bluuebunny/crossref_metadata_2025 huggingface dataset:
CHANGES IN THE SIZE OF ORTHOPHOSPHATE POOLS IN MYCORRHIZAL ROOTS OF BEECH WITH REFERENCE TO ABSORPTION OF THE ION FROM THE EXTERNAL MEDIUM
Authors: JENNINGS D. H.
Published: May 2006

Summary

At concentrations of potassium dihydrogen phosphate in the external medium below 10−3 M, the greater proportion of phosphate which enters beech mycorrhizal roots is incorporated into bound form. Above 10−3 M, an increasing proportion is accumulated unchanged as orthophos‐phate. Studies using 32P confirm, in greater detail, the observation of Harley and Loughman (1963) that phosphate in the external medium rapidly equilibrates with a small pool of ortho‐phosphate within the fungal sheath, from which the ion is incorporated into bound form or transferred either to the host core or to a larger pool in the sheath itself. Ammonium chloride at 10−2 M increases the total uptake of phosphate through an increase in the rate of both the incorporation into bound form and the primary absorption process. Ammonium chloride over the range 10−4 to 10−1 M brings about an increase in the size of the small pool. However, ammonium chloride has no detectable effect on phosphate fractions in the absence of phosphate in the external medium. Sodium azide, on the other hand, causes a breakdown of bound phosphate, although it is only at high concentration that this inhibitor has any detectable effect on the level of orthophosphate within the roots. The results suggest that the size of the small pool may be an important determinant of phosphate uptake at low concentration and that the role of potassium in the primary absorption process must not be overlooked.
INCORPORATION OF CARBON DIOXIDE INTO EXCISED BEECH MYCORRHIZAS IN THE PRESENCE AND ABSENCE OF AMMONIA
Authors: HARLEY J. L.
Published: May 2006

Summary

Excised beech mycorrhizas incorporate 14C into their tissues from dilute bicarbonate solution. The rate is doubled if the mycorrhizas are shaken in ammonium phosphate rather than potassium phosphate. The main distribution is into malic, glutamic and aspartic acids in the presence of potassium. In the presence of ammonium ions glutamine becomes the most strongly labelled compound.
THE MOVEMENT OF TOMATO AUCUBA MOSAIC VIRUS IN TOMATO
Authors: ROBB SHEILA M.
Published: May 2006

Summary

The interval which elapses between inoculation of tomato leaves with tomato aucuba mosaic virus and movement of virus into the stem varies considerably. Movement out of young apical leaves appears to be more rapid than that out of mature basal leaves, but the major source of variation is inherent in the individual plant and is not eliminated by standardizing the temperature and light of the environment. Since the time when virus enters the stem cannot be estimated accurately on any one plant, no precise estimate can be formed as to the rate of movement in the stem. Movement may be upwards or downwards. Discontinuity of virus distribution in the stem has been observed and this could be adduced as evidence against autocatalytic spread of virus; on the other hand, in other experiments virus appears to have been intercepted in its passage through the stem, which might make rapid transport through the phloem seem unlikely. This approach to the problem is insufficiently precise either for estimating the rate of movement of tomato aucuba mosaic virus through the plant or for determining its path.
A CYTOGENETIC INVESTIGATION IN A PHYLLITIS‐ASPLENIUM COMPLEX
Authors: EMMOTT JANET I.
Published: May 2006

Summary

A hybridization programme between diploid and tetraploid representatives of the genus Phyllitis has been carried out and two cases of intergeneric hybrids between Phyllitis and species of Asplenium have been synthesized and are described. Chromosome pairing involving tetraploid forms of Phyllitis scolopendrium from both North America and Japan suggests the occurrence of autosyndesis within the tetraploid genomes. This is not encountered in hybrids involving the tetraploid species P. hybrida. An allopolyploid origin for the latter and an autopolyploid origin for the former is probable although the exact parentage is not certainly known in either case. A working hypothesis concerning the possible course of evolution within the group Phyllitis is put forward in conformity with all the evidence, including that from morphology and geographical distribution, and the steps necessary to confirm or refute it are enumerated.
A NEW DESIGN FOR A PEAT SAMPLER
Authors: THOMAS K. W.
Published: May 2006

Summary

A new design for a peat sampler is described. This sampler, in the view of the author, has a number of features which are considered to be of advantage both for field work and for the subsequent laboratory investigations of peat deposits. These advantages are listed, the most important being that intact cores covering the whole depth of deposits can be recovered and brought back to the laboratory for detailed investigation.
THE EFFECT OF ALUMINIUM ON THE UPTAKE AND INCORPORATION OF PHOSPHATE BY EXCISED SAINFOIN ROOTS
Authors: RORISON I. H.
Published: May 2006

Summary

Movement of aluminium into excised root tips of sainfoin follows a normal curve which suggests little or no uptake into non‐free space. Washing in water removes very little aluminium from the roots but washing in dilute buffer solution removes a considerable exchangeable fraction. The pattern of phosphate incorporation in roots pretreated with aluminium is different from that obtained with untreated roots in several respects. Both percentage esterification and the proportions of the esterified fractions differ suggesting both a Donnan free space and a metabolic interference. The small amount of aluminium removed by aqueous washing suggests a minimum of precipitation with aluminium either external to the root, or in the water‐free space of the cortex. The importance of this aluminium‐phosphate effect as a component of aluminium toxicity, its specific sites and rates of reaction, require further experimental assessment.
THE METABOLISM OF MALONATE BY MYCELIAL SUSPENSIONS OF ASPERGILLUS NIGER
Authors: YEOMAN M. M.
Published: May 2006

Summary

The effects of malonate on the gaseous exchange and acid metabolism of mycelial suspensions of Aspergillus niger have been studied.

