bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPARATIVE BIOLOGY OF TUSSILAGO FARFARA L., CHAMAFNERION ANGUSTIFOLIUM (L.) SCOP., EPILOBIUM MONTANUM L. AND FPILOBIUM ADFNOCAULON HAUSSKN.
Authors: MYERSCOUGH P. J. , WHITEHEAD F. H. 
Published: May 2006

SummaryThe four species investigated occur in pioneer habitats but have different distributions. This study of their comparative biology is an attempt to account for these differences.The literature on the factors determining habitats and geographical distribution of each species is reviewed but this gives little or no evidence as to whether the species are causally related to, or merely associated with these factors in their ecological distribution. Experiments were therefore designed to test the causal relationship and mode of action of the factors, and this first paper describes those dealing with germination.It appeared from the literature that factors of probable importance in determining the ecological distributions of the species include mineral nutrients and light requirements. The mineral nutritional requirements of Chamaenerion angustifolium seemed to be particularly high. Tussilago farfara appeared to be the most calcicole and Chamaenerion angustifolium the most calcifuge of the species. Epilobium montanum seemed to be the most shade‐tolerant. Additional factors appeared likely to be involved at the limits of their geographical distributions; these include, along the southern limits, factors operating through the water relations of the species, and along the northern limits factors operating through the temperature relations and length of season of growth of the species.The wind‐dispersed seeds of the species are of low dry weight. Water culture experiments showed that, with regard to germination, Tussilago farfara is most successful and Chamaenerion angustifolium least successful in very low levels of mineral nutrient supply. The germination of Tussilago farfara in relation to increasing acidity is completely inhibited at a bigher pH (3.5) than it is in the other species (pH 3.0). In T. farfara germination is also restricted to the period mid‐April to mid‐June by the limited length of its seed viability and season of fruit dispersal. In the other species, though seed shedding is restricted to summer and autumn, the seed remains viable for at least a year and requires light to germinate. In Chamaenerion angustifolium this light requirement disappears as the temperature is raised to 30°C, but it remains in the two Epilobium species. At low temperatures (10°C) maximal percentage germination occurs under lower levels of illumination in E. adenocaulon than it does in Chamaenerion angustifolium, and this probably underlies the much greater percentage germination attained in Epilobium adenocaulon than in Chamaenerion angustifolium when the seeds are shallowly buried (2 mm). Germination in dry conditions also occurs more readily in Epilobium adenocaulon than in Chamaenerion angustifolium. Epilobium montanum is most similar to E. adenocaulon in germination requirements but differs in that its germination is inhibited at 30°C.
VI. PRELIMINARY STUDIES OF PHOTOSYNTHESIS AND CARBOHYDRATE METABOLISM OF THE LICHEN XANTHORIA AUREOLA
Authors: BEDNAR T. W. , SMITH D. C. 
Published: May 2006

SummaryMost of the carbon fixed in photosynthesis by Xanthoria aureola (X. parietina var. aureola) initially accumulates in sugar alcohols and relatively little is incorporated into insoluble compounds at first. Two kinds of sugar alcohol are involved—mannitol and a pentitol. During the early stages of photosynthesis, much more carbon accumulates in the pentitol than in mannitol. Within 9–15 minutes of exposure to NaH14CO3 in the hght, the level of 14C in metabolic intermediates presumably common to both symbionts (PGA, hexose monophosphates, organic acids) became more or less steady and remained so for several hours. It was concluded from this that it is likely that the flow of carbon from alga to fungus is relatively rapid and efficient, and achieved a steady rate within 15 minutes of the start of the experiment.
A METHOD OF MAINTAINING FRACTIONS OF FIELD CAPACITY IN POT EXPERIMENTS
Authors: WHITEHEAD F. H. , HOOD J. S. R. 
Published: May 2006

SummaryDifficulties in the maintenance of fractions of field capacity in pot experiments by existing methods are discussed. A new technique, only applicable at present to artificial soils, is described. It consists of blowing saturated air through the soil maintained at an appropriate temperature difference until the required field capacity is achieved. Results obtained are described briefly.
THE CUTICLE OF THE LEPIDODENDROID STEM
Authors: THOMAS B. A. 
Published: May 2006

