UDPGLUCOSE PYROPHOSPHORYLASE ACTIVITY IN THE DIATOM CYCLOTELLA CRYPTICA. PATHWAY OF CHRYSOLAMINARIN BIOSYNTHESIS 1

UDPglucose pyrophosphorylase activity was detected in cell-free extracts of the diatom Cyclotella cryptica TI3L Reimann, Lewin and Guillard. When assayed in the direction of UDPglucose formation, the enzyme had maximal activity at pH 7.8 and was stimulated by Mg²⁺and Mn²⁺ions. 3-Phosphoglycerate and inorganic phosphate had little effect on enzymatic activity, and the enzyme was relatively insensitive to feedback inhibition from UDPglucose (K, > I millimolar). A glucan was formed from UDP-[¹⁴C]glucose in cell-free extracts of C. cryptica. This glucan had a median molecular weight of 4600 (as determined by gel filtration chromatograbhy) and could be hydrolyzed by laminarinase. Partial acid hydrolysis of the glucan resulted in the formation of glucose and laminaribiose. but not cellobiose. These results suggest that the synthesis of chrysolaminarin (the major storage carbohydrate of diatoms) occurs via the activity of UDPglucose pyrophosphorylase. followed by glucosyl transfer from UDPglucose to the growing β-(1–3)-linked glucan.     

THE ALGAE OF WAIMANGU CAULDRON (NEW ZEALAND): DISTRIBUTION IN RELATION TO pH1

The pH of the main body of thermal water and of the outlet of Waimangu Cauldron (Frying Pan Lake) is 3.8, whereas hot springs flowing into this lake are alkaline, pH 8.2–8.7. Where these waters meet there are pH gradients, and it is possible to find a series of habitats differing in pH but having approximately the same temperature (54–56 C). Where the pH is above 4.8 the blue-green alga Mastigocladus laminosus is present, and where the pH is below this value the eucaryotic alga Cyanidium caldarium is the sole photosynthetic microorganism at temperatures less than 55 C. Rocks resting on the bottom of Waimangu Cauldron surrounded by water of pH 3.8 have Mastigocladus laminosus growing on them, but measurements of pH directly in these algal mats showed that the microenvironment of the alga was actually above pH 4.8. A simple experiment showed that it is probably the rock, per se, that initiates a tiny island of alkalinity in the acid lake, permitting M. laminosus to become established. The outlet of Waimangu Cauldron is a hot acid stream which becomes progressively alkaline as it descends through Waimangu Valley, due to inflow of alkaline water from springs and a cold stream. Blue-green algae were found in this stream when the pH was greater than 5.0 and C. caldarium when the pH was less than 4.0. In one region where the pH was between 4.0 and 5.0, both blue-green algae and C. caldarium were seen, although in moribund state. These data, provide further information on the lowest pH values at which blue-green algae are able to grow.     

GROWTH RESPONSES OF THE DIATOM,CYCLOTELLA CRYPTICA (BACILLARIOPHYCEAE), TO GIBBERELLIC ACID1

The plant hormone, gibberellic acid (GA), stimulated growth of a marine diatom, Cyclotella cryptica Reimann, Lewin and Guillard. Four concentrations of GA (5 × 20 × 25 × and 35 × 10^?6 g/mL) were added to axenic cultures of C. cryptica. Changes in cell densities, measured by cell counts and turbidimetric readings, confirmed that GA at 20 × 10^?6 g/mL produced maximum stimulation. There was an increase in the total number of cells produced and a shorter lag phase of growth at this concentration. Coulter counter measurements of cell size, as well as ocular micrometer measurements, indicated there was no significant variation in cell volumes of GA grown cells over that of the controls.     

峨眉山细辛属的分布及其与系统分类的关系

峨眉山细辛属植物共有6种1变种,分属于2亚属3组,它们的垂直替代现象较为明显,从山脚至山顶,依次由花脸细辛Asarum chingchengense。尾花细辛A.cauidigerum.花叶尾花细辛A.caudige-erum var.cardiophyllum、牛蹄细辛A.delavavi、长毛细辛A.pul-chellum、短尾细辛A.caudigerellvm和单叶细辛A.himalaicum组成垂直带谱。     

山西运城盐池湖区裸藻植物及其分布特点

在山西运城盐池湖区采到的裸藻门植物共１０属８３种（包括变种和变型）,其中,绿色裸藻类７７种,无色裸藻类６种。该区域的水体根据其含盐量的不同可分为４种类型：淡水水体（含盐量０．００１－０．０５％）、混盐水体（含盐量０．０５￣３％）、真盐水体（含盐量３－４％）和高盐水体（含盐量４－３４．７％）。由于含盐量不同的影响,裸藻门植物在４种水体中的分布有明显差异,总的趋势是裸藻门植物的种数随着含盐量的增加而减     