Malonate penetrated into the cells of the fungus but did not exert its normal effect as a competitive inhibitor in the TCA cycle, even at high external concentrations. On the contrary it stimulated oxidative catabohsm. Some of the malonate which penetrated was consumed by the fungus and it is inferred that the remainder was stored within the mycelium away from malonate sensitive centres in the cytoplasm.

Experiments performed with [2‐14C] malonate have shown that part of the malonate molecule may be utilized in the synthesis of larger structural molecules of the mycelium. Possible pathways of malonate metabolism are discussed in the light of work carried out with other organisms.
ENVIRONMENTAL CONTROL OF CLEISTOGAMY IN PRAIRIE GRASS (BROMUS UNIOLOIDES H.B.K.)
Authors: LANGER R. H. M. , WILSON D.
Published: May 2006

Summary

In long days (16 hours) flowers of prairie grass (Bromus unioloides H.B.K.) were almost invariably cleistogamous. In shorter photoperiods chasmogamous flowers were the rule provided soil moisture was high. Chasmogamy was attended by greater anther length but later anthesis than occurred in the cleistogamic condition. Filaments and lodicules were small in cleistogamous flowers and autogamous pollination occurred soon after emergence from the leaf sheath.
THE EFFECT OF CATIONS ON THE GROWTH OF FUNGI
Authors: JONES E. B. G. , JENNINGS D. H.
Published: May 2006

Summary

Dendryphiella salina Pugh has been grown in glucose‐tryptone media differing in their ionic composition. Of the cations which have been added singly to the basal medium, potassium produces the greatest growth in terms of dry weight. Sodium stimulates dry weight production at low concentrations hut inhibits it at high concentrations. Magnesium, calcium and strontium inhibit dry weight production at all concentrations. The inhibition of dry weight production by sodium can be removed by magnesium, calcium, strontium and barium (in order of effectiveness). Under these conditions where growth is inhibited, there is a simple relationship between dry weight and mycelial potassium content. The results are interpreted in terms of the permeability of the hyphae to potassium. A number of other fungi were grown in malt extract media differing in their ionic composition. All the fungi tested have their vegetative growth inhibited by sodium; the concentration causing inhibition can differ widely from species to species. Calcium ions in all cases can reduce the extent of this inhibition. It is clear from this study that a consideration of growth media from the point of view of ionic composition may be very important in interpreting data concerning the growth of fungi.
A NOTE ON THE EFFECT OF THE SHOOT AND ROOT APEX ON SECONDARY THICKENING IN PEA RADICLES
Authors: DIGBY JOHN , WANGERMANN ELISABETH
Published: May 2006

Summary

The effects of excision of the root or shoot apices of young pea seedlings and of their replacement with auxin paste, suggest that, (i) cambial activity in the root is stimulated by auxin coming from the shoot; and (ii) auxin from the root apex either does not travel to the older parts of the root or has no effect on cambial activity.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J.
Published: May 2006

Summary

Earher evidence that starch is not formed from sugar in plant tissues in the absence of oxygen was confirmed for potatoes. The failure to form starch is attributed to a deficiency of glucose‐1‐phosphate in nitrogen.

As in other plant tissues the dissolution of starch to sugar also appeared to be retarded in potatoes in the absence of oxygen. This observation would be explained if starch is degraded by phosphorylase to glucose‐1‐phosphate, which is then converted to sucrose before partial inversion to hexose; the rate of formation of sucrose in nitrogen would be retarded by lack of uridine triphosphate.
CYTOGENETIC STUDIES IN TUBEROUS SOLANUM SPECIES
Authors: MARKS G. E.
Published: May 2006

Summary

The results are given of crossing fifteen Central and South American wild Solanum species included in the series Conicibaccata, Demissa, Longipedicellata and Piurana. Nearly all the 210 possible combinations were examined.

Pollen tube inhibition occurred in 144 cases. It was affected by the particular species used (e.g. pollen of Conicibaccata species was strongly inhibited), by polyploidy and by the breeding system. It was progressively weaker from 2x×2x to 6x×6x crosses: in crosses of parents differing in chromosome number the probability of inhibition was greater the lower the ploidy of the pollen. The effect of different breeding systems was to introduce reciprocal differences such that pollen inhibition occurred when self‐incompatible species were crossed as females with self‐compatible ones but not in reciprocal crosses. This was so at diploid and tetraploid levels except in crosses involving tetraploid and hexaploid Conicibaccata species where the results were in complete contrast: there are indications that species in this series do not have a simple one‐locus self‐incompatibility system.

Post‐fertilization failure occurred in eighteen cases and breakdown was greatest in crosses between parents of different chromosome number.

Hybrids were obtained in forty‐seven combinations. Generally, crossability was highest in crosses that gave even polyploid (2x, 4x, 6x) progeny and lowest where uneven polyploids (3x, 5x, 7x) were obtained. All hybrids except two were vigorous.

