bluuebunny/crossref_metadata_2025 huggingface dataset:
THE IMMEDIATE RESPONSE OF THE QUIESCENT CENTRE TO X‐RAYS
Authors: CLOWES F. A. L.
Published: May 2006

Roots of Allium sativum and Zea mays were given 150 rads and 1800 rads of X‐rays respectively. Cells of the quiescent centre respond at once by coining into mitosis although most are at G, before irradiation. There is a stimulation of DNA synthesis in the quiescent centre, but not elsewhere, immediately after irradiation.

Some cells, however, undergo mitosis without having synthesized DNA and this results in prophase and metaphase nuclei without the normal 4C complement of DNA.
LIGHT‐INDUCED CHANGES IN SUCCINYL‐CoA SYNTHETASE IN BARLEY SEEDLINGS
Authors: STOBART A. K. , PINFIELD N. J.
Published: May 2006

Succinyl‐CoA synthetase activity increased with chlorophyll synthesis in etiolated barley seedlings exposed to light. The increased enzyme activity did not reside in the developing chloroplasts but appeared to be cytoplasmic in origin.
MOVEMENT OF14C‐PHOTOSYNTHATE INTO THE ROOTS OF WHEAT SEEDLINGS AND EXUDATION OF14C FROM INTACT ROOTS
Authors: McDOUGALL BARBARA M.
Published: May 2006

When 8‐day seedlings were exposed to14CO2in light, approximately 2 hours were required for14C to reach the apices of the roots. One method used to detect the progress of14C down the root was to scan the root with a radiochromatogram strip scanner. At this stage most14C in aqueous ethanol extracts of roots was present as sucrose, equally labelled in glucose and fructose. This was converted only slowly to other components of the soluble fraction so that after 12 hours almost 50% of14C was still retained in sucrose.

14C exuded from intact roots into surrounding solutions was present in both volatile and non‐volatile compounds. In the non‐volatile fraction glutamine, glutamic and aspartic acids were the main14C‐amino acids. Exudation of14C was not affected by changing the inorganic composition of the collecting solution. A change in pH of collecting solution from 6.4 to 5.9 increased exudation. Exudation also increased markedly when 2,4‐dinitrophenol or potassium cyanide was present in the collecting solution.
A COLORIMETRIC METHOD FOR THE ESTIMATION OF CERTAIN INDOLES
Authors: ANTHONY A. , STREET H. E.
Published: May 2006

The Ehrich reaction can, under standardized conditions, form the basis of a sensitive method of estimating certain indoles down to 1–2 μg/5 ml. An appropriate concentration of HCl in the Ehrich's reagent is essential. The concentration of trichloroacetic acid to give maximum sensitivity compatible with linearity between concentration of indole and absorbance must be experimentally determined. Absorbance should be measured between 530 and 580 mμ after a precisely measured time for colour development. Specificity can be increased by extraction of the colour complex into chloroform. The method has proved satisfactory for estimating the recovery of indoles from paper and thin‐layer chromatograms and from silica gel columns.
ETHER‐SOLUBLE INDOLES FROM SEEDLING ROOTS OF WHEAT
Authors: WOODRUFFE PATRICIA , ANTHONY A. , STREET H. E.
Published: May 2006

Techniques are described for the extraction, chemical detection, separation and purification of acidic, ether‐soluble Ehrlich reactive substances present in young seedling roots of wheat. The value of DEAE cellulose chromatography as a purification step is demonstrated. The presence of at least four Ehrlich reactors whose properties point to their being indole compounds can be demonstrated by paper and thin‐layer chromatography. The reactors detected did not coincide in their properties with any of the twenty‐six natural and synthetic indole compounds (these included indol‐3yl‐acetic acid and its nitrile, indole acetaldehyde and indole aldehyde) available as reference compounds.

To test the value of the isolation procedures adopted one of the reactors was purified as far as possible. Its chromatographic and chromogenic properties, its ultraviolet (uv) spectrum, its behaviour on gas chromatography, its hydrolysis and its activity in an auxin bioassay are described.
THE EFFECT OF LEAF HAIRS OF VERBASCUM THAPSUS ON LEAF ENERGY EXCHANGE
Authors: WUENSCHER JAMES E.
Published: May 2006

Energy budgets were determined for normal and hairless leaves of Verbascum thapsus L. in a wind tunnel. Leaves with the dense hair present were warmer than hairless leaves. This was shown to be due to a thicker boundary layer over normal leaves. Boundary layer resistance to heat and water vapour loss was higher for normal than for hairless leaves, resulting in lower convection and transpiration from normal hair‐covered leaves. Differences in transpiration resistance were correctly predicted by heat transfer theory. The hairs had little effect on radiation absorption by the leaves.
SPECIFICITY OF MYCORRHIZAL ASSOCIATION IN SOME AUSTRALIAN TERRESTRIAL ORCHIDS
Authors: WARCUP J. H.
Published: May 2006

Summary

Many isolations from roots of Caladenia and allied genera (Glossodia, Elythranthera and Eriochilus) from southern Australia show that these orchids are closely associated with the endophytic fungus Sebacina vermifera, and that species of Diuris are associated with Tulasnella calospora (Rhisoctonia repens). Back‐inoculation experiments with sterilized orchid seed on a medium with cellulose as the carbon source showed that Tulasnella calospora greatly stimulated germination of species of Diuris, whereas Sebacina vermifera and other species of Tulasnella from orchids had little effect. Results with Sebacina vermifera and seed of species of Caladenia have generally been less successful, but in one test the fungus greatly stimulated germination of seed of C. cornea.

