Colourless tubers in Discelium nudum Brid

Abstract

Colourless, usually unicellular, tubers occur on the rhizoids of Discelium nudum. They are evidently not the rhizoid gemmae previously claimed to occur in this species, which were multicellular.     

Efficacy of potent antagonistic yeast Wickerhamiella versatilis against soft rot disease of potato caused by Pectobacterium carotovorum subsp. carotovorum

Abstract

In this study, an antagonistic yeast isolate, Wickerhamiella versatilis was considered as a promising biocontrol agent against Pectobacterium carotovorum subsp. Carotovorum (Pcc) the causal agent of soft rot disease of potato. Antagonistic yeast inhibited the growth of Pcc in vitro, and reducing the soft rot severity of infected potato tubers (cv. Diamant) under greenhouse conditions. Consequently, cellulase and pectinase hydrolytic activities in infected potato tubers with yeast?+?Pcc were decreased compared with infected tubers with Pcc. The histological characterization of treated potato tubers with antagonistic yeast W. versatilis using scanning electron microscope showed the accumulation of extracellular substances that may induce plant resistant and protects potato tubers from hydrolysis and damages. This study may introduce the possibility of using the antagonistic yeast isolate, as a biocontrol agent against soft rot of potato tubers.     

Healthier seed potatoes. I. Effects of inoculating stem cutting stocks with Polyscytalum pustulans and Rhizoctonia solani on growth, yield and disease

Potato seed tubers of seven cultivars derived from stem cuttings in 1965 (healthier seed) were grown in 1969–72 at two sites, one clay with flints soil (Rothamsted) and the other sandy loam soil (Woburn). Inoculating sprouted tubers at planting with Polyscytalum pustulans did not affect the number of stems/plant or total yield but increased stem base and tuber infection. The yields of large tubers (57–83 cm) were increased and small tubers (>57 cm) decreased, indicating a decrease in tuber numbers. Rhizoctonia solani inoculated at planting decreased numbers of stems/plant and yield by up to 14% at Woburn but not at Rothamsted. At both sites, yields of large tubers were increased with cvs Majestic and Record and decreased with Pentland Crown. Stem canker and tuber infection were increased but infection was also prevalent on tubers from non-inoculated seed at Woburn. When both pathogens were inoculated together yields of large tubers were increased in cvs King Edward, Majestic and Record and decreased in Pentland Crown. Infection of stem bases and tubers was sometimes less than when either pathogen was inoculated singly.     

Studies of protonemal morphogenesis in mosses. X. Ephemeraceae revisited; new dimensions underground

Abstract

This systematic investigation of the filament systems in nine species of Ephemerum and two of Micromitrium revealed a range of new characters in the Ephemeraceae. Above ground most taxa have pointed chloronemata with widely spreading branches, whereas in Micromitrium, Ephemerum cohaerens and E. spinulosum, the branches are fastigiated. Four species of Ephemerum (E. sessile, E. cohaerens, E. spinulosum and E. hibernicum) have massive lipid-laden tubers, the last three with prominent spinulose side branches. Tubers, comprising chains of rounded cells, are described for the first time in Micromitrium. Unique to E. recurvifolium are starch-laden tubers and fragile chloronemal branches. The morphology of the diaspores reinforces the pottialean affinities of the Ephemeraceae. The production of long-lived tubers provides Ephemerum species predominantly found on lake and reservoir margins in the British Isles, with an alternative means of perennation on sites susceptible to inundation prior to sporophyte maturation.     

A Dote on the habitat of Scorpidium turgescens (T. Jens.) Loeske in Scotland

Abstract

Being a synonym of Bryum nitens Hook., B. cruegeri Hampe is not new to Africa. In addition to tubers, deciduous shoot tips and shoot fragments act as vegetative propagules.     

The occurrence of tubers in Pohlia pulchella (Hedw.) Lindb. and Pohlia lutescens (Limpr.) Lindb. file

Abstract

Pohlia pulehella and P. luteseens have tubers of characteristic appearance which enable these species to be readily distinguished. Many of the plants collected in Britain before 1966 were wrongly identified. A clearer picture has emerged of the distribution and habitats of the two plants. The occurrence of P. lutescens in Scandinavia, and of male plants in Britain, are reported for the first time.     

Barbula maxima,nom. nov., an endemic Irish species

Abstract

Rhizoidal tubers from field and cultured Ditrichum heteromallum are described and figured and differ in morphology from those of other mosses so far described. Protonemal gemmae are also produced in culture.     

Notes on two nominal taxa of Ephemerum (Bryophyta: Pottiaceae) described from France by Charles Douin

Abstract

Evidence is presented contradicting claims that tubers occur on the rhizoids of Ceratodon purpureus (Hedw.) Brid. These claims are believed to have arisen through confusion with other plants, particularly Dicranella staphylina Whiteh., Barbula arcuata Griff. and Ditrichum pusillum (Hedw.) Britt. An account is given of the tubers of B. arcuata.     