Meiosis is described in thirty‐seven hybrids and the patterns of chromosome association are interpreted in terms of genomic differentiation. It seems that species in series Demissa and Longipedicellata have at least one common genome, which is also present in S. Uiquerrense of series Piurana. Further, it seems that this genome is similar to that of the diploid species S. verrucosum of series Demissa and consequently it is considered as an important link between the Central and South American potatoes. Both S. fendleri and S. stoloniferum of series Longipedicellata have genomic affinities with S. santolallae of series Conicibaccata; this is evidence of another genomic link across the subcontinent. Of the species in series Longipedicellata, S. fendleri and S. stoloniferum are fundamentally similar whereas S. polytrichon is different from both. S. guerreroense and S. iopetalum of series Demissa are very similar and could be considered conspecific. Evidence suggests that S. X semidemissum is probably a hybrid between S. demissum and either S. fendleri or S. stoloniferum.
THE EFFECT OF WIND ON PLANT GROWTH AND SOIL MOISTURE RELATIONS: A RE‐ASSESSMENT
Authors: HUMPHRIES A. W. , ROBERTS F. J.
Published: May 2006

Summary

The argument that wind and soil moisture stress induce similar anatomical changes in plant leaves, and that these changes enhance the ability of the plant to restrain water loss, is examined. It is shown that the data presented by Whitehead (1963a) can be explained satisfactorily in terms of induced changes in root distribution and leaf area, without invoking any specialized adaptations for the reduction of water loss.
PLANT GROWTH AND THE AERIAL ENVIRONMENT
Authors: HUGHES A. P.
Published: May 2006

Summary

Compared to Blue‐white fluorescent light at 15°C, Blue light and low temperature (10°C) resulted in a restriction in the rate of leaf growth due primarily to a sharp fall in specific leaf area with mcreasmg plant size, which was much more pronounced in low temperature. There was scarcely any effect on the leaf weight/total dry weight distribution, hut the leaves had a much higher dry matter content than plants grown in Blue‐white light. In Blue light the unit leaf rate was depressed on an energy basis, but not on a quantum basis. It was also depressed in low temperature. The depression of both unit leaf rate and leafiness resulted in a low relative growth rate in both treatments. The interrelationship of specific leaf area and unit leaf rate did not follow the same pattern as reported previously and this is discussed. The effects attributed to low temperature in field experiments were confirmed.
EXPERIMENTAL TAXONOMY OF SOME BRITISH SPECIES OF THE GENUS DICRANUM
Authors: BRIGGS D.
Published: May 2006

An experimental taxonomic study, of a group of closely related species of the moss genus Dicranum, has been carried out. Morphologically the material studied falls into four major taxa–D. bonjeanii, D. fuscescens, D. majus and D. scoparium. Cytologically three of the taxa (only a single chromosome count is available for D. bonjeanii, n = 11) show variation both in the number of ‘A’ chromosomes and in the number of minute bivalents: D. fuscescens, n = 10, 11 (10 + 1 m), 12, 24; D. majus, n = 11, 12, 13 (12 + 2 – 5 m)’D. scoparium, n = 11, 12, 13 (12 + 1 m). These chromosome numbers suggest that each taxon is an aggregate of closely related species, but until more evidence is available it is recommended that four taxa of specific rank be recognized. This procedure receives support from the fact that the different cytotypes are indistinguishable or have not yet received thorough taxonomic study. The intraspecific variation within each of the four species has been examined. Cultivation experiments have shown that certain genotypes exhibit wide phenotypic plasticity, but distinct genotypes of D. fuscescens and D. scoparium are reported. The use of varietal names for these morphologically distinct populations is not recommended, as they cannot be distinguished (except by cultivation experiments) from genotypes which are phenotypically plastic.
THE ROLES OF ADENOSINE TRIPHOSPHATE AND GLUTATHIONE IN THE INHIBITION OF CYCLOSIS BY p‐CHLOROBENZOIC ACID IN ELODEA DENSA
Authors: BRUESKE C. H. , APPLEGATE H. G.
Published: May 2006

Summary

Adenosine triphosphate (ATP) applied alone accelerated cyclosis in Elodea densa. When applied simultaneously with p‐chlorobenzoic acid (p ClBA), ATP nullified the inhibition of cyclosis by p C1BA, However, when ATP was applied prior to p ClBA, it only partially overcame the inhibiting action of p ClBA. Gltatathione at non‐toxic levels induced acceleration of cyclosis. Exogenous sulphydryl groups, in the form of glutathione, partially reduced p ClBA‐inhibited cyclosis. It was found that p C1BA combined with sulphydryl groups in vitro. Explanations are advanced for the action of ATP and glutathione in the inhibition of cyclosis by p ClBA.
ON THE RELATIONSHIP BETWEEN TRANSPIRATION RATE AND LEAF WATER POTENTIAL
Authors: TINKLIN R. , WEATHERLEY P. E.
Published: May 2006

Summary

The aim was to vary the transpiration rate of water culture plants and to measure corresponding values of ΔW, the leaf water potential depression (= DPD = suction force), as well as relative water content (relative turgidity) and stomatal aperture. On the Ohm‐law analogy ΔW and transpiration rate should be linearly related.

Ricinus communis plants were placed in a wind tunnel and the transpiration rate was varied by changing the level of the relative humidity of the air stream. With increasing rate of transpiration, ΔW rose steeply to a value of about 6 atmospheres at which it remained virtually constant (Fig. 1). Thus from very low transpiration rates to the highest obtainable, far from ΔW rising linearly with transpiration, there was no response in ΔW and similarly no response in relative water content and stomatal resistance. When transpiration was reduced to zero the leaves still maintained a ΔW of about 3 atmospheres instead of zero, but reasons are put forward for considering this value to present water saturation.

