AGGLUTINATION OF THE CHLOROPHYCEAN FLAGELLATE DUNALIELLA TERTIOLECTA BY TREATMENT WITH LECTINS OR DIVALENT CATIONS AT ALKALINE pH1

Washed cells of Dunaliella tertiolecta Butcher became immobile and agglutinated upon exposure to 100–400 μ/mL lectins in NaCl solution. The agglutinations were strongest with Limulus polyphemus agglutinin and wheat-germ agglutinin, moderate with soybean agglutinin and weakest with Concanavalin A. All lectin-induced agglutinations were inhibited or mitigated by the simultaneous presence of specific lectin-binding sugars. The differential sensitivity of the alga to these lectins suggested that sialic acid and/or N-acetyl-D-glucosamine might be the predominant lectin-receptor sugars in the algal surface coat, with N-acetyl-D-galactosamine likely present as a lesser component. In the absence of lectins, the divalent cations Mg²⁺, Ca²⁺ or Mn²⁺ also caused agglutination, but this process required an alkaline pH of at least ca. 8.6–8.9. Such cation-induced agglutination was reversibly inhibited by the cation complexing agent EDTA as well as by lowering the pH below 8.0. SEM observations of the agglutinations revealed random flagellar attachments as well as direct body contact between agglutinated cells.     

UNIQUE LOCATION OF THE PHYCOBILIPROTEIN LIGHT-HARVESTING PIGMENT IN THE CRYPTOPHYCEAE1

The cryptophyte algae, or cryptomonads, comprise a small algal group with a unique photosynthetic apparatus. Both a chlorophyll a/c₂ light-harvesting complex and a phycobiliprotein antenna (which can be either phycoerythrin or phycocyanin) are present, with the phycobiliprotein playing the major role in harvesting light for photosynthesis. Longstanding circumstantial evidence suggested that, in cryptophytes, the phycobiliprotein is located in the intrathylakoid space (thylakoid lumen) rather than on the outer surface of the thylakoid as part of a phycobilisome as in other algae. We used immunogold labeling to show conclusively that 1) the phycoerythrin (PE) of the cryptophyte Rhodomonas lens Pascher and Ruttner is located within the intrathylakoid space, 2) the PE is not exclusively bound to the thylakoid membrane but instead is distributed across the thylakoid lumen and 3) a fraction of this PE is tightly associated with the thylakoid membrane. The thylakoids are not everted to compensate for this unusual arrangement. The location of the major light-harvesting pigment on the “wrong” side of the otherwise very normal photo-synthetic membrane is unexpected, unique to the cryptophytes, and, remarkably, does not impair the photosynthetic abilities of this organism. A model is presented which incorporates these results -with previous information to give a complete structural picture of the cryptophyte light-harvesting apparatus.     

MITOSIS,CYTOKINESIS, THE DISTRIBUTION OF PLASMODESMATA,AND OTHER CYTOLOGICAL CHARACTERISTICS IN THE ULOTRICHALES,ULVALES, AND CHAETOPHORALES: PHYLOGENETIC AND TAXONOMIC CONSIDERATIONS1

The results of previous research and a present survey of some of the cytological characteristics of 18 additional genera and 34 additional species are presented and discussed from the viewpoint of phylogenetic and taxonomic significance. A preliminary attempt is made to place these, algae, in 4 orders on the basis of comparative cytology, and in particular on the basis of variation in mitosis and cytokinesis and the distribution of plasmodesmata. Consideration is given to the evolution of the phragmoplast and to the hypothesis that the Chaetophorales are related to the ancestry of land plants.     

STRATEGIES AND KINETICS OF PHOTOACCLIMATION IN THREE ANTARCTIC NANOPHYTOFLAGELLATES1

Three Antarctic nanophytoflagellates (two cryptophyte species and a Pyramimonas sp.) were compared for their capacity to phiotoacclimate and for their kinetic responses in changing photic environments. Division rate, cell size cellular fluorescence, and chlorophyll a content were measured steady and transient states of semi-continuous cultures maintain at 1.0° C. Of all parameters tested, cell size was most affected by irradiance. Acclimation kinetics were modeled using a first-order equation. Rates of change in cell size following shifts in irradiance were comparable with rates of change in chemical composition reported for temperate algae. Response rates of cellular in vivo red and orange fluorescence were lower. In many cases, however, responses could not be described by the first-order kinetic model. Division rates remained high for approximately 3 days following a shift down in irradiance, after which new division rates were established. The nanoflagellates studied here appear to respond to small irradiance perturbations at low rates. However, they may fail to adapt and abrupt changes in photon flux density (PFD). When shade-adapted (25 μmol, m^?2, m^?2, s^?1) cells were exposed to high PFD (400 μmol, m^?2, s^?1) for 1–3 days, cell were incapable of readapting division rate and pigment content to the initial irradiance condition (25 μmol, m^?2, s^?1) for about 1 month following the shift-down step. The ecological role of the kinetics of photoacclimation in nanophytoflagellate growth performance in Antarctic ecosystems is discussed.     

