bluuebunny/crossref_metadata_2025_split huggingface dataset:
FACTORS CONTROLLING THE DISTRIBUTION OF TILIA CORDATA AT THE NORTHERN LIMITS OF ITS GEOGRAPHICAL RANGE
Authors: PIGOTT C. D. , HUNTLEY JACQUELINE P. 
Published: May 2006

SummaryPollen originating from small populations of Tilia cordata is largely deposited within a few hundred metres of the trees, so that their presence can only be detected by pollen analysis at sites within distances of this order. Pollen diagrams from such sites show a continuous curve for Tilia pollen extending to the present surface, although the values may be only about 1 % of arboreal pollen. Pollen analysis shows that T. cordata was present in the Lake District by about 5000 to 4800 B.C.; it then became plentiful in the southern valleys and extended to reach its present north‐western limit, or just beyond, by 3100 B.C., when migration ceased. While the tree was extending its range, it must have been able to produce frequent large crops of fertile seed but subsequently regeneration from seed ceased. After 3100 B.C. the proportion of its pollen initially may increase but then generally decreases. Although there are small recoveries at several horizons, these are not certain evidence of reproduction by seed. Failure to produce fertile seed renders the species particularly sensitive to woodland clearance and has resulted in a decrease in abundance within the Lake District and its virtual extinction in west Yorkshire and south Lancashire.
A CONTRIBUTION TO THE PHYTOGEOGRAPHY OF SHETLAND
Authors: HULME P. D. , DURNO S. E. 
Published: May 2006

SummaryPeat and lacustrine deposits from a basin mire in Mainland Shetland have been analysed for plant macrofossils and a number of species of particular phytogeographical interest recorded. Results of macrofossil and pollen analyses indicate that deposition started during Late Devensian times.
THE TOLERANCE OF TREE ROOTS TO WATERLOGGING
Authors: PHILIPSON J. J. , COUTTS M. P. 
Published: May 2006

SummaryInternal oxygen movement was demonstrated in woody roots of both Sitka spruce and Lodgepole pine by partially submerging detached roots in reduced indigo‐carmine solution and noting the appearance of the blue halo due to re‐oxidisation of the dye.Transport in the Hood‐tolerant pine occurred in both wood and bark and was greater than that in spruce where it was confined to the bark.The pathways of oxygen movement within the tissues are discussed and the results are considered in relation to the survival of tree roots when waterlogging of both primary and woody roots occurs.
NITROGEN FIXATION AND BIOMASS PRODUCTION IN CLONES OF ALNUS INCANA
Authors: HUSS‐DANELL KERSTIN 
Published: May 2006

SummaryNitrogen fixation, growth, biomass production and nitrogen content of seven clones from grey alder (Alnus incana (L.) Moench) were compared. Rooted green cuttings, inoculated with a root nodule suspension, were grown without combined nitrogen in a growth chamber for nine weeks. Nitrogenase activity (C2H2 reduction) was repeatedly measured in intact plants, and biomass and nitrogen content were measured at the end of the growth period.There were considerable, often significant, differences between clones in most of the studied parameters. Within each clone a very close correlation between various parameters was found. It was suggested that the value of any one variable which was easy to measure, such as shoot length, may be used for the prediction of the response of other variables when clones are grown together under the same conditions.
ECTOMYCORRHIZAL ASSOCIATIONS OF AUSTRALIAN INDIGENOUS PLANTS
Authors: WARCUP J.H. 
Published: May 2006

SummaryBesides species of Eucalyptus, Leptospermum, Casuarina and Pomaderris which are known to form ectomycorrhizas, many other Australian native plants may form ectomycorrhizal associations. The plants include many legumes, especially in the tribe Podalyrieae of the Fabaceae and Acacia in the Mimosaceae, all members of the Rhamnaceae examined, and species of such diverse genera as Opercuhria, Poranthera, Platysace, Goodenia and Stylidim. Many, perhaps most, of these ectomycorrhizal plants may also form endomycorrhizas of the VA type.The ectomycorrhizal species range from large forest trees to small non‐woody herbs. The associations vary from well‐defined mycorrhizas of the beech type to looser ones of a continuous or partial sheath, with or without a Hartig net. In soil low in available phosphate both typical and looser ectomycorrhizal associations markedly increased plant growth compared with that of uninoculated plants.
ON THE PHYCOBIONTS OF THE CYCAD CORALLOID ROOTS
Authors: GRILLI CAIOLA MARIA 
Published: May 2006

