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Thermal optima of photosynthetic functions and thermostability of photochemistry in cork oak seedlings 总被引:1,自引:0,他引:1
Temperature effects on photosynthesis were studied in seedlings of evergreen Mediterranean cork oak (Quercus suber L.). Responses to changes in temperature and the temperature optima of maximal carboxylation rate (V(cmax)) and maximal light-driven electron flux (J(max)) were estimated from gas exchange measurements and a leaf-level photosynthesis model. The estimated temperature optima were approximately 34 and 33 degrees C for V(cmax) and J(max), respectively, which fall within the lower range of temperature optima previously observed in deciduous tree species. The thermostability of the photosynthetic apparatus was estimated according to the temperature at which basal chlorophyll a fluorescence begins to increase (T(c)). The T(c) was highly variable, increasing from 42 to 51 degrees C when ambient temperature rose from 10 to 40 degrees C, and increasing from 44 to 54 degrees C with decreasing soil water availability while net CO(2) assimilation rate dropped to almost zero. When a heat shock was imposed, an additional small increase in T(c) was observed in drought-stressed and control seedlings. Maximal T(c) values following heat shock were about 56 degrees C, which, to our knowledge, are the highest values that have been observed in tree species. In conclusion, the intrinsic temperature responses of cork oak did not differ from those of other species (similar T(c) under ambient temperature and water availability, and relatively low thermal optima for photosynthetic capacity in seedlings grown at cool temperatures). However, the large ability of cork oak to acclimate to drought and elevated temperature may be an important factor in the tolerance of this evergreen Mediterranean species to summer drought and high temperatures. 相似文献
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Selection of lactic acid bacteria as candidate probiotics for Vibrio parahaemolyticus depuration in pacific oysters (Crassostrea gigas)
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Sadok Khouadja Najla Haddaji Meriam Hanchi Amina Bakhrouf 《Aquaculture Research》2017,48(4):1885-1894
The application of probiotics in food is now widespread and is widely accepted by consumers. Lactic Acid Bacteria (LAB) were isolated from traditional salted fish and then characterized by its ability to inhibit Vibrio parahaemolyticus growth using minimal inhibitory concentration tests. Five out of these strains were identified as Lactobacillus delbrueckii, Lactobacillus casei and three Lactobacillus gasseri by PCR using 16S and 23S rRNA genes. Antibiofilm activity of Lactobacillus spp. extracts were also tested in 96 polystyrene plates. A potential antibiofilm effect was demonstrated as most LAB. Although most LAB extract were able to eradicate pre‐formed biofilm, results demonstrated that five Lactobacillus spp. exhibited a stronger inhibitory effect against V. parahaemolyticus in infected oysters. Vibrio parahaemolyticus viable cells number declined from 106 UFC to 104 UFC after 3 days of incubation with Lactobacillus spp. Probiotic applications, in biological control of seafood associated pathogens can be an alternative solution, providing consumer with a product of good quality owing to the use of non‐toxic compounds. Based on our results, LAB could be used as a bioprotective culture in oyster's depuration to prevent V. parahaemolyticus growth. 相似文献
