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221.
Summary Thirty two bacteria antagonistic to a number of phytopathogenic fungi were isolated from soil samples. One bacterial strain, designated as M 51, appeared to be particularly active towardsF. oxysporum f. sp.dianthii, in vitro andin vivo and it was inhibitoryin vitro to three otherFusarium spp. used. Tests to find if there was protection against fusarium wilt were carried out by three different methods of inoculation of the cuttings: a) dipping of cuttings for ten minutes in bacterial suspension; b) spraying of suspension on perlite where the rooted cuttings were planted; c) spraying the greenhouse bench rooting boxes, where the non-rooted cuttings were planted, with bacterial suspension. Following this all the cuttings were transplanted into soil naturally highly infested withFusarium oxysporum f. sp.dianthii (3000 units/g). Good protection against fusarium wilt was obtained for cuttings inoculated by method (b). However protection decreased gradually about 60 days after they were transplanted; both control and inoculated cuttings showed a comparable mortality rate. Method of inoculation and the development of the protective effect are discussed. 相似文献
222.
223.
Facilitated membrane transport systems act as valves, or rectifiers, when the substrate affinities on the two sides of the membrane differ substantially, i.e. when the system is strongly asymmetric. The asymmetry may be intrinsic or imposed by a reversible competitive inhibitor acting on only one side of the membrane. Under non-equilibrium conditions such systems allow net movements of substrate to proceed faster, sometimes much faster, in one direction than the other, though the final equilibrium is unaffected. Obligatory exchange systems may also function as valves when inhibited unsymmetrically, permitting exchange to occur more rapidly with one distribution of substrates than with the reversed distribution. Here, unequal flux rates do not depend on unequal concentrations of the substrate on either side of the membrane, but may also occur with equal concentrations, provided the affinities of the two substrates differ.The kinetic theory leading to these conclusions is given here, and it is shown how individual parameters of a carrier system affect the efficiency, or tightness, of the valve. In addition, simple kinetic tests for the operation of a valve are outlined. Examples are cited of transport systems having inhibitor-binding sites on only one surface of the cell membrane, which could function normally as valves. Systems implicated are glucose transport in various cells, the ADP-ATP exchanger of mitochondria, the anion transporter of erythrocytes, and the Na+-K+ pump. 相似文献
224.
L. Vosselman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1980,57(4):79-85
Summary In Hylemya antiqua, a stock homozygous for an autosomal reciprocal translocation was isolated using egg-hatch reduction and karyotype analysis. Sibling translocation homozygous (TT) and heterozygous (T+) females were compared in respect to egg production and longevity. In one full-sib (5 TT and 8 T+ females) significantly higher values for both parameters for T+ than for TT females were scored, in four others (a total of 35 TT and 28 T+ females) no significant differences were found. Cage experiments were started with populations composed of equal numbers of wild type flies (++) and translocation homozygotes. The frequencies of the different karyotypes in three successive, non-overlapping generations, did not suggest substantial differences in fitness between ++ and TT flies. Possible causes of a surplus of T+ individuals found in these experiments are discussed together with the usefulness of the translocation for genetic control of H. antiqua. 相似文献
225.
A reliable assay of uridylate sequences longer than 10 is described. The procedure is based on the hybridization of [3H]poly(A) with poly(U) or oligo(U) sequences in high ionic conditions and a subsequent degradation of single stranded polynucleotides with purified Taka-diastase. A 1:2 complex between poly(A) and poly(U) is formed on which on poly(U) strand is digested by Taka-diastase. The procedure is especially suitable for the detection and quantitation of Un (n greater than 10) in RNA preparation. 相似文献
226.
227.
A new microsporidian species, Nosema pilicornis, which infects the purslane sawfly, Schizocerella pilicornis, is described. This microsporidium infects most body tissues of the host. N. pilicornis was compared to other microsporidian species infecting Hymenoptera and to a group of similar microsporidia infecting Lepidoptera. N. pilicornis could be distinguished from all other microsporidian species on the basis of host range and ultrastructural characteristics of the spore. Spores were oval, containing 11 to 12 polar filament coils, and the polar filament had an angle of tilt of about 80°. N. pilicornis infected lepidopteran larvae, but only when heavy spore dosages were fed to early larval instars. S. pilicornis is a good but sporadic biological control agent of common purslane, Portulaca oleracea, a pernicious weed of vegetable, ornamental, and orchard crops. N. pilicornis, which is transovarially transmitted and causes high mortality in infected larvae, affects the performance of S. pilicornis as a biological control agent. 相似文献
228.
The total serum protein concentrations and levels of aminopeptidase and lysozyme activities in the sera of the gastropod Biomphalaria glabrata have been determined. The groups of snails from which hemolymph samples were taken for study included (1) untampered controls, (2) sham-injected snails, (3) heat-killed Bacillus megaterium-injected, and (4) live B. megaterium-injected ones. Our results indicate that there are significant elevations in the levels of aminopeptidase activity in 2 hr in the sera of snails that had been sham-, dead bacteria-, and liver bacteria-injected. The levels of lysozyme activity were not altered in sham-, dead bacteria-, and live bacteria-injected snails. This is contrary to an earlier finding (T. C. Cheng, M. J. Chorney, and T. P. Yoshino, 1977. J. Invertebr. Pathol., 29, 170–174), and the difference is believed to be due to the age of the snails employed. Comparisons of total serum proteins have revealed that the concentration in snails injected with live B. megaterium is significantly higher than in sham-injected ones. This may be due to increase of some yet undetermined serum protein fraction. 相似文献
229.
The nematode Nothanguina phyllobia Thorne was found within large foliar galls on the perennial weed Solanum elaeagnifolium Cav. in west Texas. A two-year survey of a 6400 sq-km area in west Texas showed extensive distribution of the nematode. No hosts other than S. elaeagnifolium were observed. Densities of juvenile nematodes in the soil were high. N. phyllobia spread rapidly after small numbers of infective juveniles were applied in a foliar spray to an S. elaeagnifolium population. The host plant declined in vigor and frequently died. Artificial inoculation of an S. elaeagnifolium population with large numbers of the nematodes by broadcasting infected plant tissue resulted in high infection incidence. 相似文献
230.
Geographic variation and genetic aspects of reproductive diapause in Drosophila triauraria and D. quadraria 总被引:1,自引:0,他引:1
MASAHITO T. KIMURA 《Physiological Entomology》1983,8(2):181-186
ABSTRACT. Geographic variation and genetic aspect of reproductive diapause were studied in Drosophila triauraria Bock & Wheeler and D. quadraria Bock & Wheeler, in relation to their quantitative response to photoperiods. D. quadraria from the subtropical region had no photoperiodic diapause. In D. triauraria strains, diapause was induced under LD 10:14 or 12:12, but not under LD 14:10 or longer photoperiods. Their diapause was induced more effectively and maintained longer by LD 10:14 than by LD 12:12. The duration of diapause was longer in a northern strain, but the diapause inducing process varied little among different geographical strains. Diapause incidence was 50% or lower in F1 hybrids between D. triauraria and D. quadraria and backcross progenies between F1 and D. quadraria , and about 70% in backcross progenies between F1 and D. triauraria under LD 10:14, but very low under LD 12:12. The lower incidence of diapause in these F; and backcross progenies is assumed to be due to the less efficient induction of diapause, since once diapause was induced in them, it was maintained for a long time, especially in the backcross progenies between F1 and D. triauraria. These experiments suggest that diapause induction and maintenance are different physiological processes controlled by different genetic systems. 相似文献