东亚飞蝗的食性和食物利用以及不同食料植物对其生长和生殖的影响

一.引言 东亚飞蝗自古以来是我国农业上的剧害之一,它们摧毁植物的能力极为巨大,而且所嗜食的主要是禾本科植物,其中包括我们用以生产粮食的农作物。我们的祖先在和这种害虫作斗争之中,对于它们的取食习性早有所观察和了解。晋书石勒载记中首先记载蝗虫“不食三豆三麻”,以后如王桢的“农书”(1313),徐光启的“农政全书”(1630),     

Cellular and tissue mechanisms of recovery processes in Hordeum distichum L. under irradiation

Ionizing and UV-B irradiation of barley seedlings increased the number of chromosome aberrations in vegetative and generative meristems and disturbances in microsporo- and microgametogenesis. Other irradiation-induced changes included enhanced cytomixis and an increase in the number of pathologies in meiosis and tetrads and in the polymorphism and disturbances in pollen grains. Damages induced by different irradiation types differ primarily quantitatively. The dynamics of occurrence of chromosome aberrations in the root meristem reciprocally depended on the irradiation dose. Damages induced by low UV doses were detected throughout the ontogeny of plants. Increased irradiation doses activated cytolytic processes during premeiotic interphase, meiosis, and tetrad formation, as well as after the end of gametogenesis. Exposure to maximum doses of UV radiation and moderate doses of γ-radiation restored the fertility of grain pollens. Microsporocytes, microspores, and pollen grain components undergo degeneration primarily via apoptosis. This type of cell death is apparently autonomous, being induced by the cell population itself. The results of this study confirmed the hypothesis on the positive role of cell competition in the recovery processes and adaptation of plants to mutagens.     

Improving the performance of the EPT Index to accommodate multiple stressors in Afrotropical streams

The EPT index (Ephemeroptera, Plecoptera and Trichoptera) may be skewed by the wide tolerance to multiple stressors of the Baetid, Caenid and Hydropsychid families, which affects the performance of the EPT index as an indicator of multiple stressors in aquatic ecosystems. The effect of the BCH families on the EPT index was evaluated and alternatives were considered to improve its performance. The hypothesis that the removal of the BCH families improves sensitivity of the EPT index to human-induced stressors in streams and rivers was tested. Macroinvertebrates were collected in January–March 2009 at 22 sites in the Nyando and Nzoia Rivers, Lake Victoria basin, Kenya. Nine derivatives and modifications of the EPT index were tested for responses to a disturbance gradient, ranked into three condition categories (reference, intermediate and impaired). The sensitivity of the proportionate abundance derivative of the EPT index improved when the BCH families were removed, whereas that of the richness derivative improved marginally. Other modifications considered performed poorly when compared with the EPT-BCH metrics. Wide distribution of the BCH across all sites, irrespective of the level of disturbance, reduced the sensitivity of the EPT index in the studied streams. The removal of the BCH families enhanced the sensitivity of the index to multiple stressors in Afrotropical streams and rivers.     

Increased plasma volume in two models of portal hypertension in the rat: cirrhosis of the liver and partial portal vein ligation

Portal hypertension has been studied in the rat to see if it is associated to altered blood volume composition, as it has been shown in other species. Plasma volume was measured by isotope dilution using 99mTc labelled albumin in three groups of male Sprague-Dawley rats: normal rats (controls), partially ligated portal vein rats and rats with Cl4C induced cirrhosis. Plasma volume was significantly higher in rats with portal hypertension due to partially ligated portal vein and cirrhosis than in control animals. Similarly, the calculated blood volume was also significantly higher in the portal hypertensive animals than in control group. Portal hypertension in the rat, therefore, has been demonstrated to be associated to a marked hypervolemia and this finding should be taken into consideration in haemodynamic and pharmacokinetic studies in portal hypertensive rat models.