Mycelium of Tulasnella calospora was commonly found on and in tubers, growing or dormant, of the species of Diuris examined.
POPLAR MOSAIC VIRUS IN GREAT BRITAIN
Authors: BIDDLE P. G. , TINSLEY T. W.
Published: May 2006

Summary

Poplar mosaic virus occurs widely throughout the commercially important poplar clones grown in Great Britain. Symptoms develop from initial fine interveinal chlorotic spots to either a mosaic or veinal chlorosis, depending on the clone. The flexuous virus particle, length 679 ran, is very liable to aggregate during purification, but can be purified by precipitation with ammonium sulphate followed by density gradient centrifugation in sucrose or by gel filtration. The host range and in vitro properties of the virus are described. Infectivity and longevity in vitro of inoculum prepared from poplar leaves can be increased by the addition of insoluble poly‐vinylpyrollidone.
SOME EFFECTS OF POPLAR MOSAIC VIRUS ON THE GROWTH OF POPLAR TREES
Authors: BIDDLE P. G. , TINSLEY T. W.
Published: May 2006

Summary

Measurements have demonstrated severe growth losses in virus‐infected poplars, particularly during the first 2 years in the nursery. There is considerable clonal variation. Losses in height growth frequently exceed 10%, which in combination with a reduction in diameter of the stem, can result in a 25% reduction in the dry matter production of virus‐infected trees. These growth reductions were only apparent in the nursery, as no additional effects were noted on trees up to 11 years old in the plantations.

Quantitative measurements are presented for the first time showing effects of virus infection on wood properties, particularly specific gravity and compressive strength. These effects are most apparent in wood produced during the first 2 years in the nursery, but there was also a significant increase in strength of branchwood from older trees.
STUDIES ON THE DISTRIBUTION OF OXYGEN AROUND THE ROOTS OF MUSTARD SEEDLINGS (SINAPIS ALBA I.)
Authors: GREENWOOD D. J.
Published: May 2006

Summary

Evidence was obtained that oxygen transport through the plant greatly influenced the oxygen partial pressures in the medium surrounding the roots. Seedlings with their leaves in air had their roots embedded in agar gel that had been saturated with nitrogen, air or oxygen and after a 5‐hour period of incubation the distribution of oxygen in the gel was determined. When the gel had been saturated with nitrogen gas, oxygen partial pressures increased towards the surfaces of the roots of whole plants but not towards the surfaces of severed roots. When the gel had been saturated with air or oxygen, however, oxygen partial pressures always decreased towards the root surfaces irrespective of whether the roots had been severed or not. In oxygenated gel, the decreases were much greater towards intact roots than towards those that had been severed but in aerated gel the converse held. The results were in agreement with those expected if substantial amounts of oxygen moved from stem to root or in the opposite direction depending on the sign and magnitude of the oxygen partial pressure/distance gradients.
EVALUATION OF MENDOK AND DALAPON AS MALE GAMETOCIDES AND THEIR EFFECTS ON GROWTH AND YIELD OF LINSEED
Authors: RUSTAGI P. N. , RAM H. Y. MOHAN
Published: May 2006

Summary

Linseed plants were sprayed with aqueous solutions of Mendok (sodium 2,3‐dichloroiso‐butyrate) and Dalapon (sodium 2,2‐dichloropropionate) at 250, 500 and 1000 ppm with a view to inducing male sterility. Both compounds produced more or less similar responses except that Mendok was slightly more effective than Dalapon. Toxicity symptoms consisted of hypo‐nasty, chlorosis and slight to severe burning of young leaves and flower buds. Treated plants showed profuse branching, enhanced vegetative growth and heavy flower production. However, flowers became progressively smaller and gradually closed. Production and germination of seeds were both considerably reduced in the treated plants. Gamete fertility was reduced by almost all treatments. Female sterility was caused by decrease in size and abnormal morphology of pistils, and non‐separation of styles and stigmas. Male sterility was induced in two forms: developmental and functional. The former was characterized by fully or partially barren anthers and non‐viable pollen. Rhythms of pollen non‐viability interspersed with periods of restoration of viability were noted. Functional male sterility resulted from lack of anthesis, fusion and non‐dehiscence of fertile anthers and agglutination of pollen.

The tapetal cells in the anthers of undersized flowers were highly vacuolate, radially stretched and they persisted up to the mature pollen grain stage. Another feature of morphological interest was the differentiation of microsporangia on petals.

It is concluded that neither Mendok nor Dalapon can be used as a specific male sterilizing agent in linseed.
INTRASPECIFIC VARIATION IN CALT HA PALUSTRIS
Authors: WOODELL S. R. J. , KOOTIN‐SANWU M.
Published: May 2006

Summary

A biometric study of herbarium, wild and cultivated specimens of Caltha palustris L. s.l. in the British Isles indicates that most of the variation in the wild is environmentally determined. Further, there is no correlation of morphology with cytological differentiation. All taxa previously described within C. palustris L. are consequently regarded as untenable, with the exception of plants which differ by the single character of rooting at the nodes, and which show partial geographical differentiation. They are reduced to varietal status.
FRUIT BIOLOGY AND GERMINATION OF TWO TROPICAL POTAMOGETON SPECIES
Authors: SPENCE D. H. N. , MILBURN T. R. , NDAWULA‐SENYIMBA M. , ROBERTS E.
Published: May 2006

Summary

The drupes or achenes of Potamogeton schweinfurthii A. Benn. and P. richardi Solms. can float for long periods and germination only occurs naturally once the fruits have sunk. The factors controlling their floating, sinking and germination have been investigated. After brief reference to water depths at which these species occur in Uganda, fruit structure is described. The epicarp and mesocarp are initially green in both species and remain green in ripe, floating fruits of P. schweinfurthii. The sheathed embryo lies along the rim of the stony endocarp beneath a lid which can be detached by surgery.

