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291.
Isarangkool Na Ayutthaya S Do FC Pannangpetch K Junjittakarn J Maeght JL Rocheteau A Cochard H 《Tree physiology》2011,31(7):751-762
Effects of soil and atmospheric drought on whole-tree transpiration (E(T)), leaf water potential (Ψ(L)) and whole-tree hydraulic conductance (K(T)) were investigated in mature rubber trees (Hevea brasiliensis, clone RRIM 600) during the full canopy stage in the rainy season in a drought-prone area of northeast Thailand. Under well-watered soil conditions, transpiration was tightly regulated in response to high evaporative demand, i.e., above reference evapotranspiration (ET(0)) ~2.2 mm day(-1) or maximum vapor pressure deficit ~1.8 kPa. When the trees experienced intermittent soil drought E(T) decreased sharply when relative extractable water in the top soil was?0.4. The midday leaf water potential (Ψ(md)) on sunny days did not change as a function of soil drought and remained stable at approximately - 1.95 MPa, i.e., displaying isohydric behavior. The decrease in E(T) was mainly due to the change in K(T). K(T) remained constant over a wide range of environmental conditions and decreased sharply at low soil water availability. A simple hydraulic model incorporating critical minimum water potential and the response of whole-tree hydraulic conductance to relative extractable water correctly simulated patterns of transpiration over 6 months. We conclude that an explicit and simplified framework of hydraulic limitation hypothesis was sufficient to describe water use regulation of a mature rubber tree stand in water-limited conditions. Given the complexity of constraints in the soil-plant-atmosphere pathway, our results confirm the relevance of this approach to synthesize the overall behavior of trees under drought. 相似文献
292.
Kohomlan G. Beranger Awessou Christophe Peugeot Alain Rocheteau Luc Seguis Frédéric C. Do Sylvie Galle Marie Bellanger Euloge Agbossou Josiane Seghieri 《Agroforestry Systems》2017,91(3):403-413
Average population growth in the African Sudanian belt is 3 % per year. This leads to a significant increase in cultivated areas at the expense of fallows and forests. For centuries, rural populations have been practicing agroforestry dominated by Vitellaria paradoxa parklands. We wanted to know whether agroforestry can improve local rainfall recycling as well as forest. We compared transpiration and its seasonal variations between Vitellaria paradoxa, the dominant species in fallows, and Isoberlinia doka, the dominant species in dry forests in the Sudanian belt. The fallow and dry forest we studied are located in northwestern Benin, where average annual rainfall is 1200 mm. Sap flow density (SFD) was measured by transient thermal dissipation, from which tree transpiration was deduced. Transpiration of five trees per species was estimated by taking into account the radial profile of SFD. The effect of the species and of the season on transpiration was tested with a generalized linear mixed model. Over the three-year study period, daily transpiration of the agroforestry trees, V. paradoxa (diameters 8–38 cm) ranged between 4.4 and 26.8 L day?1 while that of the forest trees, I. doka, (diameters 20–38 cm) ranged from 9.8 to 92.6 L day?1. Daily transpiration of V. paradoxa was significantly lower (15 %) in the dry season than in the rainy season, whereas daily transpiration by I. doka was significantly higher (13 %) in the dry season than in the rainy season. Our results indicate that the woody cover of agroforestry systems is less efficient in recycling local rainfall than forest cover, not only due to lower tree density but also to species composition. 相似文献
293.
Duy Tien Do Khanh Doan Vinh Tran Anh Tuyet Quach David Lee Frank CJ Chang Carol PY Wu Toan Nguyen Tat Chanhee Chae 《Canadian journal of veterinary research》2021,85(2):93
The aim of this study was to evaluate the protective efficacy of the CIRCOQ porcine circovirus type 2 (PCV2) subunit vaccine in piglets with high maternally derived antibodies (MDAs) against disease caused by natural infection with PCV2d. A total of 130 weaned, 21-day-old healthy pigs was allocated into 3 trial groups. The signs of respiratory disorder were higher in unvaccinated pigs than in vaccinated pigs at 13 to 17 weeks old (P < 0.05), 18 to 22 weeks old (P < 0.001), and 23 to 27 weeks old (P < 0.01). The unvaccinated pigs had an early rate of dermatitis at 8 to 12 weeks old (10.0%), 13 to 17 weeks old (30.0%), 18 to 22 weeks old (46.7%), and 23 to 27 weeks old (33.3%), while there were no cases of dermatitis in vaccinated pigs. There was a significant difference (P < 0.05) in the mortality of pigs in the unvaccinated group and the 2-dosed vaccinated group. PCV2 viremia was detected in the blood and peaked at 105 days old in both unvaccinated pigs (Ct-adj = 8.40) and pigs vaccinated with 1 dose (Ct-adj = 6.37), while no detectable PCV2 virus was found in the blood of pigs vaccinated with 2 doses. At 77 and 105 days old, the PCV2 viremia load (Ct-adj) of unvaccinated pigs and those vaccinated with 1 dose was significantly higher (P < 0.05) than that of the 2-dosed vaccinated pigs. The body weight (BW), average weight gain (AWG), and average daily gain (ADG) in both groups of vaccinated pigs were significantly higher (P < 0.05) than those of unvaccinated pigs. The study vaccine was significantly efficacious in protecting vaccinated pigs against clinical symptoms, blood viral load, and mortality, as well as improving productivity, compared with unvaccinated pigs. 相似文献
294.
