bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EFFECTS OF THE AXIS AND PLANT HORMONES ON THE MOBILIZATION OF STORAGE MATERIALS IN THE GROUND‐NUT (ARACHIS HYPOGAEA) DURING GERMINATION
Authors: ALLFREY J. M. , NORTHCOTE D. H. 
Published: May 2006

SUMMARYDuring germination the lipids, triglycerides and starch stored in the cotyledons of the ground nut are mobilized. The time course of this degradation has been measured and the accumulation of mono‐ and diglycerides, free fatty acids, phospholipids, cholesterol and sucrose has been estimated during the first 8 days of development. During this time the lipase and amylase activities present in the seeds increased. The lipase appeared to be relatively unspecific. A feature of germination was the induction of isocitrate lyase activity which was not present in the seed before germination. The action of gibberellic acid, abscisic acid and ethylene on germination, mobilization of reserves and enzyme induction had been studied.Application of abscisic acid inhibited germination and also the increase in lipase activity. It also inhibited strongly the induction of isocitrate lyase, but it increased amylase activity and starch breakdown. The presence of the axis in the germinating seeds helps to restore normal metabolism when it is disturbed by the application of the exogenous growth substances.The results are discussed in relation to the balance between fat and carbohydrate metabolism of the germinating seed and the importance of isocitrate lyase as a control point connecting the two aspects of this metabolism.
STEM ELONGATION IN TULIP AND NARCISSUS: THE INFLUENCE OF FLORAL ORGANS AND GROWTH REGULATORS
Authors: HANKS GORDON R. , REES A. R. 
Published: May 2006

SUMMARYDecapitation of tulips early in extension growth resulted in a 59% reduction in stem length at flowering. Selective removal of the floral parts showed that the gynoecium controlled stem extension. The upper internodes were most affected, and the effect was largely reversed by the application of indol‐3‐ylacetic acid (IAA) but not by gibberellic acid (GA). Soil drenches of ancymidol also reduced tulip stem extension, but in this case the lower internodes were most affected and this effect was reversed by GA.The result of flower removal in narcissus was similar to that in tulip, although the narcissus scope and the tulip stem differ morphologically. Scape extension of narcissus was reduced by decapitation; this was due entirely to the removal of the gynoecium and could be reversed by IAA but not GA. In narcissus, spathe removal led to earlier flowering.Flower blasting in tulip (a drying out of the flower which occurs commercially under some conditions) resulted from a number of treatments, including floral surgery, injections and ancymidol soil drenches. The incidence of flower blasting was reduced by injecting GA or kinetin.The results are discussed in relation to commerical flower production, the control of pot‐plant height, and the prevention of flower blasting.
CHLOROPLAST DEVELOPMENT IN YOUNG SESAME PLANTS
Authors: PLATT‐ALOIA K. A. , THOMSON W. W. 
Published: May 2006

SUMMARYElectron microscopic examination of developing chloroplasts of sesame indicates that plastids in the shoot apex and leaf buds contain a membrane‐bound inclusion with electron‐dense, homogenous contents. The incipient grana of these young plastids have enlarged loculi filled with an electron‐dense material, and the membranes exhibit a ‘negative’ image. The bounding membrane of the inclusion is frequently observed in intimate contact with, and possibly contiguous with, the grana‐fretwork system of the developing chloroplast. As development continues, many of the inclusions are observed to contain partly or wholly crystalline contents, the locular content of electron‐dense material decreases, and the ‘negative’ membrane image disappears. With further maturation, the inclusions become smaller, and eventually disappear.It is suggested that, in accordance with other studies, the membrane‐bound inclusion of developing sesame leaf chloroplasts is a storage centre for thylakoid precursor materials. The ‘negative’ image observed in the incipient grana may also be a reflection of incomplete assembly of the membranes associated with the accumulation of material within the loculus.
EXPERIMENTS ON THE FACTORS INFLUENCING THE GEOGRAPHICAL DISTRIBUTIONS OF SACCORHIZA POLYSCHIDES AND SACCORHIZA DERMATODEA
Authors: NORTON TREVOR A. 
Published: May 2006

