小柴胡黄酮的分离及结构鉴定

本文对贵州产小柴胡(B.tenue Buch.-Ham.ex D.Don)黄酮成分进行了研究。从其乙醇浸膏的水溶性物质中分离出四种黄酮醇类成分。根据光谱分析、衍生物制备、酸水解及理化常数测定,分别鉴定为芸香甙(槲皮素-3-芸香糖甙)、水仙甙(异鼠李素-3-芸香糖甙)、山萘酚和槲皮素。此类成分在该种植物中首次分离得到。     

Microhabitat and morphometric variation of two Chaetophoracean (Chaetophorales, Chlorophyta) species in tropical streams of southeastern Brazil

Two populations of Chaetophora elegans (Roth) C. Agardh and two of Stigeoclonium helveticum Vischer were investigated for microhabitat characteristics and morphological variation in streams of São Paulo State, southeastern Brazil. Different patterns of microhabitat distribution were found between species investigated. Populations of C, elegans were distributed under relatively narrow microhabitat conditions (high irradiance, low depth, moderate to high current velocity, rocky substrata and lower values of niche width) and showing little morphometric variation (colony diameter, main axis cell size, and apical branch number), Stigeoclonium helveticum occurred under more diverse microhabitat conditions, revealed by lack of significant difference between sampling units with and without the alga and wider niche width, but also exhibited relatively narrow morphometric variation (plant length, main axis cell and ateral branch cell sizes). The narrow microhabitat conditions and smaller niche width of C. elegans can explain its low abundance (percentage cover) in streams from the area studied as well as in other regions of São Paulo State, In contrast, the wider variation of microhabitat conditions and the higher niche widths of S. helveticum suggest that this green alga is able to grow in a high number of stream ecosystems in the region investigated, ranging from undisturbed to highly disturbed habitats. Thus. the results suggest that S. helveticum is a generalist species.     

A New Species of Stigeoclonium (Chaetophoraceae,Ulotrichales)

This paper describes a new species, Stigeoclonium ovisporum Wei (Chaetophoraceae, Ulotrichales), from Yunnan and Sichuan provinces, China. In asexual reproduction of this alga, narrow oviod sporangia produce zoospores. The differentiation of vegetative cellsand reproductive ones is an advanced character in the genrus Stigeoclonium.     

冬眠与非冬眠刺猬小肠运动机能与对Ad、Ach反应敏感性比较

对47只冬眠季冬眠阵低温期刺猬的小肠与53只非冬眠季刺猬的小肠,在11.5℃和37℃及离体条件下的收缩强度进行比较,和在37℃条件下对肾上腺素（Ad）、乙酰胆硷（Ach）、心得安（Propranolol）、阿托品（Atr）反应进行比较,表明在11.5℃条件下,冬眠与非冬眠刺猬离体小肠都基本无运动机能,在37℃条件下,冬眠季冬眠阵低温期刺猬离体小肠运动强度明显高于非冬眠季、Ad、Ach、Propranolol、Atr使冬眠季冬眠阵低温期刺猬离体小肠收缩强度变化率明显高于非冬眠季。     

Observations on the morphology,reproduction and cytology of stigeoclonium pascheri (vischer) cox et bold (chaetophorales-chlorophyceae) and their bearing on the validity of the genus caespitella vischer

The present communication deals with the morphology, reproduction and cytology of Stigeoclonium pascheri (formerly described as Caespitella pascheri Vischer). Effects of various concentrations of nitrate and variations in intensity and duration of light period in 24 hr LD cycles were studied on cultures of this alga in relation to the type and extent of branching and occurrence or absence of hair formation. It is concluded that these traits are not of taxonomic significance and are influenced largely by environmental conditions. The present study shows a large overlapping of morphological characters between the genera Stigeoclonium and Caespitella and supports Cox & Bold's abandonment of the latter generic name and its merger into the genus Stigeoclonium. The chromosome number determined for this alga is n = 6 which indicates that the Indian strain of this alga is a distinct cytotype from the one originally isolated by Vischer.     

毛枝藻属一新种

本文报道了丝藻目、胶毛藻科、毛枝藻属的一新种—卵孢毛枝藻,此种采自我国云南省和四川 省。此藻类由狭卵形的孢子囊产生动孢子进行无性生殖,在毛枝藻属的生殖中,营养细胞和生殖细胞分化是一种进化类型。     

