bluuebunny/crossref_metadata_2025_split huggingface dataset:
PLANT GROWTH AND THE AERIAL ENVIRONMENT
Authors: HUGHES A. P. 
Published: May 2006

SummaryThe apparent efficiency of conversion of incident light energy (ɛapp/i) by whole plants of Im‐patiens parviflora in a range of natural and artificial light climates has been calculated from growth analysis data. It was found that it ranged from 1.3% in full natural daylight to 7.5% in extreme shade (metal shades transmitting 7% daylight). The corresponding figures for real efficiency, i.e. corrected for respiration losses, ɛtrue/i were 3.0% and 12.5% respectively. In the growth cabinets with light intensities roughly equivalent to 7—15% daylight a combination of two Blue/six De Luxe Warm White fluorescent tubes gave values of ɛapp/i averaging 7.4% for plants grown at 15°C, 5.9% for those at 10°C and 6.5% at 20°C. Four Daylight/four De Luxe Warm White averaged 5.8% at 20°C and Red (magnesium arsenate) at 20°C was highest with 7.7%. Blue tubes gave 6.0% apparent efficiency with plants at 15°C. In all the cabinet experiments and in the extreme shade in natural daylight the plants were small with leaves scarcely overlapping. In more open, natural daylight sites some self‐shading would have occurred. When the efficiency was expressed on a quantum basis, rather than on total energy, and correction for temperature differences applied, there was little difference between Blue, Blue‐white and Red, with Daylight‐white somewhat lower. On the basis of assimilation for a given number of lamps the combinations two Blue/six De Luxe Warm White and four Daylight/four De Luxe Warm White were the best.
THE STRATIGRAPHY AND POLLEN ANALYSIS OF A RAISED PEAT BOG AT LLANLLWCH, NEAR CARMARTHEN
Authors: THOMAS K. W. 
Published: May 2006

SummaryOrganic deposition commenced at Llanllwch in Zone VI at the site of a Post‐glacial lake. The lake was colonized by reedswamp and succeeded by fen as the lake level was lowered. Before the end of Zone VI a flushing effect of the bog surface allowed Molinietum to develop which was replaced by Callunetum until, in Zone VIIb, probably due to increased precipitation. Sphagnum bog developed. In the raised bog peat a recurrence surface has provided a radiocarbon date of 1200 B.C. Forest destruction began in Neolithic times, and there is evidence for intensive human activity from Norman times to the present.
HEAVY METAL TOLERANCE IN POPULATIONS OF AGROSTIS TENUIS SIBTH. AND OTHER GRASSES
Authors: GREGORY R. P. G. , BRADSHAW A. D. 
Published: May 2006

SummaryPopulations of Agrostis tenuis can be found growing on a variety of different mine workings in conditions of metal contamination toxic to most higher plants. Samples of such populations together with samples of populations taken from ordinary pastures were tested for tolerance to high concentrations of copper, nickel, lead and zinc by measuring the effect of these metals on the rooting of tillers. The soils in which the populations were originally growing were analysed for each of the four metals and the tolerances of the populations have been related to the levels of the metals in the soils.In general, the mine populations show remarkable tolerance to the particular metals present in high quantities in the soils of their original habitats: the pasture populations do not show this tolerance. The tolerance is specific, for, except in the case of zinc and nickel, tolerance to one metal is not accompanied by tolerance to any other. There must, therefore, be three specific tolerances in the one species. Individual tolerances can however occur together and this can be related to the occurrence of the two metals together in toxic quantities in the soil.The tolerances must be genetically controlled but the physiological mechanism involved is not clear. A number of other species were also shown to have populations tolerant to high levels of zinc.
STUDIES IN THE PHYSIOLOGY OF LICHENS
Authors: SMITH D. C. , DREW E. A. 
Published: May 2006

SummaryCarbon fixed by photosynthesis in the algal layer can move into the medulla of Peltigera polydactyla within 30 minutes. This movement continues at a steady rate equivalent to 40–50% of the total rate of carbon fixation in photosynthesis, and it can also continue for a time in darkness. Fixed carbon accumulates initially as soluble compounds, especially mannitol, both in the algal layer and in the medulla. Since translocation in the thallus is relatively rapid it follows that the first stage of this process, namely, the transfer of photosynthetic products within the algal layer from an algal cell to its associated fungal hyphae, is also a rapid process.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J. 
Published: May 2006