Of the factors relating to buoyancy and sinking in P. schweinfurthii, daylight compared with almost total darkness decreased the rate of discoloration of the green floating fruits, the rate at which the pericarp disintegrated and the rate of sinking. Measurements of respiratory oxygen uptake, net photosynthesis rates and density changes, in a series of unripe to just‐sunk fruits of P. richardi, suggest that this light‐dependence of floating fruits is connected with the maintenance of constant volume and density through gaseous relations within an intact cuticle. During prolonged darkness, fruit density increased at constant mass by shrinkage of the soft parts, caused by degenerative changes and absence of photosynthesis.

Neither species germinated in the dark, compared with 100% of light‐stored, sunken fruits or with similarly stored fruit from which epicarp and mesocarp had been scraped. In the light, substantial germination also occurred in both freshly shed and older floating fruits after surgical exposure of the embryo. No after‐ripening period is required.

Presumptive evidence was obtained for the promoting effect of red light on germination in P. schweinfurthii. Using a calibrated Schwarz thermopile and narrow‐band interference filters, the promoting effect of 0.05 J/cm2 of red light was established for P. richardi fruits with exposed embryos. Photoreversibility was established by similar doses of far‐red.These irradiation values are characteristic of the phytochrome system. Embryos within the intact stony endocarp require an irradiation of 8–10 J/cm2 (652 nm) for promotion and an equivalent dose of far‐red for reversal.

These findings are discussed in relation to the ecology and distribution of the species.
POST‐POLLINATION PHENOMENA IN ORCHID FLOWERS
Authors: ARDITTI JOSEPH , FLICK BRIGITTA , JEFFREY DAVID
Published: May 2006

Summary

Applications of ABA to Cymbidium flowers induce some, but not all, post‐pollination symptoms. Anthocyanin levels in sepals, petals, columns and labella are raised; flowers wilt; dorsal sepals become hooded; calli develop colouration while losing turgidity; columns do not swell, lose very little curvature; and stigmas do not close. Combinations of ABA and NAA induce all post‐pollination phenomena, but lower anthocyanin content than treatments with ABA only. ABA plus GA3 have effects which are similar to those of ABA alone, except that anthocyanin levels are reduced. The same is essentially true of ABA‐kinetin mixtures but intensities of the effects are different and with some concentration ratios, stigmatic closure also occurs. The effects of ABA and its interactions with GA3, kinetin or NAA are explained in terms of the roles these hormones may play in synthesis of nucleic acids and enzymes.
SOME GENETIC FACTORS AFFECTING FRUIT DEVELOPMENT IN RASPBERRIES
Authors: JENNINGS D. L.
Published: May 2006

Summary

Two diallel crosses between red raspberry parents were made and auxin applied to alternate fruits 7 days after pollination. In a diallel made in 1964 interaction effects between pollen and the maternal effect considerably influenced the set of pyrenes, but maternal effects predominated in a diallel made in 1965. Application of auxin in the first diallel reduced the interaction effects. It is postulated that the set of large pyrenes was largely determined by the interaction of physiological effects contributed by the male and female parents, but that maternal effects were so strong in the second diallel that variations in those of the male parent were less important. These factors were probably concerned with the arrest of flower growth and its subsequent recommencement following pollination. Auxin apparently affected late acting factors associated with seed tissues, but these were relatively unimportant for pyrene set. Self pollination improved the set of pyrenes in the first diallel, perhaps because the conditions were similar to those under which the varieties were originally selected. Maternal parents differed in the rate at which their fruits ripened, but the pollen parent also influenced the rate of ripening.
SOME CONSEQUENCES OF RASPBERRY POLLEN DILUTION FOR ITS GERMINATION AND FOR FRUIT DEVELOPMENT
Authors: JENNINGS D. L. , TOPHAM P. B.
Published: May 2006

Summary

Comparisons of pyrene set were made between raspberry flowers pollinated with undiluted pollen and others pollinated with pollen diluted with talc, or killed pollen. Pollen dilution reduced set but the reduction was not the same for all maternal parents. It also reduced the rate of fruit ripening, increased the proportion of pyrenes without seed content and reduced the tendency for abortive carpels to develop into small empty pyrenes. Observations of numbers of pollen grains germinating in the styles revealed differences attributable to the maternal parents, the pollen germinating poorest on the parent whose pyrene set was reduced most by pollen dilution. There were also maternal × paternal interaction effects on pollen germination. It is concluded that pollen germination was conditioned by growth substances provided partly by the grains themselves and partly by the styles of the seed parent, and that there were interactions between the two sources. Reduction in pollen concentration affected several aspects of early fruit development, but quantitative differences in the amount of pollen applied did not reduce the adverse effects of using diploid pollen. This suggests that such effects do not arise through direct action of the pollen on the maternal tissues.
LEAFLESS EUPHORBIA IN RAJASTHAN ROCKS
Authors: SEN D. N. , Sharma K. D. , Chawan D. D.
Published: May 2006

Summary

Studies of attached and detached leaves of Euphorbia caducifolia, the latter collected from morphologically different plants, suggested that this species exhibited typical crassulacean features of acid metabolism. Fluctuations in acidity were found to be due mostly to the appearance and disappearance of malic acid in dark and light respectively. Deacidification also took place when leaves were kept in dark for a longer period. The TAN showed a fall when the leaves aged and were about to fall. A remarkable feature found in this species was the high percentage of total acids which ranged up to 8240 mg/100 g fresh weight of leaves, together with great differences in the constituents analysed. This suggests that morphological diversity is correlated with physiological diversity.
RESPIRATORY ENZYME SYSTEMS IN CULTURED CALLUS TISSUES
Authors: CHONG‐JIN GOH
Published: May 2006

Summary

Respiratory enzymes of the glycolytic, pentose‐phosphate pathways and Krebs cycle were detected in cell‐free preparations from cultured callus tissues of potato and artichoke tubers. Some of the enzymes functioning in glycolytic or pentose‐phosphate pathways seemed to be associated with a particulate preparation.
A VIRESCENS MUTANT OF PHASEOLUS VULGARIS: PHOTOSYNTHESIS AND METABOLIC CHANGES DURING LEAF DEVELOPMENT
Authors: HEYES J. K. , DALE J. E.
Published: May 2006

Summary

Fixation of 14CO2, photophosphorylation, and protein, lipid and RNA composition have been compared for primary and trifoliate leaves of various ages of control and mutant plants.

