DESCRIPTION OF A NEW GENUS AND SPECIES BELONGING TO THE FAMILY PHYLLIDIIDAE (NUDIBRANCHIA: DORIDOIDEA)

A new genus of phyllidiid nudibranch, Reticulidia, is described.Distinguishing features are the reticulate pattern of smoothridges on the dorsum and the radially arranged, glandular discswhich make up the pharyngeal bulb. Additional features of theforegut are described and compared with other genera. The importanceof the alimentary system for the separation of genera withinthe Phyllidiidae is supported and its validity reinforced bythis new genus. One species, Reticulidia halgerda, is describedas new and differentiated from a second, sympatric species.Reticulidia is presently known from the eastern Indian Ocean,South China Sea and western Pacific Ocean. ^*Present address: Australian Biological and Environmental Survey,Australian National Parks and Wildlife Service. GPO Box 1383,Canberra. ACT 2601. Australia. (Received 15 August 1989; accepted 8 January 1990)     

REABSORPTION OF ORGANIC SOLUTES IN SOME MARINE AND FRESHWATER PROSOBRANCH GASTROPODS

Influx in vitro of glucose to the heart, kidney and ureter,where present, in Monodonta, Pomacea, and Viviparus, and alsoof leucine to these tissues in Viviparus, was measured using[³H]-labelledtracers. Phloridizin-sensitive, Na⁺-dependent [³H]D-glucose uptake wasevident in the papillary sac of Monodonta, the ventricle ofViviparus, and the kidney of Pomacea. Viviparus ventricle alsoshowed Na⁺-dependent uptake of [³H]L-leucine. Nevertheless Viviparusappears to excrete some amino acids (by undefined routes) andmay therefore lack the carriers for their resorption. In Viviparusand Pomacea the site of organic solute resorption (taken tobe where Na⁺-dependent tracer uptake predominates) is proximalto the sites of Na⁺resorption. The ultrastructure of the resorptivesites has been examined in the three genera and compared withthat of the nephridial gland and dorsal wall of the kidney ofLittorina. The ciliated cells comprising the epithelium of thepapillary sac in Monodonta and their homologues over the nephridialgland and dorsal wall of Littorina and dorsal wall of Pomaceashow common features typical of transporting epithelia in othermolluscs. The ventricular epicardium of Viviparus shows secondaryspecializations for resorption but lacks an endocytotic canalsystem. The site of organic solute resorption (the most highlyspecialized part of which is the nephridial gland in marinespecies), has been correlated with the anatomy of the renalveins in the four genera, and with other specializations inthe freshwater genera.The difficulty of quantifying rates oftransport of solutes from studies in vitro is discussed. ^*Present address: Dept. of Physiology, The University, DundeeDD1 4HN (Received 31 January 1989; accepted 24 March 1989)     

SPHAERIUM CORNEUM (L.) AND PISIDIUM SPP. PFEIFFER -- THE ECOLOGY OF FRESHWATER BIVALVE MOLLUSCS IN RELATION TO WATER CHEMISTRY

Populations of Sphaerium corneum (L.) and Pisidium spp. weresampled monthly for 13 months, at 11 sites with a wide rangeof water chemistry in N.W. England. Both genera showed almostyear-round reproduction, but the periods of maximum productionshowed between-population variation. S. corneum adults containedspat at different stages of development and spat size was relatedto number in the brood. Multiple regression analysis with 16water physicochemical variables showed the following to be highlysignificant factors (P<0.01) in the distribution of the molluses(factors in order of importance):- S. corneum: HCO₃, K^$, Cl^–, Mg^2$, temperature, Ca^2$, month; Pisidium spp: PO₄^3–, Mg^2$, mud, oxygen, temperature, month. (Received 25 January 1978;     

THE DISTRIBUTION OF FORMYLTETRAHYDROFOLATE SYNTHETASE IN PLANTS, AND THE PURIFICATION AND PROPERTIES OF THE ENZYME FROM PEA SEEDLINGS