SummaryThe value of the cuticle in the study of the stems of Carboniferous arborescent lycopods is discussed. The cuticle gives information about the stomata (which are very numerous suggesting that the tissues beneath were vigorously photosynthetic), it is sometimes of value in demonstrating the presence of a ligule pit where this is concealed, and it helps understanding of how the cortex enlarged in certain species. The cuticle may also be of value in elucidating taxonomic relationships between various stems.
THE USE OF EPIDERMAL CHARACTERS IN PHYLOGENETIC CONSIDERATIONS
Authors: STACE C. A. 
Published: May 2006

SummaryIn order to ascertain the phylogenetic significance associated with leaf epidermal characters eight genera of mangroves in the families Combretaceae, Rhizophoraceae and Avicenniaceae were compared with each other and with non‐mangrove genera of the same families. The mangrove genera share a number of common features, but are easily separated into three groups coinciding with the three families. Further differences, of successively lesser order, enable all eight genera and some of the species within them to be distinguished. With regard to epidermal characters the mangroves of any one family show closer resemblance to the non‐mangroves of the same family than to mangroves of other families. Differentiation by epidermal characters thus closely parallels that by characters more usually used in plant taxonomy.
EFFECT OFENDOGONEMYCORRHIZA ON PLANT GROWTH
Authors: DAFT M. J. , NICOLSON T. H. 
Published: May 2006

SummaryThe growth effects of three mycorrhizalEndogoneendophytes on tobacco, tomato and maize were examined. The extent of the stimulus obtained depended on nutrient conditions and the subsequent level of infection developed in the root system. Marked stimulation occurred with low phosphate availability and high root infection.
ABSORPTION OF NITROGEN BY MYCORRHIZAL ROOTS OF BEECH
Authors: CARRODUS B. B. 
Published: May 2006

SummaryBeech mycorrhizas are capable of absorbing ammonia and simple organic compounds from solution but nitrate is a poor source of nitrogen if it is absorbed at all. The absorption of ammonia is associated with synthesis of organic nitrogen compounds in the tissues amongst which glutamine appears as the most prominent. The factors which affect absorption are those expected to affect metabolic activity. The rate of ammonia absorption is stimulated especially at certain times of year by exogenous sugars applied during or immediately before ammonia absorption. Prefeeding with either glucose or fructose stimulates absorption and so it may be concluded that trehalose, glycogen and mannitol may all be utilized in the process. Low concentrations of bicarbonate, up to 7·5 mM, enhance ammonia absorption as do succinic, fumaric and malic acids. Other organic acids applied exogenously either do not affect uptake or reduce its rate.
THE EFFECT OF BICARBONATE ON THE UPTAKE OF IRON IN FOUR RELATED GRASSES
Authors: WOOLHOUSE H. W. 
Published: May 2006

SummaryA sodium bicarbonate concentration of 20 m‐equiv./l brought about a partial inhibition of uptake of 59Fe by intact roots of Deschampsia flexuosa; subsequent translocation of the 59Fe to the shoots was also inhibited. A similar concentration of bicarbonate produced no inhibition of uptake by the related grasses Holcus mollis, Arrhenatherum elatius and Koeleria cristata. The amount of 59Fe translocated to the shoots in the course of the experiment was less than 1% of the amount of isotope which became associated with roots. Whilst the high uptake by the roots is suggestive of some absorption on the root surface there is evidence also of uptake, probably into a substantial pool of free iron within the root.
EFFECTS OF GIBBERELLIC ACID ON GROWTH, TUBER FORMATION AND CARBOHYDRATE DISTRIBUTION IN SOLANUM TUBEROSUM
Authors: LOVELL P. H. , BOOTH A. 
Published: May 2006

SummaryTwo series of experiments have been described. In the first, plants treated with gibberellic acid (GA), together with untreated controls, were harvested at intervals from the time of planting and the growth of shoots, stolons and tubers measured and the dry weight and sugar and starch values determined. Treatment with GA enhanced both shoot and stolon growth and dry weight, but delayed tuber initiation. The appearance of starch correlated closely with tuber Initiation in both treated and untreated plants, but there was no correlation between sugar level in the stolons and their tuberization. In the second, 14CO2 was fed to single leaves of plants in which tuber initiation had just commenced. In untreated plants, almost all the translocated 14C accumulated in the tubers, in plants pre‐treated with GA a few days earlier, practically no 14C was detected in the stolons or tubers, but accumulated in the shoot, particularly at the apices. There were significant differences in the relative amounts of 14C in the ethanol‐soluble and ethanol‐insoluble fractions in the two treatments. The pattern of translocation shown is held to reflect the activity of the various metabolic sinks, the activity of these sinks being hormonally controlled.
FOLIAR SENESCENCE IN PERILLA FRUTESCEXS (L.) BRITT
Authors: HARDWICK K. , WOOLHOUSE H. W. 
Published: May 2006

