bluuebunny/crossref_metadata_2025 huggingface dataset:
A NOTE ON A LATE‐WEICHSELIAN SPLACHNUM CAPSULE FROM SCOTLAND
Authors: CONOLLY A. P. , DICKSON J. H.
Published: May 2006

Summary

A single capsule of the coprophilous genus Splachnum is reported from deposits of Late‐Weichselian (Late‐glacial) age in Berwickshire. Other Quaternary records of moss sporophytes are briefly discussed.
A RADIOCARBON‐DATED POLLEN DIAGRAM FROM NORTH‐WEST SCOTLAND
Authors: MOAR N. T.
Published: May 2006

Summary

A series of radiocarbon dates from critical levels in a pollen diagram from a site near Scourie, Sutherlandshire, proves the recorded events to be much younger than the trend of the pollen curves would suggest. Evidence of pine forest growing in the area during the late Atlantic and Sub‐boreal confirms earlier observations that these forests persisted in north‐west Scotland later than in many other parts of the British Isles. The extremely slow rate of accumulation between about 420 cm and 455 cm, 1320 years, implies a break in deposition, but there is no biostratigraphic or lithostratigraphic evidence of this.
THE GROWTH OF PEA LEAVES IN RELATION TO INTERNODE GROWTH AS AFFECTED BY GIBBERELLIC ACID AND B‐9
Authors: SPRENT JANET I.
Published: May 2006

Summary

The effects of gibherellic acid (GA) and N‐dimethylaminosuccinamic acid (B‐9) on leaf growth in several pea cultivars have heen investigated. The relationships hetween the growth of a leaf and its suhtending internode were examined. A general inverse relationship hetween growth of the two organs was found in untreated and GA‐treated plants, and in B‐9‐treated plants grown at low light intensities. At high light intensities B‐9 was inhihitory to hoth leaf and internode growth.
ASPECTS OF STALING IN LIQUID CULTURES OF FUNGI
Authors: ROBINSON P. M.
Published: May 2006

Summary

Criteria for assessing staling in liquid cultures of fungi are examined and assays based on the germinative capacity of culture filtrates are considered unsuitable for interpreting the capacity of the same filtrates to support mycelial growth. The interrelationships of nutrient level and growth inhibitors in staling systems are emphasized. The possible importance of both labile and stable metabolites is discussed in relation to staling phenomena.
APICAL MERISTEMS AND GROWTH CONTROL IN HIMANTHALIA ELONGATA (S. F. GRAY)
Authors: MOSS BETTY
Published: May 2006

Summary

The young plant shows considerable internal differentiation before an apical meristem is organized. Once formed, the apical cell segments slowly. It is triangular in transverse section and segments cut off from its three sides are actively meristematic and soon build up an extensive meristem which enlarges and functions throughout the vegetative phase of the plant's development. Experiments have shown that the apical cell is the main seat of growth control and if it is destroyed another apical cell cannot be regenerated to take over this role. Division of the apical cell followed by division of the whole meristem into two, marks the end of vegetative growth and, the onset of reproduction. Successive divisions of the meristem follow and each new meristem becomes the tip of a fertile branch or receptacle. Eventually meristematic activity at the apices declines and this decline is associated with the termination of conceptacle initiation. As the entire vegetative meristem is used up in reproductive growth, there is no meristem left to continue vegetative grovrth after gamete discharge. Hence reproduction terminates the life span of Himanthalia.
CONCERNING THE MORPHOLOGY OF ISOLATED PLANT CUTICLES
Authors: LANGE R. T.
Published: May 2006

Summary

The morphological basis of cuticle analysis is discussed. A résumé is provided of the categories of microrelief occurring on the inner and outer surfaces of isolated plant cuticles. This is illustrated with photographs obtained by electron‐scanning microscopy. Some existing interpretations of cuticle morphology are called into question.
THE OVULE AS AN INDICATOR OF EVOLUTIONARY STATUS IN ANGIOSPERMS
Authors: SPORNE KENNETH R.
Published: May 2006

Summary

The crassinucellate ovule has long been regarded as more primitive among angiosperms than the tenuinucellate. Support for this view is provided by thirteen highly significant statistical correlations between the crassinucellate condition and other dicotyledon characters, both floral and vegetative. This character is therefore included among a total of twenty‐two characters believed to be of use in assessing evolutionary status. The ‘advancement indices’ of dicotyledon families are re‐calculated, using the most recently available facts. While the most primitive families are among the Magnoliales, there are also some very primitive ones among the Myrtiflorae, Violates, Geraniales, Rosales, Guttiferales and Fagales.

It is concluded that the ancestral type of ovule in angiosperms was crassinucellate with three envelopes (two integuments and an aril) each of which received a vascular supply.
EFFECT OF LIGHT INTENSITY AND CO2 ON APPARENT PHOTOSYNTHESIS AND ITS RELATIONSHIP WITH LEAF ANATOMY IN GENOTYPES OF LOLIUM PERENNE L.
Authors: WILSON D. , COOPER J. P.
Published: May 2006

