摘要:

AbstractIn the unicellular green algaChlorogonium elongatumthe level of isocitrate lyase (ICL), the rate of its synthesis and the level of ICL‐mRNA measured byin vitrotranslation are considerably increased after addition of acetate to the culture medium of autotrophically precultured cells.Almost identical increases are obtained independently of whether the cells are cultured after the addition of acetate in the dark (heterotrophically) or in the light (mixotrophically). Transfer of heterotrophic cells to autotrophic conditions results in a fast decrease of ICL‐mRNA and ICL protein, while a transfer to mixotrophic conditions causes no alterations in both molecular species. Therefore the concentration of ICL and its translatable mRNA is controlled only by acetate and is unaffected by li

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00125.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractWith the aim of obtaining information on the degree of flexibility maintained in cyanobacteria in context with their phylogenetic position,Anacystiswas grown in the presence of thiosulphate, oxidized in a photosystem I (PSI) dependent reaction (KM7.4 × 10−3M thiosulfate). Besides DBMIB, onlyo‐phenanthroline andp‐hydroxymercuribenzoate blocked thiosulphate‐dependent PSI activity to some extent; iodonitrothymol, DCMU and cyanide had no influence. Growth ofAnacystisin the presence of thiosulphate induced a reorganization of the photosynthetic apparatus characterized by a shift in the PSII/PSI ratio in favor of PSI, comparable to low light conditions. Capability for oxygenic photosynthesis never completely disappeared; structural elements of PSII were retained in the membrane to a certain degree. The antenna pigment system signalled high light under conditions of thiosulphate oxidation as judged from the ratio of phycocyanin to chlorophyll. Besides a shift in the ratio of PSII to PSI components, the polypeptide pattern of thylakoids from thiosulphate grown cells shows several additional components compared to the controls and, moreover, higher concentrations of some polypeptides present in the controls, particularly a Mr41000 polypeptide. The process of thiosulphate oxidation appears bound to the thylakoid

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00126.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the marine red algaPolyneura hilliaephotoinhibition of photosynthesis was investigated by measuring the photosynthetic oxygen production. The extent of photoinhibition in this alga depends on the fluence rate as well as on the time of exposure. Strongly photoinhibited algae recover slowly. Full recovery is reached only in weak light after 3 days. Two phases of recovery can be distinguished: a first relatively fast phase of recovery that is independent of light, and a second slow phase which begins after about 6 hours and requires weak light. Consequently, even in complete darkness partial recovery is observed.An action spectrum of photoinhibition and its comparison with thein vivoabsorption spectrum ofPolyneurademonstrates that photoinhibition is mainly caused by light which is absorbed by phycobiliproteins, chlorophyll a and carotenoids. This fact and the ineffectiveness of light above 686 nm clearly indicate that the main photoinhibition site in this alga is PS II.No photosynthetic oxygen production is detectable after 3 h irradiation at 402 nm, 150 μmol quanta m−2s−1. As photosynthetic activity recovers slowly and to a limited extent, the suppression of oxygen production is apparently only in part the result of photoinhibitionsensu strictuand in part due to permanent photoda

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00127.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe inhibitory effect of DL‐phosphinothricin (glufosinate) on glutathione synthesis was studiedin vivoandin vitro. The influence of phosphinothricin on γ‐glutamylcysteine synthetase was compared with the already known effects ofl‐buthionine sulfoximine andl‐methionine sulfoximine. The results showed that phosphinothricin and buthionine sulfoximine are inhibitors of γ‐glutamylcysteine synthetase of plants. With both substances the enzyme was inhibited by 50 % at a concentration of 7 . 10−4M (pI50= 3.15). Methionine sulfoximine reduced the enzyme activity by 50% at 5 . 10−2M (pI50= 1.30). It is discussed that the target enzyme of phosphinothricin is the glutamine synthetase whereas the γ‐glutamylcysteine synthetase is only a

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00128.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractLaboratory cultures ofEctocarpus siliculosusoriginating from New Zealand showed a defect in gametangium formation. Nuclear divisions in gametangium initials are not followed by cell wall formation. In the resulting multinucleate cells nuclear DNA increases dramatically, and nuclear membranes disintegrate. Eventually, the entire structure is filled with hexagonal particles of approximately 130 nm diameter. These were isolated and shown by EM to consist of a dense core surrounded by a 3‐layered shell. They are released into the culture medium when the host cells burst.Ectocarpusgametes from healthy cultures could be infected by these particles. The resulting partheno‐sporophytes developed pathological symptoms, suggesting that the particles are viruses.The expression of the defect is temperature dependent. At 10°C all gametangia are abnormal, while between 15 and 20 °C defective and normal gametangia and gametes are formed on the same plant. Partheno‐sporophytes developing from such gametes carry the viral particles expressed in deformed unilocular and plurilocular sp