SummaryThe structure, ultrastructure and the developmental cycle of the phycobionts living in the coralloid roots of various cycads growing in different Italian Botanical Gardens were studied. The phycobionts were examined in the various zones of the coralloids from the top towards the base. All the phycobionts observed have the characteristics typical of Nostoc. Eucaryotic algae, fungi or bacteria have never been observed. Nostoc present in the coralloid roots of various cycads differ from each other in the trichomes and the organization of vegetative cells and heterocysts. Three main types of phycobionts have been distinguished, each having preference for a group or species of cycad. In the coralloid roots the heterocystous phase prevails with vegetative cells and heterocysts. The latter differ from the heterocysts reported in other cyano‐bacteria. Their frequency increases towards the basal parts of the coralloid roots and concomitantly they undergo changes until they become empty and stiff. Heterocysts releasing gonidia or dividing were not observed. In the sporogenous phase akinetes were not found. In the oldest coralloid roots few vegetative cells and numerous heterocysts in various stages were found.
NH4+ ASSIMILATION AND NITROGENASE REGULATION IN THE LICHEN PELTIGERA APHTHOSA WILLD
Authors: RAI A. N. , ROWELL P. , STEWART W. D. P. 
Published: May 2006

SummaryThe lichen Peltigera aphthosa consists of a green alga Coccomyxa, a fungus, and a N2‐fixing Nostoc which is located in superficial packets (cephalodia). In symbiosis the Nostoc shows only low activities of glutamine synthetase, but the cephalodia show very high activities of glutamate dehydrogenase. Alanine dehydrogenase activity is rather similar in all components. The Nostoc liberates over 95% of the N2 which it fixes as NH4+, and fungal glutamate dehydrogenase in the cephalodia appears to be important in the assimilation of this NH4+. Exogenous NH4+ (5 mM) has no effect on acetylene reduction activity by excised cephalodia but completely inhibits acetylene reduction by cephalodia attached to lichen discs (of fungus +Coccomyxa) within 24 h. This inhibition can be overcome by inhibiting main thallus glutamine synthetase activity by adding the glutamate analogue, L‐methionine‐SR‐sulphoximine (MSX). On adding exogenous NH4+ to main thallus discs with cephalodia, giutamine accumulates in the cephalodia when main thallus glutamine synthetase is active but not when it is inactivated by MSX. Exogenous glutamine also specifically inhibits nitrogenase activity by the cephalodia although exogenous alanine and glutamate (all 5 mM) have no such effect. The data indicate that glutamine produced in the main thallus may be involved in the regulation of nitrogenase activity by the cephalodial Nostoc.
EFFECTS OF OXYGEN, TEMPERATURE AND OTHER FACTORS ON THE REDUCTION OF ACETYLENE BY ROOT NODULES FORMED BY RHIZOBIUM ON PARASPONIA ANDERSONII PLANCH
Authors: TRINICK M. J. 
Published: May 2006

SummaryTest tube grown Parasponia plants formed nodules on the surface of the agar and reduced acetylene at a constant rate for a mimimun of 5.5 h at 25°C. Nitrogenase activity increased with pC2H2 to maximum activity at levels higher than 0.1 atm. No diurnal rhythm, attributable to the supply of photosynthate, was detected and decapitation of the plant had no effect on nitrogenase activity although nodule detachment lowered activity by 32 % with fürther diminution when nodules were sliced. Nitrogenase activity decreased from the tip to the base of the nodule. Soaking for 30 min did not affect activity. Repeated acetylene reduction assays made on plants adversely affected their activity. Maximum activity occurred at 25° to 35 °C. Below 20 °C nitrogenase activity ceased within minutes. Unlike that in legumes, acetylene reduction recovered slowly when plants were returned to favourable temperatures. Activity was lowered by 50% at 40 °C and to zero at 45 °C. The pO2 optimum for nitrogenase activity, in contrast to that in legume and many non‐legume nodules, was narrow and activity fell rapidly above and below 0.2 atm O2. Restoration of nitrogenase activity after inhibition by 0.4 and 0.9 atm pO2 was slow.
A BIOCHEMICAL AND ULTRASTRUCTURAL EVALUATION OF THE TAXONOMIC POSITION OF GLAUCOSPHAERA VACUOLATA KORSH.
Authors: McCRACKEN D. A. , NADAKAVUKAREN M. J. , CAIN J. R. 
Published: May 2006