Summary

A manometric technique was used to examine the effect of light intensity and CO2 on the relative photosynthetic activity of ten contrasting Lolium genotypes grown in a common environment. Relationships between leaf anatomy and photosynthesis were examined. At a given CO2 concentration, apparent photosynthesis increased with increasing light intensity until ‘light saturation’was reached. The saturating light intensity increased with increasing CO2 concentration. There were significant differences in photosynthetic rate between genotypes where light or CO2 respectively were limiting, but the relative order of the genotypes differed in these two cases. There was also independent variation in response to increasing CO2 to very high concentrations. At approximately 300 ppm CO2 and at light saturation, apparent photosynthesis was negatively correlated with mesophyll cell size. The most efficient leaves under these conditions were smaller and thinner than the less efficient. When light was limiting, apparent photosynthesis was not related to any anatomical feature. There was no indication of a stomatal effect under any conditions. The association between light‐saturated photosynthesis and mesophyll cell size was similar to that between cell size and the estimated cell surface: volume ratio.
APPARENT PHOTOSYNTHESIS AND LEAF CHARACTERS IN RELATION TO LEAF POSITION AND AGE, AMONG CONTRASTING LOLIUM GENOTYPES
Authors: WILSON D. , COOPER J. P.
Published: May 2006

Summary

The effect of leaf position, specific leaf weight and chlorophyll on light‐saturated apparent photosynthesis, and their relationships with leaf mesophyll, among contrasting Lolium genotypes are described. Within a range of up to four fully expanded leaves on a tiller, the lower (older) leaves had greater photosynthetic activity than the upper (younger). For any particular leaf, maximum photosynthesis was attained prior to full expansion. These effects were closely related to differences in mesophyll cell size. A wide range in leaf chlorophyll levels exhibited by Lolium mutants was not associated with differences in apparent photosynthesis. Specific leaf weight and chlorophyll content were greater in thin leaves with small mesophyll cells than in thick leaves with large cells. Chlorophyll content was not associated with differences in photosynthesis in limiting light (500 ft‐candles).
THE DIURNAL FLUCTUATION IN NITROGEN FIXATION IN THE NODULES OF ALNUS GLUTINOSA AND MYRICA GALE
Authors: WHEELER C. T.
Published: May 2006

Summary

Maximal rates of nitrogen fixation in the root nodules of first‐year plants of Alnus glutinosa and Myrica gale growing under natural illumination but at nearly constant temperature were found by the acetylene assay to be attained about midday. The nitrogen content of the sap exuding from the stumps of decapitated plants and the level of soluble nitrogen in the nodules were also highest close to midday, the same being true of the rate of respiration in detached nodules.

The hypothesis that in view of these findings the midday period must be that of maximum ingress of photosynthates into the nodules is not reflected in analyses of gross carbohydrate levels in the nodules at different times of day.
INFLUENCE OF HERBICIDES ON THE COMPETITIVE ABILITY OF FUNGI TO COLONIZE PLANT TISSUES
Authors: WILKINSON VALERIE , LUCAS R. L.
Published: May 2006

Summary

Experiments show that the presence of herbicide residues in plant remains may be a potent factor determining the outcome of competition between saprophytic fungi colonizing such substrates. Pairs of fungi were induced to compete with each other for a substrate both in the presence and in the absence of herbicides. In all cases the outcome of competition for a substrate incorporating the herbicide was different from that for the substrate alone. Paraquat sprayed on to potato haulm altered the outcome of competition between Trichoderma viride and Fusarium culmorum in favour of F. culmorum and the same herbicide on wheat chaff suppressed Rhizopus stolonifer in favour of Aspergillus niger. Treatment of leaves of Raphanus raphanistrum with MCPA altered the outcome of competition between Fenicillium notatum and Aspergillus niger in favour of A. niger.
NITROGEN METABOLISM IN LICHENS
Authors: MILLBANK J. W. , KERSHAW K. A.
Published: May 2006

Summary

Nitrogen fixation has been demonstrated to occur in the cephalodia of the lichen Peltigera aphthosa which contain a species of Nostoc. The rate of fixation is very high in comparison with the maximum rates for N. muscorum under optimum culture conditions. Virtually all of the nitrogen fixed is secreted to the lichen thallus at a rate equal to the rate of fixation. The possible control mechanisms of this secretion are discussed.
OBSERVATIONS ON THE NITROGEN METABOLISM OF PROTOTHECA KRÜGER
Authors: CASSELTON P. J. , STACEY J. L.
Published: May 2006

Summary

Four strains of the putative apochlorotic algal genus Prototheca Krüger (P. chlorelloides, P. moriformis, P. portoricensis and P. zopfii), could utilize either ammonium sulphate or adenine as sole nitrogen source for growth but neither potassium nitrate nor sodium nitrite could be utilized. P. zopfii could also utilize the purines hypoxanthine and guanine, and both P. zopfii and P. chlorelloides could utilize a wide range of l‐ and d‐amino acids as sole nitrogen sources for growth in media containing glucose. P. zopfii and P. chlorelloides behave similarly to one another in the experiments and may, therefore, not be separate species, while P. moriformis and P. portoricensis behaved differently from them and from each other.