1. Formyltetrahydrofolate synthetase (E. C. 6. 3. 4. 3) was foundto be widely distributed in higher plants and the high enzymeactivity was observed in green leaves of Brassica and Alliumspecies, spinach, and in pea seedlings. In pea seedlings, theenzyme activity changed during the course of germination, andmost of the enzyme activity was located in a soluble fractionof the cytoplasm.
2. The enzyme was labile and lost the activityrapidly, even whenstored at 5 in the presence of 0.1 M mercaptoethanol.It was,however, found that ammonium sulfate was very effectivein stabilizingthe enzyme activity.
3. The enzyme has been purifiedapproximately 500-fold from extractsof pea seedlings by treatmentswith ammonium sulfate, protaminesulfate, hydroxylapatite, calciumphosphate gel, and DEAE-cellulosecolumn chromatography.
4. Thepurified enzyme was specific for formate, ATP and FAH₄,andthe Michaelis constants for these reactants were 2.1 10^–2M, 5.1 10^–4 M, and 5.6 10^–3 M, respectively.
5. The optimum pH was found to be 8.0, and the optimal temperaturewas observed at 37. Both NH₄^$ and a divalent cation (Mg^SS orMn^SS) were required for the optimal activity.

¹ Studies on the Enzymatic Synthesis and Metabolism of FolateCoenzymes in Plants. II. (For the previous paper see reference(8)) A part of this paper was presented at the Meeting of theKansai Division of the Agricultural Chemical Society of Japan,Kyoto, January 29, 1966.     

THE INCORPORATION OF 32P ORTHOPHOSPHATE INTO THE PHOSPHOLIPIDS OF ELONGATING AVENA COLEOPTILES

Four phospholipids of Avena coleoptile tissue were identifiedas phosphatidyl inositol, phosphatidyl glycerol, phosphatidylethanolamine and phosphatidyl choline. IAA caused an increase in total uptake of ³²P and incorporationof ³²P in phospholipids. IAA also caused a shift in the proportionsof identified ³²P phospholipids. Incorporation of ³²P into phosphatidylcholine was greater while incorporation into phosphatidyl glyceroland phosphatidyl ethanolamine was less in IAA-treated tissuecompared with untreated control tissue. ¹Contribution No. 338 from the Department of Botany, PennsylvaniaState University and 3001 from the Pennsylvania AgriculturalExperiment Station. ²Present address: Juniata College, Huntingdon, Pennsylvania,U.S.A.     

准噶尔荒漠早春短命植物的光合特性及生物量分配特点

准噶尔荒漠分布的早春短命植物不仅具有十分独特的生物学特点,而且在荒漠植物群落演替、物种多样性维持及土壤改良与防治水土流失等方面具有重要的生态学价值。该文运用Li-6400开放式气体交换光合作用测定系统,对分布于准噶尔荒漠的16种早春短命植物生长盛期的净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)等特征进行了测定,并对其中7种植物与生长相关的生物量分配特征进行了分析。结果表明:1)16种植物的最大P_n、 最大T_r及WUE分别为8.07~35.96 μmol CO₂·m^-2·s^-1、3.16~29.64 mmol H₂O·m^-2·s^-1、0.54~4.26 μmol CO₂·mmol^-1H₂O;种间最大P_n与最大气孔导度(Stomatal conductance, G_s)之间存在正相关关系,其相关系数为0.77(p<0.05),线性回归斜率为26.36 μmol·mmol^-1;从光合速率对胞间CO₂浓度及光量子通量密度的响应曲线来看,这类植物的表观CO₂补偿点均在4~5 Pa之间(28~30 ℃),表观羧化效率为0.64~1.86 μmol CO₂·m^-2·s^-1·Pa^-1,表观量子效率为0.05~0.06。2)从生物量分配来看,所测植物的个体生物量为0.05~0.39 g;单株总叶面积为 3.24~51.40 cm²;单位叶面积干重为0.40~0.77 g·m^-2,根在总生物量中所占比例为5.72%~19.43%,单株叶面积比在2.92~9.00 m²·kg^-1之间。种间根所占生物量的比与对应的WUE之间的比较分析结果表明,二者之间存在显著的正相关关系,其相关系数r为0.93(p<0.01)。这些结果表明,所观测的早春短命植物具有典型的C₃植物特征,相比其它类型的荒漠植物具有较高的单位叶面积P_n、高T_r及低WUE,并且在生长发育过程中表现出很低的根/地上生物量比、较高的叶面积比和单位叶面积干重,说明它们具有相对高的生长速率,这与其生长发育节律相一致,反映了它们与准噶尔荒漠环境相适应的特点。     