The main resistance to water movennent in the plant was shown to reside in the roots. If a leaf was detached from a transpiring plant and allowed to continue transpiration at a similar rate, water being freely supplied to the cut end of the petiole, its ΔW fell from 6 to 3.5 atmospheres (Fig. 3). Thus the resistance must lie‘below’the petiole. Similarly it was shown to lie below the stem.

The constancy of leaf ΔW in the face of large changes in flux of water through the roots, implies that the root resistance declines in step with the rise in flux. A simple hydraulic model is presented which would behave in this way.
POLLEN ANALYSIS OF SOME LAKE DEPOSITS NEAR BAMBURGH IN NORTHUMBERLAND
Authors: BARTLEY D. D.
Published: May 2006

Summary

Late‐glacial and early Post‐glacial deposits have been examined in two areas of Northumberland. All the sites are associated with esker or kame features and the deposits show a succession from lake to bog, two of them under calcareous conditions. The pollen diagrams show a completely unforested Late‐glacial period, probably with a total absence of trees from the higher site. The spread of forest conditions, indicated by the rise in juniper pollen followed by rising values of birch, is shown to have occurred in the middle of zone IV at the lower site but closer to the end of zone IV at the higher site. At the same time attention is drawn to the persistence of Lateglacial conditions into zone IV at the higher site. Also of note are the high percentages of Quercus and very low percentages of Pinus in zone VI. Comparisons are made with previously published diagrams from other areas, especially from Tadcaster in Yorkshire, to illustrate the later date of forest spread in the more northerly localities.

The two areas described are situated in Northumberland, one on the coastal plain near Bamburgh at an altitude of 150 ft and the other some 7 miles south at an altitude of 350 ft. The country in which they lie is largely covered by a mantle of glacial drift and both sites are associated with glacial features.
OCHROMONAS OSTREAEFORMIS NOV. SP., A LARGE COMPRESSED CHRYSOMONAD
Authors: SWALE E. M. F. , BELCHER J. H.
Published: May 2006

Summary

Ochromonas ostreaeformis nov. sp. is described from a pool in the English Lake District. The motile cells have been recorded each spring for 4 years, although the formation of cysts was first observed in 1965. Possible factors influencing periodicity are discussed, especially variation in the phosphate phosphorus content of the water, which tended to show an inverse relationship with the number of cells.
EPIDERMAL STRUCTURE AND STOMATAL ONTOGENY IN SOME CELASTRACEAE
Authors: PANT DIVYA DARSHAN , KIDWAI PARVEEN F.
Published: May 2006

Summary

Leaves of Celastrus paniculatus, C. stylosus, Elaeodendron glaucum, Euonymus japonicus and E. pendulus are essentially hypostomatic, although a few stomata were observed near veins in the upper epidermis of Celastrus paniculatus. Their irregularly orientated stomata show guard cells partly underarched and partly surrounded by a ring of three to eight subsidiary cells. Surface walls of epidermal cells in Euonvmus pendulus show pits whose impressions are also seen in the cuticle.

Rehfous (1914) had suggested that the sunken subsidiary cells of Celastrus europaeus, Catha edulis and Euonymus japonicus and four other species of the genus are formed in an unusual manner from segments of the guard cells. Our studies on the contrary indicate that the subsidiary cells in all our plants, including E. japonicus, are typically perigene.

Mesophyll of all leaves is armed but the form of midrib bundles varies in different species and to some extent in different regions of the same leaf.
THE DEVELOPMENT OF CHLOROPLASTS AND PHOTOSYNTHETIC ACTIVITIES IN YOUNG BARLEY LEAVES
Authors: RHODES M. J. C. , YEMM E. W.
Published: May 2006

Summary

Carbon dioxide exchanges in the dark and in the light indicate that photosynthetic activity occurs m young leaves of barley seedlings after about 3 hours illumination under favourable conditions. Activity increases rapidly as chlorophyll is formed in the expanding leaf blade; a compensation point is reached after 30–40 hours and thereafter carbon dioxide assimilation exceeds respiration.

Changes in the fine structure of plastids in the young leaves were examined by electron microscopy; some of the chief stages in the development of the lamella system and the differentiation of grana are described. The presence of ribosome‐ and nucleoplasm‐like structures in the chloroplast stroma was indicated.

The relationship between the development of chloroplasts and their photosynthetic activity is discussed. It is suggested that the formation of distinctive double membranes between the thylakoids of the grana plays an important part in the structural organization of the pigment system. The action of light on chloroplast development indicates that a primary step in photomorphogenesis is the conversion of protochlorophyllide to chlorophyll. The further extension and development of the lamellar system probably depends upon the biosynthesis of proteins and lipids, closely linked with photosynthesis and operating under the control of nucleic acids.
THE MECHANISM OF ABSORPTION AND UTILIZATION OF PHOSPHATE BY BARLEY PLANTS IN RELATION TO SUBSEQUENT TRANSPORT TO THE SHOOT
Authors: LOUGHMAN B. C.
Published: May 2006