Except when old, leaves of control plants fix more CO2 than do those of the mutant, but the carboxylation pathways seem similar in the two plants. The level of Fraction I protein and that of ribulose diphosphate carboxylase activity are also similar, but lower in leaves of the mutant. Photophosphorylation per chloroplast mediated by photosystems I and II, tends to be slightly higher in the mutant, despite lower levels of chlorophyll in mutant plastids. Small differences in amount and composition of leaf lipids, but large differences in RNA content were found. Mutant leaves show a higher initial content of cytoplasmic ribosomal RNA than do controls; as leaves age this position is reversed. Chloroplast ribosomal RNA is initially similar, but continued synthesis is greater and more prolonged in the mutant.

The significance of these data is discussed in relation to the nature of the mutation.
THE IDENTITY OF MENYANTHES MICROSPERMA N. SP. FOSS. FROM THE GORT INTERGLACIAL, IRELAND
Authors: WATTS W. A.
Published: May 2006

Summary

‘Menyanthes microsperma’, an unknown seed from the Gort (Hoxnian) Interglacial deposit, Ireland, is a species of Nymphoides, probably the North American species N. cordata (Ell.) Fern.
THE OCCURRENCE AND SIGNIFICANCE OF AUXIN IN THE SUBSTRATA OF BRYOPHYTES
Authors: SHELDRAKE A. R.
Published: May 2006

Summary

Auxin was detected in samples of substrata supporting bryophytes in a variety of locations in both Britain and Malaya. Activity occurred on chromatograms at zones corresponding to the Rf of indole acetic acid. The range of concentrations found, 0.4–10.4 μg/1, probably represents a two‐ to five‐fold underestimate due to losses during extraction and purification. The amounts of auxin in samples of soil on which bryophytes were not growing were within the same range. The importance of this environmental auxin for the induction of rhizoids in liverworts and for roots of higher plants is discussed.
THE ACCUMULATION OF 65ZN BY ROOT HOMOGENATES OF ZINC‐TOLERANT AND NON‐TOLERANT CLONES OF AGROSTIS TENUIS SIBTH.
Authors: TURNER R. G. , MARSHALL C.
Published: May 2006

Summary

The localization of 65Zn was examined in cell‐free systems extracted from the roots of clones of Agrostis tenuis in further investigations on the mechanism of heavy metal tolerance in this grass species. The cell wall fraction was a major site for zinc accumulation especially in a zinc‐tolerant clone where more zinc accumulated at this site than in non‐zinc‐tolerant clones. In the absence of the cell wall fraction or when its zinc‐binding potential had been reduced, other particulate cellular components accumulated large amounts of zinc. Zinc uptake by the cell wall occurred by the same process in all the clones studied. Uptake was very rapid and independent of temperature and pH, suggesting an exchange adsorption process. A basis for zinc tolerance in A. tenuis is briefly discussed.
SOME ASPECTS OF THE GROWTH OF MANGO (MANGIFERA INDICA L) LEAVES
Authors: TAYLOR F. J.
Published: May 2006

Summary

Quantitative analyses for total methanol‐soluble material, methanol‐soluble carbohydrates, anthocyanin, chlorophyll, methanol‐insoluble nitrogen, saponifiable material, pectin, lignin, hemicellulose, and α‐cellulose were made at weekly intervals for the first 6 weeks of the growth of mango leaves. The results show that in the first 4 weeks, when the leaves contain anthocyanin, production of photosynthetic carbohydrates was low, and lignin and cuticle syntheses ‐were virtually absent. The increase in rigidity of the mango leaf between the second and fifth weeks was significantly correlated with an increase in the hemicellulose content of the leaf.
THE FIELD DISTRIBUTION OF INTERACTING STRAINS OF POLYPORUS SCHWEINITZII AND THEIR ORIGIN
Authors: BARRETT D. K. , USCUPLIC M.
Published: May 2006

Summary

The interaction phenomenon between cultures of Polyporus schweinitzii has been investigated and used to determine the natural distribution of different strains of this fungus in conifer plantations. The interaction behaviour of synthetic heterokaryons has shown that those derived from the pairing of completely unrelated basidiospores are those most likely to simulate the interaction potential of wild strains. The development of interacting strains from genetically complex polysporous mycelia is discussed.
CYTOLOGY AND POLLEN MORPHOLOGY OF NATURAL AND ARTIFICIAL TETRAPLOIDS IN THE LINUM PERENNE GROUP
Authors: OCKENDON D. J.
Published: May 2006

Summary

Artificial tetraploids of the Linum perenne group closely resemble their diploid progenitors in macroscopic characters, but differ markedly in their pollen morphology. The pollen of the diploids invariably has three furrows, that of the natural tetraploids normally has six pores and that of the artificial tetraploids typically has six furrows. The pollen of the artificial tetraploids is particularly variable because of tendencies towards syncolpy and the asymmetrical arrangement of furrows. The artificial autotetraploids tend to have lower pollen fertilities and more meiotic irregularities than the artificial allotetraploids. None of the artificial tetraploids resembled the natural tetraploid L. perenne subsp. anglicum particularly closely, but its origin is discussed in the light of the available evidence.
STUDIES OF AUSTRAL BRACKEN (PTERIDIUM ESCULENTUM) IN THE VICINITY OF CANBERRA
Authors: CARTLEDGE O. , CARNAHAN J. A.
Published: May 2006

Summary

Austral bracken (Pteridium esculentum) in the vicinity of Canberra is shown to behave differently from the European P. aquilinum. Studies of the morphology of the rhizomes suggest that the margins of austral bracken advance slowly and irregularly.

