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991.
R. MICHAEL C. EAGAR 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1974,7(3):219-238
In the British Pennines, from the middle of the lenisulcata Zone to the lower part of the communis Zone (Upper Carboniferous, lower Westphalian A), nine horizons, of which six are new or newly described, yield elongate specimens of the bivalve Carbonicola with evidence of former steep, near vertical burrowing in sediments of low organic carbon content. The faunas, of the groups of C. bellula (Bolton) sensu lato and of elongate C. aff. communis Davies & Trueman, were evidently invaders of the Pennine prodelta. They grade with established faunas of prolific highly variable Carbonicola found typically in richly carbonaceous shales and characterised by shallow burrowing, greater size, increased prcportionate shell height and length of anterior end, and probably increased obesity. Parallels exist with work on Anthraconaia. Anthraconauta . and the ecology of recent Unionacea. Results also bear on the palaeoecological ranges of Curvirimula and Naiadites . 相似文献
992.
993.
Seeds irradiated with red light and then re-dried will respondto this light treatment on subsequent rehydration in the dark.If such high-Pfr seeds are irradiated in the dry state withfar-red light immediately before rehydration the percentagegermination is significantly reduced in the case of Plantagomajor and Sinapis arvensis but increased in Bromus steriliswhere Pfr inhibits germination. This effect of far-red lightcan be reversed by red light despite the fact that red lightalone has no effect on dry seed. This is due to the interconversionof Pfr and the red light absorbing phytochrome intermediatecomplex meta-Fa. If there is a delay between far-red irradiationand rehydration of Sinapis seeds, the inhibitory effect of thefar-red irradiation becomes progressively less the longer thedelay. This reduction in effectiveness of far-red is interpretedin terms of a dark reversal of meta-Fa to Pfr with a half-lifeof about 46 h. The reappearance of Pfr is either veryslow or docs not occur in dehydrated Plantago seeds, as far-redtight given 96 h prior to hydration is just as inhibitory asfar-red light given immediately before hydration. Meta-Fa doesappear to revert to Pfr in darkness in Bromus seeds, but onlyvery slowly. The rapid increase in effectiveness of red irradiationduring rehydration of high-Pfr Plantago seeds suggests that,in this species, the pre-treatment used in preparation of high-Pfrseeds may increase the receptivity or amount of the Pfr reactionpartner. Key words: Phytochrome intermediates, Seeds, Germination 相似文献
994.
Maturity bronzing is a preharvest disorder of cultivar Williamsbananas (Musa, AAA group, Cavendish sub-group) involving necrosisof the peel surface Lesion development is described and is distinguishedfrom damage caused by banana rust thrips [Chaetanaphothripssignipennis (Bagnall)] Anatomical studies on the peel of thedeveloping fruit showed that (I) the area of epidermal cellschanges little during fruit expansion, and (II) epidermal cellsbecome flattened in the radial direction and tangentially-elongatedto accommodate the more rapid growth of the underlying tissuesFruit produced in the wet season in North Queensland, Australia(lat 17° 36' S, 146° 00' E) has an exceptionally highgrowth rate and is highly susceptible to maturity bronzing Underthese conditions stretching of the epidermis exceeds its elasticlimit and leads to cracks and cell disruption in the peel surface,and subsequently to formation of the lesions characteristicof maturity bronzing Musa, banana fruit, peel, disorder, lesion, banana rust thrips 相似文献
995.
HARRY A. NOYES BYRON A. ARANA MICHAEL L. CHANCE RHAIZA MAINGON 《The Journal of eukaryotic microbiology》1997,44(5):511-517
ABSTRACT. The relationships of the Leishmania hertigi complex and the lizard Leishmania species to the main groups of mammalian Leishmania and Endotrypanum parasites were examined. Restriction fragment length polymorphisms and sequences of small subunit ribosomal RNA genes and hybridization studies of kinetoplast DNA indicated that the L. hertigi complex was more closely related to the genus Endotrypanum than to the genus Leishmania . The lizard Leishmania species were found to be at the crown of the Leishmania tree. The data provides strong evidence for a Neotropical origin of the Endotrypanum/Leishmania clade since the parasites closest to the root of the tree are all found exclusively in the Neotropics. The evolution of the Leishmania/Endotrypanum clade in relation to the evolution of the known hosts of these parasites is discussed. 相似文献
996.