Cell‐free extracts of P. zopfii had transaminase and nicotinamide adenine dinucleotide phosphate (NADP) dependent glutamate dehydrogenase activities. An attempt to show that ammonium assimilation involves a coupling between the NADP glutamate dehydrogenase and the oxidative pentose phosphate pathway was complicated by the fact that uptake of exogenously supplied glucose was inhibited during ammonium assimilation. The production of [14C] carbon dioxide from [1‐14C] glucose was inhibited less than both the uptake of glucose and the production of [14C] carbon dixoide from [6‐14C] glucose, suggesting that the oxidative pentose phosphate pathway provides the reduced coenzyme for ammonium assimilation.
SEASONAL AND DIURNAL EXPANSION AND CONTRACTION OF PINUS BANKSIANA AND PICEA GLAUCA CONES*
Authors: CHANEY W. R. , KOZLOWSKI T. T.
Published: May 2006

Summary

Changes in diameter of intact first‐year Picea glauca and second‐year Pinus banksiana cones were continuously monitored during two growing seasons. Early in their development the cones made intermittent increases in diameter. Cones expanded during the evening and night while vapour pressure deficit of air was decreasing or low, and did not change in diameter during the daytime when vapour pressure deficit was high. In a mid‐stage of development, reversible diurnal shrinkage and expansion of cones occurred and these fluctuations were inversely correlated with vapour pressure deficit. Late in the development of P. banksiana cones, many rapid daytime fluctuations in diameter were recorded. Maturing cones of Picea glauca decreased in diameter in a step‐like manner. Diurnal shrinkage of maturing cones occurred when the vapour pressure deficit was increasing or high and no appreciable change in diameter occurred when vapour pressure deficit was low.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: YOUNIS M. E.
Published: May 2006

Summary

Strawberry leaves were fed with [14C] glucose either in water or in iodoacetate. The latter considerably increased the 14CO2 output and the permeability of the plasmalemma and the tonoplast as is evident from the increased leakage from the free and inner spaces of leaves. The time required to wash out the free space was most probably of the order of 10 minutes after which time the activity diffusing out was considered to come from the inner space.

The magnitude of leakage of sugars was much higher in iodoacetate than in water. The rate of leakage of sugars was dependent on their content in the inner space.

The results were thought to indicate that iodoacetate increased the accessibility in the metaholic region of substrates and enzymes normally not saturated with their substrates and so the increased respiration could be explained on this basis.
EFFECT OF SELECTION FOR MESOPHYLL CELL SIZE ON GROWTH AND ASSIMILATION IN LOLIUM PERENNE L.
Authors: WILSON D. , COOPER J. P.
Published: May 2006

Summary

Divergent selection for mesophyll cell size (mean cross‐sectional area) was made within a population of ‘Veya’ perennial ryegrass. Selection for small mesophyll cells generally resulted in smaller mesophyll cells, heavier seed, and greater yield of shoot dry matter than selection for large cells. Between the third and fifth leaf stage, families from parents with small cells exhibited greater net assimilation rate and lower leaf area ratio than those from parents with large cells. Rate of light‐saturated photosynthesis of young leaves was negatively related to cell size in the F1 generation.

Greater shoot dry matter in the small, compared with the large, cell selections was accounted for in terms of greater initial seed reserves (heavier seed) and also greater net assimilation rate at some stage prior to full expansion of the third leaf. It was concluded that mesophyll cell size is a useful criterion for selecting for light‐saturated photosynthesis in Lolium perenne.
SPORE SIZE IN THE GENUS EQUTSETUM
Authors: DUCKETT JEFFREY G.
Published: May 2006

Summary

No trace of morphological heterospory has been found in the genus Equisetum. Reports that sex may be altered by environmental conditions indicates that it is not determined by genotypic or physiological properties of the spores. Spore size is extremely dependent on viability, maturity and mounting medium, but within each species all the viable spores are spherical, bright green and vary little in size. Slight subgeneric differences exist in spore size but there is great overlap between all species rendering the spores of little use taxonomically. Colourless abortive spores are found in the two hybrids E.×moorei and E.×trachyodon and also in E. telmateia and E. palustre var. polystachyum. Of common occurrence in E. hyemale, E. ramosissimum and E. laevigatum are small, discoloured, misshapen spores which will not germinate. Considerations of the phenology of these species in relation to experiments on storage of ripe cones indicate that these spores were at one time mature and viable but had subsequently died. In E. variegatum and E. scirpoides large variations were observed between cones, in spore size and germination. This was due to the ripe cones containing variable proportions of mature and immature spores.
THE NOCTURNAL BEHAVIOUR OF XEROPHYTES GROWN UNDER ARID CONDITIONS
Authors: GINDEL I.
Published: May 2006

Summary

Stomatal apertures of seventy‐eight species of xerophytes grown under arid conditions were greater at night than during the day. Most stomata were closed during the day, and especially during the hottest period. Many stomata opened at night, especially in the presence of dew or mist. Nocturnal opening did not occur at low relative humidities.
THE EFFECT OF NITROGEN SUPPLY ON TRANSPIRATION AND STOMATAL BEHAVIOUR OF BEANS (PHASEOLUS VULGARIS L.) *
Authors: SHIMSHI DANIEL
Published: May 2006

Summary

The effect of nitrogen supply on the transpiration rate and stomatal opening of potted bean plants was studied in a series of experiments. The transpiration rates of N‐supplied plants were higher than those of N‐deficient plants when soil moisture was relatively high; as soil moisture approached the wilting range, the transpiration rates of N‐supplied plants dropped to below those of N‐deficient plants. In spite of the marked differences in transpiration rates, as influenced by soil moisture and nitrogen supply, the stomata appeared closed. By coating the upper or lower surfaces of the leaves with a vapour‐impervious compound it was shown that stomatal apertures below the limit of microscopic resolution control the rate of transpiration. Under conditions that encourage stomatal opening (covering the plants with transparent plastic bags), the stomata of the N‐deficient plants opened to a lesser degree than those of N‐supplied plants. There was some evidence that when stomata were visibly open, transpiration rates were regulated by the degree of plant hydration rather than by the degree of stomatal opening. It is concluded that N‐deficient plants fail to open their stomata as widely and to close them as tightly as N‐supplied plants.
THE ULTRAVIOLET ABSORPTION PROFILE OF STIGMATIC EXTRACTS
Authors: MARTIN FRANKLIN W.
Published: May 2006