Only two phases are recognizable in the austral bracken plant: the marginal phase and the central phase. The marginal phase is characterized by short fronds and rhizomes that are approximately parallel. The central phase generally has tall fronds, a dense rhizome system and rhizomes that lack the spatial orientation found at the margin.

Sheep and cattle tracking and vigorous rhizomatous grasses may inhibit frond emergence. These factors in association with relatively low rainfall and poor soil may be responsible for the slow rate of expansion of bracken margins.
COMPARTMENTATION AND LOW TEMPERATURE FLUXES OF POTASSIUM IN MYCELIUM OF DENDRYPHIELLA SALINA
Authors: JENNINGS D. H. , AYNSLEY J. S.
Published: May 2006

Summary

Dendryphiella salina was grown at 21° C in two media, identical except that one contained potassium labelled with 42K. The cultures were transferred to 2° C, the fungus separated from the medium, the radioactive mycelium placed in the non‐radioactive medium and the efflux of 42K measured. Under these conditions the rate of dry weight increase is reduced by at least 75%. The fungus behaves as a multicompartment system with regard to potassium with at least 75% of the ion being in the slowest‐exchanging compartment. The efflux from this compartment into a medium containing 2.5 mM potassium is of the order of 0.14 p moles cm−2 sec−1, being at least doubled when 50 mM sodium is present. Addition of 10 mM calcium in the presence of sodium reduces the efflux to a value close to that obtained when sodium is absent.
THE EFFECTS OF PHOSPHORUS DEFICIENCY ON THE GROWTH OF EPILOBIUM MONTANUM L.
Authors: ATKINSON D. , DAVISON A. W.
Published: May 2006

Summary

A study was made of the effects of altering the length and timing of a period of phosphorus deficiency on populations of Epilobium montanum L. The total amount of phosphorus per leaf increased with the length of time for which the element was supplied but the concentration of certain phosphorus fractions varied with both the length and timing of the deficiency. An initial period of deficiency before giving a phosphorus supply produced a drastic decrease in growth and prevented flowering. This appeared to be caused by non‐utilization of phosphorus rather than inhibition of uptake. All three populations were extremely plastic in their response to phosphorus; plants which had only 1 week with phosphorus produced stolons while those which had 2 weeks produced viable seed. This plasticity may partly account for the occurrence of the species in extreme environments and for its success as a weed. The main difference between the populations was not in phosphorus nutrition but in the relative proportion of seeds and stolons produced.
BACTERIAL PATHOGENS OF FRESHWATER BLUE‐GREEN ALGAE
Authors: DAFT M. J. , STEWART W. D. P.
Published: May 2006

Summary

Four bacterial isolates have been obtained which cause lysis of laboratory cultures and natural populations of blue‐green algae. Over forty algal strains belonging to all orders of the blue‐green algae and including bloom‐forming species are susceptible. The bacteria also lyse certain gram‐positive and gram‐negative bacteria. The organisms are aerobic, gram‐negative rods, aflagellate, motile and pigmented with an absorption maximum of the pigments in methanol occurring at 435 nm and with shoulders at 460 nm and 415 nm. The guanine and cytosine in the DNA is within the range of 65–69± 1 M%. The organisms are identified tentatively as members of the Myxobacterales. Lysis of vegetative cells of the algae depends on the presence of growing bacteria, bacteria‐free filtrates alone being insufficient to cause lysis. Heterocysts are not lysed. The bacterial plaques resemble viral plaques in appearance. The lytic agents rapidly inhibit metabolic activity of the susceptible algae and may cause cell lysis within 2–10 hours. The isolates can be propagated readily in the absence of the host and are probably widely distributed in freshwater habitats.
SOME GENETIC FACTORS AFFECTING THE DEVELOPMENT OF ENDOCARP, ENDOSPERM AND EMBRYO IN RASPBERRIES
Authors: JENNINGS D. L.
Published: May 2006

Summary

The sizes and shapes of different parts of pyrenes obtained from two diallel crosses of raspberry were influenced both by maternal effects and by interaction effects involving maternal and genetic factors. The relative importance of these effects depended upon the environment in which the crosses were made. For a diallel made under field conditions interactions with maternal factors were large but considerably reduced by applying auxin to the developing fruits. For a diallel made in a glasshouse maternal effects were more important and maternal interaction effects less so. Application of auxin to the fruits reduced endosperm or embryo size in some crosses and increased it in others. It is postulated that these responses were related to the endogenous content of growth substances, negative responses indicating their presence in supra‐optimal concentration, and that variations in the responses provide clues to the physiological factors which govern successful pyrene development.
VARIATION IN EUCALYPTUS OBLIQUA L'HÉRIT
Authors: GREEN J. W.
Published: May 2006