Summary

An attempt has been made to distinguish between the process of absorption of orthophosphate by the roots of whole barley plants and that of subsequent transport to the shoot. Such selection can be induced by treatment with growth regulators and inhibitors of specific biochemical stages in phosphorus metabolism. The presence of physiological concentrations of D‐mannose in the root environment has little effect on the overall uptake of radioactive phosphate. The metabolic fate of the absorbed phosphate is, however, severely affected and the ion appears to be reversibly sequestered in the form of hexose monophosphates other than those found to be labelled under normal conditions. Both glucose‐1 ‐phosphate and mannose‐6‐phosphate contain radioactive phosphorus after treatment with mannose. Although overall uptake is relatively unaffected, mannose specifically inhibits further transport of the metabolized phosphate to the shoot and it is concluded that this transport is directly dependent on the prior incorporation of the incoming phosphate into a specific sequence of organic compounds. The results are discussed in relation to the possible mechanisms involved in the separate processes of absorption and transport.
STUDIES IN SEED DORMANCY III. THE EFFECTS OF GIBBERELLIN ON DORMANT SEEDS OFCORYLUS AVELLANAL.
Authors: BRADBEER J. W. , PINFIELD N. J.
Published: May 2006

Summary

Application of exogenous gibberellin over a concentration range of 3 × 10−7M‐3 × 10−3M has been found to break hazel seed dormancy, growth of tbe embryonic axis being detectable within a few days of gibberellin application. Metabolic studies of seeds pre‐treated with 3 × 10−4M gibberellin or water have been made during the period prior to the detection of embryonic axis growth. Imbibition of seeds in the presence or absence of gibberellin resulted in an increase of the percentage of incorporated radioactivity found in RNA and protein in both cotyledons and embryonic axes. Data on the incorporation of radioactivity into DNA were not conclusive. Gibberellin pre‐treatment has so far been found to have three clear effects on cotyledonary metabolism, namely, to increase the proportion of [8−14C]adenine incorporated into nucleotide, to reduce the proportion of [2−14C]acetate incorporated into lipid and to increase the activity of isocitrate lyase (Pinfield, 1967).

It is suggested that imbibition of dormant hazel seeds initiates the synthesis of RNA and protein, both in cotyledons and embryonic axes. The primary effect of gibberellin action may occur in the cotyledons, where its role in the breaking of seed dormancy may be in the induction of increased levels of activity of certain enzymes, particularly those concerned with the mobilization of the cotyledonary oil reserves. It is not clear as to what part, if any, the gibberellin stimulated adenine nucleotide synthesis plays in the breaking of hazel seed dormancy.
EFFECT OF GIBBERELLIC ACID ON THE GROWTH AND ANATOMY OF COLEUS BLUMEI, ANTIRRHINUM MAJUS AND SALVIA SPLENDENS
Authors: BOSTRACK JACK M. , STRUCKMEYER B. ESTHER
Published: May 2006

Summary

Plants of Coleus blumei (Coleus), Antirrhinum majus (snapdragon) and Salvia splendens (Salvia) exhibited three common responses to foliar applications of 50 mg/1 aqueous solution of gibherellic acid (GA); elongation of the internodes, hyponasty and chlorosis. Elongation of subapical internodes was a result primarily of cell division in both Antirrhinum majus and Salvia splendens. Gibberellic acid at 500 mg/1 caused less elongation of the sub‐apical region than at 50 mg/1 and 100 mg/1 in S. splendens. Treated plants had a smaller stem diameter and more xylem parenchyma. Coleus blumei cuttings showed reduced rooting when treated with 50 mg/1 GA.
THE ROLE OF CARBON DIOXIDE, LIGHT AND NITRATE IN THE SYNTHESIS AND DEGRADATION OF NITRATE REDUCTASE IN LEAVES OF PERILLA FRUTESCENS
Authors: KANNANGARA C. G. , WOOLHOUSE H. W.
Published: May 2006

Summary

Nitrate reductase in leaves of Perilla is an adaptive enzyme, the induction of which is shown to require carbon dioxide, light and nitrate. Following illumination of a leaf containing nitrate, the activity of the enzyme rises to a maximum after 6 hours and then begins to decline again. However, the enzyme activity is not entirely lost in such a leaf, provided that a supply of nitrate is maintained. When leaves containing nitrate reductase are placed in darkness, the enzyme breaks down at an approximately linear rate, which is influenced by temperature and by the age of the leaf. Synthesis of the enzyme appears to depend on active photosynthesis, since, when a leaf containing nitrate is illuminated in a CO2‐free atmosphere, no detectable enzyme is formed. When a leaf possessing nitrate reductase activity is illuminated in a CO2‐free atmosphere, the enzyme activity falls at a similar rate to that which occurs when the leaf is darkened. Thus it is reasonable to conclude that synthesis of the enzyme is dependent upon both light and CO2 and that a continuous breakdown of the enzyme is taking place even during a period of net synthesis. Using this information it becomes possible to estimate and compare the capacity of leaves of different ages to s)nthesize nitrate reductase.
RATES OF INCORPORATION OF LABEL FROM d‐[14C]GLUCOSE INTO DIFFERENT REGIONS OF THE ROOT‐TIP OF MAIZE (ZEA MAYS L.)
Authors: ROBERTS R. M. , BUTT V. S.
Published: May 2006

Summary

When D‐[U‐14C]glucose was supplied externally to root‐tips of maize, uptake was linear with time, but saturation rates of incorporation into the ethanol‐xylene‐water insoluble fractions were not achieved simultaneously by the different tissues. The more deeply lying cortex and pith required longer periods to reach steady state rates than the outer regions of the root. Thus, after 30 minutes, autoradiographs showed label to be present only in the epidermis, outer cortex and marginal cells of the cap but, after 4 hours, each of the regions appeared to have reached saturation. It could not be determined how far these differences in incorporation rates were due to higher synthetic activity in the outer tissues and hence a more rapid equilibration of labelled compound with the precursor pools, or to the penetration of the tracer compound to successive tissues of the root.
LIME‐CHLOROSIS AS A FACTOR IN SEEDLING ESTABLISHMENT ON CALCAREOUS SOILS
Authors: HUTCHINSON T. C.
Published: May 2006

