基于微波遥感技术探测森林地表土壤含水率

森林地表土壤含水率是森林生态系统中的重要参数,使用微波遥感技术快速准确地估算区域尺度上的森林地表土壤含水率,对于森林生态系统研究具有重要的现实意义.本文利用TDR-300土壤含水率速测仪测得黑龙江大兴安岭地区塔河林业局盘古林场内120块样地的森林地表土壤含水率作为因变量,利用C波段全极化SAR数据的极化分解参数作为自变量,构造多元线性回归统计模型和BP神经网络模型,定量估测森林地表土壤含水率,通过模型反演获得区域尺度上森林地表土壤含水率的空间分布.结果表明: 多元线性回归统计模型的精度为86.0%,均方差根误差(RMSE)为3.0%;BP神经网络模型的精度为89.4%,RMSE为2.7%.说明利用BP神经网络模型定量估测森林地表土壤含水率优于多元线性回归模型,将全极化SAR数据通过BP神经网络模型进行仿真,最终得到研究区域的森林地表土壤含水率空间分布图.     

高温强光胁迫对苹果果皮PPO活性的影响

苹果果实日烧是一种普遍发生的生理病害,最常见的特征之一就是在果实表面出现褐变。通常认为PPO与植物的酶促褐变密切相关。研究了自然和控制条件下,高温强光胁迫对果实PPO活性的影响,以便揭示高温强光胁迫下苹果果实褐变与PPO活性之间的联系。结果表明：高温和强光胁迫与果皮PPO活性变化密切相关。就树冠不同方位而言,西南方位是高温和强光胁迫最严重的区域,其外围裸露果实的PPO活性也最强。在一定范围内,随着处理温度和光照强度的升高,果皮PPO活性也逐渐增强。短时间剧烈升温能够引起PPO活性骤然上升。在同样程度的高温胁迫下,提高环境湿度有利于抑制果皮PPO活性,从而减轻褐变症状的发生。室内外试验一致证实：果实日烧褐变现象与高温强光胁迫下果皮组织PPO活性大幅度提高有直接关系。     

遗传背景对小鼠四倍体胚胎发育的影响

不同遗传背景的小鼠2-细胞期胚胎经过电融合后,胚胎的融合效率和四倍体胚胎的发育能力存在着一定的差异。本试验采用C57(C57×C57)、ICR(ICR×ICR)、BALB/c(BALB/c×BALB/c)、B6D2F2(B6D2F1×B6D2F1)、B6C3D2F2(B6C3F1×B6D2F1)品系的二倍体2-细胞期胚胎在相同的条件下经过电融合处理,结果表明:小鼠四倍体胚胎的获得效率受小鼠遗传背景的影响,远交系小鼠胚胎B6D2F2和B6C3D2F2的融合率显著高于近交系C57,ICR和BALB/c(P<0.05);四倍体胚胎在体外的发育情况也受其遗传背景的影响,在桑椹胚发育率和囊胚发育率上B6D2F2和B6C3D2F2品系的四倍体胚胎都显著高于C57和BALB/c品系的四倍体胚胎(P<0.05);杂合和纯系遗传背景的小鼠四倍体胚胎囊胚细胞数目相比具有显著差异(P<0.05或P<0.01);不同遗传背景的小鼠四倍体胚胎着床率间不存在显著差异(P>0.05);杂合背景的小鼠四倍体胚胎得到5只发育至13.5dpc(dayspostcoitum,dpc)的胎儿,纯合背景的小鼠四倍体胚胎得到0只发育至11dpc的胎儿。     

A LONG-SNOUTED DYROSAURID (CROCODYLIFORMES, MESOEUCROCODYLIA) FROM THE PALEOCENE OF MOROCCO: PHYLOGENETIC AND PALAEOBIOGEOGRAPHIC IMPLICATIONS

Abstract:  New material of a long-snouted dyrosaurid has been discovered in the Paleocene of Morocco. It consists of a well-preserved skull with embedded mandible and four dorsal vertebrae. The particularly elongate snout, proportionally the longest of all known dyrosaurids, allows precise identification of this material as Atlantosuchus coupatezi Buffetaut, 1979 a , and presentation of an emended diagnosis for this species previously known only from a mandibular symphysis. A phylogenetic analysis of the dyrosaurids indicates a close relationship between A. coupatezi and Rhabdognathus . It also confirms a previous hypothesis that Congosaurus is distinct from Hyposaurus . It is more closely related to Atlantosuchus than Hyposaurus . The analysis also allows palaeobiogeographic interpretations to be made. Dyrosaurids ranged from North Africa to other areas. They were rare during the Maastrichtian and endemic to each continent at this time. Competition with large marine reptiles, such as mosasaurs, limited their dispersal during the Late Cretaceous. The disappearance of these rivals during the 'K-T crisis' enabled their diversification and widespread dispersal during the Paleocene, with the same genera present on several continents.     