Summary

Ultraviolet absorption profiles were examined of alcoholic extracts of stigmatic surfaces of forty‐four species. The extracts of species showed characteristic absorption peaks, and batho‐chromic shifts on the addition of NaOH. In many cases the peaks corresponded to those of simple phenolic compounds or their derivatives. The possible use of the absorption profile as a taxonomic tool is discussed.
EFFECTS OF COTYLEDON AND HYPOCOTYL PHOTOSYNTHESIS ON GROWTH OF YOUNG PINE SEEDLINGS *
Authors: SASAKI S. , KOZLOWSKI T. T.
Published: May 2006

Summary

The importance of light to development of Pinus resinosa seedlings for a short time following seed germination was studied. Treatment of seedlings with photosynthesis‐inhibiting herbicides (monuron and atrazine) partially inhibited cotyledon expansion. Expansion of primary needles was light‐dependent since darkness stopped it. When young seedlings were exposed to 14CO2 in the light, some of the label accumulated in root tips and primary needles, and some was retained in cotyledons and hypocotyls for at least 3 weeks. Although measurable photosynthesis occurred in both cotyledons and green hypocotyl tissues, the rates were much higher in cotyledons. In intact seedlings, expansion of primary needles was not significantly influenced by exposure of hypocotyls to light but in those from which cotyledons had been removed, exposure of hypocotyls to light did affect their expansion. Thus green hypocotyl tissues appeared to be important for expansion of primary needles only in the absence of photosynthesis in the cotyledons. Some growth of cotyledons, radicles and hypocotyls also depended on current photosynthate in addition to megagametophyte reserves.
PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: BRADBEER J. W.
Published: May 2006

Summary

On illumination 14‐day old dark‐grown beans showed initial lags in (i) cell growth, (ii) chlorophyll synthesis, (iii) increases in the activities of some chloroplast enzymes of the primary leaves and (iv) translocation of material to these leaves. In contrast there was no lag in the increase of leaf protein and in the rise of the activities of some enzymes which are common to cytoplasm and chloroplasts.
A POLLEN DIAGRAM FROM LAKE EURAMOO, NORTH‐EAST QUEENSLAND, AUSTRALIA
Authors: KERSHAW A. P.
Published: May 2006

Summary

Pollen analysis of organic sediments from a crater lake in north‐east Queensland provides a vegetation record from 10,000 B.P. to the present day. An initial sclerophyll vegetation was succeeded by rain forest about 7600 B.P., probably under increasing effective precipitation. Rain forest then persisted to the present day changing progressively from a ‘warm temperate’ to a ‘dry subtropical’ kind, almost certainly as a result of an increase in temperature.
A METHOD OF PREPARING GLASS TUBES FOR DISC ELECTROPHORESIS
Authors: EDIE HARRY H.
Published: May 2006

Summary

A method of preparing glass tubes of equal length with perfectly flat ends suitable for disc electrophoresis is described. The apparatus used, or alternative apparatus, is available in most laboratories.
GLYCEROL UTILIZATION IN SEEDS OF CORYLUS AVELLANA (L)
Authors: STOBART A. K. , PINFIELD N. J.
Published: May 2006

Summary

The distribution of radioactivity from [14C]glycerol in the cotyledons and embryonic axes of hazel seeds pre‐treated either with gibberellin or water for various periods has been investigated. The cotyledons of both gibberellin and water prereated seeds utilized considerable quantities of [14C]glycerol. In the cotyledons, gibberellin prereatment induced an increased percentage incorporation of radioactivity into sucrose but percentage incorporation of 14C in polar lipid and released CO2 gave higher values after pre‐treatment with water. The increase in gluconeogenesis in cotyledons from gibberellin pre‐treated seeds was accompanied by an increase in lipase activity. In the embryonic axes gibberellin pre‐treatment resulted in increases in percentage incorporation of 14C into both polar lipid and respired CO2.

The results indicate that gibberellin stimulates the following processes in the cotyledons during the first 8 days of germination: a diversion of glycerol away from the TCA cycle and into carbohydrates, an increase in lipase activity, presumably resulting in a rise in production of endogenous glycerol and an increased rate of membrane dissolution. In the embryonic axes, over the same period, gibberellin appears to stimulate a more rapid respiration of glycerol and increased production of lipid membranes.
HYBRIDIZATION IN TARAXACUM
Authors: RICHARDS A. J.
Published: May 2006

Summary

Results of hybridization experiments between twenty‐six species of Taraxacum (nine of which are sexual) are reported. Most crosses set good seed. The chief barriers to interspecific hybridization seem to be absence of sexuality, absence of pollen and restitutional pollen. There is no evidence of seed‐incompatibility. Taxonomically remote hybrids set less good seed than near interspecific hybrids.

Hybrids are intermediate in character and usually more vigorous than the parents. The progeny of diploid sexual males are fertile, diploid and sexual, those of triploid agamospermous males are mostly near‐diploid, fertile and sexual, but some are facultatively agamospermous triploids.