THE CONTRACTILE VACUOLE AS AN ENDOCYTIC ORGANELLE OF THE CHLAMYDOMONAD FLAGELLATE GLOEOMONAS KUPFFERI (VOLVOCALES,CHLOROPHYTA)1

The endomembrane system of the chlamydomonad flagellate, Gloeomonas kupfferi Skuja, consists of a complex network of endoplasmic reticulum, Golgi bodies, and various vacuoles. One of the more distinct vacuolar components is the contractile vacuole (CV) complex, which consists of two anterior contractile vacuoles that expand/contract approximately every 30 s. In this study, experimental cytochemical labeling was performed to help elucidate possible endocytic/membrane recycling mechanisms in Gloeomonas and the possible role of the contractile vacuole in this process. When incubated with 0.5 mg · mL^?1 cationic ferritin for short periods of time (2–60 min), labeling follows this route: inner membrane of CV, globular deposits in the CV and associated vesicles, and ultimately the terminal trans face cisternae of the Golgi apparatus (GA). Similar incubations with Lucifer yellow and concanavalin A—gold conjugates support distinct uptake of exogenous ligands by the CV and associated vesicles. Our results suggest that the contractile vacuole may be a site of endocytosis and that the trans GA loci may be a key site of membrane recycling.     

VOLVOX POCOCKIAE,A NEW SPECIES WITH DWARF MALES1

Volvox pocockiae is described as the second species in the section Janetosphaera. The somatic protoplasts are connected by cytoplasmic strands approximately the same diameter as flagella, and the construction of the spheroid is identical to that of V. aureus. Asexual reproduction by the division of gonidia differs from that in V. aureus in the enlargement of the gonidium prior to its division to form the embryo. Sexual reproduction is very similar to that in V. spermatosphaera, a species in the section Merrillosphaera without cytoplasmic connections. Dwarf males are formed in the posterior end of the parental spheroid, and, as in V. spermatosphaera, the dwarf males are composed exclusively of androgonidia with no sterile somatic cells. Females are facultatively asexual spheroids, the gonidia of which function as eggs. The single biflagellate zoospore produced by the germinating zygote undergoes cleavage to form a germling spheroid. The differentiation of gonidia in the asexual embryo and in the germling spheroid is evident only after inversion and enlargement of the spheroid have begun.     

青藏高原一些种子植物的核型研究

本文对产于青藏高原地区的１１个属１２个种植物进行了核型分析。大部份种为首次报道。它们的核型公式和核型不对称性如下：云雾雀儿豆Ｃｈｅｓｎｅｙａ ｎｕｂｉｇｅｎａ（Ｄ．Ｄｏｎ）Ａｌｉ,为２ｎ＝１６＝１０ｍ＋６ｓｍ,属２Ｂ型;变色锦鸡儿Ｃａｒａｇａｎａ ｖｅｒｓｉｃｏｌｏｒ Ｂｅｎｔｈ．,为２ｎ＝１８＝１４ｍ＋４ｓｍ,２Ｂ型;异叶青兰Ｄｒａｃｏｃｅｐｈａｌｕｍ ｈｅｔｅｒｏｐｈｙｌｌｕｍ Ｂｅｎｔｈ．,     

ULTRASTRUCTURE OF THE FLAGELLA OF THE COLORLESS PHAGOTROPH PERANEMA TRICHOPHORUM (EUGLENOPHYCEAE).II. FLAGELLAR ROOTS1

Peranema trichophorum (Ehrenberg) Stein, a colorless phagotrophic euglenoid flagellate, has a typically euglenoid microtubular root complement. Striated root components, relatively uncommon in euglenoids, are connected to the basal bodies and to a microtubular root. The flagellar system of Peranema consists of three unequal microtubular roots which extend anteriorly beneath the reservoir membrane, and narrow-band striated roots (periodicity = 29–33 nm) which connect one of the four basal bodies to the movable rodorgan of the feeding apparatus. An inter basal body striated fiber forms a three-way connection between one particular microtubular root, a flagellar basal body, and the striated roots. A striated fibril (periodicity = 18–25 nm), which may be an extension of the striated root system, extends beneath the reservoir membrane. Associated with the striated fibril and the striated roots are cisternae of smooth endoplasmic reticulum.     

CHLAMYDOMONAS GYMNOGAMA,A NEW HOMOTHALLIC SPECIES WITH NAKED GAMETES1

The life history of a new homothallic species of Chlamydomonas is described. Sexual reproduction involves the pairing and fusion of naked gametes.     

东北产6种苔类植物细胞学观察

本文对东北产6种苔类植物进行了染色体数目报道,它们是阔叶裂叶苔Lophoziaexcisa,皱叶裂叶苔L.incisa,倾立裂叶苔L.ascendens,细裂瓣苔Barbilophozia barbata,裂萼苔Chiloscyphus polyanthus,指叶苔Lepidozia reptans,其染色体数目均为n=9。其中阔叶裂叶苔和倾产裂叶苔为首次报道。     

LEAF PARENCHYMA WITH TRANSFER CELL-LIKE CHARACTERISTICS IN THE MOSS,POLYTRICHUM COMMUNE HEDW

Mature leaves of Polytrichum commune Hedw. were examined in regard to structural features and possible solute transport mechanisms. The leaf bundle is organized into several parenchyma layers which are termed passage cells, deuters, and socci. The deuters (leptoids of some authors) are large-diametered parenchymatic elements which exhibit papillate wall ingrowths characteristic of transfer cells. The deuter cytoplasm is typical of transfer cells, including a large number of mitochondria, numerous polysomes, and a peripheral network of ER associated with the wall ingrowths. Deuters show little ultrastructural similarity to leptoids (sieve elements of bryophytes) of the stem. Socci parenchyma and passage cells have a distinct inner wall layer which is convoluted in places, and therefore, these cells as well as the deuters might be involved in intensive short-distance fluxes of solutes. A possible translocation mechanism involving an active, carrier-mediated loading of leaf parenchyma is discussed in relation to these structural features.