The Secondary Metabolite Euplotin C Induces Apoptosis-Like Death in the Marine Ciliated Protist Euplotes vannus

ABSTRACT. The sesquiterpenoid euplotin C is a secondary metabolite produced by the ciliated protist Euplotes crassus and provides a mechanism for damping populations of potential competitors. Indeed, E. crassus is virtually resistant to its own product while different non-producer species representing an unbiased sample of the marine, interstitial, ciliate diversity are sensitive. For instance, euplotin C exerts a marked disruption of different homeostatic mechanisms in Euplotes vannus . We demonstrate by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay that euplotin C quickly decreases viability and mitochondrial function of E. vannus with a very high efficacy and at micromolar potency. In addition, euplotin C induces apoptosis in E. vannus as 4,6-diamino-2-phenylindole and terminal transferase dUTP nick end labeling staining show the rapid condensation and fragmentation of nuclear material in cells treated with euplotin C. These effects occur without detectable permeabilisation or rupture of cell membranes and with no major changes in the overall morphology, although some traits, such as vacuolisation and disorganized microtubules, can be observed by transmission electron microscopy. In particular, E. vannus show profound changes of the mitochondrial ultrastructure. Finally, we also show that caspase activity in E. vannus is increased by euplotin C. These data elucidate the pro-apoptotic role of euplotin C and suggest a mechanism for its impact on natural selection.     

Habitat selection by the swamp wallaby (Wallabia bicolor) in relation to diel period,food and shelter

Patterns of resource selection by animals may be influenced by sex, and often change over a 24‐h period. We used a dry sclerophyll landscape managed for commercial timber production to investigate the effects of sex and diel period on habitat selection by the swamp wallaby (Wallabia bicolor). We predicted that selection would be (i) affected by both sex and diel period; and (ii) positively related to lateral cover during the day, but to food resources at night. Non‐metric multidimentional scaling indicated that some of the available habitats differed markedly with respect to visibility (an indicator of lateral cover), fern cover, forb cover, wallaby density and a forage quality index, providing the basis for non‐random habitat selection. At the landscape scale, wallabies showed strong selection for 5‐year‐old regenerating sites, selected against 10‐year‐old regenerating sites and unharvested forest, and avoided recently harvested (3–10 months post‐harvest) sites completely. At the scale of individual home ranges, a pooled male and female sample demonstrated selection for unharvested forest over recently harvested sites during both diurnal and nocturnal periods. A separate analysis showed that both sex and diel period influenced the selection of 5‐ and 10‐year‐old sites and the surrounding unharvested forest. Using a novel approach, we demonstrated that diurnal habitat selection by both sexes was negatively correlated with visibility, representing stronger selection for areas with more lateral cover. Nocturnal selection by females was positively correlated with values of a forage quality index, but this was not the case for males. We hypothesise that the observed patterns of selection were driven by the need to find food and avoid predators, but were also affected by the different reproductive strategies of males and females. Our results demonstrate the importance of incorporating factors such as sex and diel period into analyses of habitat selection.     

Remote sensing of larch phenological cycle and analysis of relationships with climate in the Alpine region

This research aims at developing a remote sensing technique for monitoring the interannual variability of the European larch phenological cycle in the Alpine region of Aosta Valley (Northern Italy) and to evaluate its relationships with climatic factors. Phenological field observations were conducted in eight test sites from 2005 to 2007 to determine the dates of completion of different phenological phases. MODerate Resolution Imaging Spectrometer (MODIS) 250 m 16‐days normalized difference vegetation index (NDVI) time series were fitted with double logistic curves and the dates corresponding to different features of the curves were determined. Comparison with field data showed that the features of the fitted NDVI curve that allowed the best estimate of the start and end of the growing season were the zeroes of its third derivative (MAE of 6 and 4 days, respectively). The start and end of season were also estimated with the spring warming (SW) and growing season index (GSI) phenological models. MODIS start and end of season dates generally agreed with those obtained by the SW and GSI climate‐driven phenological models. However, phenological models provided erroneous results when applied in years with anomalous meteorological conditions. The relationships between interannual variability of the larch phenological cycle and climate were investigated by comparing the mean start and end of season yearly anomalies with air temperature anomalies. A strong linear relationship (R²=0.91) was found between mean spring temperatures and mean start of season dates, with an increase of 1 °C in mean spring temperature leading to a 7‐day anticipation of mean larch bud‐burst date. Leaf coloring dates were found to be best related with mean September temperature (R²=0.77), but with higher spring temperatures appearing to lead to earlier leaf coloring.     

百合组织培养和遗传转化的研究进展

百合是单子叶球茎类观赏花卉,具有食用和药用的作用。本文综述了国内外百合组织培养和遗传转化研究进展。包括营养器官、生殖器官和原生质体再生系统的建立。详细介绍了基因转化的方法,例如农杆菌、基因枪、电激穿孔等。浅析百合外源基因的表达,例如GUS、半夏凝集素基因、几丁质酶基因等。同时,讨论了百合遗传转化中存在的问题,以期为百合基因工程方面的研究提供依据。     

锁阳多糖提取工艺的研究

以浸膏得率和浸膏中多糖质量分数综合评价,利用L9(34)正交实验从水提和醇沉两方面优选锁阳中水溶性多糖最佳提取工艺条件,为锁阳活性多糖的开发提供科学依据和实验基础。最佳水提工艺条件为:m(锁阳):v(水)=1:12,回流提取0.5 h,提取2次;最佳醇沉工艺条件为:在m(生药):v(水提液)=1 g:2 mL溶液中加入乙醇,使φ(乙醇)=70%,静置6 h。