The existence of several intraspecific character differences is noted in some sexual species and the nature of character inheritance is noted in interspecific hybrids.

The nature of hybrids in the field is discussed and examples of hybrid populations reported. The scarcity of reports of hybrids is noted and reasons for this are discussed.
THE EVALUATION AND SELECTION OF CHARACTERS IN ANGIOSPERM TAXONOMY: AN EXAMPLE FROM CROTALARIA
Authors: BISBY F. A.
Published: May 2006

Summary

The evaluation and selection of characters are both of great importance in Angiosperm taxonomy. Fifty‐two morphological characters, observed in two hundred and seventy‐three African species of Crotalaria L., are analysed using a taximetric procedure, ‘Character Analysis’, which provides a quantitative measure of their potential taxonomic value, the ‘information contribution’. The characters are listed in descending order of information contribution and compared with the relative importance given to them by Polhill in his previously published orthodox study of the genus. The four characters used by Polhill for his major division are among those highest on the list, and only two of the twenty that he used for the delimitation of sections occur in the lower half of the list.

The taxonomic value of a character is dependent on how it is defined. The way in which the information contribution measure can be used in the production of better definitions of poor characters is described, and one successful example of ‘Character Improvement’ is given.

The potential value of these taximetric procedures in taxonomic revisions of large genera and families with complex reticulate patterns of variation is discussed.
POLLEN ANALYSIS OF LATE‐WEICHSELIAN DEPOSITS AT CORSTORPHINE, EDINBURGH
Authors: NEWEY W. W.
Published: May 2006

Summary

The stratigraphy, pollen and other organic material of deposits at Corstorphine, Edinburgh, have been investigated. These deposits are shown to be of lacustrine origin and represent the three zones, I, II and III of the Late‐Weichselian. Herbaceous dominance is indicated in all three zones, and this was particularly marked during the colder climate of Zones I and III; but in Zone II, warmer conditions are suggested by higher tree‐pollen frequencies, with other organic and stratigraphic evidence.
EFFECTS OF FRUITING ON THE GROWTH OF APPLE TREES ON FOUR ROOTSTOCK VARIETIES
Authors: AVERY D. J.
Published: May 2006

Worcester Pearmain apple trees on four rootstock varieties with a range of vigour were grown in pots for 3 years. The effects of fruiting, determined by comparison with deblossomed trees, were qualitatively similar on all the rootstocks. The growth of all parts, particularly the roots, was less on fruiting trees. The greatest differences occurred in trees on the very dwarfing 3426 rootstock which bore the largest crops relative to the size of the tree; their root systems were severely reduced. When differences in fruitfulness were taken into account, the quantitative effects of fruiting on the dry weight increment of the combined perennial parts, and of the roots alone, were apparently the same on all the rootstocks.

Trees with low levels of fruitfulness produced less dry matter, including fruit, than deblossomed trees because of lesser shoot growth. Trees of high fruitfulness produced as much, or even more dry matter than deblossomed trees because of increased photosynthetic efficiency.

Comparisons of the shoot growth and stem‐to‐root ratios of the deblossomed trees on each rootstock variety indicated that the hypothesis put forward in a previous paper to explain the dwarfing mechanism of M.1X may be valid for 3426 also.
OBSERVATIONS ON THE CYTOLOGY AND SEED‐PROTEINS OF VARIOUS AFRICAN SPECIES OF CROTALARIA L. (LEGUMINOSAE)
Authors: BOULTER D. , DERBYSHIRE E. , FRAHM‐LELIVELD J. A. , POLHILL R. M.
Published: May 2006

Mitotic metaphase plates of fifty‐seven species of Crotalaria have been studied to determine the chromosome number and compare the size and shape of the chromosomes. The predominance of 2n= 16 is confirmed, but 2n= 14 is general in Section Incanae subsection Incanae and the first instance, in the Old World, of 2n= 32 is reported for C. massaiensis. The shorter and thinner types of chromosome seem most common in the apparently more derived groups of the genus, when a recent classification is adopted.

Globulins extracted from thirty‐six species (twenty‐four also examined cytologically) and subjected to disc electrophoresis show four recognizable protein‐band patterns. The two major types of pattern show reasonable correlation with the generic subdivisions and a comparable distribution to the major types of chromosome form.

Evidence from both lines of investigation suggests that subsections of Incanae should perhaps be raised to sectional rank.
SUGAR CONTENT IN FLORAL AND EXTRAFLORAL EXUDATES OF ORCHIDS: POLLINATION, MYRMECOLOGY AND CHEMOTAXONOMY IMPLICATION
Authors: JEFFREY DAVID C. , ARDITTI JOSEPH , KOOPOWITZ HAROLD
Published: May 2006

Sugars present in the floral and extrafloral exudates from a number of orchid species have been analysed. All contain fructose, glucose and sucrose. Raffinose is the next most common sugar and stachyose occurs less frequently. Cellobiose, gentiobiose, lactose, maltose, melibiose, melezitose and a few large oligosaccharides may also be present. The distribution of these sugars in orchids may have some chemotaxonomic implications. There appears to be no correlation between the sugar content of exudates and orchid pollinators. This would seem to suggest that scent, form and colour are the major attractants to pollinators in orchids. Floral and extrafloral exudates in orchids may also function as attractants for ants which probably feed on them and repel grazers.
PHOTOSYNTHESIS AND ZONATION OF FRESHWATER MACROPHYTES
Authors: SPENCE D. H. N. , CHRYSTAL JEAN
Published: May 2006