SummarySubjecting peas to high pressures of oxygen produced a progressive decrease in CO2 output with accumulation of citrate, pyruvate, alcohol and acetate (Turner and Quartley, 1956; Pritchard, 1961). The present results show that the progressive decrease in CO2 output in high oxygen was also, in general, accompanied by large and continuing decreases in adenosine triphosphate and in the glycolytic intermediates, dihydroxyacetone phosphate, 3‐phosphoglycerate and phosphoenolpyruvate. Fructose diphosphate also decreased more rapidly initially in oxygen than in air in three of the four experiments.Oxygen poisoning thus appears to ‘block’ partially or completely, certain respiratory pathways, the most important ‘block’ in plant tissues probably being that at aconitase (Pritchard, 1961). The ‘blocks’ are visualized as decreasing both the CO2 output and the rate of formation of adenosine triphosphate. Thus in the present experiments the decreased CO2 output in oxygen was associated with a decrease in content of adenosine triphosphate. The decrease in the content of the latter may in turn reduce the rates of hexokinase and phosphofructokinase phosphoryla‐tion and so cause the observed decreases in contents of fructose diphosphate, and, at late stages, of glucose‐6‐phosphate. The decrease in fructose diphosphate appeared to reduce the rate of glycolysis, as shown by the decrease in the contents of glycolytic intermediates.
CARBOHYDRATE PHYSIOLOGY OF MYCORRHIZAL ROOTS OF BEECH
Authors: LEWIS D. H. , HARLEY J. L. 
Published: May 2006

SummaryThe presence of several classes of reducing substances in mycorrhizal roots of beech is demonstrated, throwing considerable doubt on the values of ‘easily soluble reducing substances’ which have been used for correlation with degree of mycorrhizal infection by several workers. The soluble sugars of beech mycorrhizas are glucose, fructose, sucrose and trehalose, together with the acyclic polyol, mannitol and two cyclic polyols, myo‐inositol and an unidentified inositol. Trehalose and mannitol are absent from uninfected roots showing their presence to be dependent on fungal infection. Methods for the individual assay of the soluble carbohydrates are presented. The main sugars obtained by acid hydrolysis of the insoluble residue of mycorrhizas are galactose, glucose, mannose, arabinose, xylose, fucose, ribose, rhamnose and a deoxypentose provisionally identified as deoxyribose. The mannose and deoxypentose polymers are absent from beech tissue and deoxyhexose polymers from the fungus. Much of the glucose is derived from fungal glycogen. Mycorrhizas accumulate principally trehalose and glycogen from exogenous glucose and trehalose, and mannitol from fructose and mannitol. The pattern of synthesis from exogenous sucrose is intermediate between glucose and fructose. The results are compared with those obtained for other fungi by other workers and a possible ecologically significant role for mannitol is suggested.
THE DURATION OF THE G1 PHASE OF THE MITOTIC CYCLE AND ITS RELATION TO RADIOSENSITIVITY
Authors: CLOWES F. A. L. 
Published: May 2006

SUMMARYThe duration of each phase of the mitotic cycle in four regions of the root meristem of Zea mays has been determined by pulse labelling with 3H thymidine. S, G2 and mitosis are similar in length in all the regions, but G1 differs considerably and is largely responsible for the diversity in rates of mitosis. G1 is non‐existent in the cap initials, 151 hours in the quiescent centre, and 2–4 hours in the stele.These data, together with information on sensitivity to ionizing radiation, suggest that it is the ratio of the lengths of G1 to the rest of the mitotic cycle that decides how resistant a tissue will be to radiation and they lead to a general explanation of the law that rapidly dividing cells are more susceptible than slowly dividing cells. The extreme sensitivity of the cap initials and the high resistance of the quiescent centre are correlated with the brevity of G1, in the former and the prolongation of G1 in the latter. The fraction of the mitotic cycle spent in G1 (when each nucleus has only the 2C amount of DNA) therefore probably determines both radio‐sensitivity and rates of division.
UPTAKE OF 22Na BY INTACT SEEDS
Authors: GIFFORD G. F. , NELSON E. D. 
Published: May 2006