ORGANIZATION OF THE CHLOROPLAST GENOME OF THE FRESHWATER CENTRIC DIATOM CYCLOTELLA MENEGHINIANA1

We constructed a complete physical map and a partial gene map of the chloroplast genome of Cyclotella meneghiniana Kützing clone 1020-1a (Bacillariophyceae). The 128-kb circular molecule contains a 17-kb inverted repeat, which divides the genome into single copy regions of65 kb and 29 kb. This is the largest genome and inverted repeat found in any diatom examined to date. In addition to the 16S and 23S ribosomal RNA genes, the inverted repeat contains both the ndhD gene (as yet unexamined in other diatoms) and the psbA gene (located similarly in one of two other examined diatoms). The Cyclotella chloroplast genome exists as two equimolar populations of inversion isomers that differ in the relative orientation of their single copy sequences. This inversion heterogeneity presumably results from intramolecular recombination within the inverted repeat. For the first time, we map the ndhD, psaC, rpofi, rpoCl, and rpoC2 genes to the chloroplast genome of a chlorophyll c-containing alga. While the Cyclotella chloroplast genome retains some prokaryotic and land plant gene clusters and operons, it contains a highly rearranged gene order in the large and small single copy regions compared to all other examined diatom, algal, and land plant chloroplast genomes.     

EFFECTS OF SILICON DEFICIENCY ON LIPID COMPOSITION AND METABOLISM IN THE DIATOM CYCLOTELLA CRYPTICA1

The effects of silicon deficiency on the metabolism and composition of lipids in Cyclotella cryptica T13L Reimann, Lewin, and Guillard were examined. Silicon-deficient cells had higher levels of neutral lipids (primarily triacylglycerols) and higher proportions of saturated and monounsaturated fatty acids than silicon-replete cells. After 4 h of silicon deficiency, the percentage of newly assimilated NaH¹⁴CO₃ partitioned into lipids increased from 27.6% to 54.1%, whereas the percentage partitioned into chrysolaminarin decreased from 21.6% to 10.6%. In addition, pulse-chase experiments with NaH¹⁴CO₃ indicated that the amount of ¹⁴C in the total cellular lipid fraction increased by 32% after 12 h of silicon deficiency despite the absence of additional photoassimilable ¹⁴C. Therefore, the accumulation of lipids in response to silicon deficiency appears to be due to two distinct processes: (a) an increase in the proportion of newly assimilated carbon partioned into lipids, and (2) a slow conversion of previously assimilated carbon from non-lipid compounds into lipids     

THE DISTRIBUTION OF APHID INFESTATION IN RELATION TO LEAF AGE

Infestations of apterous Aphis fabae Scop, on potted sugar beets have been followed in detail for several weeks. The plants were somewhat stunted and their crowns presented an unusually complete series of leaf ages. Records were kept of the changing number and size of the leaves and of their stage of growth. Parallel records were kept of the changing population of aphids on every leaf, and the figures are analysed in various ways to show how suitability for the aphids varied through the life cycle of the leaves.
The leaves were very suitable when young, became unsuitable as they matured, became suitable again just after maturity and then unsuitable again as they senesced. But among leaves at any given stage, those which were growing or senescing rapidly were more suitable than those changing slowly, unless the rate of senescence was very high. The differences of population density on different-aged leaves were due largely to the preferences exercised by the apterous adults. The added effect of differences in the fecundity of these mothers while feeding on different leaves was not excluded, but could not be assessed. It is concluded that the physiological development of the plant as a whole determines, through the growth and senescence among its total complement of leaves, the progress and pattern of its aphid infestation.     