The mean, range and standard deviation are given of the depths of water above the soil surface in which a number of Potamogeton species occur in Scottish lochs. Sun leaves of these species were produced in unscreened containers in a glasshouse and their rates of net O2 production were measured at irradiances of from 1.34 to 7.08 cal/cm2/hour in a Warburg apparatus, using Warburg buffer no. 11 as bathing solution. Using only leaves of species of which the rates appeared to be unaffected by buffer solution during the short experiments, it was shown that the shade tolerance of these leaves is correlated with the natural depth distribution of the species. This valid contrast in inherent photosynthetic response between some deep water species (e.g. P. praelongus, P. obtusifolius) and some of shallow water (e.g. P. polygotiifolius) indicates that light may be as important as substrate or competition in controlling the zonation of freshwater macrophytes.
PHOTOSYNTHESIS AND ZONATION OF FRESHWATER MACROPHYTES
Authors: SPENCE D. H. N. , CHRYSTAL JEAN
Published: May 2006

Comparison is made of the photosynthetic response of leaves produced in a glasshouse in unscreened (sun) and screened (shade) conditions, from two species rooted in significantly different depths of water; the shallow‐water Potamogeton polygonifolius, a ‘sun’ species and the deep‐water P. obtusifolius, a ‘shade’ species. Their rates of net O2 production at various irradiances and of O2 uptake were estimated, and chlorophyll content (a + b), specific leaf area (SLA: cm2 leaf area per mg leaf dry weight) and leaf thickness were measured.

Of the curves of rate of net O2 production/cm2 leaf area and light intensity, only that of shade obtusifolius was light‐saturated, and lines of best fit were applied to the remainder, which also had high values of r. Slopes were significantly steeper in the order sun obtusifolius shade polygonifolius sun polygonifolius. Under comparable growing conditions, the mean SLA of obtusifolius was twice that of polygonifolius, the range of the two species was mutually exclusive, and that of obtusifolius was narrower than that of polygonifolius, SLA was inversely correlated with the slope of the line of best fit of each leaf‐type.

Only at 0.22 cal/cm2/hour did shade obtusifolius have a significantly higher net rate than sun polygonifolius. From calculation of relative rates of photosynthesis/cm2 leaf area, maximum energy yield, φ0, and total CO2 uptake/mg chlorophyll, at 0.22 cal/cm2/hour, of sun and shade leaves of both species, it is shown that P. obtusifolius had a rather similar photochemical capacity to P. polygonifolius; indeed its φ0 was lower.

From these facts, increased SLA and reduced respiration and leaf thickness, we conclude that a higher net photochemical capacity/unit area of shade leaves and shade species of Potamogeton in low irradiances (c. 1% summer daylight) is achieved by lowered respiration rate/unit area which itself may result from reduction in leaf weight/unit area. Perhaps the limitation of net photosynthesis in shade species at higher irradiances is a function in a species like P. obtusifolius of its inability to reduce SLA, thicken its leaves and hence increase its capacity to absorb light.
FIXATION OF NITROGEN IN TWO AFRICAN SPECIES OF MYRICA
Authors: BOND G.
Published: May 2006

Summary

By means ofgrowth experiments and 15N tests on whole plants and their parts, it is shown that the root nodules present on Myrica cordifolia and M. pilulifera fix atmospheric nitrogen to an extent which suffices to sustain good growth of the plants in a rooting medium free of combined nitrogen. Thus the nodules have the same properties and physiological significance as the nodules of M. gale and M. cerifera. The possession of this internal source of combined nitrogen doubtless explains in part the ability of M. cordifolia to flourish on sand dunes.
THE ULTRASTRUCTURE OF LICHENS
Authors: JACOBS J. B. , AHMADJIAN V.
Published: May 2006

Summary

High resolution radioautography was used to demonstrate the transfer of carbon compounds from alga to fungus in Cladonia cristatella Tuck. After a 24 hour incubation with 14CO2, most of the label appeared in the algal chloroplast around the pyrenoid and in starch. The label in the fungus was present largely in the hyphal wall.
CARBOHYDRATE METABOLISM IN CHAETOMIUM GLOBOSUM
Authors: ADOMAKO D. , KAYE M. A. G. , LEWIS D. H.
Published: May 2006

Summary

The uptake of the hexoses, glucose, fructose and mannose, by resting mycelium of Chaetomium globosum results in synthesis of the reserve carbohydrates, trehalose and glycogen, which form, respectively, 5–7% and 12–23% of the dry mycelium. Glucose is the only free reducing sugar present in detectable amounts. The presence of galactose and mannose in acid extracts of mycelium suggests that polymers of the galacto‐mannan type are important components of the cell wall. Mannitol forms a very small proportion of the total cellular carbohydrates but its level is two to three times greater in mycelium incubated on fructose or mannose than when incubated on glucose. There is an increase in the level of polyol during starvation of the mycelium as glycogen disappears and glucose accumulates. These observations are discussed in relation to the distribution and metabolism of fungal reserve carbohydrates in general.
STUDIES ON THE SUPPLY OF OXYGEN TO THE ROOTS OF MUSTARD SEEDLINGS (SINAPIS ALBA L.)
Authors: GREENWOOD D. J. , GOODMAN D.
Published: May 2006

Summary

Most of the requirements of roots for oxygen were met by oxygen from the air entering the leaves and travelling through the plants to the roots in oxygen‐free media. The amount of oxygen supplied in this way decreased proportionately with rise in oxygen partial pressure at the root surface. Although roots offered a considerable barrier to the passage of oxygen out of them, experiments in which transport from the aerial parts was prevented indicated that the roots could obtain almost all the oxygen they required from the surrounding media provided the oxygen partial pressure at the root surface exceeded the low value of 0.05 atmospheres.