SUMMARYWhen the intact seeds of forty‐two species were exposed to a salt‐isotope solution containing 22Na it was found that about 75% of the different seeds showed signs of accumulation of the 22Na. All halophytes and species associated with halophytes, with one exception, displayed the above‐mentioned pattern. The seeds responded to a 24 hour exposure period by either decreasing, remaining essentially the same, or increasing in uptake of 22Na as compared with an 8 hour exposure period. Surface area of the seeds, as determined for twenty species, had no apparent relationship to 22Na uptake. The time interval to first germination showed a relationship to sodium uptake for grasses only, and this was valid only up to a 48 hour germination period. The two grasses Oryzopsis hymenoides and Secale montanum. were for some reason an exception to the above trend. The per cent total germination of the seeds after 149.5 hours showed no relationship to 22Na uptake.
AN IAA‐INDUCED STIMULATION OF GROWTH OF ROOTS OF VICIA FAB A PREVIOUSLY TREATED WITH COLCHICINE
Authors: DAVIDSON D. , MACLEOD R. D. , TAYLOR JANET 
Published: May 2006

SUMMARYRoots of Vicia faba were treated with a 0.02% solution of colchicine for 2 hours. Some roots were also treated, 22 hours later, with 10‐6 M IAA for I day. All beans were grown on for a further 6 days and the total growth of primary and lateral roots was determined.Primary roots treated with colchicine and then IAA showed significantly greater growth than roots treated only with colchicine. Lateral roots produced by the treated primary roots showed significantly less growth when treated with colchicine and IAA than when treated only with colchicine. Primary‐ roots treated with colchicine and IAA had fewer polyploid cells, in division, than roots treated only with colchicine, indicating that recovery of the diploid condition is related to the rate of root growth.IAA treatment does not produce an immediate stimulation of growth; no effect was seen for 3 days. Its effect appears to be one of facilitating the normal mechanisms by which an apical meristem recovers from a colchicine treatment. The stimulation of root growth by concentrations of IAA that are normally inhibitory leads us to conclude that one result of a treatment with colchicine is a reduction in the level of natural auxin in a root.
PLANT GROWTH AND THE AERIAL ENVIRONMENT IX. A SYNOPSIS OF THE AUTECOLOGY OF IMPATIFNS PARVIFLORA
Authors: HUGHES A. P. 
Published: May 2006

SUMMARYMany features discussed in detail in earlier papers are correlated with particular emphasis on (i) the partition of dry material into leaf, stem and root, (ii) the leaf auxochrone, (iii) the interrelationship of flower opening, leaf number and vascularization, (iv) the extension of the hypocotyl, (v) ontogenetic drifts in specific leaf area, (vi) the relationship between specific leaf area and unit leaf rate, and (vii) a general synopsis in the form of a flow diagram. The flow diagram summarizes the overall autecology of the species and indicates the relative importance of factors affecting dry‐weight distribution, leaf expansion and the inverse relationship between specific leaf area and photosynthesis (as measured by growth analysis), in determining the growth rate of the plant in various conditions.
THE INHERITANCE OF MATING TYPE IN DESMIDS
Authors: BRANDHAM P. E. , GODWARD M. B. E. 
Published: May 2006

SUMMARYFertile cultures of eight species of desmids have been established. Six are homothallic, one is heterothallic and one has homothallic and heterothallic varieties. Two incompatible pairs of mating types have been found in the last species (Cosmarium botrytis). Incompatibility and isolation of mating types in natural habitats may be responsible for the apparent sterility of many species of desmids. Conjugation between two morphologically distinct varieties has been induced. The inheritance of mating type has been studied. A lethal factor affecting this inheritance has been noted in one species. Mechanisms for the inheritance of the lethal factor are suggested.
INTERACTION OF GIBBERELLIC ACID AND INDOLE‐ACETIC ACID IN THE DIFFERENTIATION OF WOUND VESSEL MEMBERS
Authors: ROBERTS L. W. , FOSKET D. E. 
Published: May 2006

SummarySucrose‐agar media supplemented with indole‐acetic acid (0.05 ppm) and gibberellic acid (0.05 or 0.5 ppm) increased the formation of wound vessel members in transverse tissue slices excised from the second internode of Coletis blumeni (Bentb.) stems. The treated tissue slices showed the initiation of cambial activity, whorls of wound vessel members in the cortex, and adventitious root formation after prolonged incubation. Also, incompletely differentiated secondary xylem cells and wound vessel members were observed which exhibited relatively thin secondary wall striations, and stained weakly with phloroglucinol‐HCl and Safranin O.
THE UTILIZATION OF ACETATE BY NEOCOSMOSPORA VASINFECTA
Authors: BUDD K. 
Published: May 2006