EVOLUTION OF THE CASUARINACEAE: MORPHOLOGICAL COMPARISONS OF SOME EXTANT SPECIES

The Casuarinaceae consists of the 4 genera Gymnostoma, Ceuthostoma, Casuarina and Allocasuarina. All the genera are found living today in Australia, Malaysia, Melanesia, and Southeast Asia. An abundant and widespread fossil record of the genus Gymnostoma is known from New Zealand, Argentina, South Africa, and Australia. This paper provides a compilation of basic vegetative and reproductive morphological data of the 4 genera of the Casuarinaceae with special emphasis on these features in Gymnostoma. The features are presented in tabular form and the data are compared and discussed. Most of the genera can be clearly distinguished by the morphology of their vegetative and reproductive organs. Species differences within the extant genera often are difficult to distinguish; therefore, comparative systematic analysis of these fossils from fragmentary and incomplete remains ranging through time will be very difficult, and care must be taken when interpreting evolutionary trends from them.     

A SYNOPSIS OF THE GENERA AND SPECIES OF THE TRIBE THELEBOLEAE (= PSEUDOASCOBOLEAE)

Examination of genera of the Pseudoascoboleae (Ascomycetes, Discomycetes, Ascobolaceae) revealed that many were polytypic. Characters presently used to distinguish these genera are considered to be artificial and true relationships cut across accepted generic lines. Of the genera treated, Thecotheus and parts of Ascophanus, since their asci blue in iodine and their spores bear callose-pectic markings, are considered more closely related to the Pezizeae. Other genera are excluded from the Pseudoascoboleae because of other striking characters. Since the Pseudoascoboleae is shown to be an artificial grouping, it is proposed to abandon the name, using instead the tribe name Theleboleae, placed in the Pezizaceae rather than the Ascobolaceae, for all of those genera with asci that do not blue in iodine, with smooth, elliptical spores without oil guttules, and with eight-spored and multispored species. Four new genera are described: Iodophanus, for species of Ascophanus with iodine-positive asci; Coprotus, for segments of Ascophanus and Ryparobius; Caccobius, for species intermediate to Ascozonus and Thelebolus; and Trichobolus, for the setose members of Thelebolus. The species of Ryparobius not belonging to Coprotus are transferred to Thelebolus.     

DEGRADATION AND FORMATION OF SULFOLIPID OCCURRING CONCURRENTLY WITH DE- AND RE-GENERATION OF CHLOROPLASTS IN THE CELLS OF CHLORELLA PROTOTHECOIDES

1. It has been demonstrated that when the cells of Chlorella protothecoidesare grown mixotrophically under illumination in a medium richin nitrogen source (urea) and poor in glucose, the normal greencells are obtained, while in a medium rich in glucose and poorin the nitrogen source, entirely chlorophyll-less cells withprofoundly degenerated plastids ("glucose-bleached" cells) areproduced, irrespective of whether in the light or in darkness.The "glucose-bleached" cells turn green with regeneration offully organized chloroplasts when incubated in a nitrogen-enrichedmedium in the light ("light-greening"), while in the dark theybecome pale green with formation of only partially organizedchloroplasts ("dark-greening"). When, on the other hand, thegreen cells are transferred into a medium enriched with glucose,they are bleached fairly rapidly with degeneration of chloro-plastsin the light as well as in darkness ("bleaching"). Using ³⁵Sas a tracer, investigations were made on the changes of contentsof the algal cells in sulfolipid and other sulfur compoundsduring the processes of the greening and bleaching.
2. By determiningthe radioactivities of chromatographically separatedsulfur-containingcompounds of the uniformly ³⁵S-labeled green("G") and "glucose-bleached"("W") cells, it was found thatthe concentration of a speciesof sulfolipid (discovered byBENSON et al.) as well as thoseof glutathione, sulfotriosesand most of the other sulfur-containingcompounds were at least5 times higher in the "G" cells thanin the "W" cells, whilesulfoquinovosyl glycerol was presentin approximately equalamounts in the two types of cells.
3. Phospholipidcontents and compositions in the two types of algalcells werefound to be practically identical.
4. The sulfolipid contentof algal cells increased and decreasedalmost in parallel withthe processes of greening and bleaching,respectively.
5. Studyingthe mode of incorporation of radiosulfate into varioussulfurcompounds of algal cells during the processes of "light-anddark-greening" and "bleaching" (lasting about 70 hr), itwasfound that active ³⁵S-incorporation into sulfolipid occurredthroughout the process of "light-greening," while in the "dark-greening"and "bleaching" the active incorporation abruptly ceased afterthe initial 24 hr period of experiments. It was suggested thatthe biosynthesis of the sulfolipid is closely related to theformation of photosynthetic apparatus in chloroplast.
6. Whenthe ³⁵S-labeled green cells were bleached in a medium containingno radiosulfate, the ³⁵S-sulfolipid and most of other ³⁵S-sulfurcompounds decreased markedly but the ³⁵S-sulfoquinovosyl glycerolincreased considerably. It was inferred that the deacylationof the sulfolipid, a surfactant lipid, with formation of watersoluble sulfoquinovosyl glycerol may be a cardinal event ofbleaching process, causing a disintegration of the intact architechtureof photosynthetic apparatus.
7. Based on these observations itwas concluded that the sulfolipidis an integral component ofphotosynthetic structure.