SUMMARYTo investigate the possible causes of the contrasting geographical distributions of Saccorhiza polyschides (Lightf.) Batt. and S. dermatodea (Pyl.) J. Ag., sporophytes of both species were cultured from zoospores under a variety of conditions. The spores of both species were able to survive in the dark for at least 6 months. Thus although, unlike S. dermatodea, S. polyschides is not found within the Arctic Circle, it too can survive the equivalent of the Arctic winter night without light.Water temperatures from 3° C to 25° C were found to influence every stage in the development of both plants from spore settlement and germination, to the production and rate of growth of the sporophytes and it was particularly critical to the fertility of the female gametophyte and to the survival of the sporophyte. The female gametophytes of S. dermatodea became fertile only between 3°C and 10°C, producing numerous sporophytes at 3°C and 5°C but rather few at 10°C. In contrast, those of S. polyschides produced an abundance of sporophytes from 5°C to 17°C, relatively few at 20 and 23°C and none at either 3°C or 25°C. Some grossly abnormal sporophytes were produced at the temperatures close to the tolerance limits of the species. Gametophytes cultured at temperatures unfavourable for sporophyte production survived, but rapidly lost their ability to produce sporophytes.The close correlation between these tolerances and the sea temperatures prevalent at the geographical limits of each species strongly suggests that the absence of S. polyschides from within the Arctic Circle is related to its inability to reproduce sexually or to survive at low water temperatures and that the southward extension of both S. dermatodea and S. polyschides and the unusual distribution of the latter species in the Mediterranean are probably the result of their failure to tolerate the higher sea temperatures during the growing period in summer.
HYPERSENSITIVE REACTIONS OF TOMATO LEAVES TO PHYTOPHTHORA INFESTANS
Authors: MATTHEWSON D. K. 
Published: May 2006

SUMMARYTomato and potato leaves were inoculated with either a compatible or an incompatible strain of Phytophthora infestans. The progress of the ensuing progressive or hypersensitive reactions were followed using light microscopy. Transverse sections of tissue as well as strips of living epidermis were examined. Cell death was found to occur within 10 min of infection by an incompatible strain of the fungus. The migration of the host nucleus to the site of infection, in the hypersensitive reaction, was observed.
SOME FACTORS LIMITING NITRATE UTILIZATION IN ACIDIC AND CALCAREOUS GRASSLANDS
Authors: HAVILL D. C. , LEE J. A. , DE‐FELICE J. 
Published: May 2006

SUMMARYFactors limiting nitrate utilization by plants in acidic and calcareous grassland were examined by analysis of control and ammonium‐fertilized plant and soil material from the field. Plants from these habitats maintained their maximum capacity to synthesize nitrate reductase throughout the growing season. In both soil types, nitrate formation was limited by the ammonium supply. Increasing the availability of soil ammonium stimulated the rate of nitrate utilization. However, in plants from calcareous soils, water stress often impaired nitrate reductase activity. Consequently, during periods of drought, nitrate utilization may be higher in acidic soils than in closely adjacent calcareous sites.
SELF‐POLLEN REDUCES THE NUMBER OF CROSS‐POLLEN TUBES IN THE STYLES OF BRASSICA OLERACEA L.
Authors: OCKENDON D. J. , CURRAH LESLEY 
Published: May 2006

SUMMARYThe number of cross‐pollen tubes in the styles of self‐incompatible kale plants was reduced by 46–94% when self‐pollen was applied to the stigma immediately before the cross‐pollen. Similar reductions were found when the cross‐pollen was applied at time intervals of 2–16 h after the self‐pollen, but little or no reduction occurred when the time interval was 24 h or 32 h. No reductions were found when cross‐pollen was applied before self‐pollen nor when dead cross‐pollen was applied before the live cross‐pollen. Application of onion pollen before cross‐pollen gave a mean reduction of 69%. The results are discussed in the context of current views on the mechanism of self‐incompatibility in Brassica, and their practical implications for the breeding of F1 hybrid brassicas.
MODERN POLLEN RAIN IN FINNISH LAPLAND INVESTIGATED BY ANALYSIS OF SURFACE MOSS SAMPLES
Authors: HICKS SHEILA 
Published: May 2006

SUMMARYThe results of pollen analyses from ten surface moss samples collected from the different regional vegetation types of northern Finland are presented. The main features distinguishing the pollen assemblages and the trends observable in transecting the series of vegetation types are outlined and compared with the results of similar studies from elsewhere. With the aim of using the modern pollen assemblages to interpret fossil ones, a simple graphical method of classifying the boreal assemblages is given and specific limits for the forest types presented are suggested. The inability of this graph to distinguish ‘tundra’ assemblages is noted and additional criteria for separating out this regional type are detailed. Emphasis is also placed on the importance of having absolute pollen frequency values to supplement the relative ones.
A LATE‐GLACIAL AND EARLY POST‐GLACIAL POLLEN DIAGRAM FROM DRIMNAGALL, NORTH KNAPDALE, ARGYLLSHIRE
Authors: RYMER LESLIE 
Published: May 2006