Summary

A comparative study under uniform laboratory conditions has been made of the relative susceptibility to lime‐chlorosis of 135 British species. These species were chosen as being either (a) largely confined to calcareous soils or (b) largely confined to non‐calcareous, especially acidic, soils. A number of species of wider soil tolerance were also grown. It was found that the species of groups (a) and (b) differed markedly from each other in chlorosis susceptibility. More than 90% of the species of calcareous soils were either resistant to lime‐chlorosis or were only mildly affected, whilst more than 60% of the species of acidic soils were susceptible to the condition. Evidence is presented that divergence in chlorosis susceptibility has occurred both within genera and within species. Family differences would also seem to occur. A possible mechanism for the origin of these differences and their ecological significance is discussed.
ABSORPTION OF NITROGEN BY MYCORRHIZAL ROOTS OF BEECH
Authors: CARRODUS B. B.
Published: May 2006

Summary

The effects of ammonium chloride, potassium nitrate and potassium chloride on the rate of 14CO2 incorporation into beech mycorrhizas were compared. It was confirmed that the rate of incorporation of 14CO2 was increased by ammonia and that glutamine became heavily labelled in its presence. No such effect was evident in the case of nitrate. Both potassium chloride and potassium nitrate stimulated 14CO2 incorporation as compared with samples kept in water but the extra radioactivity was found primarily in malate. This is the result to be expected if potassium is absorbed more readily than the associated anion. It is concluded that nitrate is not readily utilized by excised beech mycorrhizas. The primary destination of absorbed ammonia appears to be the fungal sheath.
A DISC ELECTROPHORETIC STUDY OF GLOBULIN PROTEINS OF LEGUME SEEDS WITH REFERENCE TO THEIR SYSTEMATICS
Authors: BOULTER D. , THURMAN D. A. , DERBYSHIRE E.
Published: May 2006

Summary

The globulins extracted from a number of different species of legume seeds have been subjected to disc electrophoresis. In the limited sample surveyed, the tribes Vicieae, Phaseoleae, Diocleae, Trifolieae and Daibergieae were each characterized by a distinctive protein band pattern. When the globulins of genera from the Loteae, Galacteae and Glycineae were examined, two types of protein band patterns were obtained which were distinctive for each tribe. A wider range of protein band patterns were obtained when genera of the Cajaneae were examined. The one species of Abrus examined possessed a globulin protein band pattern which differed from the patterns found in any other genera of the tribes examined.

If the findings reported here can be extended to a much greater range of genera without significant change, then for some tribes within the Leguminosae a distinctive protein band pattern can be obtained when their seed globulins are electrophorized.
FINGERPRINT PATTERNS OF THE GLOBULIN FRACTION OBTAINED FROM SEEDS OF VARIOUS SPECIES OF THE FABACEAE
Authors: JACKSON P. , MILTON J. M. , BOULTER D.
Published: May 2006

Summary

The patterns (fingerprints) of the peptides separated from tryptic digests of the globulin fraction of seeds of five genera of the Vicieae have been compared and shown to be very similar. Patterns obtained with Phaseolus vulgaris, and two species of Canavalia (Phaseoleae, sensu lato), were different from those of the Vicieae; the two Canavalia species gave an identical pattern. Fingerprints of the globulin fraction of Abrus precatorius (Abreae) differed from those of Phaseolus vulgaris and also from those of the various members of the Vicieae.

The usefulness of this method for supplying data for systematic purposes is discussed.
EXPERIMENTS ON THE ECOLOGICAL SIGNIFICANCE OF PHYCOMYCETOUS MYCORRHIZAS
Authors: BAYLIS G. T. S.
Published: May 2006

Summary

The mixed rain forest of New Zealand is dominated by conifers and dicotylous trees all of which form phycomycetous mycorrhizas. They may be present only intermittently in the field, but they become conspicuous in seedlings potted in forest soil. The time required to establish infection is variable, and may exceed 1 year. Growth is limited meanwhile by the reserve of phosphorus in the seed.

Heating forest soils to temperatures above 55°C had two contrasted effects on the growth of tree seedlings—a small favourable effect associated with a rise in available phosphate measured hy the Truog test, and a larger deleterious effect associated with destruction of potential endophytes.

Coprosma robusta (Rubiaceae) was the species principally used for experiments. By adding sufficient soluble phosphate to either heated or unheated soil vigorous non‐mycorrhizal plants were obtained. In the unheated soil there were also mycorrhizal plants which were, if anything, smaller. With less phosphate plants with numerous mycorrhizas were always larger than those with little or no infection; with no added phosphate there was virtually no growth unless mycorrhizas were formed. The relatively slow‐growing Griselinia littoralis differed in that when mycorrhizal it was insensitive to added phosphate. In steamed soil the growth of non‐mycorrhizal plants of both species was directly proportional to the amount of phosphate added.

In Coprosma robusta shading to about one‐third of full daylight did not reduce mycorrhizal infection.

Chemical analyses are given which demonstrate the low availability of phosphorus in the soils employed, and the greater uptake by mycorrhizal plants.

