Observations on Furcellaria fastigiata (L.) Lam. forma aegagropila Reinke in Danish waters together with a note on other unattached algal forms

Summary The unattached populations of Furcellaria fastigiata forma aegagropila in Danish waters exhibit characteristics which are paralleled to a remarkable degree by those possessed by communities of unattached algae in other parts of the world. These characteristics include sterility, multiplication by vegetative means, and the adoption of a form, devoid of holdfast organs, which commonly has a globular or subglobular habit suited to rolling about on the sea bottom. Branching is often profuse and patent and may be accompanied by a thallus diameter far smaller than that of the attached form. Vegetative multiplication may be effected by fragmentation, and, as in F. fastigiata forma aegagropila, by a small accessory lateral branches which function as propagulae. The latter originate in a manner somewhat different from that of the axial regenerated branches produced on decapitated thalli and on thalli which have been more than superficially wounded. Evidence suggests that much of the unattached population of this latter species in the central Kattegat is made up of diploid thalli.All loose lying forms ultimately originate from attached species, which possess or can adopt certain characteristics which enable them to survive in the unattached state.

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Résumé Les colonies sans attaches de Furcellaria fastigiata forma aegagropila dans les eaux danoises montrent des carat`eres qui sont parallèles à un degré remarquable à ceux possédés par d'autres communautés d'algues flottantes dans les autres parties du monde. Ces caractères comprennent la stérilité, la multiplication par des moyens végétatifs, et l'adoption d'une forme, dépourvue d'organes de préhension, généralement sphérique ou quasi sphérique, adapté à se mouvoir sur le fond de la mer. La formation de branches est souvent abondante et évidente et peut être accompagnée d'un diamètre thallique bien plus petit que celui de la forme fixe. La multiplication végétative peut être effectuée par fragmentation, et comme chez F. fastigiata forma aegagropila, par moyen de petites branches latérales accesoires qui fonctionnent comme des propagulae. Ces dernières prennent leur naissance d'une manière quelque peu différente de celle des branches axiales régénérées produites sur thalles décapités et sur thalles qui ont été plus que superficiellement blessés. Léxpérience suggère que beaucoup de colonies flottantes de cette dernière espèce dans le Kattegat central sont formées de thalles de forme diploide.Toutes les formes libres et flottantes prennent leur origine en dernier ressort des espèces fixes, qui poss`edent ou peuvent adopter certains caractères qui leur permettent de survivre dans l'état de liberté.

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Most of the observational work in this paper was carried out in the Department of Botany, Aberystwith.

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Personal communications with Herr Fuglede of Skiber.     

Observations on Furcellaria fastigiata (L.) Lam. forma aegagropila Reinke in Danish waters together with a note on other unattached algal forms

The unattached populations of Furcellaria fastigiata forma aegagropila in Danish waters exhibit characteristics which are paralleled to a remarkable degree by those possessed by communities of unattached algae in other parts of the world. These characteristics include sterility, multiplication by vegetative means, and the adoption of a form, devoid of holdfast organs, which commonly has a globular or subglobular habit suited to rolling about on the sea bottom. Branching is often profuse and patent and may be accompanied by a thallus diameter far smaller than that of the attached form. Vegetative multiplication may be effected by fragmentation, and, as in F. fastigiata forma aegagropila, by a small accessory lateral branches which function as ‘propagulae.’ The latter originate in a manner somewhat different from that of the axial regenerated branches produced on decapitated thalli and on thalli which have been more than superficially wounded. Evidence suggests that much of the unattached population of this latter species in the central Kattegat is made up of diploid thalli. All loose lying forms ultimately originate from attached species, which possess or can adopt certain characteristics which enable them to survive in the unattached state.     

Life History and Reproduction of Furcellaria fastigiata (L.) Lam: With two Plates and two Figures in the Text: The Tetrasporophyte and Reduction Division in the Tetrasporangium

The tetrasporophyte of Furcellaria fastigiata (L.) Lam. is diploidand has 68 chromosomes. The plant is morphologically similarto, though slightly greater in stature than, the gametophyticplants, both of which have 34 chromosomes. Tetrasporangial initialsappear in May and reduction division takes place in early November.The process of meiosis is basically very similar to that ofhigher plants. A modified iron alum aceto-carmine staining schedulegives satisfactory staining of the chromosomes of this plant.     

