Photosynthesis limitations of grapevine after treatment with the fungicide fludioxonil

The aim of this work was to determine the major limitations to photosynthesis induced by the fungicide fludioxonil (fdx) on nontarget grapevines using cutting as a model. The fdx treatments (1.2, 6, and 30 mM) induced a net photosynthetic rate ( P n) decrease without changes in stomatal conductance, suggesting a nonstomatal limitation. Fdx effects on P n were related neither to photosynthetic capacity alteration in leaves nor to loss in PSII activity. The mechanism underlying photosynthesis reduction differed according to the concentration. Fdx at 6 mM led to an increase of light requirement for photosynthesis while 30 mM fdx induced an increase in the respiration rate in the light. P n decrease after 1.2 mM fdx could rather be related to wetness caused by the spraying than to fungicide toxicity. P n recovered 10 days after treatment, meaning that fdx had little deleterious effect on plant physiology or that grapevine has a great capacity to overcome this temporary stress.     

Ground cover, photosynthetic rate and tuber yield of potato (Solanum tuberosum L.) crops from seed tubers with different physiological age modified by foliar applications of plant growth regulators

Summary The modifying effects of applying the plant growth regulators (PGRs) benzylaminopurine (BAP), gibberellic acid (GA₃) and BAP+GA₃ on physiological age were studied. Two experiments with two cultivars, differing in rate of physiological ageing (medium-early Pampeana, medium-late Huinkul) and two storage systems were performed during 1988/89 and 1989/90 in two different potato areas of Argentina. In both seasons seed tubers stored in heaps reached an advanced physiological age at planting, compared with tubers from the cold store. Seed tubers of cv. Pampeana were older than those of Huinkul. compared with control crops, those sprayed with BAP maintained ground cover and photosynthesis for longer, and those sprayed with GA₃ for a shorter period. Consequently tuber yield was decreased by GA₃ in 1988/89, but in 1989/90 all crops treated with PGRs outyielded the control. BAP could overcome effects of advanced physiological age on crop senescence and tuber yield. CIC BA This work was carried out with a research grant from CAFPTA (249/89).     

Productivity of beef cattle grazing Brachiaria brizantha cv. Marandu with and without nitrogen fertilizer application or mixed pastures with the legume Desmodium ovalifolium

The use of forage legumes to contribute biologically fixed nitrogen (N) to pastures is an alternative to increase beef cattle production in tropical regions. The objective was to compare the impact of the introduction of a legume with that of N fertilizer application on forage and animal production in Brachiaria pastures. This two-year study assessed three pasture treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha [syn. Urochloa brizantha] cv. Marandu) and the legume “ovalifolium” (Desmodium ovalifolium) cv. Itabela (Mixed), (2) Marandu palisadegrass pastures with 150 kg N ha⁻¹ (Fertilized), and (3) Marandu palisadegrass without N fertilizer (Unfertilized). Rotational stocking with a variable stocking rate was used with a target herbage allowance of 1.0 kg forage kg body weight⁻¹. The pre-grazing green herbage mass was similar for Fertilized and Mixed pastures, with 54% and 63% more mass than Unfertilized pasture, respectively (p < .001). Cattle that grazed the fertilized pasture had the greatest average daily gain (ADG; p = .017). The stocking rate and liveweight gain per area were greatest for the Fertilized and Mixed pastures (p < .001 and p < .001, respectively). No differences between treatments were found for DM forage intake (p = .555). Organic matter digestibility was lowest (p < .001) for the Mixed pasture. The inclusion of the ovalifolium legume in the Marandu pasture had the same impact on beef cattle production as annual fertilization with 150 kg N ha⁻¹. The potential and environmental benefits of ovalifolium are discussed.     

Etude en Microscopie Optique et Electronique a Balayage de l''Evolution Structurale des Parois du Caecum et du Colon, Durant la Periode Perinatale, Chez le Lapin (Oryctolagus cuniculus L.)

The study, through optical and scanning microscopy, of various developmental stages, from the 24th day of gestation to the 13th day after birth, shows a quick development of the structures of the caecal and colic mucosal layers to the adult forms, from the very first week of postnatal life. The distal part of the colon is full-grown before the other parts of the alimentary canal, and is particularly rich in mucous cells. The caecum is the place where an early lymphoid defense is provided, from the 30th day of gestation.     