Summary

Open‐pollinated seedling progenies of Eucalyptus obliqua grown in a uniform environment showed evidence of genetic variation among geographically different localities and among parent trees within localities. Locality variation did not appear habitat‐correlated, so no predictor of a superior locality for tree‐improvement purposes could be suggested, other than appearance of the trees; breeding strategy should include tree selection within localities. Several superior localities were indicated consistently but many showed marked fluctuations, suggesting the need for caution in interpreting seedling data.
SOME ASPECTS OF THE GROWTH OF MANGO (MANGIFERA INDICA L) LEAVES
Authors: TAYLOR F. J.
Published: May 2006

Summary

Young's modulus and tensile strength have been measured on mango leaves at weekly intervals up to the age of 35 days. Both increase with age, but there is a fall in the rate of increase of Young's modulus at 21 days. The relative plastic/elastic extension increased to a maximum at day 21. Prior to day 21, turgidity played an important role in the elasticity of the leaf, but not after that date. These changes are discussed in relation to the composition of the cell wall. Removing the cuticle and cell wall constituents sequentially showed that pectin was responsible for all the mechanical properties of the leaf up to day 14, when leaf expansion ceased. At day 35 the cuticle and the lignin together contributed about 80% to the tensile strength, and the cuticle alone about 70% to the Young's modulus.
INTERACTION EFFECTS OF GLUCOSE AND AUXINS IN ROOTING ETIOLATED STEM SEGMENTS OF SALIX TETRASPERMA
Authors: NANDA K. K. , JAIN M. K.
Published: May 2006

Summary

Etiolated, 2·5 cm long stem segments of Salix tetrasperma did not root when cultured in agar even with 0·1% glucose, but rooted with 1·0% glucose in the medium. Rooting decreased with 2·0% and was completely inhibited by 5·0% glucose. Both IAA and IBA induced rooting when added to 0·1% glucose, the number of rooted segments decreasing with the concentration of IAA but increasing with that of IBA. Both auxins increased the number of roots when added to 1·0 and 2·0% glucose, the effect increasing with concentration except that 5·0 mg/1 IBA lowered the number as compared to 1·0 mg/1 added to 1·0% glucose. Auxins also induced rooting when added to 5·0% glucose, which alone inhibited it completely. The effect of auxins on the number of roots, however, decreased with the increasing concentration of glucose in the medium except with 5·0 mg/1 IAA which increased it. The results show that auxin effects on rooting are influenced by nutritional status of stem cuttings and that a proper balance of the two is necessary for this purpose.
THE MOVEMENT OF GROWTH REGULATORS AND HERBICIDES INTO THE SIEVE ELEMENTS OF WILLOW
Authors: FIELD R. J. , PEEL A. J.
Published: May 2006

Summary

Using an aphid technique to obtain samples of sieve element sap, the movement of certain growth regulators and herbicides, IAA, NAA, MCPA, 2,4‐D, 2,4,5‐T, MH, TCA and paraquat, into the sieve elements of bark strips and stem segments has been investigated.

Two pathways were found to be operative in bark strips, a direct one from the free space, and an indirect one via the storage parenchyma. The compounds IAA and NAA, are extensively metabolized. The mobility of IAA into the sieve elements of bark strips and stem segments was considerably greater than that of its principal metabolite, IAA asp, though the latter could enter the sieve elements. The metabolites of NAA could not be detected in the sieve tube.

The relative mobilities of the non‐metabolized compounds differed according to the pathway of transport. MCPA and 2, 4‐D were the most mobile on the direct pathway in bark strips, paraquat the least mobile. On the indirect pathway MH and MCPA were the most mobile, paraquat once again being the least mobile. Movement into the sieve elements from the bark of stem segments showed a reversal of the order of mobility found in strips. Here paraquat had the highest relative mobility, TCA the lowest.
PHOSPHATASE ACTIVITY OF INTACT YOUNG WHEAT ROOTS UNDER STERILE AND NONSTERILE CONDITIONS
Authors: RIDGE E. H. , ROVIRA A. D.
Published: May 2006

Summary

In assays of acid phosphatase activity with p‐nitrophenyl phosphate as substrate, the low activity found in fluids removed from around roots in liquid medium was not affected by the presence of micro‐organisms. Most phosphatase activity of intact seedling roots was associated with the root surface and was not increased by micro‐organisms in the rhizoplane; in some experiments activity was significantly reduced by soil micro‐organisms. Inoculation of roots with pure cultures of bacteria and a fungus known to have phosphatase activity did not increase this activity of the roots. These results are contrasted with those of other workers. Possible application to the soil situation is discussed.
DESICCATION INJURY IN MOSSES
Authors: LEE J. A. , STEWART G. R.
Published: May 2006

Summary

Intra‐specific differences in desiccation injury are shown in collections of Acrocladium cuspidatum, Climacium dendroides and Hypnum cupressiforme from habitats subjected to a wide range of moisture stresses. The degree of desiccation tolerance is correlated with degree of moisture stress in the habitat. Desiccation injury was measured as the decline in the initial rate of photosynthesis on remoistening. Collections of species from habitats in which severe moisture deficits occur show a slower decline in photosynthesis on desiccation and a more rapid recovery of function on wetting than collections from habitats with no appreciable moisture deficits. The results are discussed in terms of their ecological and physiological significance.
THE GROWTH OF PHLEUM ALPINUM L. IN CONTRASTING HABITATS AT A SUB‐ANTARCTIC STATION
Authors: CALLAGHAN T. V. , LEWIS M. C.
Published: May 2006

Summary

The effects of aerial microclimate and edaphic conditions on the growth of young vegetative tillers of Phleum alpinum L. from contrasting habitats on South Georgia have been investigated using growth analysis concepts. Relative growth rate (Rw) was found to be negatively correlated with habitat severity, there being a strong relationship between Rw and the amount of lateral production per tiller. Unit leaf rate (EA) was depressed at the highest altitude. Specific leaf area increased with habitat favourability but no simple relationship was apparent between leaf area ratio (FA) and site conditions. Native soils were shown to be severely limiting, although there was considerable variation in edaphic conditions between the various sites.