Chemical and environmental growth regulation of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro

The need for conservation of biotic diversity is well recognized. However, improved techniques for the efficient, cost effective-preservation of plant germplasm are needed. The conservation and distribution of plant germplasm in vitro is gaining acceptance. However, increased usage is dependent upon the ability of curators to minimize culture maintenance requirements. This report examines the effect of various levels of sucrose, photoperiod, temperature, sorbitol and mannitol on minimal growth storage of Ipomoea batatas (L.) Lam. Growth was reduced 50% with a temperature reduction of from 21.1 to 15.6°C. Sucrose concentrations of 15 and 20 g l^-1 resulted in reduced plant stature with few adverse effects on plantlet viability or morphology. Reduction of photoperiod from 16 to 4 h produced smaller, slightly chlorotic, but otherwise normal plants. The addition of sorbitol or mannitol to culture media generally produced undesirable effects on gross plant morphology and loss of apical dominance. Genotype x growth retarding treatment interactions were observed for all variables examined.Abbreviations PL plant introduction - f.w. fresh weight - SE standard error     

Observations on the Cytology of Halidrys siliquosa (L.) Lyngb.

A study of the cytology of Halidrys siliquosa suggests thatit has a haploid thallus with reduction division immediatelyfollowing fertilization. There appear to be eight chromosomesin vegetative cells and developing antheridial and oogonialcells. Typical ‘bouquet’ and diakinesis stages suggestinga reduction division have been seen on germination of the zygote.     

Vegetative and reproductive phenology of the mangrove Bruguiera gymnorrhiza (L.) Lam. on Okinawa Island, Japan

Vegetative and reproductive phenology of the subtropical mangrove Bruguiera gymnorrhiza was investigated at Manko Wetland, Okinawa Island, Japan. Phenology was assessed using litterfall data over 4 years. Leaf and stipule litterfall occurred throughout the year, with distinct seasonal patterns. Kendall’s coefficient of concordance, W, revealed that the monthly changes in leaf and stipule litterfall were strongly and significantly concordant among years. Leaf litterfall was linked to monthly day length and maximum wind speed, and stipule litterfall was linked to monthly mean air temperature, monthly rainfall, and maximum wind speed. Branch litterfall showed no clear monthly pattern, but tended to vary with monthly maximum wind speed. Mean leaf longevity was 19 months. Mean total litterfall was 10.1 Mg ha^?1 year^?1, with the largest component being vegetative organs (58 %). Flower and propagule litterfall were highest in autumn and summer, respectively, and lowest in winter. The W values revealed that, of the reproductive organs, only flower litterfall had a significant monthly trend. Flower litterfall was correlated with monthly mean air temperature and relative humidity. The average development periods from flower buds to flowers and from flowers to mature propagules were approximately 1 and 8 months, respectively. It took 9 months to produce mature propagules from flower buds. Except for branches, all vegetative and reproductive components of litterfall had clear annual cycles.     

The growth,reproductive phenology,and longevity of non-tide-pool Fucus distichus (L.) powell in New England

The growth, reproductive phenology, and longevity of in situ populations of Fucus distichus L. ssp. edentatus (De la Pylaie) Powell and F. distichus L. ssp. evanescens (C. Agardh) Powell were evaluated in New England. Both subspecies exhibited maximum growth during early summer, a slight decline in late summer, and a brief resurgence in the early fall. The maximum growth rates (in terms of elongation) for F. distichus ssp. edentatus and ssp. evanescens were 3.5 and 3.7 cm/28 days, respectively. Populations of both subspecies showed a distinct bimodal reproductive periodicity, with maxima in the spring and fall. Even so, individuals were either reproductive in the spring or fall but never in both seasons. After reproduction, receptacles dehisced and plants either became vegetative or died. Higher rates of plant attrition were observed during periods of reproduction than during non-reproductive periods.     

Observations on the biology of Glossiphonia heteroclita (L.)