¹This work was partly reported at the Symposium on Biochemistryof Lipids, sponsored by the Agricultural Chemical Society ofJapan, Sapporo, July, 1964.     

西双版纳热带森林树种幼苗的组成、空间分布和旱季存活

林下树种幼苗是森林生态系统的一个重要组成部分, 在森林的自然更新过程中发挥着重要作用。于2007年10月底在西双版纳20 hm²热带森林动态监测样地内设置了450个幼苗样方(1 m²), 对样方内的树种幼苗(胸径＜1 cm)进行了调查, 并观测了当年的实生苗(H≤30 cm)在2007~2008年旱季期间的存活变化。结果表明, 该区森林林下树种幼苗的组成比较丰富, 但个体数在物种间的分布极为不均匀。除4.17%的幼苗个体未鉴定外, 调查到的已知树种幼苗共计6 367株, 隶属于49科116属161种, 并且Simpson、Shannon-Wiener和Pielou指数分别达到了0.69、2.29和0.45。个体数少于5株的幼苗贡献了50.31%的物种数; 在1 m²的样方尺度上, 幼苗密度和种丰富度两者的平均值分别为(14.15±0.72)株·m^-2和(3.73±0.10)种·m^-2(Means±SE, n=450); 优势幼苗为望天树(Parashorea chinensis)、短刺锥(Castanopsis echidnocarpa)和假海桐(Pittosporopsis kerrii)等, 它们的空间分布格局与地形、海拔和母树分布三者之间存在着密切的相关性; 旱季期间, 幼苗的死亡比例较大(26.49%), 主要集中在优势幼苗。幼苗在干旱胁迫环境下的死亡格局表现出了明显的种间差异: 香花木姜子(Litsea panamanja)和望天树两优势幼苗的死亡率分别为62.65%和35.87%, 而假海桐和蚁花(Mezzettiopsis creaghii)等7种优势幼苗的死亡率较低(＜ 9%), 除望天树等13种优势幼苗外, 其余692株幼苗(共129种)仅死亡了10.40%, 而且有91种幼苗均没有发生死亡。幼苗间的存活差异有待于从种子大小、幼苗的形态和生理特性及其所在空间位置的生境特征等多方面开展深入的研究。     

COMPARATIVE STUDIES OF THE NODAL AND VASCULAR ANATOMY IN THE NEOTROPICAL CYATHEACEAE. I. METAXYA AND LOPHOSORIA

Comparative studies of the nodal and vascular anatomy in the monotypic genera Metaxya and Lophosoria are discussed as they relate to the taxonomy and phylogeny of the Cyatheaceae. Both genera are distinctive and primitive with respect to habit, stem and petiole indument, stelar pattern, and nodal anatomy. Metaxya possesses a prostrate, dorsiventral rhizome, whereas a short, upright radial stem occurs in Lophosoria. Trichomes occur on the stems and leaf petioles of these genera. Both Metaxya and Lophosoria have a spiral phyllotaxy, and adventitious buds occur on the petiole bases. The stelar pattern is basically a siphonostele, although frequently a dictyostele is found in Lophosoria. Accessory bundles are lacking in both genera. A characteristic petiole pattern is found in these genera, with an increase in complexity from an undivided strand in Metaxya to the three-parted petiole pattern in Lophosoria. Data from nodal and vascular anatomy indicate that these taxa are distinct from the other genera in the Cyatheaceae and belong in an independent position at the base of the Cyatheoid line, although in some respects an affinity to members of the Dicksoniaceae is indicated.     