CARBON‐USE STRATEGIES IN MACROALGAE: DIFFERENTIAL RESPONSES TO LOWERED PH AND IMPLICATIONS FOR OCEAN ACIDIFICATION1

Ocean acidification (OA) is a reduction in oceanic pH due to increased absorption of anthropogenically produced CO₂. This change alters the seawater concentrations of inorganic carbon species that are utilized by macroalgae for photosynthesis and calcification: CO₂ and HCO₃^? increase; CO₃^2? decreases. Two common methods of experimentally reducing seawater pH differentially alter other aspects of carbonate chemistry: the addition of CO₂ gas mimics changes predicted due to OA, while the addition of HCl results in a comparatively lower [HCO₃^?]. We measured the short‐term photosynthetic responses of five macroalgal species with various carbon‐use strategies in one of three seawater pH treatments: pH 7.5 lowered by bubbling CO₂ gas, pH 7.5 lowered by HCl, and ambient pH 7.9. There was no difference in photosynthetic rates between the CO₂, HCl, or pH 7.9 treatments for any of the species examined. However, the ability of macroalgae to raise the pH of the surrounding seawater through carbon uptake was greatest in the pH 7.5 treatments. Modeling of pH change due to carbon assimilation indicated that macroalgal species that could utilize HCO₃^? increased their use of CO₂ in the pH 7.5 treatments compared to pH 7.9 treatments. Species only capable of using CO₂ did so exclusively in all treatments. Although CO₂ is not likely to be limiting for photosynthesis for the macroalgal species examined, the diffusive uptake of CO₂ is less energetically expensive than active HCO₃^? uptake, and so HCO₃^?‐using macroalgae may benefit in future seawater with elevated CO₂.     

PHYSIOLOGICAL AND ULTRASTRUCTURAL RESPONSES OF CYCLOTELLA MENEGHINIANA (BACILLARIOPHYTA) TO LIGHT INTENSITY AND NUTRIENT LIMITATION1

Photosynthetic characteristics and chloroplast ultrastructure of Cyclotella meneghiniana Kütz. were quantified while the organism was simultaneously adjusting to light and nutrient stress. Cells were grown in batch culture at either low or high light intensity on medium with a nitrogen/phosphorus molar ratio of 2:1 as a control, or with nitrogen or phosphorus deleted from the medium to create nutrient deficiencies. Analysis of variance indicated that light intensity, nutrient deficiency and duration of nutrient deficiency all had significant effects on cell growth, chlorophyll (Chl) concentration/cell, cellular fluorescence capacity (CFC), chloroplast volume and thylakoid surface density. Because interactions existed among nutrient deficiency, extent of nutrient deficiency, and light intensity, all three must be considered together in order to describe accurately the physiology and chloroplast ultrastructure of the diatom. Significant correlations were found between the Chl/cell or CFC/cell and chloroplast volume and thylakoid surface density. Through an increase in Chi concentration, chloroplast volume and thylakoid surface density, the cells successfully adapted to the conditions of low light intensity even while under nutrient stress. In contrast, less Chl/cell, smaller chloroplast volume and less thylakoid surface density were found at high light intensity.     

PHOSPHATE AND SILICATE GROWTH AND UPTAKE KINETICS OF THE DIATOMS ASTERIONELLA FORMOSA AND CYCLOTELLA MENEGHINIANA IN BATCH AND SEMICONTINUOUS CULTURE1

Information on the nutrient kinetics of Asterionella formosa Hass. and Cyclotella meneghiniana Kutz. under either phosphate or silicate limitation was obtained for use in a Monod model and in a variable internal stores model of growth. Short-term batch culture growth experiments were fit to the Monod model and long-term semicontinuous culture experiments and short-term uptake experiments were fit to the variable internal stores model. Mathematical analysis indicates that the parameters of the 2 models may be expressed in terms of each other at steady state. The qualitative results of both batch and steady state culture methods agree. For limiting phosphate experiments. A. formosa is better able to grow at low PO₄-P concentrations than C. meneghiniana, as shown by its lower K for PO₄-P limited growth. The k_Q of A. formosa compared to C. meneghiniana found in long-term semicontinuous culture indicates that A. formosa is almost an order of magnitude more efficient at using internal phosphate for growth. The qualitative results under silicate-limited growth of C. meneghiniana is less than that of A. formosa. The k_Q from semicontinuous culture experiments indicates that C. meneghiniana is the more efficient at using internal silicate for growth. Nutrient uptake experiments showed more variability from a Michaelis-Menten relationship than short-term growth experiments. There were no significant differences between the 2 species in half saturation constants for either phosphate or silicate uptake. We observed a marked dependence of the coefficient of luxury consumption (R) of phosphate on the steady state growth rate. A. formosa has a higher R than C. meneghiniana.     