These results were obtained by means of a new experimental technique which enabled the effect of oxygen partial pressure at the root surfaces on oxygen uptake and root elongation to be studied. It was based on circulating a small volume of nutrient solution around roots in a gas‐free enclosed system sufficiently rapidly for the partial pressure in the solution to be almost the same as at the root surfaces.
THE RELATIONSHIP OF COMPARTMENTATION OF ORGANIC ACID METABOLISM TO BICARBONATE‐ION SENSITIVITY OF ROOT GROWTH IN CALCICOLES AND CALCIFUGES
Authors: LEE J. A. , WOOLHOUSE H. W.
Published: May 2006

Summary

It was shown previously that cell elongation in the roots of certain calcifuge grasses was inhibited by concentrations of bicarbonate and malate which promoted cell elongation in related calcicole species. The present paper reports experiments in which [2‐14C]‐acetate was supplied to excised roots of a calcifuge Deschampsia flexuosa and a calcicole species Arrhenatherum elatius. Time course studies of the pattern of [2‐14C] incorporation into the organic and amino acids of the roots indicates an active tricarboxylic acid cycle in both species but differing in that in Deschampsia the respiratory malate pool was more completely compartmented from other malate pools in the cells, whereas in Arrhenatherum a progressive mixing of the malate pools occurred. Treatment of roots with a pulse of [2‐14C]‐acetate followed by exposure to 10 m‐equiv./1 HCO−3 for 3 hours resulted in a substantial modification in the pattern of 14C incorporation from acetate in Deschampsia but not in Arrhenatherum. The results are discussed in relation to the differential effects of bicarbonate on root growth in the two species.
SOME ASPECTS OF POTASSIUM LOSS FROM EXCISED BARLEY ROOTS
Authors: NASSERY H.
Published: May 2006

Summary

The process of efflux of potassium from excised barley roots was measured during 2 hours under different conditions of treatment. Under normal metabolic rates a rapid loss of potassium occurs during the first 40 minutes, followed thereafter by a very slow rate of loss. 10−5 M DNP not only increases the potassium loss but also alters the pattern of potassium efflux such that the efflux continues its rapid initial rate for 2 hours. The potassium loss during the rapid phase is metabolically dependent, but is not proportional to the total potassium absorbed. This indicates that under normal metabolic conditions, potassium loss is mainly from the cytoplasmic fraction. 10−2 M CaCl2 reduces the potassium loss more at 25° C than at I° C.
THE EFFECT OF HYDRATION‐DEHYDRATION ON SEED GERMINATION
Authors: BERRIE A. M. M. , DRENNAN D. S. H.
Published: May 2006

Summary

Seeds of tomato and oats were subject to hydration‐dehydration treatments at various times during germination. Desiccation has little harmful effect if carried out before cell division and enlargement has commenced. Some advancement of the onset of germination was apparent due probably to slight changes in the seed covering and also to the initiation of metabolic events which could withstand the dehydration, e.g. the increased protease activity was maintained in the dried seed.

Dehydration can be done more than once. The effects are only truly accumulative if the prior imbibitions are of substantial duration.

Physical changes associated with hydration are fairly easily reversed but some of the chemical changes beginning in oat within 8–12 hours of imbibition cannot be returned to the original dry seed condition by desiccation. Once embryo growth is apparent, embryo damage of some sort usually results.
THE ROLE OF THE ENDOSPERM IN UPTAKE AND DISTRIBUTION OF EXOGENOUS LEUCINE IN GERMINATING LETTUCE SEEDS
Authors: KLEIN S. , NEGBI M. , WITZTUM A. , ROTHBERG LIORA
Published: May 2006

Summary

When lettuce embryos with their endosperm of two cell layers were germinated in a solution containing [3H]‐leucine, very little was taken up and its incorporation into protein occurred mainly in the endosperm. Uptake and incorporation were higher in isolated endosperms and isolated embryos and more label was found in the embryo than in the endosperm. Germination‐inducing irradiation did not affect the amount or the distribution of the label in the endosperm and the embryo. The results show the existence of a permeability barrier on the outside of the endosperms, and indicate that in experiments with intact seeds the distribution of the incorporated leucine cannot be taken as a measure of the specific synthetic activity of the embryo and the endosperm.
ROUTINE ANALYSIS BY GAS‐LIQUID CHROMATOGRAPHY OF SOLUBLE CARBOHYDRATES IN EXTRACTS OF PLANT TISSUES
Authors: HOLLIGAN P. M. , DREW E. A.
Published: May 2006

Summary

Retention times for the trimethylsilyl ethers of more than fifty carbohydrates on 2% SE 52 columns and for the acetate derivatives of monosaccharides and polyols on 5% PEGA columns are given. The results of subsequent analyses of the soluble sugars and polyols in representatives of the following plant groups are described: algae (seven spp.), fungi (four spp.), lichen (ten spp.), bryophytes (six spp.), pteridophytes (five spp.) and angiosperm (seven spp.).
POLYMORPHISM IN PSILOCYBE MERDARIA
Authors: WATLING ROY
Published: May 2006