In vitro vegetative multiplication of Fuchsia hybrida

Rapid development of axillary buds from shoot-tips and nodes of 18 cultivars of Fuchsia hybrida was obtained on solid Murashige and Skoog medium with BAP (1 mg l^?1 and an auxin (0.1 mg l^?1). NAA as the auxin appeared to be more active than IAA or IBA. Vegetative shoots were subsequently isolated and developed up to 15 supplementary axillary shoots on the same solid medium. Agitated and non-agitated liquid media of the same composition were less effective. One-cm long shoots could be rooted in 20 days in the presence of IBA before being transferred to soil.     

Convulsive and allied syndromes of the neonatal foal

This article discusses the clinical signs, etiology, management, and prognosis for the neonatal foal afflicted with a convulsive or allied syndrome.     

Field experiments for the evaluation of pesticide spray-drift on arable crops

Two distinct approaches were used to characterise spray-drift during the application of atrazine and alachlor to a maize crop. The first consisted in determining the quantities which did not reach their target. A first experiment was carried in 2001 to improve the sampling method. A second experiment in 2002 showed that losses represented 46 and 38% for atrazine and alachlor, respectively. The second approach was to follow the spatiotemporal evolution of the cloud formed during application. The concentrations observed near the application zone during spraying reached 4.5 microg m(-3) for atrazine and 8.5 microg m(-3) for alachlor. With alachlor these concentrations decreased rapidly when increasing distance from the plot or time following treatment, whereas in the case of atrazine they stabilised rapidly (between 0.5 and 0.3 microg m(-3)) both in space and in time. Deposits around the plot were light and slightly higher for alachlor (from 20 to 130 microg m(-2)). Alachlor was more rapidly diluted in space than atrazine, reflecting a differentiated evolution of physical form during the process. Alachlor, being more volatile than atrazine, is quickly transferred to the gaseous phase which was more rapidly dispersed than aerosols.     

Histopathology, parasite density and cell phenotypes of the popliteal lymph node in canine visceral leishmaniasis

While enlargement of popliteal lymph nodes (LN) is frequently described in canine visceral leishmaniasis (CVL), there are few histopathologic studies of lymph nodes during this chronic immunopathological condition. Besides a detailed histopathologic analysis, we have characterized the parasite load and major immunophenotypic features of the LN in Leishmania (Leishmania) chagasi-infected dogs. Our major histopathological findings highlight that hypertrophy/hyperplasia of LN cortical and medullary zones was the principal characteristic observed in asymptomatic dogs (AD), whereas atrophy of LN cortical zone was predominant in symptomatic animals (SD). The LN parasite density detected by anti-Leishmania immunohistochemical assay or expressed as Leishman Donovan Units was also highly correlated with the skin parasitism, the most reliable parameter to decode the clinical status of CVL. The major LN immunophenotypic changes during ongoing CVL were an increased frequency of T-lymphocytes, particularly CD8+ T-cells, up-regulation of MHC-II expression by lymphocytes and decreased levels of CD21+ B-cells. Our findings further demonstrated that changes in the LN B-lymphocyte compartment exhibited a negative correlation with the skin parasite load. Conversely, we also showed evidence for a positive association between skin parasitism and LN T-cell-mediated immunity, suggesting that T-cells, especially CD8+ lymphocytes, may have a Type-2 immunological profile in this lymphoid tissue in response to CVL.     

Mixed infection by Libyostrongylus douglassii and L. dentatus (Nematoda: Trichostrongylidae) in Struthio camelus (Ratites: Struthioniformes) from Brazil with further morphological characterization of adults

The genus Libyostrongylus includes three species, L. douglassii, L. dentatus and L. magnus that occur as parasites in the proventriculus of Struthio camelus. We confirmed a mixed infection by L. douglassii and L. dentatus in farmed ostriches from the southeast of Brazil for the first time, and provided new information on some morphological characters that differentiate these species. Adult nematodes collected from the proventriculus of ostriches were observed by light and scanning electron microscopy. Morphologic characterization and morphometric analysis of the nematodes enabled the distinction of both species and corroborated results of prior studies. Specimens of L. dentatus have a buccal capsule with a prominent esophageal tooth. Furthermore, males and females of L. dentatus were larger (4954 and 9347 microm) than those of L. douglassii (3411 and 4229 microm), but measurements for most characters in both species were smaller then those previously reported. Besides, the cephalic structure based on scanning electron microscopy differs, and L. dentatus has thick lips with round papillae, whereas L. douglassii has fine lips with lengthened papillae. The confirmation of both species in South America strongly suggests that the mixed infection may be common in farmed ostriches.