Summary A population of Glossiphonia heteroclita (Linnaeus) was studied in a pond situated in the grounds of the University College of North Wales, Bangor, Caernarvonshire, from November 1965 to September 1966.Monthly samples were obtained by placing roofing slates in the pond and collecting the leeches which settled on their undersides. These leeches were weighed, and examined for the presence of food in their gut. This provided the data for the construction of histograms of weight frequency, from which their life-history could be inferred.During the summer, breeding leeches were kept in the laboratory, at an average temperature of 14°C. Experiments were carried out to investigate the relationship of the young leeches with their parent, and the feeding behaviour of G. heteroclita.The evidence suggests that G. heteroclita is an annual. A proportion of the leeches which had over-wintered, began to reach maturity in April and breeding commenced in May. By September most of these had produced offspring and many of the heavier leeches had died.About twenty-five eggs were laid into a thin-walled cocoon, which was held under the posterior end of the body. After three or four days the eggs became arranged in a single layer, and were firmly attached to the parent by means of the embryonic attachment organ. The embryos hatched sixteen days later, at 14°C, and then attached to the parent by their posterior suckers. The young leeches remained attached to the parent for at least ten days, by which time their store of yolk was used up. Young leeches separated from their parent soon after hatching died.Although young leeches which were placed in a separate dish from their parents several days after hatching, survived well, they were not able to take advantage of certain types of food.Young leeches separated from their parents, but kept in the same dish usually re-attached in a few hours. They also readily attached themselves to other adult G. heteroclita, but not to other species in the same family e.g. Glossiphonia complanata and Helobdella stagnalis.In the field, leeches which hatched early in the summer, weighed up to 8 mg in September. Those which hatched later did not grow so rapidly. Many small leeches were found in the population throughout the winter. The data on feeding showed that it occurred infrequently during the winter. There was considerable mortality in April, just before the onset of breeding.The behaviour experiments, supported by immunological evidence, suggested that the main food of G. heteroclita in the College Pond, was Lymnaea stagnalis. The leeches did not accept undamaged snails. They also fed on damaged Enchytraeus albidus.

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Zusammenfassung Von November 1965 bis September 1966 wurde in einem Teich im Gelände des University College of North Wales, Bangor, Caernarvonshire, eine Population von Glossiphonia heteroclita (Linnaeus) wissenschaftlichen Untersuchungen unterzogen.An der Unterseite von Dachschiefern, die in den Teich gestellt wurden, siedelten sich Egel an. Jeden Monat wurden these Egel, die einen Ausschnitt der ganzen Population im Teich darstellten, gesammelt. Diese Egel wurden gewogen und der Darm auf das Vorhandensein von Nahrung geprüft. Die Untersuchungen ergaben Daten zur Aufstellung von Histogrammen der Gewichtsfrequenz, von denen der Lebenszyklus konstruiert werden konnte.Im Sommer wurden Egel während der Vermehrung im Laboratorium bei einer Durchschnittstemperatur von 14°C gehalten. Die Beziehungen von jungen Egeln zum Muttertier und die Art und Weise der Nahrungsaufnahme von G. heteroclita wurden experimentell untersucht.Die Beobachtungen weisen darauf hin, daß G. heteroclita eine einjährige Lebensdauer hat. Ein Teil der Egel, die überwintert hatten, begannen im April ihre Geschlechtsreife zu erreichen und sich im Mai zu vermehren. Bis September hatten die meisten dieser Egel Junge produziert, und viele der schwereren Egel waren eingegangen.Etwa 25 Eier wurden in einen dünnwandigen Kokon gelegt, der sich unter dem hinteren Ende des Körpers befand. Nach 3 bis 4 Tagen batten sich die Eier einschichtig gruppiert und waren mit Hilfe der embryonischen Haftorgane fest an dem Muttertier befestigt. Bei 14°C schlüpften- die Jungen nach 16 Tagen aus und befestigten sich mit ihren hinteren Saugnäpfen an das Muttertier. Nach Verbrauch des Dottervorrats blieben die jungen Egel nach mehrere Tage an dem Muttertier festgesaugt. Die Jungen, die kurz nach dem Ausschlüpfen vom Muttertier getrennt wurden, gingen ein.Obwohl junge Egel, die mehrere Tage nach dem Ausschlüpfen vom Muttertier getrennt und in einem anderen Behalter untergebracht wurden, gut überlebten, waren sie jedoch nicht fähig, gewisse Arten von Nahrung aufzunehmen.Junge Egel, die vom Muttertier getrennt wurden, jedoch in demselben Behälter blieben, saugten sich gewöhnlich nach wenigen Stunden wieder fest. Sie saugten sich ohne weiteres nicht nur bei dem Muttertier sondern auch bei anderen erwachsenen G. heteroclita wieder fest, nicht aber bei anderen Arten der gleichen Familie, z.B. Glossiphonia complanata und Helobdella stagnalis.Freilebende Egel, die am Anfang des Sommers ausschlüpften, wogen im September bis zu 8 mg. Diejenigen, die später ausschlüpften, wuchsen nicht so schnell. Während des ganzen Winters wurden viele kleine Egel in der Population gefunden. Die Daten der Ernährungsfrequenz zeigen, daß während des Winters Nahrung nicht häufig aufgenommen wurde. Kurz vor Beginn der Vermehrung im April war die Sterblichkeit beträchtlich.Die Verhaltensexperimente, gestützt auf immunologische Nachweise, deuten darauf hin, daß die Hauptnahrung von G. heteroclita im College-Teich Lymnaea stagnalis war. Die Egel nahmen unbeschädigte Schnecken nicht an. Sie frassen auch verletzte Enchytaeus albidus.