COMPONENTS OF THE ELECTRON-TRANSFERRING SYSTEM IN ACETOBACTER SUBOXYDANS AND RECONSTRUCTION OF THE LACTATE OXIDATION SYSTEM

1. Cytochromes a₁⁵⁹⁰, b⁵⁶⁰, c₁⁵⁵⁴ and c₁⁵⁵² were isolated andpurifiedfrom a strain of Acetobacter suboxydans. The proceduresusedwere described in detail.
2. The main cytochrome band at550-560 mµ in intact cellssplitted at liquid air temperatureinto two bands, 551 mµ(strong) and 559 mµ (weak).
3. Optical and physiological properties of the four cytochromeswere investigated. Lactic dehydrogenase activity was found tobe associated with cytochrome c₁⁵⁵⁴. The two c₁-type cytochromes,especially cytochrome c₁⁵⁵⁴, persisted in their reduced formafter the purification through many steps.
4. By some combinationsof isolated components reconstruction ofthe oxygen uptake systemcould be realized.
5. The oxygen-consuming activity of purifiedoxidase preparationswas accelerated by a-tocopherol but notby Emasoll 4130 andTween 80.
6. Some discussions were made onthe nature of terminal oxidase,the role of cytochrome c₁⁵⁵²in the electron-transport system,and persistence of reducedstate of c₁-type cytochromes.
7. A possible scheme of the electron-transferringsystem of Acetobactersuboxydans was presented.

(Received May 16, 1960; )     

PENETRATION OF SUGARS FROM THE CHEMOSENSORY HAIR TIP IN THE FLESHFLY

(1) The penetrations of ¹⁴C-D-glucose and 3-O-methyl-¹⁴C-D-glucoseinto the isolated head of the fleshfly, Boettcherisca peregrina,from the tip of the longest chemosensory hair on the labrumwere investigated. (2) Both ¹⁴C-D-glucose and 3-O-methyl-¹⁴C-D-glucosepenetrated into the hair almost linearly with time and movedrapidly into the labrum. The isotopic activity was finally detectedin the head. (3) The isotopic activity of the hair dipped into¹⁴C-D-glucose solution increased in the preparation which hadbeen pretreated with 7.5 x 10^–2M colchicine for 30 min,whereas in the case of 3-O-methyl-¹⁴C-D-glucose no effect by7.5 x 10^–2M colchicine was found. (4) Both ¹⁴C-D-glucoseand 3-O-methyl-l4C-D-glucose which penetrated from the poreof the hair tip were detected in the dendritefree lumen andin the dendrite-containing lumen of the chemosensory hair. (5)These results suggest that D-glucose not only moves in the dendrite-freelumen and the dendrite-containing lumen but also in the dendrite(s).The suggestive results that 3-O-methyl-D-glucose moves in thedendrite(s) could not be obtained. ^*Present address: Department of Physiology, Medical Collegeof Miyazaki, Miyazaki, Japan.     

INVESTIGATION OF THE ACIDIC ALLOMONE OF THE GASTROPOD MOLLUSC PHILINE APERTA BY MEANS OF ION CHROMATOGRAPHY AND HISTOCHEMICAL LOCALISATION OF SULPHATE AND CHLORIDE IONS

Improved methods of collection of acidic allomones from theskin of the gastropod mollusc Philine aperta minimised contaminationby the anions of sea water and of blood. Neat allomone extractsremained stable in the laboratory for up to 15 months at 5–8°C,having a pH value of 2–3. Diluted extracts (1: 9 or 1:99) gradually lost their activity. Analyses by the Dionex H.P.ion chromatography apparatus showed that organic ions were presentonly in trace quantities in the allomone samples, and the principalinorganic anions were chloride and sulphate (their concentrationsapproached parity in the purest preparations). Measurementsof Cl^– varied in different samples from 2062 to 3989 p.p.million, and of SO₄^2–from 1272 to 3152 p.p. million. TheSO₄^2- CI^- ratios varied from 0.62 to 0.84. New observations are presented on the rate of in situ precipitationof BaSO₄ in preparations of the skin of Philine. The rate ofpenetration of BaCl₂ into the skin was approximately linear,even when the animal had become moribund (30 min). BaSO₄ crystalgrowth increased during the first 30 min of exposure, but laterdeclined, for reasons that are not clear. The method yieldedclear outlines of the acid sacs in histological preparations. A silver nitrate irrigation method was devised in order to investigatechloride ions in the acidic epithelium of Philine. The advanceof AgNO₃ into the tissue was usually smooth-fronted, but siteswere evident where the acid sacs had acted as channels for penetration.The silver deposits took the form of uniform small particles,often precipitated against the inner wall of an acid sac, butsometimes forming a central cluster. The method was of valuein building up a picture of structural relations as well asthe chemical composition of the acid sacs of Philine (Received 18 February 1985;     