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00129.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPollination by hummingbirds was observed in two species ofVellozia(Velloziaceae) in southeastern Brazil. Both species have purplish‐pink to dark purple tepals, tube‐like arrangement of stamens, large and protected nectar chamber, and no odour. Tepals are reflexed inV. leptopetalaand narrow inV. declinans, further enhancing the tube‐like effect given by the long yellow anthers. Nectar is very dilute (ca. 10%). Three species of hummingbirds were observed pollinating theseVelloziaspecies:Colibri serrirostris, Augastes scutatus, andChlorostilbon aureoventris. The first species established feeding territories in the vicinity ofV. leptopetalaflowers. A bee‐pollinatedVelloziaflower‐type may give rise to a hummingbird‐flower by relatively simple adjustments, consisting mainly of the reflexion of tepals, increase in stamen length, enhancement of reddish pigments, enlargement of nectar chamber and dilution of nectar.Vellozia declinansmay be likened to one of the hypothetical stages of this trend towards ornithophily, whereasV. leptopetalais possibly one of the extremes withi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00130.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFamilies of the Campanulales‐Asterales‐complex are characterized by special mechanisms for secondary pollen presentation: pump mechanism, brushing mechanism, deposition mechanism, cup mechanism and combination of cup mechanism with brushing mechanism. These different mechanisms are based on three successive events: elongation of the filaments, opening of the anthers, elongation of the style. The diversity of the mechanisms arises through different auxiliary structures such as an indusium, hairs or an anther tube, and the relative rate and time of filament and style growth. An advantage of secondary pollen presentation lies in the prolongation of the male phase of anthesis through portioned pollen release. A probable phylogeny of the different mechanisms of secondary pollen presentation is proposed (Fig.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe climate of the loess‐hill area near Lanzhou, on the Yellow River, Gansu‐Province, NW‐China is arid throughout the year. The vegetation is xerophilic and mainly dominated by species of Zygophyllaceae, Chenopodiaceae, Plumbaginaceae, Tamaricaceae, Asclepiadaceae and Asteraceae. Among 11 species sampled of these families, δ13C‐analyses only indicated C4‐photosynthesis for 2 species. This relatively low frequency of C4‐plants may be due to elevation (1978 m a.s.l.) and the relatively cold temperatures (annual

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFlagellar development during the asexual synchronous cell cycle ofChlamydomonas reinhardtii(11.32 aM) was studied by light microscopy. Cell walls of sporangia of different developmental status were dissolved using gamete lysin (g‐lysin) enabling direct observation of flagellar development. Flagellar growth in progeny cells exhibits a linear kinetic with a growth rate of 28 nm/min at 30°C leading to a flagellar length of 7–7.5 μm in 4–4.5 h. After this time the flagellar growth rate drops to 2.8 nm/min (as in interphase). Both flagella of a single cell and all flagella within a sporangium grow out at the same time and with the same rate. Cycloheximide (10 μg/ml) completely blocks flagellar development. If cycloheximide is removed flagellar growth resumes at the normal rate with no lag‐phase.Flagellar development during the cell cycle inC. reinhardtiidiffers considerably from the well‐studied model system of flagellar regeneration following amputation in the

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractExperiments with isolated epidermal strips of maize coleoptiles, pretreated with auxin and further incubated on sucrose agar containing different concentrations of auxin (indole‐3‐acetic acid, IAA or naphthalene‐1‐acetic acid, NAA) and/or naphthylphthalamic acid (NPA), are described. Preincubation for 2h with 2 . 10−4M IAA or 10−5M NAA in buffer, followed by 30 min wash in buffer results in measurable cell elongation during a subsequent incubation for 6 h on sucrose agar. Addition of 10−4M NPA inhibited the response to auxin and this inhibition could be reversed by providing IAA in addition to NPA. Inner tissue fragments (without outer epidermis) did not respond to external IAA. These results lead to the conclusion that auxin secretion at the outer epidermis may be an essential step in auxin‐regulated co

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY