Chemotaxis in Laminaria digitata (Phaeophyceae): I. ANALYSIS OF SPERMATOZOID MOVEMENT

The chemotactic behaviour of Laminaria digitata spermatozoidsupon stimulation with sex pheromone was studied using videomicroscopyand high speed cinematography. The cells show phobic (‘shock-’)reorientation reactions when perceiving decreasing stimulusconcentrations in a pheromone gradient and are able to adaptto constant concentrations. The phobic responses are executedby regulation of flagellar activity: drastic changes in thedirection of cell movement are induced by rapid deflexions ofthe posterior flagellum. Key words: Laminaria, chemotaxis, pheromone, flagellar movement.     

Lipid Biosynthesis in the Blue-Green Alga (Cyanobacterium), Anabaena variabilis III. UDPglucose:Diacylglycerol Glucosyltransferase Activity in vitro

The synthesis of glyceroglycolipids was studied in membraneand soluble fractions of Anabaena variabilis. The membrane fractionexhibited a high activity of UDPglucose: diacylglycerol glucosyltransferase,but practically no activity of UDPgalactose: diacylglycerolgalactosyltransferase. The glucosyltransferase activity wasmaximal at about pH 7.0 and dependent on Mg²⁺ The Michaelisconstant (K_m) for UDPglucose was 45?10^–6 M. The solublefraction catalyzed the incorporation of galactose from UDP galactoseinto digalactosyl diacylglycerol. These in vitro results werecompatible with the biosynthetic pathway of glyceroglycolipidsin this alga that we previously elucidated on the basis of tracerexperiments in vivo. ¹ Present address: Department of Biology, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan. (Received June 1, 1982; Accepted July 1, 1982)     

Induction of Callus from the Marine Brown Alga Dictyosiphon foeniculaceus

A method for callus induction from an alga was established forthe first time. Callus tissues from the microthallus of themarine brown alga Dictyosiphon foeniculaceus were induced onASP 12-NTA medium of Provasoli (1963) supplemented with 3% mannitol,0.1% yeast extract and 1.5% agar. The addition of auxins andkinetin to the medium did not show any effect on the formationand growth of the callus. (Received November 24, 1981; Accepted March 30, 1982)     

Ecotypic Variation in the Osmotic Responses of Enteromorpha intestinalis (L.) Link.

Young, A. J., Collins, J. C. and Russell, G. 1987. Ecotypicvariation in the osmotic responses of Enteromorpha intestinalis(L.) Link.—J. exp. Bot. 38: 1309–1324. The physiological basis for salt tolerance has been studiedin the euryhaline marine alga Enteromorpha intestinalis. Adaptationto dilute and concentrated seawaters has been investigated inthree separate populations of this alga: marine, rock pool andestuarine. Internal K⁺, Na⁺ and Cl^– levels have been determined usingtracer efflux analyses. K⁺ has been shown to be the major osmoticsolute within this alga. Cellular levels of Cl^– and, inparticular, Na⁺ are low although levels in the cell wall arehigh. Levels of these ions varied considerably between the separateplants; K⁺ levels within marine plants of E. intestinalis aretwo to four times those found in the other populations. Thetertiary sulphonium compound ß-dimethylsulphonio-propionateis maintained at relatively high levels, although it remainsfairly insensitive to change in the external salinity. Changes in the tissue water content and cell volume are large,particularly within the estuarine plants. The thin cell wallsof these plants allow large changes in volume in the diluteconditions experienced in an estuary, while low turgor preventscell rupture. Thicker cell walls and small cells of the marineand rock pool plants assist in tolerating high and low externalosmotic potential—the estuarine plants respond poorlyto concentrated seawater. Key words: Enteromorpha, osmoregulation, ecotypes     

