Restoration and creation of freshwater wetlands using seed banks

The minimum information about a seed bank needed for a wetland restoration or creation project is a species list. There are two basic techniques for determining the composition of seed banks: (1) mechanical separation of seeds from a volume of soil and (2) germination of seeds from a volume of soil under appropriate environmental conditions. The latter method always gives biased results. It is best to collect as many random samples as possible when sampling a wetland seed bank. These can be combined as needed for processing. Field studies in India have demonstrated that vestigial seed banks can be used to re-establish a former vegetation type in a monsoonal wet-land that had become overgrown by a species of grass. In less than a year, 9 of 1 I species in the vestigial seed bank were found growing in areas cleared of the grass. Vestigial seed banks of drained prairie wetlands in the northcentral United States contained a few wetland species after 70 years, although species diversity and seed density declined significantly after 20 to 30 years of drainage and cultivation. In Florida, U.S.A., wetlands have been established in strip-mined areas using donor soils from existing wetlands. Newly established wetlands quickly developed a dense cover of vegetation, although this vegetation often lacked many desirable wetland species. Experimental studies of soil moisture conditions using a seed bank from the Delta Marsh, Canada, demonstrated that soil moisture affected both the total number of seeds, and the relative proportion of seeds of each species that germinated from a seed bank. The density of seedlings of emergent wetland species in the treatments was directly proportional to soil moisture, while that of terrestrial annuals was inversely proportional. Emergent species made up nearly 90% of the seedlings in the wettest treatment and 0% in the driest.From a paper presented at the Third International Wetlands Conference, 19–23 September, 1988, University of Rennes, France.     

荧光探针Bis-ANS和磷酸丙糖异构酶的相互作用

研究了极性荧光探针Bis-ANS和磷酸丙糖异构酶的相互作用。我们发现由磷酸丙糖异构酶(TIM)中Trp残基和结合在TIM分子上的Bis-ANS之间的能量传递引起的Trp残基荧光的淬灭呈双相性,表明Bis-ANS在TIM分子上可能有2个不相同的结合位点,其结合的解离平衡常数Kd分别为3.3μM和17.0μM。底物GDP引起已结合的Bis-ANS荧光强度进一步增强和荧光谱的蓝移说明GDP可影响Bis-ANS在TIM分子上结合部位的构象,使其疏水性增强。我们还观察到由于结合在同一TIM分子上的Bis-ANS之间的能量传递引起的退偏振,进一步证明Bis-ANS有2个结合部位在1—2800bar压力范围里,增高压力引起结合在TIM分子上的Bis-ANS荧光进一步增强和光谱蓝移,说明TIM在压力下解离成亚基的过程中发生了Weber提出的"conformationaldrift。     

脂肪族类两亲物对肌浆网膜脂区结构的影响

C18饱和脂肪酸和胺可增加DPH标记肌浆网(SR)的荧光偏振度,而C18单不饱和脂肪酸。胺和醇则使其偏振度下降。加入MgATP,可除去单不饱和脂肪胺引起的DPH标记的荧光偏振度下降,并使之高于未加脂肪胺的对照水平。饱和酸及相应胺可使标记于膜脂中层和深层的TAS和12AS的荧光偏振度上升,不饱和酸及相应胺和醇仅使12AS荧光偏振下降。说明脂肪族类两亲物对SR膜流动性的影响与脂肪链饱和程度有关。饱和者主要使膜中、深层流动性下降.不饱和者主要使膜深层流动性升高。     

八种针阔叶幼树清晨叶水势与土壤含水量的关系及其抗旱性研究

一、前言土壤是植物根系的生活环境,是供给植物赖以生存的水分和养分的源泉。干旱区的植物尤其是树木常常由于土壤供水不足而限制其自然分布和生长。根据土壤-植物-大气连续体系     

广西森林土壤丝状真菌的生态分布

真菌种类多,分布广,对人类的生产和生活关系非常密切,因此近来对真菌特别是丝状真菌的研究日益引起高度重视。1981—1990年我们对桂北龙胜县里骆林区、桂中宜山县庆远林区、桂南岑溪县七坪林区和桂西田林县老山林区森林土壤微生物区系进行了分析,其中丝状真菌是我们重点研究的内容之一。在上述森林土壤中共分离出丝状真菌2084株,经鉴定归属于25属。现将广西森林土壤丝状真菌生态分布的研究结果报道如下。     