     

Root-Tiller Interrelationships in Spring Barley (Hordeum distichum (L.) Lam.)

Root-tiller relations were investigated in spring barley grownin soil in deep pots. The total dry wt of the root system reachedits maximum 6 weeks from sowing, when the shoot weight was only50 per cent of its value at maturity. Seminal and nodal rootscomprised 40 and 60 per cent, respectively, of the total rootdry wt at maturity; the majority of the nodal root weight wasassociated with the main shoot. The main shoot had approximatelytwice as many nodal roots as either of the first two primarytillers (T1 and T2), and the primary and secondary tillers appearinglater were very poorly rooted. Some tillers, especially secondarytillers that died prematurely, produced no nodal roots. Theweight of the seminal roots and nodal roots attached to themain shoot continued to increase up to maturity but the drywt of nodal roots on tillers declined with time. This patternof growth was closely related to the pattern of ¹⁴C assimilateddistribution within the root system. A very small proportionof ¹⁴C assimilated by the main shoot and T1 and T2 was exported.The majority of the exported assimilate went to the seminalroot system and to nodal roots attached to the main shoot. Individualnodal and seminal roots seemed to have different roles in supplyingnutrients to the shoot system, with the former mainly providing³²P-phosphate to its tiller of origin and the latter generallysupplying the main shoot and primary tillers. Hordeum distichum. (L.) Lam., barley, root growth, nodal roots, seminal roots, tillering, assimilate distribution, ³²P-distribution     

Observations on the age, growth, reproduction and food of the chub Squalius cephalus (L.) in the River Stour, Dorset

Opercular bones from 399 chub from the River Stour, Dorset were used for age and backcalculated growth measurements. Scales were only used to aid the interpretation of difficult operculars. Annuli were laid down through the period mid-April to mid-June. Growth in length was minimal between October and March. Growth rates were similar to those published for chub in other European waters, but the Stour chub were longer-lived and attained a greater ultimate size. Female chub grew faster than the males. Spawning occurred from late May into June and elaboration of the gonads took place between September and May. Immature chub had an annual cycle of condition; the 0 group having a maximum in August and older immature fish reaching their maximum in June. Both categories had a minimum condition in early spring. The cycle of gonad development affected the condition of mature fish. The numbers of eggs in chub of lengths 359–467 mm ranged from 27 000–65 000. Some females attained sexual maturity at age V or VI, but most by age VII. The majority of males matured at age V, though some at ages III or IV. Growth rates and year-class strengths varied from year to year but independently of one another. Thirty-one per cent of chub aged II and over belonged to the 1959 year class. Young chub ate insect larvae and small crustacea, but the occurrence of fish and macrophytes was greater in the diet of older fish.     

Observations on effects of feeding level on growth and reproduction in haddock, Melanogrammus aeglefinus (L.) in captivity

Individual haddock, Melanogrammus aeglefinus (L.) were maintained at different feeding levels in an aquarium from November until the completion of spawning. The mean duration of spawning was 33.2 days (range 19–59) during which an average of 16.6 (range 10–25) batches of eggs were produced. The size and dry weight of the eggs declined during the spawning period. Egg production and feeding level were correlated positively. There was some suggestion that when female haddock received low rations (< 5 kcal day^-1) a lower proportion spawned, and the dry weights of the eggs were lower compared with females on high rations (> 13 kcal day ^-1). The relation between daily growth in wet weight, g, and daily surplus energy intake, kcal, was: G =(0.295 E )— 0.328. When food energy is restricted, haddock appear to achieve a balance between somatic growth and reproduction.     