SummaryMycelium of Neocosmospora vasinfecta, harvested during active growth, was incubated for up to 10 minutes in dilute solutions of [1‐14C]acetate or [2‐14C]acetate. Radioactivity in the respiratory CO2 and in identifiable compounds extracted from the mycelium was measured. Closely similar results were obtained with both [1‐14C]acetate and [2‐14C]acetate except for the loss of radioactivity to CO2, which took place much more rapidly from the [1‐14C]acetate. Water‐soluble compounds accounted for over 80% of the radioactivity of the mycelium. With incubation periods of up to 2.5 minutes, most of the radioactivity in the water‐soluble material was associated with organic acids, whereas with longer incubation, the label in basic compounds predominated, Glutamate was consistently the most heavily labelled basic compound, with small amounts of radioactivity in glutamine and aspartic acid. Radioactivity in the organic acid fraction was practically confined to citric acid after 2.5 minutes incubation; succinic, malic and other acids were significantly labelled after 10 minutes. The specific activities of these acids after 10 minutes decreased in the order citrate, succinate, malate, suggesting their involvement in the tricarboxylic acid cycle.The results are discussed in relation to the importance of the tricarboxylic acid cycle in acetate utilization, nitrogen assimilation and respiration.
THE REPRODUCTIVE CAPACITY OF JUNCUS SQUARROSUS
Authors: WELCH D. 
Published: May 2006

SummaryThe six attributes which govern the reproductive capacity of Juncus squarrosus have been measured in plants from a variety of habitats at different altitudes, mainly in an area of moorland at the head of Teesdale in the north Pennines.It was found that about eighty inflorescences per square metre were produced, but this number was reduced in adverse conditions such as at high altitudes in unfavourable seasons, or when there was a spring drought. The average number of florets per inflorescence varied from about six on well‐drained sites and at high altitudes to twenty‐two in moist conditions at lower levels. Up to 60% of the florets ripened into capsules, but in 1962, a very poor summer, less than 10% ripened at 550 m, and in 1963 only 19% ripened at 700 m. Altitude and the seasonal climate also had a marked effect on the number of seeds per capsule, and their viability. In good conditions fifty seeds developed per capsule, and viability approached 100%, but in 1962 at all altitudes, and in 1963 at high levels, values were much lower than this. Normally most of the seeds produced are dispersed, but close to the limit of capsule maturation the capsules may never open.The total number of viable seeds dispersed was estimated. Even in 1962 about 150 viable seeds per m2 were dispersed at 550 m, and in 1963 the figures varied between 2000 and 13,500 seeds per m2, according to the soil conditions. At the lower levels more seeds may be produced but this is counterbalanced by losses caused by larvae of the moth Coleophora alticolella.
POLLINATION AND BREEDING BEHAVIOUR IN THE TRIFOLIUM RUEPPELLIANUM COMPLEX IN KENYA
Authors: BOGDAN A. V. 
Published: May 2006

SummaryThe pollination and breeding behaviour of Trifolium baccarinii, T. mattirolianum and of four varieties of T. rueppellianum, all allied taxa constituting the T. rueppellianum complex, were studied at the National Agricultural Station, Kitale, Kenya. T. baccarinii and varieties minimiflorum and lanceolatum of T. rueppellianum have cleistogamous flowers which need no treatment for seed formation similar to var. preussii which, however, opens its flowers during the flowering. Var. rueppellianum does not form seed without tripping which, in the field, is done by bees.A recessive white‐flowering form was used for assessing the amount of natural cross‐pollination, which was found to be from under 1% to 10%. Two unusual forms: erect and giant were also studied. T. mattirolianum sets seed only under eross‐pollination and T. rueppellianum may serve as a male parent. F1 crosses of T. mattirolianum×T. rueppellianum form seed without cross‐pollination although tripping is necessary.
THE GERMINATION OF POLYGONUM CONVOLVULUS L.
Authors: TIMSON J. 
Published: May 2006

SummaryThe dormancy found in fresh nuts of Polygonum convolvulus L., which persists in nuts stored dry in the laboratory, and their germination has been studied. Methods of breaking this dormancy by means of low temperature treatment and by the use of gibberellic acid, thiourea, uracil, thymine, adenine, guanine and cytosine are described. A method of recording germination ability which weights the rapid germination necessary for the establishment of this species in nature has been used. Mechanisms of the dormancy and dormancy‐breaking are discussed.
THE MOVEMENT OF RUBIDIUM ACROSS THE ROOT OF HORDEUM VULGARE (L)
Authors: CROSSETT R. N. 
Published: May 2006