Two new species of Alstroemeria L. (Alstroemeriaceae) from Brazil

Alstroemeria hygrophila andA. orchidioides are both described as new from the state of Goiás (including Distrito Federal) in Brazil.Alstroemeria hygrophila is a cerrado bog-dwelling species that grows semi-epiphytically on the culms of a sedge. The vegetative stems of this species characteristically zig-zag between the pseudonodes. Like other wetlandAlstroemeria in Brazil (e.g.,A. apertiflora, A. isabellana, andA. sellowiana),A. hygrophila has wiry stems bearing narrow, lanceolate, nonresupinate leaves, and does not form root tubers.Alstroemeria orchidioides is a hysteranthus forest understory species with large vegetative leaves aggregated at the apex of the stems. The leaves on flowering stems are reduced to scarious bract-like scales. Its flowers are a pale, nearly white, greenish yellow, a color not reported in any other Brazilian species. Both species have 2n=16 chromosomes.     

The influence of potato harvesting and grading machinery on contact spread of Phoma exigua var. foveata on tubers

The incidence of wounds infected by Phoma exigua var. foveata was increased if freshly damaged tubers (recipients) were shaken in a bag with diseased tubers (donors) to simulate the tuber-to-tuber contact that occurs during potato handling. An increase in the number of gangrene rots on damage points also occurred if the recipient tubers were wounded after contact with the diseased tubers, rather than before, and when the donor tubers were heavily infested with P. exigua var. foveata but were free of gangrene lesions. Increasing the proportion of donor to recipient tubers increased the percentage of infected wounds on recipients. Increased incidences of infection in recipient tubers also occurred after they had been passed over an elevator digger when it was lifting stocks of tubers heavily infested with P. exigua var. foveata. When spores of an E +ve isolate of P. exigua var. foveata were sprayed onto the webs of manned potato harvesters, tubers harvested immediately after developed gangrene rots from many of which the E +ve isolate was cultured. An E +ve isolate was also used to demonstrate the transfer of P. exigua var. foveata inoculum from tubers onto soil on riddles of a potato grader and from these soil-coated surfaces onto other tubers during grading.     

Revision of Cyanidium caldarium. Three species of acidophilic algae

Abstract

The authors carry out a systematic revision of three unicellular eucaryotic algae, often living in mixed population in thermal acidic environment. Such algae were often confused under the binomium Cyanidium caldarium.

The authors state that the following specific binomia are to be attributed to the three algae: Galdieria sulphuraria (Galdieri) Merola comb. nova; Cyanidium caldarium Geitler non (Tilden) Geitler emend.; Cyanidioschyzon merolae De Luca, Taddei & Varano.

The family Galdieriaceae is instituted for the first of these algae, whereas the other two algae are included in the family Cyanidiaceae Geitler emend.

The class Cyanidiophyceae Merola, a new class of the Rhodophyta, is instituted for these two families.     

Effects of treating seed potatoes from commercial and stem cutting stocks with benomyl, thiabendazole and 2-aminobutane on yield and disease

Potato seed tubers of six cultivars from commercial stocks and from stocks derived from stem cuttings (healthier seed) were fumigated with 2-aminobutane 2 wk after lifting or treated with benomyl or thiabendazole in January. 2-aminobutane prevented skin spot and gangrene developing on treated tubers. Experiments were planted at Rothamsted (clay with flints soil) and at Woburn (sandy loam soil) in 1973–75. Healthier seed produced more stems/plant than commercial stocks and yielded on average 8% more at Rothamsted in 1973 and 1974 and respectively 5 and 10% more at Woburn in 1973 and 1975. Seed treatments did not consistently affect stem numbers or increase yield although all treatments tended to decrease tuber size. Infection of stem bases and tubers by Polyscytalum pustulans and Rhizoctonia solani was usually less from healthier than from commercial seed and was decreased by benomyl and thiabendazole in 1973 and 1974. Infection by Helminthosporium solani of the skin around tuber eyes was greater from healthier than from commercial seed but was decreased by benomyl and thiabendazole. 2-aminobutane sometimes decreased infection of tubers by P. pustulans and R. solani but neither of stem bases nor of tubers by H. solani. Gangrene on tubers uniformly wounded at lifting was not consistently affected by seed source or seed treatment. Treating seed with benomyl or thiabendazole in 1975 decreased skin spot and black scurf in tubers stored until March 1976. These treatments also decreased silver scurf on the produce of commercial seed at Rothamsted but gangrene was not consistently affected by seed treatments.     