SPECIES-SPECIFIC CHARACTERISTICS EXPLAIN THE PERSISTENCE OF STIGEOCLONIUM TENUE (CHLOROPHYTA) IN A WOODLAND STREAM1

The heterotrichous alga Stigeoclonium tenue Küetzing is dominant in many streams with high densities of herbivores. Previous in situ studies in Walker Branch (WB), a woodland stream in eastern Tennessee, indicated that dominance by Stigeoclonium basal cells was “grazer-dependent”; however, Stigeoclonium also appeared to have a lower biomass–specific productivity rate than other species that dominated when snails were experimentally removed. Here, an explicit test of the grazing dependence of Stigeoclonium was made with unialgal cultures established in the laboratory. Five different “assemblage types” were tested: 1 and 2) unialgal cultures of Stigeoclonium at low and high biomass, 3 and 4) a mixed assemblage of diatoms at low and high biomass, and 5) a natural stream community. Reduction in chlorophyll a after exposure to snail grazing was dependent on assemblage type (one-way ANOVA, P < 0.0001); low biomass Stigeoclonium tiles and tiles from the stream (on which basal cells of Stigeoclonium were dominant) were most grazer-resistant. In addition, Stigeoclonium had a lower biomass-specific productivity rate (measured as H¹⁴CO₃^? uptake) than a mixed assemblage of diatoms, regardless of biomass level, suggesting an underlying tradeoff between resistance to herbivory and competitive ability. Additional laboratory experiments were conducted to determine the response of Stigeoclonium to high (approx. 150 μmol quanta ·m^?2· s^?1)and low (approx. 25 μmol quanta · m^?2· s^?1) irradiance when nutrients were at 1) ambient WB concentrations and 2) increased 1000× ambient concentrations. There was a positive response of growth to increased irradiance only under high nutrient conditions. This suggests that observed reductions in the abundance of Stigeoclonium under high irradiance/low nutrient conditions that occur on a seasonal basis in WB can be explained in part by autecological resource requirements of this alga. We use these results to model the response of algal communities dominated by basal-regenerating species (e.g. Stigeoclonium) to gradients in herbivory and productivity. The results of our culture studies, combined with an overview of factors affecting communities dominated by grazer-resistant species, illustrate how both broad-scale (e.g. functional form) and species-specific studies can be combined to achieve an understanding of community dynamics.     

Blood Parasites of Pekin Robins (Liothrix luteus)*

SYNOPSIS. The Pekin Robin (Liothrix luteus) is a species of babbler (Timaliidae) native to Southeast Asia. Except for Plasmodium tenue, a malaria parasite of the subgenus Novyella and much like P. vaughani, with which they are very commonly infected, these birds seem remarkably free of blood parasites. Of 152 birds examined, 4 harbored Leucocytozoon; no infections with Haemoproteus, trypanosomes, Atoxoplasma, or microfilariae were observed. Blood inoculation from 50 Pekin Robins into canaries revealed 3 P. relictum infections. Experimental inoculation of Pekin Robins with no evidence of prior malarial infection, with 6 species of Plasmodium, P. cathemerium, P. circumflexum, P. elongatum, P. octamerium, P. paranucleophilum, and P. vaughani, gave negative results; evidently the birds have a very unusual resistance to malaria (other than P. tenue). Their insusceptibility to P. vaughani is additional evidence of the validity of P. tenue as a species.     

EFFECTS OF HERBIVORE SIZE AND HUNGER LEVEL ON PERIPHYTON COMMUNITIES1

The effects of herbivore size and hunger level were tested on lotic periphyton community structure and ash-free dry mass (AFDM). My hypotheses were 1) that small herbivores would remove more periphyton per unit biomass than large herbivores of the same species because of energetic demands and 2) that within the same size class, starved herbivores would remove more periphyton than nonstarved herbivores. The herbivore used was the prosobranch snail Elimia clavaeformis Lea. Seven treatments were employed: 1) no snails (control); 2) small “starved” snails; 3) large “starved” snails; 4) small and large “starved” snails; 5) small fed snails; 6) large fed snails; and 7) small and large fed snails. Although snails removed significant amounts of periphyton AFDM relative to controls, neither snail size nor degree of starvation had a significant effect on loss of total AFDM. Small snails removed significantly more erect forms of Stigeoclonium tenue (C. A. Ag.) Kütz. than large snails, but snail size had no other significant effect. Starved snails removed significantly more Cocconeis placentula Ehr. than fed snails, suggesting that after the more susceptible growth forms (e.g. erect Stigeoclonium) were removed, Cocconeis cells became more vulnerable to grazing by hungry snails. When small and large snails were combined in chambers, large snails gained weight over time, whereas small snails lost weight. These results suggest that intraspecific competition may occur within populations of Elimia.     

Morphology, cytology and taxonomic remarks of four species of Stigeoclonium (Chaetophorales, Chlorophyceae) from Argentina

Four species of Stigeoclonium from Argentina were studied by means of transmission electron microscopy and light microscopy. For species identification, we collected data related to the prostrate system and zoospore germination. We also determined the chromosome number for each species. Stigeoclonium aestivale showed a more developed erect system than the prostrate one, zoospore germination was predominantly of erect type and the chromosome number was 8. Stigeoclonium tenue presented well developed, erect and prostrate systems, zoospore germination was initially of the prostrate type and the chromosome number was 5. In Stigeoclonium variabile the prostrate system predominated over the erect one, zoospore germination was strictly of the prostrate type and the chromosome number was 3. Stigeoclonium farctum presented a more developed prostrate system than the erect one, zoospore germination was strictly of the prostrate type and the chromosome number was 8. The ontogeny of the zoospore germination was related to the final relative development of the prostrate and erect portions of adult thalli.