SummaryAn automatic system is described for the continuous measurement of absorption and translocation of radioactive nuclides by living plants growing in a controlled environment. The system is suitable for studying the behaviour of nuclides emitting β particles in the energy band between 0.5 and 2.5 MeV. The reliability and precision of the system are discussed.Experiments on the absorption and translocation of 86Rb by 10‐14‐day‐old seedlings of barley are reported. It was found that when 86Rb was absorbed from 10−5 M 86RbNO3 the rate of movement into the shoot (translocation) increased with time, but that when absorption was from a higher concentration of RbNO3 a constant rate of translocation was observed after the initial rise during the first 3 hours. When radioactive seedlings were placed in an inactive 10−5 m RbNO3 solution no loss of 86Rb to the solution was detected, but 86Rb moved to the shoot, the decrease of 86Rb in the root following first‐order kinetics. When radioactive seedlings were transferred to a 10−4 m RbNO3 solution more complex kinetics of decrease in 86Rb in the root were observed. The findings are discussed and found to be compatible with a simple two‐compartment model of the root.
CHANGES IN MITOTIC INDICES IN ROOTS OF VICIA FABA L.
Authors: MacLEOD R. D. , DAVIDSON D. 
Published: May 2006

SummaryRoots of Vicia faba were treated with IAA (6.26 × 10−4 m) for 3 hours and fixed immediately or 5, 11 or 23 hours later. Mitotic indices (MI) fell in these treated roots; the decrease was apparent at 5 hours and was significant at 11 and 23 hours, indicating that IAA was inhibiting some interphase processes.Other V. faba roots were treated with colchicine (0.025%) or IAA (4.7 × 10−4 m) or they were given successive treatments with colchicine or IAA and fixed up to 201 hours later. (a) In roots treated with colchicine, the MI rose for the first 24 hours and then fell to values below 1, where it remained for several days. (b) In roots treated with IAA, a fall in MI was observed within the first 2 days but it eventually returned to normal. This recovery of normal levels of mitotic activity was dependent upon the age of the roots at the time of treatment, the youngest roots died after treatment with IAA while older roots recovered completely. (c) Roots treated with IAA 24 hours after treatment with colchicine showed a decrease in MI in the following 24 hours similar to that found in roots treated only with colchicine. However, the MI of these roots subsequently rose to values that were not significantly different from those of the controls, i.e. there is an IAA induced stimulation of mitotic activity.Polyploid cells are found in division following treatment with colchicine. Changes in the frequencies of polyploid metaphases occur if roots are also treated with IAA, suggesting, as we have seen above, that IAA affects the duration of mitotic cycles.These results provide further evidence that a decrease in the endogenous levels of auxins occurs in roots treated with colchicine and this decrease can be partially restored by exogenous auxin. It is suggested that the changes in levels of mitotic activity in treated meristems is due, at least in part, to the colchicine induced fall in endogenous auxins.
THE MANIFOLD EFFECTS OF GENES AFFECTING FRUIT SIZE AND VEGETATIVE GROWTH IN THE RASPBERRY
Authors: JENNINGS D. L. 
Published: May 2006

SummaryA mutation found in the raspberry variety Mailing Jewel had bigger fruiting laterals, flowers and fruits than the parent stock. The results of breeding experiments were consistent with the hypothesis that the change was caused by mutation of a single gene from the homozygous to the heterozygous state, and that the gene concerned has functions whose effects are seen at each stage of development. These effects were to depress slightly the amount of vegetative, or first year's, growth and to increase the amount of reproductive, or second year's, growth. It is suggested that genes of similar function may account for differences which distinguish the raspberry from certain related species. The mutant gene is useful for plant breeding purposes. Its possible effects on the physiology of the plant are also discussed.
THE MANIFOLD EFFECTS OF GENES AFFECTING FRUIT SIZE AND VEGETATIVE GROWTH IN THE RASPBERRY
Authors: JENNINGS D. L. 
Published: May 2006

SummarySeedlings with ‘miniature’ fruits or with ‘blind’ fruiting laterals were found to segregate when the raspberry varieties Norfolk Giant and Baumforth's Seedling B, were inbred. It was concluded that in each family both abnormalities were caused by the same recessive gene (l2), which had pleiotropic effects on each stage of growth. Its action was to decrease growth by amounts which increased progressively with each stage of the plant's development. The effects of the gene are compared and contrasted with those of gene L1.