共查询到20条相似文献,搜索用时 15 毫秒
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Dagmar Dykyjová 《Folia Geobotanica》1986,21(1):27-64
Measurements were made, for several seasons, both of the growth rate and biomass production of stands ofBolboschoenus maritimus, the seasonal development of the vertical stand structure together with parallel measurements of microclimatological data including incoming global radiation. Water and bottom soil chemical analyses in relation to the nutrient content in the biomass were compared. The ecological adaptation of the acidophilic subspeciesB. m. ssp.maritimus, growing in south-Bohemian oligotrophic fishpond waters with that of the halophilic ssp.compactus was studied in experimental hydroponic cultures and the results discussed with the findings of other authors from different European habitats. The efficiency of solar energy conversion of incoming radiation was calculated by means of energy content biomass analysis. 相似文献
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The life cycles of Leptophlebia vespertina (L.) and L. marginata (L.) (Ephemeroptera) in Llyn Dinas, North Wales 总被引:2,自引:0,他引:2
J. E. BRITTAIN 《Freshwater Biology》1972,2(3):271-277
Data is presented on the life cycles of Leptopblehia vespertina (L.) and L. marginata (L.) in Llyn Dinas, an oligotrophic North Wales lake. Both species are univoltine and growth continues throughout the winter although somewhat retarded. Except during July and August there is a clear size separation of the two species, L. marginata being larger and emerging earlier. The egg incubation period was determined directly from laboratory studies. The results are discussed in relation to previous research in the English Lake District. 相似文献
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Allozymic variation in seven enzymes coded by eight loci was studied in seven populations of terrestrial Epipactis orchids, including four populations of E. helleborine, one population of E. palustris and two of E. microphylla, from Latium (Central Italy).Heterozygosity estimates reveal that E. helleborine (EH) is the most variable species (HET=0.233; P=0.59; A=1.8), followed by E. palustris (EP) (HET=0.085; P=0.29; A=1.3) while E. microphylla (EM) is monomorphic for all the loci examined.It is suggested that the two EM populations examined, with a total lack of genetic variability, could originate from the same genetically impoverished ancestral population. Also the low variability amount of EP can be ascribed to genetic drift, probably due to a founder event.Nei's identity coefficients were also calculated. These show a high similarity in EH (=0.987) and EM (=1.000) populations. Average identity value between EP and EM is 0.289, between EP and EH is 0.336 and between EM and EH is 0.784. These data reveal that E. palustris presents a remarkable genetic, besides geographical and ecological, differentiation. 相似文献
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Intermatings between sexual diploids (2n=36) and facultative apomictic tetraploids (2n=4n=72) of Tripsacum dactyloides var. dactyloides, (L.), L., have been generated. Subsequent exchange and addition of genetic material between the two cytotypes, via a backcrossing program, provides one method for the manipulation of genetic elements involved in apomictic reproduction (diplospory) of this species.Identification and development of fertile triploids, and their innate tendency to exhibit a high frequency of unreduced egg cells which remain receptive to fertilization by a sperm nucleus, allows for the unique development of B
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(2n=3x+n) tetraploids by genome accumulation. The resultant B
III
progeny provide new breeding stock for investigating the inheritance and generation of such materials also allows for the occurrence of genetic recombination between sexual diploids and apomictic tetraploids. Potential use of fertile triploids, their tendency for genome accumulation and their use in exploiting apomictic tetraploid germplasm resources are also discussed.All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. 相似文献
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Roland H. Mulvey 《Journal of nematology》1979,11(4):363-371
Heterodera canadensis n. sp. is described and illustrated from the roots of spike-rush, Eleocharis acicularis (L.) R. &S., in Deschenes, Quebec. This new abullate species is related to Heterodera graminophila Golden and Birchfield, 1972, but differs significantly in cyst shape, cone top structures, body length of the second-stage larva (520-600 μm, vs. 380-400 for H. graminophila) and tail length (110-120 μm, vs. 57-67 for H. graminophila). A taxonomic key based on cyst and second-stage larva characters is provided for identification of the fifteen species in the Heterodera goettingiana group. 相似文献