SummaryData are presented from analyses of the changes in dry weight, chlorophyll, protein and RNA content of the third pair of leaves of Perilla frutescens from the time of completion of leaf expansion to abscission. It is shown that the amounts of these leaf constituents change at different rates and that the changes occur at different rates in different parts of a leaf.
THE ULTRASTRUCTURAL BASIS OF HYPHAL GROWTH
Authors: MARCHANT R. , PEAT A. , BANBURY G. H. 
Published: May 2006

SummaryTwo vesicular systems associated with wall synthesis have been observed in Phycomyces blakesleeanus, Fusarium culmorum and Coprinus lagopus; these fungi have chitin in their walls. A system of vesicles produced by the endoplasmic reticulum is believed to be responsible for ‘primary’ wall synthesis. These vesicles fuse with the plasmalemma. Multi‐vesicular bodies from which lomasomes are formed are also produced by the endoplasmic reticulum; these are seemingly associated with ‘secondary’ wall synthesis, and it is suggested that they may be concerned with chitin deposition in the wall. Pythium ultimum, which has non‐chitinous walls, lacks multi‐vesicular bodies. Structures which have some features in common with lomasomes are present in Coprinus lagopus and Pythium ultimum, but they are postulated to arise by elaboration of the plasmalemma.
PERFECT STATES OF RHIZOCTONIAS ASSOCIATED WITH ORCHIDS
Authors: WARCUP J. H. , TALBOT P. H. B. 
Published: May 2006

Summary Rhizoctoma isolates obtained from terrestrial orchids in South Australia and Great Britain have been induced to fruit in culture. The perfect states thus obtained belong to Thanatephorus cucumeris (Frank) Donk, T. sterigmaticus (Bourdot) Talbot, T. orchidicola Warcup and Talbot, Ceratobasidiinn cornigerum (Bourdot) Rogers, C. obscurum Rogers, Ceratobasidium sp. indet., Tulasnella calospora (Boudier) Juel, T. asymmetrica sp. nov., Tulasnella sp. indet. and Sebacina lermifera Oberwinkler. Tulasnelta calospora was found to be the perfect state of three cultures considered to be Rhizoctonia repens Bernard. The status of the orchid‐fungus association is discussed.
THE EFFECT OF THE LEAF ON DIFFERENTIATION OF PRIMARY XYLEM IN THE INTERNODE OF COLEUS BLUMEI BENTH.
Authors: WANGERMANN ELISABETH 
Published: May 2006

SummaryIf a very young leaf blade of Coleus bluinei Benth. is excised, the differentiation of primary xylem in the traces belonging to the treated leaf virtually ceases and all the cells in that half of the internode below the leaf are reduced in size. If the excised blade is replaced by auxin paste, differentiation of xylem proceeds almost normally and cell size is restored. Autoradiographs of sections of internodes treated apically with radioactive auxin paste indicate that after trans‐location auxin is heavily concentrated in the vascular bundles.
COMPARATIVE BIOLOGY OF TUSSILAGO FARFARA L., CHAMAFNFRION ANGUSTIFOLIUM (L.) SCOP., EPILOBIUM MONTANUM L., AND FPILOBIUM ADFNOCAULON HAUSSKN.
Authors: MYERSCOUGH P. J. , WHITEHEAD F. H. 
Published: May 2006