SummaryThe Late Devensian and early Flandrian pollen and sediment stratigraphy of a site from a valley fen at Drimnagall, North Knapdale, Mid Argyll, are described. Six pollen assemblage zones are recognized, of which five arethought to be Late Devensian, and one to be Fiandrian. The assemblage zones, which are more similar to those recognised from Caernarvonshire than to those recognised from the north‐west of Scotland, are interpreted in terms of the vegetational and environmental history of the site.
CHANGES IN CHLOROPHYLL AND CAROTENOID CONTENT, SPECIFIC LEAF AREA AND DRY WEIGHT FRACTION IN SITKA SPRUCE, IN RESPONSE TO SHADING AND SEASON
Authors: LEWANDOWSKA M. , JARVIS P. G. 
Published: May 2006

SUMMARYThe response of chlorophyll and carotenoid concentration, specific leaf area and dry weight fraction in shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) to season and photon flux density has been measured. Shoots were sampled from different heights in the canopy at two forest sites, one thinned, the other unthinned. An increase in specific leaf area and a decrease in dry weight fraction was found in shaded shoots. At both sites, there was a seasonal variation in pigment content, with a summer maximum for chlorophyll and a winter maximum for carotenoid. Pigment content was constant throughout the canopy on the thinned site, but was higher in shaded shoots from the unthinned site.
CADMIUM TOLERANCE OF HOLCUS LANATUS FROM A SITE CONTAMINATED BY AERIAL FALLOUT
Authors: COUGHTREY P. J. , MARTIN M. H. 
Published: May 2006

SUMMARY Holcus lanatus, collected 2.8 km from a large smelting complex, exhibited distinct tolerance to cadmium. Tolerant plants grew less well on normal culture solution than non‐tolerant plants but grew roots at normal rates in the presence of concentrations of cadmium related to those present in the field. These results are discussed in relation to the previous literature of metal tolerance and reference is made to the problems associated with the quantitative measurement of tolerance.
A NOTE ON THE GERMINATION OF NARCISSUS BULBOCODIUM L.
Authors: THOMPSON P. A. 
Published: May 2006

SUMMARYSeeds of Narcissus bulbocodium were exposed to a series of successive temperature treatments involving transfers between incubators and thermogradient bars. Freshly harvested seeds were dormant and failed to germinate at any temperature over the range 3–38°C. A conditioning treatment at 26°C applied to imbibed seeds induced changes which resulted in rapid germination of very high proportions of seed after transfer to temperatures between 5 and 16°C. A conditioning treatment at 16°C was less effective, and at 6°C was practically ineffective. It is suggested that the seed is protected from premature germination under natural conditions by high summer temperatures which themselves act as conditioning treatments and induce the changes which result in rapid spontaneous germination as temperatures fall in autumn at the start of the winter rains.
RESPONSE OF A WILD‐TYPE AND A NON‐NITROGEN‐FIXING MUTANT OF NOSTOC LINCKIA TO DIFFERENT CARBON SOURCES
Authors: LADHA J. K. , KUMAR H. D. 
Published: May 2006

SUMMARYThe wild‐type parental strain and a het+nif− mutant of Nostoc linckia grow heterotrophically in light, with and without DCMU, and in darkness when supplemented with a source of carbon. Glucose and sucrose stimulated heterocyst production. Glucose enhanced the uptake of ammoniacal nitrogen from the medium when parent and mutant were grown in an ammonium‐supplemented medium. Effects of cAMP (sodium salt and dibutyryl), with and without glucose, on growth and heterocyst differentiation of parent and mutant were studied. Dibutyryl cAMP, in general, was found to be toxic to the alga, but the sodium salt of cAMP enhanced growth with glucose. The mutant grew well in a nitrogen‐free medium supplemented with cAMP.
ROOT ORGANOGENESIS FROM FOLIAR DISCS OF CREPIS CAPILLARIS L. WALLR. CULTURED IN VITRO: CYTOCHEMICAL AND MICROSPECTROPHOTOMETRIC ANALYSIS
Authors: BROSSARD DOMINIQUE 
Published: May 2006

SUMMARYNeoformed roots always arose at the upper surface of Crepis capillaris foliar discs grown in vitro on Murashige and Skoog's medium supplemented with indolylacetic acid (10−5 M). Root meristems originated endogenously but direct dedifferentiation of parenchymatous cells located in the vicinity of the leaf veins, in a perivascular position and without any previous callus formation. Their initiation was accompanied by an increase in the starch content of the explants and a strongly starch‐positive zone was always detected in the parenchyma underlying their site of initiation. Cytophotometric examination of the nuclear DNA contents of foliar tissues confirmed their non‐polyploid constitution. The exclusively diploid condition of all the neoformed root meristems was also established.
A MORPHOLOGICAL AND CYTOLOGICAL INVESTIGATION OF COCHLEARIA POPULATIONS ON THE GOWER PENINSULA, GLAMORGAN
Authors: FEARN G. M. 
Published: May 2006