SummaryThe ultrastructure and carbohydrate chemistry of Glaucosphaera vacuolata Korsh. were studied to clarify the uncertain taxonomic position of this alga. Serial thin sections reveal that the double membrane bounded photosynthetic apparatus of Glaucosphaera, described by previous investigators to consist of many chromatophores or cyanelles, is a single, highly lobed chloroplast without a pyrenoid. Thylakoids are single and bear phycobilisomes. The single nucleus is centrally located and surrounded by Golgi bodies. Starch granules are located outside the chloroplast and are not membrane bounded. Chemical analysis of the solubilized starch granules by butanol precipitation, iodine staining, and enzymatic digestion indicates the presence of both amylose and amylopectin. It is concluded that Glaucosphaera is a red alga and should be assigned to the order Porphyridiales.
FLORAL MORPHOLOGY AND REPRODUCTIVE BIOLOGY OF FOUR SPECIES OFCYANELLA(TECOPHILAEACEAE)
Authors: DULBERGER RIVKA , ORNDUFF ROBERT 
Published: May 2006

SummaryIn the South AfricanCyanella alba, C. lutea, C. hyacinthoidesandC. orchidiformisthe androe‐cium consists of an upper group of five or three stamens and one or three low stamens. Anthers of the upper and lower stamens differ in size and shape, and lower anthers produce much more pollen than upper ones. Pollen is released only when the poricidal anthers are forcibly beaten. The configuration of the androecium suggests that ‘feeding’ and ‘pollinating’ stamens are present; the manner of pollen discharge suggests vibratile pollination by heavy‐bodied bees. According to the direction in which the style is deflected,C. albaandC. luteahave right‐handed and left‐handed flowers. In these two species, the lower stamen is deflected in a direction opposite to that of the style. Artificial pollinations were carried out with plants sampled from various field populations of the four species. The seed set data obtained indicate the presence of physiological self‐incompatibility. No significant differences have been found in fertility of pollen from lower and upper anthers. InC. albaandC. lutea, the floral dimorphism together with a low number of flowers open at any time may be effective in promoting outbreeding. The ratio of pollen grains per flower to the number of seeds produced is much smaller inC. albaandC. luteathan in the other two species. It is possible that smaller numbers of pollen grains are required here, because the floral dimorphism enhances pollinations between flowers of different types.
DIVERSITY OF METAL TOLERANCES IN PLANT AGO LANCEOLATA L. FROM THE SOUTHEASTERN UNITED STATES
Authors: POLLARD A. J. 
Published: May 2006

SummaryPopulations of Plantago lanceolata L. from a variety of habitats in the southeastern United States contaminated with zinc, copper or arsenic (from mining), or lead (from motor vehicle exhaust fumes) were found to be more tolerant to the metals present at the collection site than was a control population from uncontaminated soil. This is the first record of copper or arsenic tolerance in this species. Testing was based on root growth of young seedlings in aqueous solutions of metal salts. In the case of arsenic, there was extremely high tolerance in seedlings from plants in contaminated soils, but the seedlings from plants growing on uncontaminated soil, although severely inhibited on average, contained a few individuals of high tolerance, suggesting a potential for rapid evolution of tolerance to this contaminant.
RELATION OF INTERNAL PHOSPHORUS CONCENTRATION AND PLANT WEIGHT IN PLANTS INFECTED BY VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: STRIBLEY D. P. , TINKER P. B. , RAYNER J. H. 
Published: May 2006

SummaryOur own results and a search of the literature have shown that shoots of plants infected with vesicular‐arbuscular mycorrhiza normally contain higher internal concentrations of P than those of uninfected plants of equal size, over wide ranges of external P supply and of host plants. Increased demand for carbon by infected roots is a possible explanation for this, and simple graphical methods of estimating the resulting dry wt loss are suggested.
ALLELOPATHIC ACTIVITY OF CAMELINA SATIVA (L.) CRANTZ IN RELATION TO ITS PHYLLOSPHERE BACTERIA
Authors: LOVETT J. V. , JACKSON HELEN F. 
Published: May 2006