SummaryThis paper describes the results of experiments on the growth of Tussilago farfara, Chamaenerion angustifolium, Epilobium montanum and E. adenocaulon in glasshouse conditions and also results of field experiments with Chamaenerion angustifolium and Epilobium adenocaulon. These results and results of work on germination, reported in the previous paper of this series, are discussed in relation to the ecology of the species.Glasshouse experiments showed that the growth forms of Epilobium montanum and E. adenocaulon are under the control of daylength but the growth form of Chamaenerion angustifolium is not controlled by it. All four species were found to make adequate growth under a range of shade conditions and nutrient supply. In all four species, plasticity of form of adaptative significance was shown to occur with respect to both light and mineral nutrient supply.Certain attributes of the species appear to be of high significance in determining, under natural selection, their ecological distributions. These include the longevity of dormant seed and the efficiency of dormancy mechanisms. Differences in these between the species appear to lead to differences in their occurrence in deciduous woodland and in their occurrence as weeds of cultivated ground.The small seed size of the species together with their commitments to large amounts of seedling growth relative to seed weight, operate to restrict seedling establishment to open sites in which supplies of light and mineral nutrients are adequate. The growth commitments of C angustifolium appear to be appreciably larger than in the other species and in C. angustifolium seedling establishment was found to be restricted by the nutritional status of certain experimental sites to a greater extent than in Epilobium adenocaulon.Differences between the species in growth form and pattern of vegetative reproduction appear, in part, to account for the differences in their occurrence in sites with mobile soil surfaces and in closed communities.The species differ in capacity for germination and viable growth on acid substrates. Also, between the species there are differences in their growth in regimes of high calcium/low potassium concentrations. Both these differences are considered to be of importance in determining respective differences of distribution of the species on acid and on lime‐rich soils.Finally, some assessment is made of the relative importance of genetic diversity and phenotypic plasticity to the survival of the species in the wide ranges of habitats in which they occur. The importance of differences in breeding system in maintaining different levels of diversity in the species is discussed.
STUDIES IN SEED DORMANCY
Authors: BRADBEER J. W. , COLMAN B. 
Published: May 2006

SummaryThe dormancy of hazel seeds (Kent cob nuts) has been found to be broken by less than 30 days chilling at 5° C. During 50 days chilling there was no detectable growth of the embryonic axes although growth rapidly commenced when the temperature of 50‐day chilled seeds was raised to 20° C.Both cotyledon slices and embryonic axes from dormant seeds showed active metabolism of [2‐14C] acetate, the operation of the following enzymes and enzyme systems being inferred: TCA cycle, glutamate dehydrogenase, aspartate aminotransferase and those involved in the syntheses of lipid, protein, sucrose, DNA and RNA. As no evidence has been found of the appearance of further metabolic pathways during chilling it is suggested that the block to the germination of dormant seeds may be in the partial blockage of a metabolic pathway. Quantitative changes in the distribution of [2‐14C]acetate label, which occurred during chilling, have been interpreted as indicative of a fall in the lipid synthesizing ability of cotyledons and a rise in the aspartate, glutamate and protein synthesizing ability of the embryonic axes. The embryonic axes also appeared to develop increased TCA cycle activity and showed increased sucrose labelling. However, none of these changes appeared to occur at as early a stage of the chilling process as the change in nucleotide metabolism previously reported.
STUDIES IN SEED DORMANCY
Authors: WOOD A. , BRADBEER J. W. 
Published: May 2006

SummaryThe nucleic acids of the cotyledons of hazel (Corylus avellana L.) seeds have been extracted by a modified phenol method and subsequently fractionated on a methylated serum albumin‐kieselguhr (MAK) column. Fractions which appear to contain soluble RNA (sRNA), ribosomal RNA (rRNA) and messenger RNA (mRNA) have been found in addition to one which contains both DNA and RNA (DNA‐RNA).During the first 10 days after imbibition there was little nucleic acid synthesis in seeds kept at either 4° C or 20° C. However, changes in the sRNA appear to have occurred at both temperatures and the formation of additional sRNA from other nucleic acid molecules has also been inferred. It is suggested that imbibition may result in the activation of a postulated stable and inactive form of sRNA occurring in the dry seed. Imbibition also induced the appearance of the light and heavy fractions of rRNA. After 10 days at 4° C 20 % of the seeds were able to germinate at 20° C. Further chilling caused a substantial fall in seed dormancy together with considerable nucleic acid synthesis. It would appear that nucleic acid synthesis does not play a part early in the process of breaking hazel seed dormancy by chilling, but it is possible that it plays a part at a later stage of the process.Seeds, chilled at 4° C for 50 days and then transferred to 20° C for 5 days showed an apparently large increase in the rate of cotyledonary nucleic acid metabolism. A net fall in the content of rRNA and DNA‐RNA was also found.
THE DIFFERENTIATION AND FATE OF THE BRACKEN (PTERIDIUM AQUILINUM) FROND AND THEIR RELATION TO THE AGE‐STRUCTURE OF THE SHOOT AND FROND POPULATION
Authors: WATT A. S. 
Published: May 2006

