The Burgundy-blood phenomenon: a model of buoyancy change explains autumnal waterblooms by Planktothrix rubescens in Lake Zürich

Buoyancy changes of the cyanobacterium Planktothrix rubescens- the Burgundy-blood alga - were modelled from its buoyancy response to light and irradiance changes in Lake Zürich during autumnal mixing. The daily insolation received by filaments at fixed depths and circulating to different depths was calculated from the measured light attenuation and surface irradiance. The active mixing depth, za5, was determined from the vertical turbulent diffusion coefficient, Kz, calculated from the wind speed, heat flux and temperature gradients. The fixed depth resulting in filament buoyancy, zn, decreased from 13 to 2 m between August and December 1998; the critical depth for buoyancy, zq, to which filaments must be circulated to become buoyant, decreased from >60 m in the summer to <10 m in winter. When za5 first exceeded zn, in September, P. rubescens was mixed into the epilimnion. In October, zq > za5: circulating filaments would have lost buoyancy in the high insolation. Often in November and December, after deeper mixing and lower insolation, za5 > zq: filaments would have become buoyant but would have floated to the lake surface (the Burgundy-blood phenomenon) only under subsequent calm conditions, when Kz was low. The model explains the Burgundy-blood phenomenon in deeper lakes; waterblooms near shallow leeward shores arise from populations floating up in deeper regions of the lake.     

Photoheterotrophy and light-dependent uptake of organic and organic nitrogenous compounds by Planktothrix rubescens under low irradiance

1. Planktothrix rubescens is the dominant photoautotrophic organism in Lake Zürich, a prealpine, deep, mesotrophic freshwater lake with an oxic hypolimnion. Over long periods of the year, P. rubescens accumulates at the metalimnion and growth occurs in situ at irradiance near the photosynthesis compensation point. Experiments were conducted to evaluate the contribution of photoheterotrophy, heterotrophy and light‐dependent uptake of nitrogenous organic compounds to the carbon and nitrogen budget of this cyanobacterium under conditions of restricted availability of light quanta. 2. We used both purified natural populations of P. rubescens from the depth of 9 m and an axenic culture grown under low irradiance at 11 μmol m^?2 s^?1 on a light : dark cycle (10 : 14 h) to determine the uptake rates of various amino acids, urea, glucose, fructose, acetate and inorganic carbon. The components were added to artificial lake water in low amounts that simulated the naturally occurring potential concentrations. 3. The uptake rates of acetate and amino acids (glycine, serine, glutamate and aspartate) were strongly enhanced at low irradiance as compared with the dark. However, no difference was observed in the uptake of arginine, which was taken up at high rates under both treatments. The uptake rates of glucose, fructose and urea were very low under all conditions. Similar results were obtained for both axenic P. rubescens and for purified natural populations of P. rubescens that were separated from bacterioplankton and other phytoplankton. 4. Metalimnetic P. rubescens that was stratified at low irradiance for weeks exhibited much higher uptake rates than filaments that were entrained in the deepening surface mixed layer and experienced higher irradiance. The added organic compounds contributed up to 62% to the total carbon uptake of metalimnetic P. rubescens. On the basis of a molar C : N ratio of 4.9, the nitrogen uptake as organic compounds satisfied up to 84% of the nitrogen demand. 5. The experiments indicate that photoheterotrophy and light‐dependent uptake of nitrogenous organic compounds may contribute significantly to the carbon and nitrogen budget of filaments at low irradiance typical for growth of P. rubescens in the metalimnion and at the bottom of the surface mixed layer.     

道孚香茶菜的二萜成分

从河南省新县产道孚香茶莱[Rabdosia dawoensis(Hand. Mazz.)Hara]叶中分离到两个二萜化合物,根据各种光谱数据推断一个为新化合物,其化学结构为:对映-11α-羟基-3α,6β,7α-一三乙酰氧基-16-贝壳杉烯-15-酮,命名为道孚香茶菜甲素(dowoensin A),另一个为已知化合物信阳冬凌草甲素(xindongnin A).     

香茶菜属一新种和一新变种

本文报道在广西发现的唇形科一新种和一新变种。     

Chemical Structure of Macrocalyxoformin D

Macrocalyxoformin D, an new diterpenoid having a spiro secokaurene- skeleton, was isolated from the leaves of Rabdosia macrocalyx (Dunn.) Hara from (Labiatae) collected in the south of Anhui. On the basis of chemical and spectroscopic data, the chemical structure of macrocalyxoformin D was established as (Ⅲ). Macroca- lyxoformin D was shown to have inhibitory action on Hela cells, staphylococcus aureus and bacillus hay in vitro.     

细锥香茶菜甲素和乙素的化学结构

从细锥香茶菜中分得两个新的二萜类化合物,命名为细锥香茶菜甲素和乙素(coetsinA&B)根据其光谱和化学数据,推定其化学结构为[1]和[2]。     

冬凌草水溶性化学成分研究

新鲜冬凌草用70％丙酮水溶液组织破碎提取,然后经Diaion HP-20、Toyopearl HW-40、MCI Gd、silica gel等柱层析方法分离得到5个单体化合物,经波谱分析鉴定为α-D-呋喃果糖(1),阿魏酸(2),丹参素甲正丁酯(3),3,4-二羟基苯乳酸(4),延命素-1β-D-吡喃葡萄糖苷(5)。除延命素-1β-D-吡喃葡萄糖苷外,其它4个化合物均为首次从冬凌草及其同属植物中分离得到。     

冬凌草中一新的二萜成分--冬凌草辛素

从河南省鹤壁地区产冬凌〖Ｉｓｏｄｏｎ ｒｕｂｅｓｃｅｎｓ（Ｈｅｍｓｌ．）Ｈａｒａ〗叶中分得一个新地二萜化合物,命名为冬凌草辛素（Ｒｕｂｅｓｃｅｎｓｉｎ Ｈ）〈经ＮＭＲ谱等确定其结构为６β,７β,１４β,１５Ｒ－四羟基－１１β－甲酰氧基－７α,２０－环氧－对映－贝壳杉－１６－烯。     

A comparative study on the alkaloids of Zanthoxylum leprieurii, Z. lemairei and Z. rubescens from Ghana

Previous reports on the alkaloids of Z. leprieurii, Z. lemairei and Z. rubescens are reviewed. The alkaloids from nine specimens collected in Ghana have been examined chromatographically and the implications of the findings discussed, with special reference to the distinction between Z. leprieurii and Z. rubescens. In addition three further compounds, dihydrochelerythrine, lupeol and sesamin are reported for the first time from Z. leprieurii. The overall value of alkaloids as systematic markers in Zanthoxylum in Africa is briefly discussed.