Simulations of the Ontogeny of Spongiophyton, a Devonian Plant

Mathematical representations of the cellular organization anddimensions of Spongiophyton Krusel, a Middle Devonian thallophytewere projected by means of a computer to simulate patterns ofdevelopment and organization. Extrapolation of the cellularpatterns observed on the surface of the fossil may be comparedwith those derived from living plants of which the ontogenycan be directly observed. Spongiophyton is compared in thisrespect with the growth of Protosalvinia (an Upper Devonianplant of enigmatic affinity), Pellia (a thallose liverwort)and Cutleria (a brown alga). The growth pattern of Spongiophytondeveloped by computer shows a closer similarity to that of thepseudoparenchymatous alga Cutleria than to the truly parenchymatousPellia or the fossil Protosalvinia. Computer simulations ofthe growth process throw light on the affinity of Spongiophytonwhich cannot be derived from direct observation of the fossil.Broader applications of computer simulations of tissue organizationand gross morphology are suggested with regard to the studyof living and fossil plants.     

Analysis of Lipids in Prochloron sp.: Occurrence of Monoglucosyl Diacylglycerol

Prochloron contained monogalactosyl diacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyl diacylglycerol, phosphatidylglyceroland, as a minor component, monoglucosyl diacylglycerol, butno phosphatidylcholine. With respect to the lipid and fattyacid compositions, this alga is similar to the blue-green algaerather than the chloroplasts of eukaryotic plants. ¹ Present address: Department of Biology, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan. (Received August 24, 1982; Accepted November 18, 1982)     

The Movement of Hormosira banksii (Fucales, Phaeophyta) Spermatozoids in Response to Sexual Pheromone

The swimming behaviour of Hormosira banksii spermatozoids wasstudied using videomicroscopy under different conditions, includingmovement on glass surfaces, on solvent droplets containing thespecies-specific gamete attractant at different concentrationsand in relation to eggs. The results indicate a chemotaxis mechanisminvolving phobic responses as well as a kinesis in which theturning rate is reduced upon stimulation by pheromone. Preliminarydata on respiration and carbon assimilation of spermatozoidsare also reported. Key words: Hormosira, Fucales, Chemotaxis, Pheromone, Movement     

Studies on Nitrogen Fixation by Blue-green Algae: II. NITROGEN FIXATION BY MASTIGOCLADUS LAMINOSUS COHN

Mastigocladus laminosus Cohn, a blue-green alga of hot springs,has been obtained in pure bacteria-free culture and has beenshown to be capable of fixing elementary nitrogen. This appearsto be the first instance in which this capacity has been demonstratedin a blue-green alga belonging to a family other than the Nostocaceae.     

The Effects of Salinity upon Cellular Volume of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in cell volume of the marine red alga Porphyra purpureahave been investigated using photomicroscopic and radioisotopictechniques. There is an inverse relationship between cell volumeand external salt content. The alga responds to changes in thewater potential of its bathing medium by rapid swelling in hyposalinemedia and shrinkage in hypersaline conditions. Cells P. purpureabehave as osmometers in concentrated sea-waters, obeying theBoyle-Van't Hoff law. A non-osmotic volume, 20–25% ofthe total cell volume in sea-water, can be predicted from thelinear plot of volume versus reciprocal pressure in concentratedsea-water media. In dilute sea-waters the presence of non-rigidcell walls serves to limit any increases in cell volume. Theprimary response to dilution stress is thus an increase in turgor.Cell volume is not returned to its original value followingprolonged immersion in either hyposaline or hypersaline media,showing that the alga does not ‘osmoregulate’ sensustricto.     

Complementary Association of an Endophytic Red Alga and a Shell-encrusting Green Alga

Endophytic filaments of a red alga in the shell-encrusting greenalga Pseudulvella consociata S. & G. collected from subtidaland intertidal habitats in the San Juan Islands, WashingtonState, U.S.A., have been identified as Audouinella sparsa (Harvey)Dixon. The association appears to be complementary. Pseudulvella consociata, Audouinella sparsa, alage, Rhodophyta, Chlorophyta, endophyte     

LEARNING AS A FACTOR IN DIET SELECTION BY ELYSIA VIRIDIS (MONTAGU) (OPISTHOBRANCHIA).