SUMMARYPopulations of Cochlearia officinalis L. and C. danica L. have been investigated on the Gower Peninsula (v.c. 41) and introgressive hybridisation between the two species is suspected of occurring on Worms Head. Individuals in the hybrid population are apparently highly fertile and preferential backcrossing to C. officinalis is thought to be responsible for the enrichment of that species with morphological characters from C. danica. Evidence is presented in support of the theory that plants carrying the ‘B’ chromosomes which are found in certain populations of C. officinalis are segregants from such hybrids.
TOLERANCE TO SALT, PARTIAL ANAEROBIOSIS, AND OSMOTIC STRESS IN AGROSTIS STOLONIFERA
Authors: AHMAD I. , WAINWRIGHT S. J. 
Published: May 2006

SUMMARYThe tolerance to sodium chloride of clones of Agrostis stolonifera from salt marsh, spray zone, and inland habitats was measured in water cultures by a rooting technique and by growth analysis. The order of tolerance was found to be: salt marsh > spray zone > inland. The two methods of measurement of tolerance were found to show good agreement. Salt marsh plants were found to be more resistant to low dissolved oxygen concentrations in the culture solution than plants from the spray zone and inland habitats. With polyethylene glycol 6000 in culture solution, the pattern of resistance to osmotic stress in the absence of sodium chloride was similar to the pattern of resistance to salt.
PLANT COMMUNITIES OF THE ISLAND OF ARRAN, SCOTLAND
Authors: ADAM P. , BIRKS H. J. B. , HUNTLEY B. 
Published: May 2006

SUMMARYThe vegetation of the saltmarshes, raised‐beaches, inland mires, dwarf‐shrub heaths, mountains, and woodlands of the Isle of Arran are described using conventional European phytosociological methods. The floristic affinities of these communities with previously delimited units elsewhere in Britain and in western Europe are described, and the problems of assigning many of the Arran communities into the existing central European phytosociological hierarchy are discussed.
THE BIOLOGY OF MYCORRHIZA IN HELIANTHEMUM MILL
Authors: READ D. J. , KIANMEHR H. , MALIBARI A. 
Published: May 2006

SUMMARYThe mycorrhizal status of Helianthemum chamaecistus was assessed. Vegetative and reproductive tissues of mature plants were free from infection by a fungus capable of producing mycorrhizas and were normally free from any internal fungal infection. The mature gelatinous sheath of the seed was infected by a number of non‐mycorrhizal fungi of which the commonest were the saprophytes, Cladosporium herbarum and Ulocladium chartarum. The so called ‘tuberous roots’ are typical ecto‐mycorrhizal short roots. They develop following infection by a soil‐borne sclerotium‐producing fungus. Isolates of the sclerotia and roots produced typical mycorrhizal short roots in sterile cultures of both Helianthemum and Betula pubescens. This mycorrhizal associate is believed to be Cenococcum graniforme. It is concluded that cyclic infection does not occur in Helianthemum and that the mycorrhizal status of members of this genus is comparable with that of many woody species. The possible ecological significance of the mycorrhizal association is discussed.
SEED ACTIVATION AND SEED GERMINATION UNDER MOISTURE STRESS
Authors: HEGARTY T.W. 
Published: May 2006

SUMMARYSeeds of calabrese and carrot were held at 10°C or 20°C for periods of up to 21 days in water or polyethylene glycol ‘6000’ solutions of from −5 to −20 bars. Seeds were subsequently placed to germinate in a favourable environment or were first dehydrated before transfer to this environment. The seeds’ ability to germinate was virtually unaffected by any of the temperature, water potential or duration treatments. Increasing water stress progressively reduced the levels of water content and oxygen uptake rates after initial imbibition, and delayed the onset of germination with the accompanying increase in these factors. At −15 and −20 bars, water content remained approximately constant throughout the experiment but oxygen uptake rates fell after day 6. The results have a direct bearing both on the seed ‘priming’ treatment used to accelerate seed germination and on the tolerance to drought of seeds in the field.
ACETYLENE REDUCTION BY BLUE‐GREEN ALGAE IN SUB‐TROPICAL GRASSLAND
Authors: JONES KEITH 
Published: May 2006