These observ'ations suggest that mycorrhizas are normally essential for the uptake of phosphorus from forest soils, the phycomycetous type being particularly important in the Tropics and Southern Hemisphere, where the ectotrophic type has been little recorded.
ANALYSIS OF A CORE FROM SLAPTON LEY
Authors: CRABTREE K. , ROUND E. E.
Published: May 2006

Summary

Detailed analyses of pollen, chemistry and diatoms have been carried out on material taken with a Livingstone corer from the Lower Ley, near Slapton, South Devon, The stratigraphy and the three approaches to reconstructing past events all point to a series of marked changes within the short section sampled, and all within pollen zone VIII. The degree of correlation between the different analyses is stressed and used to suggest ecological changes within tbe Ley and on the surrounding land surface, The permanence of the shingle ridge separating the Ley from the sea is verified, at least for the period under consideration, by the lack of any evidence of a period of marked marine incursion into the Ley.
STUDIES IN THE PHYSIOLOGY OF LICHENS
Authors: DREW E. A. , SMITH D. C.
Published: May 2006

Summary

A method for directly isolating cells of the algal symbiont (Nostoc) in quantity from the thallus of Peltigera polydactyla is described. Such directly isolated algae excrete much of the photosynthetically fixed carbon into the medium as glucose, but they lose this property after only 48 hours in culture, at which time the cells begin to release only small amounts of a compound which may be a polysaccharide. These results are discussed in the context of the transfer of fixed carbon from alga to fungus in the lichen thallus during photosynthesis. After the lichen algae had been in pure culture for some time, they showed a carbohydrate metabolism intermediate in a number of respects between the directly isolated Nostoc and a strain of free‐living N. muscorum. All three kinds of algae were able to utilize externally supplied glucose. The Nostoc from lichens could not utilize mannitol.
STUDIES IN THE PHYSIOLOGY OF LICHENS
Authors: DREW E. A. , SMITH D. C.
Published: May 2006

Summary

Several lines of evidence confirm that glucose moves from alga to fungus in the thallus of Peltigera polydactyla during photosynthesis. When thallus discs are incubated in NaH14CO3 solutions in the light, [14C]glucose is detectable after i minute but [14C]mannitol—the principal product of photosynthesis—is not apparent until after 2 minutes. If high concentrations (2% w/v) of [12C]glucose are included in the media, then [14C]glucose diffuses out of the tissues, no [14C]mannitol is formed, and no translocation of 14C from algal layer to medulla occurs. These effects are explained on the basis that the [14C]glucose released by the algal cells is prevented from entering the fungus because of competitive inhibition by the non‐radioactive glucose in the medium. The concentration of glucose in the medium required to achieve a 50% inhibition was approximately 0.004 M. It was found that 2‐deoxy‐glucose and 3‐methylglucose had similar effects to glucose, but fructose, galactose, mannose and mannitol had no effect on the movement of 14C between the symbionts and they were unable to prevent discs taking up glucose from very dilute (approximately 10−6m) solutions. The rate of movement of glucose between the symbionts was rapid. No penetration of algal cells by fungal haustoria could be detected.
LEAF CHLOROSIS AND STOMATAL APERTURE *
Authors: SHIMSHI D.
Published: May 2006

Summary

Under conditions which encourage stomatal opening, nitrogen deficiency (induced in wheat, sugar beets, maize and groundnuts) and iron deficiency (induced in groundnuts) markedly reduce stomatal aperture, as evaluated by means of a porometer. The effect of these deficiencies on stomatal behaviour seems to be mediated through their effect on leaf chlorophyll content. Foliar applications of urea to chlorotic leaves of nitrogen‐deficient maize restore both normal chlorophyll content and normal stomatal behaviour to the treated leaves, indicating that both variables are related on a localized, rather than a systemic level. In groundnuts the relation between chlorophyll content and stomatal aperture is the same, regardless of whether chlorosis was caused by nitrogen or iron deficiency. Chlorotic leaves had a lower apparent water saturation deficit than green leaves.
INTERACTIONS OF CARBON DIOXIDE CONCENTRATION, LIGHT INTENSITY AND TEMPERATURE ON PLANT RESISTANCES TO WATER VAPOUR AND CARBON DIOXIDE DIFFUSION
Authors: WHITEMAN P. C. , KOLLER D.
Published: May 2006

Summary

Exchange of water vapour and carbon dioxide, between whole sunflower plants and an atmosphere controlled to required CO2 and water vapour concentrations, was measured in a polythene chamber. Plant resistances to diffusion of CO2 and H2O were calculated. From the combined data of net flux of CO2(“P”), resistances to CO2 uptake, and atmospheric CO2 concentration [CO2]atm, the intercellular space CO2 concentration [CO2]int could be calculated.

[CO2]int was linearly related to [CO2]atm and this relationship was modified by light intensity. Plant age, between 3 and 6 weeks, did not alter the relationship. The ratio of [CO2]int to [CO2]atm was shown to be equivalent to the ratio of mesophyll resistance to CO2 diffusion (rm) to total resistance to CO2 diffusion (RCO2).