SummaryIn the presence of phyllosphere bacteria, aqueous washings of foliage of Camelina sativa stimulate early growth of several species of higher plants. At least two bacteria can promote the observed effects, however, suitable substrates for bacterial activity may be limited to cruciferous plants.The stimulatory principle is produced rapidly by bacterial activity and is probably an organic chemical produced by bacterial degradation of more complex compounds commonly found in the Cruciferae.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: STRIBLEY D. P. , READ D. J. 
Published: May 2006

SummaryYoung mycorrhizal plants of Vaccinium macrocarpon could utilize amino acids as a nitrogen source as readily as ammonium whereas aseptically grown plants and plants inoculated with common soil saprophytic fungi were unable to utilize the organic nitrogen compounds. Seedlings of Festuca ovina grown as controls in the sterile condition and in the presence of the ericaceous endophyte also failed to utilize the amino compounds. The capacity of the ericaceous plant to exploit these compounds is therefore dependent upon mycorrhizal infection. In contrast to cultures of Marasmius oreades, the endophyte failed to grow on complex nitrogenous humic and fulvic acids extracted from soils under ericaceous plants. The capacity to utilize simple organic nitrogen compounds could be of importance for mycorrhizal ericaceous plants in mor‐humus soils which are characterized by slow rates of nitrogen mineralization.
SYMPLASTIC CONTINUITY DURING HARTIG NET FORMATION IN NORWAY SPRUCE ECTOMYCORRHIZAE
Authors: NYLUND JAN‐ERIK 
Published: May 2006

SummaryPits with plasmodesmata were observed by scanning and transmission electron microscopy in cortical cells of uninfected short roots, grown in vitro, and ectomycorrhizal roots grown in vitro and in vivo, of Norway Spruce, Picea abies (L.) Karst. The ectomycorrhizal fungus, Piloderma bicolor (Peck) Jülich, while forming a Hartig net during mycorrhiza synthesis in vitro, did not separate the host cell walls in the pit zones. In natural spruce ectomycorrhizae with P. bicolor and an unidentified ascomycete, the cortex symplast remained continuous by means of frequent pits with plasmodesmata. The tanniferous cells bordering the fungal mantle were never pitted.The symplastic continuity, which has not been previously demonstrated in the cortical cells of the host of ectomycorrhizae, is essential for the exchange of substrates between the fungus and the host.
DIAMOND‐BARK DISEASES OF SYCAMORE IN BRITAIN
Authors: BEVERCOMBE GAY P. , RAYNER A. D. M. 
Published: May 2006

SummaryOutbreaks of disease in sycamore (Acer pseudoplatanus) characterized by development of variously sized diamond‐shaped patches of necrotic bark (diamond‐cankers) are described. It is suggested that apparently similar symptoms may be caused by a variety of agencies. The fungus Dichomera saubinetii was closely associated with diamond‐cankers in many localities but it was sometimes absent and other fungi were then present, e.g. Cryptodiaporthe lebiyesi.Callous tissue frequently develops at the margin of diamond‐cankers, allowing their time of origin to be determined by an annual ring count. The most recent, major development of the disease, associated with particularly large cankers, occurred following the drought summer of 1976. There was also evidence of previous disease outbreaks from which trees had recovered, for previously wounded surfaces had often been completely sealed over by overgrowth and fusion of callous tissue.During the 1976 outbreak, callus often failed to form effectively around diamond‐cankers, and this was associated with death of the whole, or upper part of the tree. In the most severe cases (generally not associated with D. saubinetii) this resulted in considerable numbers of often quite large trees being destroyed within an area. Here the largest trees affected were as much as 15 to 25 m high and 0.5 to 0.75 m diameter near the base and in excess of a hundred separate cankers might be present on an individual trunk.
THE SECRETORY CYCLE OF DIONAEA MUSCIPULA ELLIS IV. THE ENZYMOLOGY OF THE SECRETION
Authors: ROBINS R. J. , JUNIPER B. E. 
Published: May 2006