Elysia viridis (Montagu) occurs naturally in populations feedingon the fleshy, siphonalean green alga Codium or on the coarse,filamentous green alga Chaetomorpha. Only about half of theE. viridis transferred from Codium to Chaetomorpha in the laboratorywere able to learn to feed on this alga. Handling time decreasedsignificantly during the learning-period. All E. viridis transferredfrom Chaetomorpha to Codium in the laboratory were able to learnto feed on the latter alga. Handling time also decreased withexperience in these animals. Ingestive conditioning occurredin animals transferred from Chaetomorpha to Codium. These animalshad to go through a learning-period again when they were offeredChaetomorpha after 6–9 weeks with Codium Ingestive conditioningwas also evident from preference experiments; animals preferredthe food they had been kept on prior to the experiments. Thesefindings are discussed in relation to optimal diet theory. (Received 14 December 1987; accepted 22 March 1988)     

A Model of Leaf Tissue Growth, Acclimation and Senescence

A model for leaf growth, acclimation and senescence is described.The approach is mechanistic and the model, which is carbon-based,has eight state variables: substrate carbon and machinery carbon;primary, secondary and cross-linked cell wall; and two whichcorrespond to parameters of the photosynthesis light responsecurve—namely, the initial slope and light-saturated photosyntheticrate. The model is used to simulate responses to light and temperature,and predicts quantities such as final leaf area, the time atwhich the leaf becomes an exporter, senescence time, and thetwo photosynthetic parameters. The results are in good qualitativeagreement with observational responses that have been reported.The model also simulates the effects of changing the light environmentof a mature leaf: for instance, it predicts that increasingthe light level can increase leaf longevity and vice versa,although, in general, leaves grown continuously in high lighthave a shorter life than leaves grown continuously in low light. Leaf, model, growth, senescence, acclimation     

Cytokinins from the tRNA of the Red Alga Porphyra perforata J. Ag.

Isopentenyladenosine and cis-zeatin riboside have been identifiedby GC-MS from the tRNA of a red alga Porphyra perforata. (Received March 12, 1991; Accepted December 7, 1991)     

A Yellow Marine Chiamydomonas: Morphology and Pigment Composition

A unicellular yellow marine microorganism was isolated fromwater samples collected in Hachinohe Harbor, on the northerncoast of Japan, and Off Tsushima Island, on the western coastof Japan, and its structure and pigment composition were investigated.Light and electron microscopy indicated that the alga belongsto the genus Chlamydomonas and it is identified as C. parkeae. Pigment analysis by high-performance liquid chromatography revealedthe presence of 2,4-divinylprotochlorophyllide (DVP) as a thirdchlorophyll in addition to chlorophylls a and b. Such a pigmentcomposition has been reported previously only for some prasinophytesamong autotrophically grown algae. With respect to carotenoids,the alga contains, in addition to the carotenoids of higherplants (neoxanthin, violaxanthin, zeaxanthin, lutein, ß-carotene),siphonaxanthin and siphonein (siphonaxanthin dodecenoate); thelatter have been detected previously only in marine benthiculvophycean algae and in some prasinophytes. However, the coexistenceof DVP, siphonein and siphonaxanthin in a single species hasnever been reported for either ulvophycean or prasinophyceanalgae. In addition to siphonaxanthin dodecenoate, the alga wasfound to contain two "siphoneins", siphonaxanthin decenate andsiphonaxanthin octanoate. ³ Present address: Nippon Roche Research Center, Kajiwara, Kamakura,Kanagawa, 247 Japan.     

The role of hypersalinity in the persistence of the Texas 'brown tide' in the Laguna Madre