模拟酸雨对主要酸性土壤中铝的溶出及形态的影响

本文研究了模拟酸雨对主要酸性土壤中铝的溶出及形态变化的影响。结果表明,模拟酸雨对土壤酸化的影响较小,但对土壤铝的溶出却影响明显,尤其在pH<4.0时;模拟酸雨对不同类型土壤的影响是不同的,其中以高度风化的酸性土壤较为敏感。模拟酸雨对土壤游离铝形态的影响是重要的,酸处理后,交换性铝略有增加,无定形活性铝增加较多,而有机络合态铝有减少的趋势。这表明在酸雨的长期作用下,铝终将转化为交换性铝和水溶性铝而进入环境并危害生态系统。     

森林土壤氮转化的微生物功能研究

本文研究了不同林型下土壤(A+6层和A_1层)微生物、土壤酶活性在森林土壤氮转化中的作用。结果表明不同林型下土壤具有不同的固氮作用、反硝化作用、氨化作用和硝化作用速率,即阔叶林>针阔混交林>针叶林。已经证明,固氮作用主要存在于森林土壤的A_1层,反硝化作用主要存在于A_0层。森林土壤存在2种硝化作用过程,即由自养微生物所引起的自养硝化作用过程和异养微生物所引起的异养硝化作用过程。它的存在与林型有关,某些森林土壤中这2种硝化作用过程都存在,如针阔混交林下的A_0层和A_1层。有些林型下土壤,则以异养硝化作用过程为主,如针叶林的A_0层。     

Keratinolytic and keratinophilic fungi in the soils of Papua New Guinea

A study was made of soil samples collected during an expedition to the Highlands of Papua New Guinea. Fungi were isolated from the samples by the method of hair baiting (To-Ka-Va). Of the 33 species isolated, about half showed keratinolytic activity. Such activity is previously unreported for Mucor hiemalis f. hiemalis, Myrothecium roridum, Paecilomyces carneus, P. marquandii, Penicillium brevicompactum, Rhinocladiella mansonii and Verticillium lecanii. The species most active keratinolytically were Chrysosporium an. Arthroderma cuniculi, C. an. A. curreyi, C. indicum, Myceliophthora vellerea and Trichophyton ajelloi. The spectrum of fungi with keratinolytic activity isolated from the different sites differed considerably according to the frequency of use by man, heaviest use being correlated with greatest activity. The pH of the soil (varying from 5.8–7.5) had little influence on the type of such fungi isolated.     

Lipid fluidity and composition of the erythrocyte membrane from healthy dogs and labrador retrievers with hereditary muscular dystrophy

Erythrocyte membranes and their liposomes were prepared from clinically normal dogs and Labrador retrievers with hereditary muscular dystrophy. The static and dynamic components of fluidity of each membrane were then assessed by steady-state fluorescence polarization techniques using limiting hindered fluorescence anisotropy and order parameter values of 1,6-diphenyl-1,3,5-hexatriene (DPH) and fluorescence anisotropy values ofdl-2-(9-anthroyl)-stearic acid anddl-12-(9-anthroyl)-stearic acid, respectively. Membrane lipids were extracted and analyzed by thin-layer chromatography and gas chromatography. The results of these studies demonstrated that the lipid fluidity of erythrocyte membranes, and their liposomes, prepared from dystrophic dogs were found to possess significantly lower static and dynamic components of fluidity than control counterparts. Analysis of the composition of membranes from dystrophic dogs revealed a higher ratio of saturated fatty acyl chain/unsaturated chains (w/w) and lower double-bond index. Alterations in the fatty acid composition such as decrease in levels of linoleic (18:2) and arachidonic (20:4) acids and increase in palmitic (16:0) and stearic (18:0) acids were also observed in the membranes of dystrophic animals. These associated fatty acyl alterations could explain, at least in part, the differences in membrane fluidity between dystrophic and control dogs.