There was striking uniformity in Rw values between plants from different populations when grown under similar conditions, this stabilization effect being produced by compensatory mechanisms involving the contributory growth parameters, EA and FA the specific leaf areas of the different populations when grown at one site were also very similar.
CYTOKININS AND THE GROWTH OF CULTURED SYCAMORE CELLS
Authors: MACKENZIE I. A. , KONAR APARNA , STREET H. E.
Published: May 2006

Summary

Externally supplied cytokinins can induce cell division in sycamore cultures at cell densities at which, in the absence of a supply of cytokinin, they fail to grow. When cultures are initiated at cell densities where growth occurs in the absence of added cytokinins only after a long lag phase, the addition of cytokinins reduces the length of the lag phase. In these effects zeatin is fully effective at much lower concentrations than kinetin.

As the duration of stationary phase is increased in the stock cultures, the ability of the cells to grow from a low initial cell density declines. This appears to be due to their declining endogenous cytokinin activity and declining ability to take up added cytokinin from their culture medium. It is postulated that, during the lag phase, the cells develop a critical level of cytokinin activity by an excess of endogenous synthesis over loss to the culture medium and internal degradation. When the phase of cell division has been initiated, the subsequent growth of the cultures is unaffected by low external levels of cytokinins.
STUDIES IN THE VEGETATIONAL HISTORY OF SCOTLAND
Authors: BIRKS HILARY H.
Published: May 2006

Summary

Loch Maree, West Ross, is in an area of outstanding floristic and vegetational interest today. Native pinewoods occur on the south shore, and the largest northern oakwood on the north shore. High ground supports a range of montane communities.

A pollen diagram is presented from the upper 460 cm of a 542 cm continuous core from Loch Maree. Six radiocarbon age determinations have been made from the sediments in relation to pollen stratigraphical changes. The constant sedimentation rate thus revealed has been used to interpolate ages for other events in the pollen diagram.

During the last 9000 years of organic sedimentation in Loch Maree, many changes have occurred in the flora and vegetation of the landscape. After the instability at the end of the last glaciation, a climatic amelioration allowed juniper scrub colonization and organic soil development. Birchwoods, with some hazel, succeeded juniper, followed by the entry and rapid attainment of dominance by pine on all acidic soils, especially on the south shore of the loch, at about 8250 radiocarbon years ago. Meanwhile oakwoods with some ash and elm, developed in areas of more favourable soil and microclimate on the north shore. Alder immigrated and rapidly occupied all suitable habitats at about 6500 radiocarbon years B.P., and the pine forest began to degenerate. This process culminated in its rather rapid replacement by moorland and bog, perhaps due to climatic changes, at about 4200 radiocarbon years B.P. AS the oakwoods declined at the same time, human activity may have been an additional factor. However, there is little evidence for subsequent human interference in the area. The constant sedimentation rate suggests that deforestation was primarily by natural means, rather than by burning, felling, or grazing.

Comparisons with pollen diagrams from other areas reveals an area of West Ross with a consistent Flandrian pollen stratigraphy. To the north and west, Betula and Corylus are the most important tree pollen types. In the eastern Highlands, Pinus pollen is again dominant, but the time of its expansion and the arrival of Alnus is different. The floristic composition of the pollen diagrams also differs, particularly in the abundance of pteridophytes.
AN APPLICATION OF FLUORESCENCE MICROSCOPY TO THE PROBLEM OF DERIVED POLLEN IN BRITISH PLEISTOCENE DEPOSITS
Authors: PHILLIPS LINDA
Published: May 2006

Summary

The fluorescence of fossil pollen and spores changes in colour and intensity with increasing age. By a study of Ipswichian Interglacial and Lower Pleistocene samples, it is shown that it is possible to distinguish Pleistocene from earlier pollen and spores by their different fluorescence colour and to a lesser extent by their different fluorescence intensity. The method can be employed in solving various problems of derivation in Pleistocene palynology.
PLANTS UNDER CLIMATIC STRESS
Authors: ROWLEY J. A. , TAYLOR A. O.
Published: May 2006

Summary

The composition of the atmosphere influenced the apparent photosynthetic rate of Sorghum bicolor and the degree of permanent damage to the photosynthetic capacity of the leaves when plants were transferred to low‐temperature, high‐light (10° C; 170 W m‐2) environmental stress. High CO2 (1000 μl/l) or low O2 (3%) both partially protect the plants compared to normal atmospheric levels, while low CO2 (30 μl/l) or O2 (50%) enhanced the damaging effects of stress. Oxygen levels are the more significant in control of permanent photosynthetic damage.
THE ROOTING OF ACTIVELY GROWING AND DORMANT LEAFY CUTTINGS IN RELATION TO ENDOGENOUS HORMONE LEVELS AND PHOTOPERIOD
Authors: SMITH N. G. , WAREING P. F.
Published: May 2006

Summary

A series of poplar cuttings, Populus×robusta (Schneid.), excised at intervals during the summer showed a decline in rooting ability until mid‐August when cultured in long‐days. This was correlated with a decline in auxin at the RF of IAA. Leafy cuttings with growing apices rooted no better than dormant leafy cuttings when both were cultured in long days, and the bases of both types of cuttings possessed similar quantities of hormone at the RF of IAA.