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针对苹果叶片病害图像识别存在数据集获取困难、样本不足、识别准确率低等问题,提出基于多尺度特征提取的病害识别网络(Multi-scale feature extraction ConvNext, M-ConvNext)模型。采用一种结合改进的循环一致性生成对抗网络与仿射变换的数据增强方法(Improved CycleGAN and affine transformation, CycleGAN-IA),首先,使用较小感受野的卷积核和残差注意力模块优化CycleGAN网络结构,使用二值交叉熵损失函数代替CycleGAN网络的均方差损失函数,以此生成高质量样本图像,提高样本特征复杂度;然后,对生成图像进行仿射变换,提高数据样本的空间复杂度,该方法解决了数据样本不足的问题,用于辅助后续的病害识别模型。其次,构建M-ConvNext网络,该网络设计G-RFB模块获取并融合各个尺度的特征信息,GELU激活函数增强网络的特征表达能力,提高苹果叶片病害图像识别准确率。最后,实验结果表明,CycleGAN-IA数据增强方法可以对数据集起到良好的扩充作用,在常用网络上验证,增强后的数据集可以有效提高苹果叶片病害图像识别准确率;通过消融实验可得,M-ConvNex识别准确率可达9918%,较原ConvNext网络准确率提高0.41个百分点,较ResNet50、MobileNetV3和EfficientNetV2网络分别提高3.78、7.35、4.07个百分点,为后续农作物病害识别提供了新思路。 相似文献
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[目的]开展不同附着藻类生物学特征的试验,分析水质指标与藻类生物学特征的关系,为筛选科学合理的附着基质,丰富附着藻类着生提供科学支持。[方法]通过模拟试验,分析3种不同建材基质(花岗岩、聚乙烯网、木板)附着藻类的生物学特征,筛选出效果好且易于资源化利用的附着基质类型。[结果]花岗岩和木板基质的附着藻类群落更加稳定,生物学特征更优,功能性藻类种类更多,更有利于发挥附着藻类在水环境中的生态效应。[结论]综合考虑可利用程度和操作的难易程度,花岗岩基质是3种基质中最合适的基质。 相似文献
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苏南稻田麦套春玉米关键栽培技术优化研究 总被引:1,自引:0,他引:1
以田间试验资料为基础,研究了苏南地区稻田小麦套种玉米生产力和技术优化组合问题。结果表明,该地区稻田种植麦套玉米可获得7000-7500kg/hm^2以上的产量,技术优化后单产可达9000-10500kg/hm^2。统计分析表明,播期、密度施肥总量三项技术因子对产量影响较大,密度和产运筹对净收入影响较大,肥料运筹麦幅比和播期对利润影响最大。 相似文献
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Regulated intramembrane proteolysis by members of the site-2 protease (S2P) family is an important signaling mechanism conserved from bacteria to humans. Here we report the crystal structure of the transmembrane core domain of an S2P metalloprotease from Methanocaldococcus jannaschii. The protease consists of six transmembrane segments, with the catalytic zinc atom coordinated by two histidine residues and one aspartate residue approximately 14 angstroms into the lipid membrane surface. The protease exhibits two distinct conformations in the crystals. In the closed conformation, the active site is surrounded by transmembrane helices and is impermeable to substrate peptide; water molecules gain access to zinc through a polar, central channel that opens to the cytosolic side. In the open conformation, transmembrane helices alpha1 and alpha6 separate from each other by 10 to 12 angstroms, exposing the active site to substrate entry. The structure reveals how zinc embedded in an integral membrane protein can catalyze peptide cleavage. 相似文献
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Chyraz Daas Pierre Montpied Belgacem Hanchi Erwin Dreyer 《Annals of Forest Science》2008,65(3):305-305
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体重 2 2~ 32kg的绵羊 8只 ,单次按 10mg/kg剂量交叉内服氧阿苯达唑和阿苯达唑 ,采用高效液相色谱法检测血清中阿苯达唑 (ABZ)、氧阿苯达唑 (亚砜 ,ABSO)及代谢物阿苯达唑砜 (砜 ,ABSO2 )。绵羊分别内服氧阿苯达唑和阿苯达唑后 ,血清中ABZ低于仪器最低检出限 ,ABSO和ABSO2 的药时曲线下面积 (AUC)两药比较无显著性差异 ,内服氧阿苯达唑分别为 (2 9.34± 11.38)和 (2 1.98± 5 .88) μg/h·ml,内服阿苯达唑分别为 (2 8.86±8.78)和 (2 2 .80± 7.0 3) μg/h·ml。内服后代谢物达峰时间 (Tmax)氧阿苯达唑较阿苯达唑短 ,两药ABSO的Tmax分别为 (7.2 5± 3 .5 7)和 (8.75± 2 .6 1)h ,ABSO2 的Tmax分别为 (11.0 0± 6 .0 5 6 )和 (19.5 0± 8.12 )h(P <0 .0 5 )。内服后代谢物的消除氧阿苯达唑较阿苯达唑快 ,血清中ABSO的平均滞留时间 (MRT)两药分别为 (12 .89± 3 .0 0 )和 (15 .6 6± 2 .34)h(P <0 .0 1) ,ABSO2 分别为 (17.93± 3.2 5 )和 (19.2 7± 5 .0 8)h。本项研究表明 ,绵羊内服氧阿苯达唑和阿苯达唑后 ,两药代谢物的吸收程度相近 ,吸收和消除速度氧阿苯达唑则较阿苯达唑快 相似文献