At a given [CO2]atm, [CO2]int decreased with increasing light intensity between 500 and 5500 ft‐candles but was little affected by leaf temperatures between 18 and 34° C. On the other hand, the minimum internal CO2 concentration Γ, measured as the equilibrium CO2 compensation point, increased linearly over the same temperature range but was little affected by light intensity above 500 ft‐candles. The effects of temperature and light on [CO2]int are in contrast to their effects on the Γ value. Therefore, it is less likely that temperature effects on [CO2]in, measured in the normal photosynthetic [CO2]atm range, are responsible for‘midday stomatal closure’as inferred from observations of temperature effects on Γ alone.

By comparing the effects of temperature and light intensities on stomatal resistance over the same range of [CO2]int values, direct effects of light and temperature, not mediated through changes in [CO2]int were demonstrated. The interactions of the factors involved are discussed.
THE ORIGIN AND DEVELOPMENT OF THE PHELLOGEN IN ROBINIA PSEUDACACIA L.
Authors: ARZEE TOVA , LIPHSCHITZ NILI , WAISEL Y.
Published: May 2006

Summary

The ontogenetic development of the phellogen in Robinia pseudacacia plants was studied. The first phellogen differentiates in the seedling stage from collenchyma cells in the second or third layer beneath the epidermis. The subsequent phellogen is periodically derived from phloem parenchyma cells.

The site of phellogen initiation was shown to be affected by climatic conditions as well as by various growth substances. Under long‐day and high‐temperature conditions the phellogen was initiated in a lower internode, as compared with plants grown under the other three combinations of photoperiod and thermoperiod, Gibberellic acid and naphthalene acetic acid had distinct retarding effects on initiation Kinetin and tri‐iodo‐benzoic acid treatments showed no effect.
SUGAR ABSORPTION AND COMPARTMENTATION IN POTATO TUBER SLICES*
Authors: HARDY P. J. , NORTON G.
Published: May 2006

Summary

The uptake and utilization of [14C]sucrose, [14C]glucose and [14C]fructose by mature and immature potato tuber slices was studied. Both tissues absorbed [14C]glucose faster than [l4C]fructose but once absorbed, the hexoses were utilized similarly. In contrast, the greater part of the labelled sugars formed on administration of [14C]sucrose was sequestered at sites separate from the metabolic centres. Sucrose was taken up from the medium against a concentration gradient and transferred to metabolically inactive storage compartments without being hydrolysed either at the cell surface or at any stage during transit.
POLLEN TUBE GROWTH AND SEED SET IN SELF‐INCOMPATIBLE AND SELF‐COMPATIBLE LEAVENWORTHIA (CRUCIFERAE) POPULATIONS
Authors: LLOYD D. G.
Published: May 2006

Summary

Four geographic races of Leavenworthia crassa and one race of L. alabamica are described as self‐incompatible, since the average frequencies of fruit set and of pollen tube growth into the style are significantly lower after self‐pollination than after cross‐pollination. The frequency of successful self‐pollination in individual plants of these races varies from zero to 100%, and is positively correlated with the average number of seeds in self‐pollinated siliquas. Eleven races of L. crassa and three races of L. alabaimca are adapted to self‐pollination and are described as self‐compatible, although self‐pollinations succeed 2% less frequently than cross‐pollinations. Self‐pollinated siliquas of these races contain an average of 12% fewer seeds than cross‐pollinated siliquas; this is probably an expression of cryptic self‐incompatibility and not the result of the exposure of seed lethals on inbreeding. There is, therefore, no absolute distinction between self‐incompatibility and self‐compatibility in Leavemcorthia.

The growth of pollen tubes is compared in successful and unsuccessful pollinations of the same type, in self‐ and cross‐pollinations of the same individuals, and in self‐incompatible and self‐compatible races. Pollen grains react with the stigma even in unsuccessful pollinations and some pollen grains are inhibited in successful pollinations. In both self‐incompatible and self‐compatible races, the average number of emptied pollen grains on the stigmata of successful pollinations (an estimate of the number of pollen tubes in the styles) is similar after self‐ and cross‐pollinations. But the average number of emptied pollen grains is lower in self‐incompatible races than in self‐compatible races. The results are interpreted in terms of the response of pollen grains to an essential growth substance supplied by the stigma.
LICHEN PHYSIOLOGY
Authors: RICHARDSON D. H. S. , HILL D. JACKSON , SMITH D. C.
Published: May 2006

Summary

The identity of the carbohydrate moving between the symbionts of a lichen depends on the genus of alga present. Twenty‐seven lichen species, involving eight different genera of algae, have been examined. In lichens containing five genera of Chlorophyceae, carbohydrates move to the fungus as polyols (ribitol in Trebouxia, Myrmecia and Coccomyxa; erythritol in Trentepohlia; and sorbitol in Hyalococcus). In lichens containing three genera of Cyanophyceae (Nostoc, Calothrix and Scytonema) glucose was the carbohydrate moving, although there is a possibility that in the one lichen with Calothrix which was investigated, it may have been a glucan.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J.
Published: May 2006

Summary

The changes of various phosphate compounds were determined during the increase in rate of CO2 output and of sugar content which occurred in low‐sugar potatoes at 1° C. The contents of phosphate compounds were also estimated in high‐ and low‐sugar potatoes at 10° C. The increase in rate of CO2 output associated with higher sugar content could not be attributed wholly to an increase in the amounts of the hexose mono‐ and di‐phosphates; possible explanations are given.

The changes observed in glucose‐1‐phosphate do not afford any explanation of the mechanism of sweetening and de‐sweetening in potatoes. In different metabolic data the quotient, glucose‐1‐phosphate/glucose‐6‐phosphate, remained close to that for phosphoglucomutase in vitro.