SUMMARY In situ measurements using the acetylene reduction technique showed that mats of blue‐green algae found amongst kikuyu grass fixed nitrogen throughout the day and night. Daylight fixation increased throughout the morning, fell during the hottest part of the day, and reached a peak (19.2 mg C2H4 m−2 h−1) during the afternoon. Nitrogen fixation was higher on overcast days than on hot sunny days. Nocturnal fixation was also due to blue‐green algae and was sensitive to temperature changes.
THE CYANOPHYTE‐HEPATIC SYMBIOSIS I. MORPHOLOGY AND PHYSIOLOGY
Authors: RODGERS G. A. , STEWART W. D. P. 
Published: May 2006

SUMMARYThe Anthoceros punctatus‐Nostoc and Blasia pusilla‐Nostoc symbioses were investigated. In both associations the Nostoc colonies develop in mucilaginous cavities on the undersurface of the gametophyte. The sporophytes of Anthoceros have no Nostoc colonies; no sporophytes of Blasia were found. The symbiotic algae have been identified as Nostoc sphaericum ex. Born et Flah. The heterocyst frequency of the free‐living isolates is 3–6% but this increases to 30% (Blasia) and 43% (Anthoceros) when the algae are growing symbiotically. On infecting alga‐free gametophytes of Blasia pusilla with Nostoc, algal colonies develop in the cavities within 72 h. The developing Nostoc colonies stretch the cells of the cavity wall and there also arise from a point on the host cavity wall, usually opposite the cavity pore, septate, branched, filamentous protrusions, which increase the surface area of contact between phycobiont and host by about 30% within 4 weeks of colony formation. Such outgrowths may facilitate interchange of metabolites between the alga and liverwort. The Nostoc phycobiont of Anthoceros may infect Blasia and vice‐versa. A strain of Nostoc punctiforme isolated from Gunnera also infects Blasia, but four other Nostoc isolates, including one from cycad root nodules, do not. Five other heterocystous algae, five non‐heterocystous filamentous algae and one unicellular alga tested do not infect Blasia. The nitrogen contents of thalli with Nostoc colonies are significantly higher than those treated with algae which do not develop colonies. The symbiotic algae differ physiologically and biochemically from free‐living algae. They show higher rates of nitrogenase activity (acetylene reduction assay), are depleted of nitrogen‐storing phycobilin pigments and structured granules and although metabolically active do not evolve O2 or fix CO2 photosynthetically, but do have polyhedral bodies which contain the key CO2‐fixing enzyme ribulose‐l,5‐diphosphate carboxylase. The Blasia symbiosis grows well and remains established in the pH range 4–8, at low levels of combined nitrogen (<100 mg I−1 of nitrate‐nitrogen) but not at high levels (100–1000 mg I−1), in the temperature range 10–25°C, and under moist but not waterlogged or desiccated conditions.
DIURNAL PERIODICITY IN SOME COMMON FLOWERS
Authors: EWUSIE J. YANNEY , QUAYE E. C. 
Published: May 2006

SUMMARYThe time of flower opening and closure has been observed in twenty species belonging to nine different families. Increasing light initiates opening in some flowers and different species have different thresholds of response. Other species appear to be unaffected by light intensity.Experiments on the effect of photoperiod on petal movement in Talinum triangulare and Mirabilis jalapa indicate that the photo‐fraction affects the period of the rhythm by altering phase‐timing. A close correlation is suggested between phase‐timing and the automatic self‐pollination mechanism in Talinum possibly also in Mirabilis.Temperature also modifies the period of the rhythm in Tradescantia and Talinum; in the latter, a temperature of 24°C promoted closing.
A HOXNIAN INTERGLACIAL SITE AT FISHERS GREEN, STEVENAGE, HERTFORDSHIRE
Authors: GIBBARD P. L. , AALTO M. M. , BEALES P. W. 
Published: May 2006

SUMMARYInterglacial deposits resting on glacial till and overlain by fluviatile sand and gravel 2 km (1.5 miles) north‐north‐west of Stevenage are shown to be of Hoxnian age. The lower part of the deposit consists of calcareous silty clay formed under late‐glacial and early interglacial conditions with Hippophaë shrubs and Betula woodland in a shallow water pool which contained an abundant flora and fauna. The upper part of the deposit consists of organic sediment and represents the second half of the interglacial during which coniferous trees were dominant. The fragmentary sequence, which is also found at other Hoxnian sites in Hertfordshire, is shown to result from water level changes. The recognition of these changes elsewhere in Eastern England indicates that they may be climatically controlled and thus reflect periods of alternating moister and drier conditons.