Redox profile in liver of Leporinus macrocephalus exposed to different dissolved oxygen levels

Aquatic organisms are continuously exposed to environmental variations, which can lead to physiological and biochemical alterations. Leporinus macrocephalus, known as piavu?u, is a migratory species that may be exposed to variations in dissolved oxygen levels. Studies evaluating oxidative changes undergone by this species in these conditions are scarce. Therefore, this investigation aimed at evaluating oxidative alterations in L. macrocephalus exposed to different oxygen levels for 96?h: 6.12?±?0.18, 3.99?±?0.17, 3.22?±?0.17, 2.47?±?0.30 and 0.710?±?0.07?mg?L(-1). At the end of the experimental period, fish were euthanized and livers used to determine lipid hydroperoxides, thiobarbituric acid reactive substances, catalase, glutathione-S-transferase, superoxide dismutase and thiol groups, which are an indirect measure of reduced glutathione. Results indicated a decrease in the studied parameters in hypoxic situations, suggesting a possible metabolic depression.     

南非克鲁格斯多普禁猎区珠鸡的社群组织

1982年3月至1984年2月,在南非豪登省的克鲁格斯多普禁猎区(Krugersdorp Game Reserve),通过翼标观察对珠鸡(Numida meleagris)的社群组织进行了研究.珠鸡必须以社群的方式才能在野外存活,而集群(7-10只珠鸡)并非随机组成.地位最高的雄鸟(雄鸟A)是群体日常活动的核心,例如决定觅食方向等.地位较高的雄鸟(雄鸟A和B)密切协作以驱赶闯入者.在繁殖期,繁殖雌鸟与高地位雄鸟的结合更为紧密.尽管雄鸟中存在明显的等级差异,但群内争斗频率很低,这些争斗只是在维系群体稳定时才发生.雌性成鸟始终位于优势雄鸟和亚成体之间,以免受天敌伤害.但优势雄鸟与其配偶暂时离开群体进行繁殖时,次优势雄鸟(雄鸟B)成为集群中心,其余个体聚集在其周围以保持集群的稳定.大多数成鸟都协助抚育优势雄鸟的雏鸟.珠鸡的集群具有监视天敌的作用,以保障其在地表植被有限的环境中觅食并在冬季最大限度地获得食物.     

In vitro evaluation of the antagonistic properties of Trichoderma spp. against Pyrenochaeta lycopersici and Phomopsis sclerotioides1

In vitro evaluation of the antagonistic properties of Trichoderma spp. against Pyrenochaeta lycopersici and Phomopsis sclerotioides was carried out, using two different methods: the cellophane-agar plate method and the duaí culture method. With these methods, the direct interaction between pathogen and antagonist was demonstrated, showing very remarkable differences between the different isolates. Growth inhibition ranging from 20 to 100% was found. Proliferation in non-sterilized soil was investigated for the isolates showing the most interesting antagonistic properties. A Belgian isolate of Trichoderma hamatum was found to be able to proliferate very well in soil and to maintain a high population density during the whole experimental period.     

Albugo Candida, the cause of a serious white rust of Lunaria biennis in Crete

Albugo Candida, the causal agent of white blister rust of Lunaria biennis and other crucifers. is recorded for the first time in Crete.     

Rhizobacteria with broad-spectrum antifungal activity*

Antifungal rhizobacteria were obtained from maize, barley and chicory using direct or indirect isolation procedures. Effective isolates were tested for broad-spectrum activity against a set of phytopathogenic fungi. Isolates with broad-spectrum activity were identified as Pseudomonas fluorescens, P. cepacia, Serratia liquefaciens, S. plymuthica and Bacillus sp. Broad-spectrum compounds produced by P. cepacia and Erwinia herbicola were characterized as pyrrolnitrin and herbicolin-like compounds respectively.     

Germination of Chromolaena odorata (L.) K. & R. achenes: effect of temperature, imbibition and light

Chromolaena odorata (L.) K. & R. (= Eupatorium odoratum L.) has invaded large areas of the coastal belt of Natal province in South Africa. Propagation is predominantly by means of windborne achenes. The germination of these achenes was investigated. Of the temperatures tested, alternating 15/30°C was optimal for germination. These achenes are positively photoblastic and an imbibition period prior to exposure was required to sensitize the achenes to light. The promotive effect of red light on the germination of imbibed achenes could be reversed by subsequent exposure to far-red light while the inhibitory effect of far-red light could be nullified by a subsequent red light treatment. This is typical of a phytochromemediated germination response. Germination d'akènes de Chromolaena odorata (L.) K. & R.: effets de la température, de l'imbibition el de la lumière Chromolaena odorata (L.) K. & R. (= Eupatorium odoratum L.) a envahi de grandes superficies dans le littoral de la province de Natal en Afrique du Sud. La plante se répand surtout par moyen d'akènes portés par le vent. La germination de ces akènes a fait l'objet d'une étude. Parmi les températures essayées, 15/30°C s'est révélée optimale pour la germination. Les akènes font preuve d'une photoblasticité positive et pour les sensibiliser à la lumière, il leur faut une période d'imbibition avant de les y exposer. La promotion de germination provoquée par la lumière rouge chez les akènes imbibés a pu etre inversée par une exposition ultérieure à la lumière extrême-rouge (700 à 750 nm) tandis que l'effet inhibiteur de celle-ci s'est trouvé annulé par un traitement ultérieur à la lumière rouge. Cette réaction est caractéristique d'une germination réglée par le phytochrome. Die Keimung von Achaenen von Chromolaena odorata (L.) K. & R.: der Einfluss von Temperatur, Quellung und Licht. Chromolaena odorata (L.) K. & R. (= Eupatorium odoratumL.) hat sich auf grossen Flächen des Küstengürtels der Provinz Natal (Südafrika) ausgebreitet. Durch den Wind verbreitete Achaenen sind hauptsächlich für die Vermehrung verantwortlich. Thema der vorliegenden Untersuchung war die Keimung dieser Achaenen. Alternierende Temperaturen von 15° und 30°C waren optimal für die Keimung. Die Achaenen waren positiv photoblastisch; eine Quellungsperiode war notwendig um die Achaenen für die Lichtreaktion zu sensibilisieren. Der die Keimung vorgequollener Achaenen fördernde Einfluss von Rotlicht konnte durch eine nachfolgende‘Fern-Rot'-Exposition rückgängig gemacht werden. Hingegen wurde der Hemmungseffekt von ‘Fern-Rot’ durch eine darauffolgende Rotlicht-Exposition aufgehoben. Dieser Befund ist charakteristisch für eine phytochromregulierte Samenkeimung.     

Germination of Chromolaena odorata (L.) K. & R. achenes: effect of storage, harvest locality and the pericarp

The percentage germination of achenes of Chromolaena odorata (L.) K. & R. stored dry in the dark at 25°C for 7 months was markedly higher than that of freshly harvested achenes. This is indicative of an after-ripening requirement that may be of benefit to the species by ensuring temporal distribution of germination. Germination of freshly harvested achenes from various sites differed. However, after 7 months of dry, dark storage at 25°C no differences were present, thus, confirming the after-ripening requirement. Although the total number of achenes per capitulum did not vary from site to site, there were distinctive differences in the number of filled (presumably viable) achenes. It is suggested that this is a reflection of the environmental conditions prevailing at the sites. Puncturing of the achene pericarp did not influence dark germination but its removal increased percentage germination significantly. Natural degradation of the pericarp in the field may, therefore, permit germination of buried achenes in the absence of a suitable light stimulus.