Refika Ceyda Beram Ayşe Gülden Aday Kaya Hatice Tuğba Doğmuş Lehtijärvi Asko Lehtijärvi Steve Woodward 《Forest Pathology》2023,53(5):e12827
Heterobasidion species are the most important pathogens causing root and stem rot on conifers in northern hemisphere forests. The host list of this complex is very wide and includes over 200 species of trees and shrubs. Among the members of this complex, Heterobasidion annosum s. s. has the largest host range. In this study, young plants of Pinus sylvestris, Picea orientalis, Abies nordmanniana, Cedrus libani and Pinus brutia (three different origins) were inoculated on the lower stem with known genets of Heterobasidion annosum s.s. collected from Pinus brutia stands in south-western Türkiye. Infection frequency, assessed as presence of the conidial stage in stem discs following incubation, in the inoculated seedlings was 100%. The Heterobasidion annosum s. s. isolates were re-isolated from all inoculated host species. Control seedlings showed no symptoms of disease. Mortality in inoculated plants was 11.5% of the 735 inoculated plants, which died over an 8-weeks incubation period. The isolates showed greater growth on Cedrus libani, Pinus sylvestris and Picea orientalis seedlings compared to other species tested. On the other hand, it was found that the least affected seedlings were Pinus brutia TB12 and Abies nordmanniana. This study proved that differences occur in aggressiveness of Heterobasidion annosum s. s. to host species. A striking point in the results is that, despite being the host species from which the isolates were obtained, Pinus brutia seedlings showed lower sensitivity to Heterobasidion annosum s. s. than the other conifer species tested. Inoculations of three different Pinus brutia provenances suggested there was no significant difference in mean lesion lengths and fungal growth values in Pinus brutia plants, except in Pinus brutia TB14, which was more susceptible to extension growth of the pathogen. 相似文献
295.
Maria Do Carmo Antunes-Madeira Leonor M. Almeida Vitor M. C. Madeira 《Pest management science》1991,33(3):347-357
The effects of DDT (0-100 μM) in pure phospholipid and phospholipid/cholesterol bilayers were investigated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), a probe located in the bilayer interior, and by excimer to monomer fluorescence intensity ratio (I′/I) of 1,3-di(l-pyrenyl)propane (Py(3)Py), a probe sitting closer to the polar region. In the gel phase of dimyristoylphosphatidylcholine (DMPC) bilayers, DDT induces concentration-dependent fluidizing effects into the hydrophobic membrane regions, but no effects are observed in the outer regions of the membrane, as evaluated by DPH and Py(3)Py, respectively. Furthermore, in the fluid phase of DMPC and for DDT concentrations higher than 10 μM, I′/I of Py(3)Py decreases, reflecting an order increase of the probe environment and DPH fails to detect any apparent effect. Similar effects were observed in other pure lipid bilayers, namely dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC). Unlike DPH, Py(3)Py is very sensitive to DPPC and DSPC pre-transitions which are not abolished by 50 μM DDT. This DDT concentration inhibits to some extent the cholesterol-induced ordering in DMPC bilayers and high cholesterol concentrations (? 30 mol%) do not prevent insecticide interaction, as evaluated by DPH. On the other hand, the effects of DDT reported by Py(3)Py depend on temperature and cholesterol content of DMPC bilayers. Thus, for cholesterol levels ranging from 10 to 50 mol% and for temperatures below the phase transition temperature of DMPC, Py(3)Py fails to detect any significant effect. Nevertheless, above the phase transition temperature of DMPC, Py(3)Py detects either ordering effects of DDT at low cholesterol contents (< 20 mol%) or fluidizing DDT effects at high cholesterol levels (> 20 mol%). 相似文献
296.
Doç. Dr. A. Demirbaş 《Wood Science and Technology》1991,25(5):365-370
Summary Soxhlet and supercritical fluid extracts of freshly cut oriental beech (Fagus orientalis) have been obtained using acetone. While the yield of the Soxhlet extract was 2.54% the yield of the supercritical acetone extract obtained at 240°C and 6.0–6.5 MPa was 9.55% (dry wood basis). The fatty acids present in the extracts were separated by chemical and Chromatographic methods and analysed by combined gas chromatography and mass spectrometry. Linoleic acid was the major fatty acid in both extracts. 相似文献