摘要:

AbstractThe crayfish plague parasiteAphanomyces astaciwas compared with some other species ofAphanomycesin several physiological respects to detect signs of specialization in the plague fungus which could be connected with its life as a parasite.Thus, A.astacishowed good growth in crayfish serum in contrast to the other species. Zoospore germination showed a similar hut not so distinct pattern. Chemo‐taxis in zoospores was weak and restricted in its substrate range in A.astacibut was stronger and less restricted in the saprophytic species. Electrotaxis was quite apparent in A.astaci.Virulence in A. astacin was correlated to linear growth rate of individual hyphae in crayfish serum but neither to spore germination percentage in serum of resistant or susceptible crayfishes nor to motility of the zoospores. The saprophyticAphanomycesstrains did not penetrate the soft cuticle of crayfish in vitro but A.astacistrains did, regardless of virulence.Zoospore production in A.astaciwas restricted to lower concentrations of mineral salts Mum in the other fungi.No sexual or other resting structures were found in infected crayfish but thick walled as well as gemmae‐like hyphal portions were formed in some media in vitro.Infection of crayfish can take place between 2 and 25°C and zoospores are able in survive at least a week in an aquarium of redistilled water at 14°C and still infect the animals, but in highly bacterium‐contaminated water they do not cause infection.The results were discussed with respect to the origin of the “abnormal” parasite. Together with those of earlier experiments they suggest Unit A.astaciis physiologically adapted as a parasite on fresh water arthropods.This investigation was supported by a grant from the Swedish Natural Science Research Council and by funds paid to the Swedish state by the Swedish water power industry.The author is deeply indebted to the head of this institute Professor Nils Fries, for his encouragement. advice, and support, let Mr Andrew Watson for help in carrying out the electrotaxis experiment, to Docent Karin Aschan‐Aberg for criticizing the manuscript, to Mrs. Linda Fryktund for revising the English text, and to Mr. Can Wihma for skilful technic

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07371.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAphunomgces astaci, Saprolegniaceae, the crayfish plague parasite, grows well in a buffered peptone ‐ glucose ‐ mineral salt medium but does not normally produce spores during growth in this medium. Sporulation is, however, easily induced by transfer to pond water. None of the components of the complete medium inhibited sporulation more than partly when tested solely or in combinations. Neither lack of oxygen, high carbon dioxide concentrations, nor osmotic phenomena could satisfactority exlpain the absence of spore formation in the complete medium. In a peptone ‐ glucose growth medium low in phosphate and metal salts a sporulation inhibiting factor was formed by the mycelium. In this medium both good growth and good spore production could, however, occur simultaneously and spore production was here stimulated by a reduction in the oxygen tension. Liberation of formed spores into the medium was inhibited by mineral salts. It was less sensitive to lack of oxygen, respiratory inhibitors, and a factor formed during growth than was sporangial development. Development and maintenance of spore motility occurred even at very low oxygen tensions but was probably dependent upon an intact respiratory s

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07372.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe influence of the stem on delivery of Ca Sr to the plant top was studied by noting the extent to which the stem interfered with through passage of these elements. Tagged Ca Sr solutions were forced through bean stem sections, and solute which completed passage to the exudate was considered indicative of the nutrition normally available to the plant top. Tests were conducted over two widely different xylem stream flow rates, and with or without the addition of dinitrophenol to the source solution. Approximately identical amounts of cation were introduced into the stem for all test situations.In all cases, the stem retained the bulk of introduced cation and allowed only a fraction (ca 25 percent) to complete passage to the exudate. Within this pattern, less stem retention and greater through passage occurred at the high (versus the low) stream flow rate, and also where dinitrophenol was present in the source solution.In all cases, the stem preferentially retained Sr over Ca so that the exudate was relatively dilute in Sr. Such discrimination was less at the high (versus the low) stream flow rate. It was enhanced by the presence of dinitrophenol.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07373.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAcetone, ethanol and water extracts of mature fruits of yaupon(llex vomitoriaAit.) inhibited germination of mesquite(Prosopis julifloraSwartz DC. var.glandulosa(Torr.) Cockerell and sorghum (Sorghum bicolor(L.) Moench). Extracts of guava fruit (Psidium guajavaL.) inhibited cucumber (Cucumis sativusL.) seed germination. Water soluble inhibitors were found in fruits, leaves, roots and bark of several tropical species representing 10 different families.Strong inhibition of cucumber seed germination and growth did not occur in sand when water extracts containing inhibitors were applied. Growth of corn, sorghum, cucumber and bean was reduced in soils collected beneath Malay apple (Eugenia malaccensisL.) trees. Plant growth‐inhibitors occurred in all species studied in various plant parts, and some apparently affect the growth and ecology of other plant specie

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07374.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractMaleic hydrazide (MH) inhibits corn root elongation through an effect on cell division apparently without inhibiting cell enlargement. The decrease in the rate of elongation was apparent only after a considerable lag, over 14 hours, even with a concentration as high as 5 mM. MH (1 mM) did not inhibit His growth of roots from corn seeds given very large doses of γ‐irradiation or excised corn root segments including the elongation Zone or the cell enlargement induced by IAA in corn coleoptile sections. Many compounds including purines, pyrimidines, nucleosides. cysteine, pyridoxal, pyruvate. kinetin and CoCl2, many of which had previously been reported to alleviate MH inhibition in other tissues, were tested for their ability to prevent the inhibition of corn root elongation by MH, but none were effective. These data do not support the theory that MH acts by inhibiting the synthesis of or competing with some simple metabolite or hormone. Whatever its mechanism of action the failure of MH to inhibit cell enlargement in most systems indicates that it is fairly selecti