IONIC COMPOSITION OF THE CYTOPLASM OF NITELLA FLEXILIS

The K, Na and Cl concentrations of the chloroplast layer andthe flowing cytoplasm of Nitella flexilis have been determinedby applying an internal perfusion technique, which enabled usto avoid contamination of ions from the cell sap. K, Na andCl concentrations of the chloroplast layer are 110, 26 and 136mM and those of the flowing cytoplasm are 125, 5 and 36 mM respectively.The cell sap contains 80 mM K, 28 mM Na and 136 mM Cl. Althoughthere are some variations in these values among samples, theflowing cytoplasm is rich in K and poor in Cl and especiallyin Na. The exchange of K and Na across the tonoplasl occursfairly easily (half-time, a few hours), while that of Cl occursextremely slowly (half-time, a few days). ¹This work was supported by Research Grants from the Ministryof Education of Japan     

Investigations of Carbon Transport in Plants: I. THE USE OF CARBON-11 TO ESTIMATE VARIOUS PARAMETERS OF THE TRANSLOCATION PROCESS

A technique is described which enables several components ofthe translocation system to be measured routinely, in vivo andsimultaneously. Plants are exposed to a 1-min pulse of ¹¹CO₂and the movement of the ¹¹C pulse through the plant followedusing an array of scintillation counters. It is possible toestimate the time taken for the ¹¹C to enter the sieve tubes.In addition, the speed of translocation can be obtained frommeasurements of the arrival of the ¹¹C pulse at different positionsalong the translocation pathway. The increasing half-width ofthe pulse as it enters and moves through the sieve tubes givessome indication of the extent of the delays in the differentparts of the translocation system. The short half-life of the¹¹C allows the measurements to be repeated on the same plantseveral times per day. A technique is discussed whereby dataon the movement of ¹¹C could be combined with simultaneous measurementsof the rate of uptake of carbon dioxide to provide an estimateof the rate of movement of carbon.     

青海省三江源区人工草地生态系统CO2通量

 了解三江源人工草地净生态系统CO₂交换(Net ecosystem CO₂ exchange, NEE)的季节变化规律和主要生物因子及环境因子对这些过程的影响将有助于认识青藏高原人工草地生态系统碳循环、生态价值、功能,以及对三江源区的生态安全的重要意义。该研究利用涡度相关技术,于2005年9月1日至2006年8月31日对位于青海腹地的垂穗披碱草（Elymus nutans）人工草地的NEE及生物和环境因子进行观测, 阐明NEE及其组分的动态变化特征和影响因子。三江源区人工草地生态系统的日最大吸收量为2.38 g C·m^－2·d^－1,出 现在7月30日。日间最大吸收率和最大排放率都出现在8月,分别为-6.82和2.95μmol CO₂·m^－2·s^－1。在生长季, 白天的NEE主要受光合有效辐射(Photosynthe tically active rad iation, PAR)变化控制,同时又与叶面积指数和群落多样性交互作用,共同调节光合速率和光合效率的强度。最大光合同化速率为2.46～10.39μmol CO₂·m^－2·s^－1,表观初始光能利用率为0.013～0.070μmol CO₂·μmol^－1 PAR。 在碳交换日过程中,NEE并不完全随着 PAR的增加而增大,当PAR超过某一值（>1 200μmol ·m^－2·s^－1）时,NEE随PAR的增加而降低。受温度的影响,生长季的生态系统的呼吸商Q₁₀（1.8）小于非生长季节的 2.6）。 生态系统呼吸主要受温度的控制,同时也受到叶面积指数的显著影响。生长季昼夜温差大并不利于生态系统的碳获取。 三江源区人工草地生态系统是一个较强的碳汇,为-49.35 g C·m^－2·a^－1。     

THE MORPHOLOGY, ULTRASTRUCTURE AND FUNCTION OF THE FEEDING APPARATUS OF SAYELLA FUSCA (C.B. ADAMS, 1839) (GASTROPODA: PYRAMIDELLIDAE)

Scanning and transmission electron microscopy in conjunctionwith histology and dissection were employed to investigate theforegut anatomy of Sayella fusca (C.B. Adams, 1839), a commonNew England pyramidellid snail. Certain aspects of the feedingapparatus of S. fusca, including the buccal pump and proboscisanatomy, depart from the characteristic pyramidellid plan. Somedifferences such as the position of the introvert/proboscisaperture and the common oral and stylet canal are shared withthe genera Turbonilla, Eulimella, and Pyramidella. Three characteristicsof the feeding apparatus are unique to S. fusca: (1) the buccalpump is not divided into two pouches but exists as a singlemuscular bulb; (2) the entire lumen of the buccal pump, notsimply a portion of it, possesses a cuticular lining; and (3)the salivary ducts never enter the muscular walls of the buccalpump. Histological studies of the salivary gland indicate thatthree types of secretory cells are intermittently distributedthroughout the entire gland rather than characterizing distinctregions as described for other members of the family Pyra-midellidae.In contrast to previous findings, the gland cells of S. fuscaexhibit a merocrine secretion. The taxonomic value of the buccalpump and proboscis morphology are discussed. ^*Present address: Dauphin Island Sea Lab, 101 Bienville Boulevard,Post Office Box 369–370, Dauphin Island, Alabama 36528USA. (Received 9 November 1993; accepted 1 October 1997)     

THE ULTRASTRUCTURE AND FUNCTION OF THE OESOPHAGUS OF PATELLA VULGATA LINNAEUS

The oesophagus of Patella vulgata Linnaeus is divisible intotwo histologically and functionally distinct regions, a centralfood channel and a series of lateral pouches forming the oesophagealglands: both are lined by a glandular ciliated columnar epithelium.Subepithelial mucous cells are restricted to the epitheliumlining the food channel and posterior section of oesophagus,whilst amylase-secreting cells occur only in the oesophagealglands. The activity of the ciliated cells lining the food channelmixes ingested food with saliva and mucus to form a food stringthat is carried towards the stomach. Amylase-secreting cellsproduce an extracellular amylase in the form of proteinaceoussecretory granules, which are released by apocrine secretionwithin cytoplasmic blebs. Release is correlated with periodsof immersion when feeding is possible. The free blebs are carriedout of the pouches and into the food channel where the amylaseinitiates carbohydrate digestion. The oesophageal epitheliumabsorbs tritiated D-glucose by a Na⁺-dependent mechanism inhibitedby 2,4-DNP and phloridzin and the amylase-secreting cells pinocytoseferritin. It is suggested that the oesophagus absorbs smallsolute molecules derived from ruptured algal cells and theirpartially digested polysaccharide storage products. There alsoappears to be pinocytosis of dissolved organic matter. ^*Current address: The R L. Weston Institute for NeurologicalStudiet, University College & Middlesex Medcal School, MortimerSt., London Wl. (Received 8 March 1988; accepted 29 April 1988)     

Studies on the Growth in Culture of Plant Cells: XV. UPTAKE AND UTILIZATION OF URIDINE DURING THE GROWTH OF ACER PSEUDOPLATANUS L. CELLS IN SUSPENSION CULTURE

[2-¹⁴C]-uridine is rapidly taken up by sycamore cells in suspensionculture. A proportion of the radioactivity enters RNA withoutmeasurable delay, whilst the remainder equilibrates with a largepool of phosphorylated compounds, the major radioactive componentof which is 5'-UMP. Both the uracil and cytosine residues ofRNA receive label from [¹⁴C]-uridine and, when the cells aresupplied with high concentrations of uridine, these bases arederived almost exclusively from the nucleoside. [¹⁴C]-uridine is incorporated into RNA at all stages of thegrowth cycle of batch cultures; its continuing incorporation,when the total RNA content of the cells is rapidly decreasing,indicates a high rate of turnover of the total RNA. Long-termlabelling experiments also indicate turnover of RNA during thephase of active cell division and suggest that a large proportionof the degradation products are not re-utilized for RNA synthesis. Sycamore cells degrade [2-¹⁴C]-uridine with release of ¹⁴CO₂.The proportion degraded increases from 25 per cent at an externaluridine concentration of 10^–6M to 75 per cent at 10^–3M. Despite this, nucleic acids are the only macromolecules thatreceive a significant amount of radioactivity from [2-¹⁴]C-uridine.