MICHAEL HEADS 《Botanical journal of the Linnean Society. Linnean Society of London》1998,127(3):239-285
The trees and shrubs in Olearia sect. Divaricaster, sect. nov., are found in North, South, and Stewart Islands of New Zealand. They are distinguished by their small, opposite leaves borne on brachyblasts (short shoots), long shoots which abort apically, solitary or fascicled capitula, flowers with purple style arms, and a very distinctive insect fauna. The ten species and three subspecies, including the new O. fimbriata, O. gardneri and O. virgata subsp. centralis are revised and a key and distribution maps provided. The section includes four threatened species: O. hectorii, O. polita and the two new species. Species density is mapped in grid cells 1° latitude by 1° longitude. Areas west of the geological Median Tectonic Zone (Nelson, Westland and Fiordland) show relatively low diversity. The highest diversity, six species in one grid cell, is recorded in north-west Otago, around Mt Aspiring and the Humboldt Mountains. This region is also geologically significant as several allochthonous terranes are juxtaposed there. In the central South Island O. laxiflora, O. fimbriata and O. odorata have concentric distributions around what were Tertiary basins and inland seas. Members of the section favour fertile, lowland sites on alluvium and have suffered reduction in population size over the last century due to agricultural development. Several species, such as O. hectorii, the 'swamp gum', occur in sites which are periodically flooded. Olearia solandri is a coastal species, often growing as a mangrove associate, but occasionally found inland. The anomalous inland populations are discussed and their location attributed to geological uplift. 相似文献
997.
VARIATION IN GENOMIC FORM IN PLANTS AND ITS ECOLOGICAL IMPLICATIONS 总被引:28,自引:6,他引:22
MICHAEL D. BENNETT 《The New phytologist》1987,106(S1):177-200
998.
MARK S. LENARZ MICHAEL E. NELSON MICHAEL W. SCHRAGE ANDREW J. EDWARDS 《The Journal of wildlife management》2009,73(4):503-510
ABSTRACT The earth is in the midst of a pronounced warming trend and temperatures in Minnesota, USA, as elsewhere, are projected to increase. Northern Minnesota represents the southern edge to the circumpolar distribution of moose (Alces alces), a species intolerant of heat. Moose increase their metabolic rate to regulate their core body temperature as temperatures rise. We hypothesized that moose survival rates would be a function of the frequency and magnitude that ambient temperatures exceeded the upper critical temperature of moose. We compared annual and seasonal moose survival in northeastern Minnesota between 2002 and 2008 with a temperature metric. We found that models based on January temperatures above the critical threshold were inversely correlated with subsequent survival and explained >78% of variability in spring, fall, and annual survival. Models based on late-spring temperatures also explained a high proportion of survival during the subsequent fall. A model based on warm-season temperatures was important in explaining survival during the subsequent winter. Our analyses suggest that temperatures may have a cumulative influence on survival. We expect that continuation or acceleration of current climate trends will result in decreased survival, a decrease in moose density, and ultimately, a retreat of moose northward from their current distribution. 相似文献
999.
MOHAMMED S. ALI-SHTAYEH MICHAEL W. DICK F.L.S 《Botanical journal of the Linnean Society. Linnean Society of London》1985,91(1-2):297-317
Five new species of Pythium are described, following ecological studies of the genus in the Reading (U.K.) area. Two of the new species were found abundantly, three were rarely isolated. Neither of the abundant species produces sporangia and both have very small oospores. Of the rarer species, two have filamentous sporangia and all three have rather large oospores. 相似文献
1000.
Sipwise and flowise presentation of taste stimuli were compared and better taste discrimination was noted for flowise presentation. Using a model system, discrimination between NaCl solutions and purified water, analysis with atomic absorption spectrophotometry indicated that the superiority of flowise presentation was due to reduction in stimulus variance. Flowise presentation was also superior for discrimination between commercially available natural spring waters. 相似文献