A bean hypocotyl bioassay of the ‘neutral’ ether fraction of an extract of terminal zones of poplar stems in August showed that the major root‐initiating hormone (RF 0.8 in 4:I, isopropanol: water) promoted no extension growth when assayed with wheat coleoptiles. Comparisons of the auxin levels at the base of July cuttings during the first 5 days after their excision showed an increase of auxin at the RF of IAA and of a neutral hormone near the solvent front.
A PHOTOELECTRIC DIGITAL SCANNER FOR MEASURING LEAF AREA
Authors: COX E. F.
Published: May 2006

Summary

A scanning photoelectric method has been devised which is capable of measuring up to 680 cm2 of leaf tissue in 10 seconds. Its principle of operation is based on the number of dark pulses generated by a screw‐driven bank of photocells which is electronically scanned as it moves beneath an illuminated Perspex platform on which the leaves to be measured are arranged.
UTILIZATION OF SUGARS AND STARCH AS CARBON SOURCES IN THE ROOTING OF ETIOLATED STEM SEGMENTS OF POPULUS NIGRA
Authors: NANDA K. K. , JAIN M. K.
Published: May 2006

Summary

Stem segments of Populus nigra L. did not root in water or auxin alone but did so in 0.5% ribose, glucose and sucrose, sucrose being most effective. The addition of 0.1 mg/1 IAA or IBA to the medium stimulated rooting; IBA being more effective. Starch also induced rooting especially in combination with auxins. Starch was hydrolysed by enzymes that leached out of the segments and auxins enhanced their activity.
THE INHIBITION OF FUNCTIONAL RNA SYNTHESIS IN CHLORELLA PYRENOIDOSA BY 6‐METHYL PURINE
Authors: McCULLOUGH WILLIAM , JOHN PETER C. L.
Published: May 2006

Summary

Addition of 10‐3 M 6‐methyl purine caused immediate inhibition of total RNA synthesis in Chlorella pyrenoidosa, 211‐8p, whereas inhibition of total protein synthesis developed progressively with time. 50% inhibition of adenine incorporated into RNA, and of de novo isocitrate lyase synthesis, was caused by 5 × 10‐5 M 6‐methyl purine, but a ten‐fold higher concentration was required to give a similar inhibition of total RNA synthesis. The inhibition of isocitrate lyase synthesis was reversed competitively by adenine. Isocitrate lyase synthesis was inhibited by 91% at a concentration of 10‐3 M 6‐methyl purine, which gave only 12% inhibition of glucose respiration. It is suggested that 6‐methyl purine acts by replacing adenine in RNA metabolism. It is concluded that 6‐methyl purine may be used as an inhibitor of functional RNA synthesis in Chlorella and that the synthesis of isocitrate lyase during the cell cycle is dependent upon concurrent transcription.
THE DISTRIBUTION OF ORGANIC FLUORINE IN SOME TOXIC TROPICAL PLANTS
Authors: HALL R. J.
Published: May 2006

Summary

The tissues of numerous species of toxic plants from Africa, Australia and South America have been analysed for organic and inorganic fluorine. The presence of organically combined fluorine was established in most of the species but was very variable in concentration. The stems and roots of the African Dichapetalaceae generally contained much more fluorine than did the leaves and the reversed situation was found in the same tissues of the Australian Gastrolobium and Oxylobium species and in the Brazilian Palicourea marcgravii. The seeds of most of the specimens analysed contained large amounts of organic fluorine but was absent in those of Acacia georginae. None of the plant species examined grew in soils which were high in fluorominerals; on the contrary some of the plants grew in soils containing exceptionally low levels of fluorine. A waxy exudate on the outside of the toxic leaves of A. georginae contained significant amounts of organic fluorine and is believed to be part of an excretory mechanism. Only a small proportion of the exudate was identified as fluoroacetate and there appear to be other fluorinated organic compounds present. A crystal formation which contains fluorine was observed in the bark of the roots and stems of Dichapetalaceae and is thought to be also associated with a detoxication process. The crystals appear to be a complex mixture containing calcium oxalate, chloride, fluorine, magnesium and silica. The analytical findings suggest that in the plants in which carbon‐fluorine compounds have been established, the site of the synthesis of organic fluorine may vary with the species and that metabolism to inorganic fluoride may take place continuously and simultaneously with the organic bio‐synthesis.
VESICULAR‐ARBUSCULAR MYCORRHIZAS OF THE SPECIES OF A MOLINIETUM COERULEAE L.I. ASSOCIATION: THE ECOLOGY
Authors: MEJSTRIK V. K.
Published: May 2006

Summary

The frequency and intensity of vesicular‐arbuscular mycorrhizas in the species of a Molinietum coeruleae association was studied during the vegetative period. From the total number of fifty‐five species in the association only nine species were nonmycorrhizal. There was dependence of the frequency of entry points on the root depth and the vegetative season. The ground water table was relatively stable during the year and it did not exert strong direct influence on the intensity of mycorrhizal infection.
PRELIMINARY OBSERVATIONS ON THE ULTRASTRUCTURE OF MATURING CORK‐CELLS FROM TUBERS OF SOLANUM TUBEROSUM L.
Authors: RAINBOW ARNOLD , WHITE D. J. B.
Published: May 2006

Summary

The normal cork of young tubers of Solanum tuberosum L. cv.‘King Edward’ was used as a source of maturing cork‐cells. The cells are periclinally flattened and highly vacuolated. Electron‐micrographs reveal that the cytoplasm, although sparse, is rich in mitochondria, ribosomes and membrane‐bound vesicles. Electron‐opaque crystals and endoplasmic reticulura are also present, but neither the plasmalemma, nor the tonoplast, are visible. Microtubules are seen at the interface between the cell wall and the cytoplasm. The layered appearance of the cell wall is compatible with the observations of other workers. No pits are visible but there is evidence that plasmadesmata were present earlier in the ontogeny of the cell. The significance of these observations is discussed in the light of existing information on cork‐cell differentiation.