SummaryThe proteolytic activity of the secretion is examined using inhibitors and site‐specific substrates. The major protease present is not peptic, tryptic or chymotryptic, but may be a thiol protease as activity is inhibited by alkylation with iodoacetamide. Acetylation causes an inhibition of activity, suggesting that one of the major proteases may have an amide group involved in its action. Carboxypeptidase A is found to be present. The secretion is shown to contain chitinolytic and peroxiditic activities but not N‐acetyl‐β‐d‐glucosaminidase. The possible origin of the secretion is discussed.
GROWTH ANALYSIS OF MAIZE VARIETY HYBRIDS OBTAINED FROM TWO RECURRENT SELECTION PROGRAMMES FOR GRAIN YIELD*
Authors: FAKOREDE M. A. B. , MOCK J. J. 
Published: May 2006

SUMMARYA reciprocal recurrent selection programme was initiated in 1949 to improve the grain‐yield performance of Iowa Stiff Stalk Synthetic [BSSS(R)] and Iowa Corn Borer Synthetic no. 1 [BSCB(R)] maize (Zea mays L.) populations. In the same year, a half‐sib selection programme was initiated in an open‐pollinated maize variety, ‘Alph’ (i.e. BS12), with the same objective. Inbred B14 was the tester variety in the half‐sib programme. Previous studies showed that significant grain‐yield increases resulted from seven cycles of reciprocal recurrent selection and six cycles of half‐sib selection. Growth analysis was used to examine productivity and distribution of dry matter by the unimproved and improved variety hybrids of BSSS(R) × BSCB1 (R)and BS12 × B14A.Only leaf area, leaf‐area duration, leaf‐area index, and leaf‐area index duration were significantly larger in the improved than the unimproved hybrids. These differences occurred mostly during grain filling. Evidently, increased grain yields from recurrent selection in these programmes were consequences of prolonged photosynthetic activity, increased production of photosynthate during grain filling, and increased translocation of photosyntheate from source to sink, in both BSSS(R) × BSCBl(R) and BS12 × B14A.
A RE‐INVESTIGATION OF CHARACTER CORRELATIONS AMONG DICOTYLEDONS
Authors: SPORNE KENNETH R. 
Published: May 2006

SUMMARYA computerized analysis of the occurrence among 291 dicotyledon families of 107 morphological or biochemical characters is described. The results confirm earlier work and increase the number of characters that are shown to be statistically associated from 26 to 39. Many of these occur more often in rain‐forest floras than in the rest of the world. They also occur more often in families that are represented in the fossil record than they do in the present‐day world flora, and are therefore regarded as primitive.Using 30 of these correlated characters, the percentage advancement index of the various families is calculated. Among the most advanced families are Dipsacaceae, Valerianaceae and Hippuridaceae. The most primitive ones are Aextoxicaceae and Degeneriaceae, with Stachyu‐raceae and Magnoliaceae also very primitive.
THE GENECOLOGY OF LAWN WEEDS VI. THE ADAPTIVE SIGNIFICANCE OF VARIATION IN ACHILLEA MILLEFOLIUM L. AS INVESTIGATED BY TRANSPLANT EXPERIMENTS
Authors: WARWICK S.I. , BRIGGS D. 
Published: May 2006

SUMMARYThe performance of 21 populations of Achillea millefolium L., originating from I lawns, II grazed sites, III grasslands seasonally reduced in height by cutting and/or grazing and IV grassy areas not seasonally reduced in height by cutting and/or grazing, was investigated by transplanting clone‐propagated material into a mature lawn. The response of a small number of contrasting populations was also studied in mown and tall grass plots of a reciprocal transplant experiment.There was no evidence, from the mown treatment of either experiment, to support the hypothesis that A. millefolium populations originating from certain lawns or grazed sites, and notably dwarf in standard cultivation, were more successful than others in vegetative spread, dry wt yield or reproduction. In both experiments plants originating from lawns were not uniformly successful. Also, individuals from all four habitat groups proved to be vegetatively vigorous in mown plots. Six plants (three from lawns, two from pasture and one from waste ground) fruited successfully in the mown plots of the reciprocal transplant experiment.Experiments with tall grass plots did not support the notion of tall grass races of A. millefolium. Such plots revealed considerable variability in all populations and plants from several habitat groups produced mature achenes in tall grass plots.Fruiting of A. millefolium is very rare in well‐kept lawns and the apparent clones in such habitats are likely to be the result of achene dispersal from habitats where the intensity and/or periodicity of grazing and/or mowing is insufficient to prevent fruiting.