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07375.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe relationship between Young's modulus and longitudinal growth has been studied on growing segments of etiolated sunflower hypocotyls. The modulus was determined by means of the resonance frequency method. IAA in a concentration of 2.8 10−5M produces a decrease in the modulus with a time lag of 4 minutes, while an increase in growth is observable only after 6 minutes. Addition of IAA results in a stronger decrease in the modulus if the segments are placed in a solution of 0.1 M mannitol rattier Hum in water. Through plasmometric measurements it has been found that the elastic extensibility is insignificant compared with the growth. After the addition of IAA, there occurs a marked elongation both in 0.1 M mannitol and in water, and at the same time a decrease in the elastic extensibility of the segments is observed. In the growing segments an increased modulus causes an in creased elastic extensibility, a matter which is directly contrary to the relationship found in a physical system with an applied external force. An explanation of this discrepancy has been given. With an excess of calcium the modulus increases, while the elongation decreases. Calcium deficiency implies both a decreased modulus and a decreased growth. With the addition of 10−3M Ca(NO3)2to segments raised without calcium the modulus increases after only 10 minutes, while an increase in longitudinal elongation is observable after 30 minutes. With the addition of IAA to the calcium deficient segments the modulus decreases to the same extent as in an optimal supply o f calcium. The results are discussed with reference to other investigations about elasticity and growth. It has been concluded that plastic extensibility cannot he of great importance in longitudinal growth. Time studies of the auxin effect and I he interaction between auxin and calcium have confirmed the hypothesis that one of the primary actions of auxin consists in a loosening of the cell wall matrix. Calcium always increases Youngs modulus and gives the cell wall a more rigid structure. Furthermore, calcium in a certain concentration is necessary for longitudinal gro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07376.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe effect of the tissue age of dark‐grown bean plants on the chlorphyll formation under continuous illumination or short impulses of white light has been studied. It was found that the protochlorophyllide present in the tissue is age‐dependent and reaches a plateau at about 10 days of age, as judged by the chlorophyll formed in etiolated plants of various ages after 5 min illumination.The amount of chlorophyll a and chlorophyll b formed under short impulses of while light increases up to about 9 days of age and thereafter decreases. However, the decrease in chlorophyll a is sharper than that of chlorophyll b, the amount of which remains almost constant.The ratio of chlorophyll a lo chlorophyll b under the short impulses of white light is higher in the younger plant. Similar results are obtained after transfer of the plants from the flashing light to continuous illumination In the young plant there is no lag phase in the chlorophyll biosynthesis while as the age is increased the lag phase is evident and its duration increases as the plant ages.After protochlorophyllide phototransformation under continuous illumination the lag phase in chlorophyll biosynthesis is also age‐dependent. Leaves up to 5 days old show no lag phase in chlorophyll synthesis; after this point, however, the lag phase's duration increases continuously wit

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07377.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe polarographic technique (Armstrong 1967) has been found suitable for the detection of significant intervarietal differences in oxygen diffusion from rice roots. All the evidence obtained supports the thesis that intervarietal differences in oxygen diffusion rate occur and the varieties tested may be arranged in order of increasing oxygen flux as follows N 36

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07378.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractWhen a cell suspension of Chlorella vulgaris is treated with a mixture of copper and fluoride ions, the respiration almost ceases even though the two ions individually have lit t le inhibitory effect. If instead of adding the ions simultaneously, the cells are subjected to a period of pretreatment with copper sulphate before sodium fluoride the inhibition of respiration becomes more severe as the pretreatment time is lengthened, except at copper levels so high that inhibition is almost complete at all lengths of pretreatment. When, however, pretreatment is with fluoride ions, the inhibition becomes less as the pretreatment time is lengthened, eventually disappearing when the time interval is 90 min or more. Measurements of the amount of copper in the cells indicate that this asymmetry of response cannot be ascribed to differences in the rate at which copper is taken up. It is suggested that fluoride blocks the main respiratory pathway and that copper probably blocks the hexose monophosphate shunt.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07379.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAction of riboflavin, isoriboflavin and 2‐thiouracil in the induction of 2‐dimensional growth of fern prothallia.—The inhibition of cell division induced by 2‐thiouracil in prothallia ofDryopteris filix‐masandAnemia phyllitidisis reversed by riboflavin as well as by its physiological inactive analogue isoriboflavin. This antagonism is not due to anin vivointeraction as stated by Yeoh and Raghavan, but is rather caused by anin vivosensibilisation of photo destruction of the inhibitor during early phase of spore germination.Riboflavin as well as isoriboflavin strongly inhibit cell divisions in the prothallia ofAnemia phyllitidis.In spite of a significantly reduced growth rate NO retardation of the onset of the 2‐diniensional differentiation, as related lo a critical cell number, can be slated in the Anemia

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1969.tb07380.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY