additive (target–neighbour) design was conducted to examine the above‐ground and below‐ground growth of three spring wheat (Triticum aestivum L.) cultivars when grown alone and in mixtures at three levels of water availability. The effects of competition and water availability were compared by observing patterns of growth, biomass allocation and below‐ground outcomes. Competitive interactions were investigated among cultivars ‘HST’, ‘GY602’ and ‘LC8275’, target plant of each cultivar grown without neighbouring plants are referred to herein as control plant and one target plant of each cultivar sown surrounded either by same or another cultivar as intra‐ or inter‐cultivar competition. Competitive ability was assessed as the response ratio (lnRR) between the target plant surrounded by six other plants and the target plant in isolation. Our results showed that the cultivar ‘HST’, released over a century ago, produced a higher biomass and grain yield than the more recently released cultivars ‘LC8275’ and ‘GY602’ when grown as isolated plants with sufficient water supply. However, competition for resources from neighbours led to target plant biomass and grain yield being significantly reduced relative to controls in all three cultivars, particularly in ‘HST’. When subjected to intra‐cultivar competition, the two recently released cultivars ‘LC8275’ and ‘GY602’ had higher grain yields and water use efficiency for grain than ‘HST’ in all three water regimes. The landrace ‘HST’ had better and significantly linear relationships between biomass and biomass allocation, root length and specific root length, whereas the recent and modern cultivars had much more water‐related species‐specific changes in root morphology and allocation patterns. These results suggest that crop traits that influence competitive ability, such as biomass allocation to roots and root plasticity in response to drought have changed in modern wheat cultivars because of breeding and selection.     

Old and New Cultivars of Soya Bean (Glycine max L.) Subjected to Soil Drying Differ in Abscisic Acid Accumulation,Water Relations Characteristics and Yield

Two old (Huangsedadou and Longxixiaohuangpi (LX)) and two new (Jindou 19 (JD) and Zhonghuang 30 (ZH)) soya bean (Glycine max (L.) Merr.) cultivars were used to investigate the influence of soil drying on the abscisic acid (ABA) accumulation in leaves, stomatal conductance (g_s), leaf water relations, osmotic adjustment (OA), leaf desiccation tolerance, yield and yield components. The greater ABA accumulation was induced by soil drying, which also inducing g_s decreased at higher soil water contents (SWC) and leaf relative water content (RWC) significantly decreased at lower SWC in the new soya bean cultivars than in the old soya bean cultivars. The soil water threshold between the value at which stomata began to close and the RWC began to decrease was significantly broader in the new cultivars than in the old cultivars. The new cultivars had significantly higher OA and lower lethal leaf water potential than old cultivars when the soil dried. The old cultivars had greater biomass, but lower grain yield than the new cultivars in well‐watered, moderate stress and severe stress conditions. Thus with soil drying, the new soya bean cultivars demonstrated greater adaptation to drought by inducing greater ABA accumulation, stomatal closure at higher SWC, enhanced OA and better water relations, associated with increased leaf desiccation tolerance, greater water use efficiency and higher yield.     

Case series: Persistent dorsal displacement of the soft palate in eight horses

Persistent dorsal displacement of the soft palate (pDDSP) is a relatively rare equine disorder. This case series reports histories and clinical findings in 8 cases of pDDSP, and outcome after treatment of concurrent epiglottic entrapment (n = 3), laryngeal tie‐forward (n = 6) ± laser staphylectomy (n = 2), and/or sectioning of mucosa ventral to the epiglottis and the hyoepiglotticus muscles (n = 2). Four of 6 horses that underwent tie‐forward ± laser staphylectomy had complete resolution of pDDSP and returned to their previous level of work, as did one horse that had a subepiglottic releasing incision. Correction of concurrent epiglottic entrapment in 3 horses with pDDSP did not result in resolution of pDDSP in any case. Previous laryngeal surgery including laryngoplasty and ventriculocordectomy appear to be risk factors for the development of pDDSP.     

Single agent gemcitabine chemotherapy in dogs with spontaneously occurring lymphoma

BACKGROUND: Gemcitabine has been shown to be effective as a single agent in a variety of tumors including nonHodgkin's lymphoma. Its use in veterinary medicine has been limited and to date this drug has not been used as a first-line therapy in dogs with lymphoma. HYPOTHESIS: Gemcitabine as a single agent may be efficacious in dogs presented for the first time with lymphoma. ANIMALS: Twenty-four dogs with spontaneously occurring lymphoma. METHODS: All dogs were clinically staged and given gemcitabine at 400 mg/m(2) over a 30-minute intravenous infusion weekly for 3 weeks and then given 1 week off treatment before starting a second cycle. RESULTS: A single dose of gemcitabine lowered both neutrophil count (decrease in mean neutrophil count from 10,640 cells/ microL to 3,140 cells/microL) and platelet count (decrease in mean platelet count from 201,290 cells/microL to 139,190 cells/microL) 7 days after administration. Consequently gemcitabine dosage was reduced at the second treatment in 8 of 21 dogs or a dose delay of 1-7 days and a reduction of dosage was used in 7 of 21 dogs. Seven dogs completed the assigned 4-week cycle. Two of these dogs had progressive disease and 5 had stable disease. No objective responses were seen in dogs treated with a second cycle of gemcitabine. CONCLUSIONS AND CLINICAL IMPORTANCE: Gemcitabine administration as a single agent resulted in hematologic toxicity and did not reduce lymphoma burden. If gemcitabine is to be used in veterinary medicine, additional prospective pharmacologic studies should be done to determine the appropriate dosage, regimen, and schedule of use before it can be recommended for use in the treatment of dogs with lymphoma as a single agent.     

Selenium supplementation of young red deer (Cervus elaphus)

Two selenium (Se) supplementation trials were conducted in successive years involving a total of 70 red deer calves 3-15 months of age grazing pasture containing 30-57 ppb of Se on a dry matter basis. The trials compared growth rate, whole blood Se and glutathione peroxidase (GSHpx) concentrations of calves which received periodic doses of oral Se or a single injection of barium selenate (equivalent to 50 mg Se) or no Se supplementation. There were no significant weight gain differences between treated and untreated groups in either trial. Whole blood GSHpx levels were strongly correlated with blood Se levels (r = 0.9278) and produced the following regression equation: GSHpx = 0.0155 Se - 2.292. In both years the 3 month old calves had GSHpx levels of 6-9 kU/I which probably derived from maternal transfer of Se. The GSHpx levels in unsupplemented calves declined from these levels to a minimum in winter (group means approximately 2.6) and then progressively rose the following spring and summer. Periodical oral dosing with Se or a single injection of barium selenate significantly elevated blood Se and GSHpx levels throughout the trials.     

The evaluation of isoxsuprine hydrochloride for the treatment of navicular disease: a double blind study

A randomised double-blind clinical trial of 28 horses was undertaken to evaluate the efficacy of isoxsuprine hydrochloride at four different doses:- 0.0 mg/kg bodyweight (bwt) (placebo), 0.6 mg/kg bwt, 1.2 mg/kg bwt and 1.8 mg/kg bwt for treatment of navicular disease. The results showed that horses treated with isoxsuprine hydrochloride (N = 22) responded significantly with respect to clinical assessment score (P less than 0.01) when compared with the control group (N = 6). Furthermore, there were no dose-related differences in the responses of the horses treated with increasing levels of isoxsuprine. No correlation was found between radiological evidence of the extent of navicular disease and severity of lameness or response to treatment.