Life cycle and ultrastructure ofDucellieria chodati (Oomycetes)

Ducellieria chodati forms colourless, evidently plastid-lacking aggregates. For the first time, details of the reproduction cycle are reported: Biflagellate zoospores, released from the aggregates, infest coniferous pollen grains drifting on lake surfaces. The unicellular thallus growing inside the pollen grain develops into a sporangium. 10 to c. 60 spores are discharged, gather at the mouth of the discharge tube, and form new aggregates. After more than 30 cycles, the formation of aggregates ceases in favour of the direct production of zoospores which again infest pollen grains. If several zoospores infest the same grain, a resting spore can be produced, probably by a sexual process. It is evident from this complex life cycle thatDucellieria chodati is misplaced inChlorophyceae orXanthophyceae and needs to be grouped within theOomycetes. Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

Capsular polysaccharides facilitate enhanced iron acquisition by the colonial cyanobacterium Microcystis sp. isolated from a freshwater lake

Microcystis sp., especially in its colonial form, is a common dominant species during cyanobacterial blooms in many iron‐deficient water bodies. It is still not entirely clear, however, how the colonial forms of Microcystis acclimate to iron‐deficient habitats, and the responses of unicellular and colonial forms to iron‐replete and iron‐deficient conditions were examined here. Growth rates and levels of photosynthetic pigments declined to a greater extent in cultures of unicellular Microcystis than in cultures of the colonial form in response to decreasing iron concentrations, resulting in the impaired photosynthetic performance of unicellular Microcystis as compared to colonial forms as measured by variable fluorescence and photosynthetic oxygen evolution. These results indicate that the light‐harvesting ability and photosynthetic capacity of colonial Microcystis was less affected by iron deficiency than the unicellular form. The carotenoid contents and nonphotochemical quenching of colonial Microcystis were less reduced than those of the unicellular form under decreasing iron concentrations, indicating that the colonial morphology enhanced photoprotection and acclimation to iron‐deficient conditions. Furthermore, large amounts of iron were detected in the capsular polysaccharides (CPS) of the colonies, and more iron was found to be attached to the colonial Microcystis CPS under decreasing iron conditions as compared to unicellular cultures. These results demonstrated that colonial Microcystis can acclimate to iron deficiencies better than the unicellular form, and that CPS plays an important role in their acclimation advantage in iron‐deficient waters.     

猫爪草中的脂肪酸类化合物

为了解小毛茛(Ranunculus ternatus Thunb.)的化学成分,采用色谱技术从其干燥块根猫爪草中分离纯化得到5个脂肪酸类化合物,经波谱分析,他们的结构分别鉴定为(R)-3-hydroxy-11-methoxy-11-oxoundecanoic acid(1)、十六烷酸(2)、棕榈酸乙酯(3)、已二酸(4)和硬脂酸(5)。其中,化合物1为新化合物,这些成分对耐药结核分枝杆菌(耐INH+RFP)有一定的体外抑制活性。     

Pohlia integra (Card.) Shaw a neglected species,recorded from southern Africa and South America

Abstract

Mniobryum bracteatum Bartr. from Ecuador is reduced to a synonym of Pohlia integra (Card.) Shaw, previously known only from Mexico. The species, characterized by the occurrence of rhizoidal tubers, is also recorded from Bolivia and southern Africa.     

Instability at the y-1 locus of Chlamydomonas reinhardtii

Summary Twenty-three spontaneous yellow mutants were isolated from two stable green strains of the unicellular green alga Chlamydomonas reinhardtii. Genetic characterization indicated that 22 of 23 mutants had a mutation at the y-1 locus, and all 22 y-1 alleles were unstable. Crosses designed to follow the inheritance of instability at the y-1 locus showed that instability is caused by a single genetic factor located at the y-1 locus or very close to it.     

Gametophyte development and reproduction of the Asian fern Polystichum polyblepharum (Roem. ex Kunze) C. Presl (Dryopteridaceae,Polypodiopsida)

Abstract

The gametophytic generation of Polystichum polyblepharum (Dryopteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and reproduction strategies, was studied. Spore germination was of the Vittaria model and the developmental pattern was of the Aspidium model. Adult gametophytes were cordate and hairy, with unicellular hairs located at the margins and at the prothallus surface. The marginal ones were secretory. The gametophytes produced archegonia located in the central area between the notch and the rhizoids, but antheridia were never detected. Archegonia were of the normal type described for leptosporangiate ferns. Apogamous sporophytes appeared from a cellular outgrowth developed just under the apical notch. Initially, the outgrowth appeared completely surrounded by glandular hairs and scales, which persisted throughout the subsequent stages of leaf development.     

Alaticosta,a new subgenus of Acaulon,in Australia

Abstract

Two new species of Acaulon, A. chrysacanthum and A. leucochaete are characterized by lamellae on the adaxial surface of the nerve and are placed in a new subgenus, Alaticosta. Acaulon chrysacanthum has leaves with the nerve excurrent as a stout reddish-gold arista, and brown papillose spores, 30–35 µm in diameter. Acaulon leucochaete has the nerve excurrent as a long colourless flexuose hair point and buff-coloured spores, more finely papillose and 23–25 µm in diameter. Both are species of semi-arid areas usually growing on red sandy soil in mallee scrub.     

The phylogeny of Prochloron

Abstract

Prochloron, a unicellular alga that combines some features of cyanophytes with others of chlorophytes, is a phylogenetic enigma. Mounting evidence from electron microscopy, comparative biochemistry and molecular biology now suggests that prochlorophytes probably arose from blue-green algal ancestors, perhaps less than 10³ years ago.