Effect of Light and NaCI Salinity on the Growth of Callus Cultures of Ipomoea pes-caprae (L.) R. Brown and Ipomoea batatas (L.) Lam

Callus cultures of Ipomoea pes-caprae and I. batatas were establishedon MS medium containing 10^–5 M 2,4-D and 10^–8 Mbenzyladenine. Ipomoea pes-caprae calli exhibited green pigmentationand grew better in the light than in darkness. Callus tissuesof I. batatas showed a pale-yellow colouration and they grewat the same rate in light as in dark conditions. I. pes-capraeand I. batatas callus cultures were sensitive to the presenceof 60 mM NaCl in the culture medium, the growth of the formerbeing more sensitive in light than in darkness. The significanceof the responses of I. pes-caprae callus cultures in relationto the mechanism of salt tolerance is discussed. Ipomoea batatas, Ipomoea pes-caprae, sweet potato, railroad vine, callus cultures, salinity, light     

甘薯与牵牛EST资源的SSR信息分析

为挖掘番薯（Ipomoea）属EST-SSR资源,从NCBI数据库下载23406条甘薯（Ipomoea batatas (L.) Lam.）EST和62282条牵牛（Ipomoea nil (L.) Roth）EST,利用生物信息学软件预处理、去冗余、拼接处理后得到12812条无冗余的甘薯EST（6.70 Mb）和28422条牵牛唯一序列（17.19 Mb）。对这些序列进行SSR搜索,在甘薯上获得328个SSR位点,发生频率为2.56%;牵牛上筛选到962个SSR位点,出现频率为3.38%。甘薯和牵牛EST-SSR具有多个共同特征：在SSR位点中,主要是二核苷酸重复类型,其次是三核苷酸重复;在二核苷酸重复中,出现最多的重复基序为AG/CT,其次是AT/AT;在三核苷酸重复中,主要基序是AAG/CCT;SSR位点的长度主要集中在20~22 bp。结果表明,这些搜索出的EST-SSR重复基序类型丰富、多态性潜能高,具有较高的开发和利用价值。     

Hoary cress (Cardaria draba (L.) Desv.) seed germination ecology,longevity and seedling emergence

The effects of gibberellic acid (GA₃), potassium nitrate (KNO₃), prechilling, temperature, salt stress and osmotic potential on seed germination and sowing depth on seedling emergence and burial depth on seed viability of hoary cress (Cardaria draba (L.) Desv.), were studied in a series of laboratory, glasshouse and outdoor experiments. The optimal temperature for hoary cress seed germination was 20°C, both in light/dark and darkness regimes. Seed germination of hoary cress at 400 ppm concentration of GA₃ in a light/dark regime was maximal. Potassium nitrate concentrations increased the percentage of germination in comparison with the control treatment. Increasing the duration of dry prechilling to 30 and 45 days promoted the seed germination of hoary cress. Germination of hoary cress markedly decreased as salt and drought stress increased. Seed germination of hoary cress occurred at a range of pH from 3 to 11. Seedling emergence significantly decreased as planting depth increased. Total seed viability decreased with increasing burial depth. The maximum increase in mortality occurred in seeds that were buried at 5‐cm depth.     

Ultrastructure and development of the megagametophyte in Eleusine tristachya (Lam.) Lam. (Poaceae)

Eleusine tristachya (Lam.) Lam. is native from subtropical South American climates. Widespread in Argentina and Uruguay, it is frequently found in landscape prairies of the province of Buenos Aires. Megasporogenesis and megagametogenesis in this species were studied using light and transmission microscopy. The ovule is hemitropous, bitegmic and tenuinucellate. The megaspore mother cell enlarges and undergoes meiosis division resulting in a T-shaped tetrad of megaspores. The three micropylar megaspores degenerate, and the chalazal one develops into the Polygonum-type megagametophyte. The synergid cells have the cytoplasm very electron dense because it has got a rich complement of organelles. The synergid wall is strongly thickened at the micropylar pole, developing the filiform apparatus. At maturity, the antipodals originate a wall with large projections into the cytoplasm, acquiring transfer cells characteristics. The antipodals cytoplasm, enriched with organelles shows a high metabolic activity, and it is suggested that these cells perform as an efficient system for metabolites transport.