A brown tide bloom of the alga Aureoumbra lagunensis was presentwithout interruption in the Laguna Madre of Texas from January1990 through October 1997. This is the longest continual phytoplanktonbloom of which we are aware. Although the factors leading tothe initiation of this bloom have been well documented, thefactors contributing to its persistence are still being investigated.Two physical characteristics of the Laguna Madre may play animportant role: the long turnover time for waters in this coastallagoon (–1 year) and the hypersaline conditions that usuallyexist (40–60 PSU) due to evaporation exceeding precipitation.In this study, we examined the effects of salinity on the growthrates of the brown tide alga and on the growth of one of itsprotozoan grazers. Historical data from before the onset ofthe brown tide provide evidence for the suppression of microzooplanktonpopulations and mesozooplankton growth caused by hypersalinity.The brown tide alga will grow in a remarkably wide range ofsalinities ranging from 10 to 90 PSU. Maximum growth rates areachieved at salinities ranging from 20 to 60 PSU. One commongrazer on the brown tide alga, the heterotrophic dinoftagellateOxyrrhis marina, was found to grow more slowly under hypersalineconditions. The normally hypersaline conditions of the LagunaMadre may, therefore, favor the brown tide alga over other phytoplanktonspecies that do not grow well under hypersaline conditions,and also suppress the growth and feeding rates of potentialgrazers.     

Direct distributional response in Daphnia pulex to a predator kairomone

The hypothesis that zooplankton are capable of direct and differentiatedbehavioural responses to different biotic factors was tested.A multichamber flow-through technique enabled predeterminedfood levels of the green alga Scenedesmus acutus to be maintainedconstant throughout the experiments. By adding water from aculture of fourth instar Chaoborus flavicans larvae to one ofthe end chambers, a concentration gradient of the chemical substancewas established across the parallel chambers. Evidence is presentedfor a direct avoidance response in the water flea Daphnia pulexto a substance released by the predatory midge C.flavicans.This response occurs in the absence of visual cues and is independentof food availability. Finally, the results indicate that swarmingin D.pulex may occur in the absence of both light and predatorscent, but is influenced by food concentrations.     

A Biochemical and Autoradiographic Study of the Role of the Golgi Bodies in Thecal Formation in Platymonas tetrathele

Hydrolysates of the theca of Platymonas tetrathele have shownthat it is a pectin-like material with galactose, galacturonicacid, and arabinose as the major components. Exogenous glucoseor galactose taken up by the alga is incorporated into the thecaand into starch, but is not respired. Electron microscopic autoradiographyhas been used to trace the incorporation of tritiated glucoseinto starch and into polysaccharides in the Golgi bodies andsubsequentlyinto the theca. The extracellular polysaccharideproduced by this alga is similar to the theca in compositionand may have a common origin.     

Changes of algal biomass as carbon, cell number and volume, in bottles suspended in Lake Constance

Changes of algal biomass, as carbon, cell numbers and volumewere determined for phytoplankton of Lake Constance suspendedin situ in 2 l glass bottles. Phytoplankton placed at the 6%surface penetrating light level (photosynthetically availableradiation) were close to the compensation depth for growth estimatedas total particulate carbon and total cell volumes. Cell countsof individual alga] species however, showed appreciable growthof diatoms offset by the decline of flagellates. Bottles suspendedat two shallower depths in a separate experiment showed somegrowth of all species and indicated a vertical niche separationof growth of Rhodomonas minuta Skuja and R. lens Dascher andRuttner in accordance with their vertical distribution. ^*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP) First International Workshop heldat the Limnological Institute, University of Konstanz, in April1982.     

A Mutational Study of the Nitrogen-fixing Blue-Green Alga Anabaena doliolum

A heterocystous, non-nitrogen-fixing mutant of the nitrogen-fixingblue-green alga Anabaena doliolum has been isolated followingtreatment with nitrosoguanidine and UV radiation. Some reversiblevariations in the habit and morphology of the alga were inducedfollowing its treatment with nitrosoguanidine.     

Measurement of Simultaneous Oxygen Evolution and Uptake in Hydrodictyon africanum

Oxygen uptake and evolution in illuminated and darkened cellsof Hydrodictyon africanum have been measured using ¹⁸O₂ massspeetrometry. Under conditions of light and CO₂ saturation forphotosynthesis, light stimulates oxygen uptake more than two-fold.This stimulation is prevented by DCMU but is not affected bycyanide or the uncoupler CCCP. The data are consistent withthe occurrence of a pseudocyclic electron flow and photophosphorylationin vivo in H. africanum; this agrees with data on light-dependentactive phosphate influx in this alga. Part of the light-stimulatedoxygen uptake might be involved in glycolate synthesis by thepathway proposed by Coombs and Whittingham.