THE INFLUENCE OF pH ON ALGAL CELL MEMBRANE PERMEABILITY AND ITS IMPLICATIONS FOR THE UPTAKE OF LIPOPHILIC METAL COMPLEXES1

Uptake of lipophilic metal complexes by freshwater algae has recently been shown to be pH dependent. Here we look at different physiological aspects that could influence the diffusion of the lipophilic Cd complex, Cd(diethyldithiocarbamate)₂⁰ (Cd(DDC)₂⁰), into algal cells at different exposure pH values. Changes in cell membrane permeability were assessed as a function of pH for three species of green algae [Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, and Chlorella fusca var. vacuolata Shihira et R. W. Kraus] using two neutral, nonionic probes, fluorescein diacetate (FDA) and D‐sorbitol. In parallel experiments, we exposed algae to inorganic Cd or to Cd(DDC)₂⁰ and monitored Cd intracellular metal distribution, together with phytochelatin synthesis. For the three algal species acclimated at pH 5.5 (w/wo DDC 1 μM) and exposed at this pH, their permeability to FDA and D‐sorbitol was consistently lower than for algae growing at pH 7.0 and exposed at this pH (P < 0.001). The ratio of the FDA hydrolysis rate measured at pH 7.0 with respect to the rate measured at pH 5.5 (both in the presence of DDC) correlated with the ratio of the Cd(DDC)₂⁰ initial internalization rate constant obtained at pH 7.0 versus that obtained at pH 5.5 (three algae species, n = 9, r = 0.85, P = 0.004). Our results strongly suggest that acidification affects metal availability to algae not only by proton inhibition of facilitated metal uptake but also by affecting membrane permeability.     

MODELLING THE DISTRIBUTION OF BIRD SPECIES IN SWAZILAND IN RELATION TO ENVIRONMENTAL VARIABLES

Parker, V. 1996. Modelling the distribution of bird species in Swaziland in relation to environmental variables. Ostrich 67: 105–110.

Logistic regression was used to model the observed distributions of 335 species in Swaziland in relation to variables representing the geology, topography, climate and vegetation types of the study area. Reporting rates were used to represent the relative densities of the species. For each species, the variables which were significantly associated with the distributions were identified. The combination of geological, topographic and climatic variables was found to account more fully for the variation in relative densities than the vegetation types. The models accurately predicted the observed distributions of most bird species.     

乌桕的地理分布和环境的关系

<正> 乌柏是我国重要的油料树种,其种子既含油又含脂,油脂含量高达40％以上。乌柏油脂广泛用于制皂及生产硬脂酸和油漆中。虽然我国的乌柏栽培历史悠久,产区辽阔,但现有柏林不到1,000万亩,且经营粗放。至今全国柏油总产只有3万余吨,未达到历史最高产量水平,还不能满足工业发展的需要。因此,目前我国南方不少省、区正在利用荒山荒地发展乌柏生产,北方一些地方也拟进行引种试种。     

ENVIRONMENTAL FACTORS CORRELATED WITH CHRYSOPHYTE CYST ASSEMBLAGES IN LOW ARCTIC LAKES OF SOUTHWEST GREENLAND1

We analyzed the relationship between chrysophyte cyst assemblages in surface sediment samples and limnological and geographical variables for 70 lakes located along Søndre Strømfjord in southwest Greenland. Over 247 stomatocysts were identified and of these, 153 were sufficiently abundant for use in statistical analyses. Eight stomatocysts were considered to be new and are described formally. Canonical correspondence analysis indicated that conductivity was the dominant variable explaining cyst distribution, reflecting the large conductivity gradient in lake water chemistry in this area. High conductivity lakes had distinctive cyst assemblages with lower diversity than low alkalinity lakes, where assemblages were similar to alpine soft‐water lakes elsewhere. The high conductivity lakes, however, had similar cysts to other saline lakes elsewhere in the arctic. Additionally, pH, calcium, maximum depth, longitude, sulfate, total phosphorus, and altitude all explained significant amounts of variability of cyst assemblages. Longitude was the only geographical variable that explained cyst variability independently of other variables (i.e. had a unique effect), which suggests that the climatic gradient from the coast to the head of the fjord has a structuring effect on cyst assemblages. Conductivity (weighted‐averaging partial least squares, r²=0.917; root mean square error=0.142; r²_jack=0.861, root mean square error of prediction=0.191) and pH inference models (weighted averaging, r²=0.924; root mean square error=0.158; r²_jack=0.826, root mean square error of prediction=0.240) were developed. For the pH model, high conductivity lakes (>800 μ S₂₀·cm^?1) were removed. Both models are statistically robust and could be applied to lakes in west Greenland to reconstruct conductivity and/or pH. Such paleolimnological reconstructions provide the means of acquiring long‐term data for use in the evaluation of, for example, regional paleoclimatic models.