SummaryOn an acid, dry infertile soil in a frost pocket, there are more short shoots (potential fronds) in bracken than differentiated fronds, and more differentiated fronds than emerge from the soil, and more emergent fronds than live in August.Factors affecting the inception, differentiation and fate of fronds are examined. The inherent tendency of fronds from young shoots to develop and to emerge before those from old renders them more liable to lethal winter and spring frosts and to crippling spring frosts. Drought acts mainly on the late emerging fronds. The normal sequence of emergence may be upset.Through their destruction of reserves and their effect on the means of replenishing them, annually fluctuating frost and drought influence the number of shoots initiated yearly, and hence the age‐structure of the shoot population. A senescent population of bracken is defined as one in which the proportion of young to old shoots is low, and fronds from young shoots to fronds from old is also low. Frost and drought are the causes (not necessarily exclusive) of senescence in this area.
NOTE ON THE DETERMINATION OF LEAF WATER‐POTENTIAL
Authors: TINKLIN R. 
Published: May 2006

SummaryA simplified modification of the micro‐osmometer of Macklon and Weatherley (1965a) for the determination of depressions of water‐potential in leaves, ΔW (DPD), is described.The apparent minimum ΔW of 31/2 atm for non‐transpiring water‐culture plants of Ricinus communis reported by Tinklin and Weatherley (1966) is considered further. Evidence is provided that this is in fact a zero value, the level recorded being due to the errors induced by water loss on sampling and by water uptake by continued growth of tissue during determinations. However, a simple subtraction of 31/2 atm from all ΔW values is not proposed as there are indications that a threshold AH’may exist above which continued growth does not occur, so that higher ΔW records will approach more closely the true value.
STUDIES IN THE GERMINATION AND ESTABLISHMENT OF JUNCUS SQUARROSUS
Authors: WELCH D. 
Published: May 2006

SummaryObservations and experiments on the germination and establishment of Juncus squarrosus are described. Germination is confined to seeds lying on the ground surface and normally occurs in the spring. It was shown experimentally that germination can occur on a variety of media, including a calcareous soil, but that the germination percentages were reduced on dry soils. Complete germination of viable seeds occurred in 13 days in suitable conditions (frequent watering, 12 hours of light per day, and a room temperature of 23° C), but the rate was lower when less light and lower temperatures were given. At 14° C, germination did not occur in darkness and it would appear that light is either necessary for germination at this temperature, or raises the temperature of the medium surface sufficiently for germination to occur. Upland winter conditions had no effect on the viability of the seeds.Development of both root and shoot is very slow and evidence is presented that lack of competitive ability is the reason for the infrequency of successful establishment of seedlings. Colonization on blanket peat was found to be encouraged by lime and fertilizer treatments, but very few seedlings became established unless competition from Calluna, Eriophorum or a sown grass was reduced.
RECOVERY FROM DORMANCY IN ROOTS
Authors: CLOWES F. A. L. , STEWART HELEN E. 
Published: May 2006

SummarySeedlings of Zea mays have been grown at 5° C to induce dormancy in their root apices. Recovery has been studied when the plants were returned to 21° C by observing the changes in cell patterns, in the labelling of nuclei with [6‐3H]thymidine and in rates of mitosis measured by metaphase accumulation. Recovery involves stimulation into division of the cells of the quiescent centre and the consequent repopulation of other regions of the meristem from the quiescent centre. We suggest that the reason for this behaviour is that the quiescent centre cells are less badly injured during the cold because their nuclei, which are normally at G1, rest there. By contrast, in the surrounding meristem, many of the cells being at S or G2 at the onset of cold, proceed through mitosis to the following G1 and, in so doing, suffer chromosomal damage and impairment of reproductive potential. This view is supported by the hypersensitivity found in the cap initials, which normally have no G1 phase. Some previous work on dormancy and on the organization of meristems is discussed in the light of this theory.
A NOTE ON SUCROSE AND GLUCOSE UPTAKE BY APICAL SEGMENTS OF TOMATO ROOTS
Authors: THOMAS D. R. , WEIR N. R. 
Published: May 2006

SummaryAccumulation and uptake of sugars from glucose and sucrose by apical segments of excised tomato roots were compared. Greater uptake and accumulation occurred from sucrose which may, in part, contribute to the characteristically better growth of the roots in sucrose.