Summary

An isolate of the purple‐brown spored agaric Psilocybe merdaria (Fr.) Ricken, which had been collected on Mull, Scotland, was found to be unstable in its morphological characters when in pure culture. Apart from normal fruit‐bodies a series of forms developed, ranging from laterally stipitate to gasteromycetoid ones. The morphological characters of the two extreme forms, before and after several subcultures were made, are described. How these abnormal fruit‐bodies might amplify past and present theories on the origin of the Gasteromycetes is considered. The shape of the basidium in this one isolate was also found to be plastic and several deviations from the typical basidium are described. It is suggested that the origin of at least some types of pleurocystidia should be sought in modifications of the basidium. The use of the basidium as a major character in the classification of the Basidiomycetes is not discredited, but a closer relationship than previously expressed between the different groups of the higher fungi is argued. It is suggested that useful information might be obtained from the further study of teratological forms similar to those of P. merdaria whenever they are found in other higher fungi. In the field aberrant forms are not as rare as might be at first supposed.
SHORT TERM RESPONSES AND CHEMICAL CONTROL OF RIBONUCLEASE ACTIVITY IN TOMATO LEAFLETS
Authors: DOVE LEWIS D.
Published: May 2006

Summary

Ribonuclease (RNase) activity of tomato leaflets increased 3–6 hours after excision in air and then declined to attached leaf levels within 12 hours after excision. Leaflets submerged in a c bar mannitol solution during excision failed to exhibit a significant RNase ‘pulse’ while more dilute mannitol solutions and a dilute nutrient solution failed to suppress this increase in RNase activity; the RNase ‘pulse’ appears to be a response to a disrupted water balance in the leaflet. The RNase response to leaf excision was also reduced by immersing air‐detached leaflets in 0.2 ppm indoleacetic acid (IAA). Kinetin solutions were effective at 2 ppm when leaflets were immersed in kinetin solutions for 4 hours before excision as well as after detachment. Kinetin and IAA also suppressed gradual increases in RNase activity characteristic of tomato leaflet senescence. IAA and kinetin together were somewhat less effective than IAA applied alone. Cytidylic and adenylic acids as well as chloramphenicol were also effective in inhibiting this long term increase in RNase activity.
A NEW METHOD FOR DESCRIBING LEAF SHAPE
Authors: DALE M. B. , GROVES R. H. , HULL VALERIE J. , O'CALLAGHAN J. F.
Published: May 2006

Summary

A new method for the description of leaf shape is presented, based on an interactive computer program for describing rosette leaves of Chondrilla juncea. In addition to the usual measures of length, breadth and area an alternative description is provided based on a coding of the boundaries of the leaves. The efficiency of the machine‐assisted description is assessed and a comparison of the alternative descriptions provided.
ANALYSIS OF THE POST‐INFECTION GROWTH STIMULUS IN ORCHID MYCORRHIZA
Authors: HADLEY G. , WILLIAMSON B.
Published: May 2006

Summary

The sequence of symbiotic infection of Dactylorhiza purpurella protocorms shows that commencing shortly after infection there is a linear increase in length and breadth whereas growth of uninfected protocorms is negligible.

From the time when external hyphae make physical contact with epidermal hairs of the host the processes of penetration, infection of the cortex and formation of the first pelotons occupy approximately 29 hours. There is a linear relationship between the number of pelotons and time but the size of protocorms is not directly related to the number of pelotons. Evidence suggests that stimulation of growth can take place before intracellular lysis of the endophyte occurs.

In the absence of external nutrients infecting hyphae are rapidly lysed and little or no growth stimulus occurs. The hypothesis is posed that ‘digestion’ of the endophyte is a defence reaction not a pre‐requisite for a growth stimulus and that nutrients are transferred across the living fungus‐host interface and stimulate growth.
THE FUNGUS‐ALGA ASSOCIATION IN THE LECIDEACEAE: AN ULTRASTRUCTURAL STUDY *
Authors: GALLUN MARGALITH , BEN‐SHAUL Y. , PARAN NAVAH
Published: May 2006

Summary

The relationship between fungus and alga in three Lecidea species was examined by electron microscopy. The contact between the symbionts ranged from intracellular fungal invasion in the primitively organized thallus to a looser association of wall‐to‐wall attachment in the more highly differentiated growth‐forms.

The correlation between the symbiont association and thallus development has been compared with a similar correlation found in the Lecanoraceae.
THE CAUSATION OF THE DIURNAL CHANGES IN NITROGEN FIXATION IN THE NODULES OF ALNUS GLUTINOSA
Authors: WHEELER C. T.
Published: May 2006

Summary

The translocation of 14C‐labelled photosynthate to the nodules of first‐year alder plants growing under natural illumination, but at constant temperature, is shown to be a rapid process which results in a maximum influx of new photosynthate at the time of the mid‐day peak in fixation. Analysis of fluctuations in the levels of the main free sugars present in the nodules at different times of day, and a study of the effects of interrupting supplies of photosynthate to the root system by stem ringing, suggests that a substantial part of the nodule carbohydrate is unavailable for fixation and that maximal rates of fixation are only attained when new photosynthates are entering the nodules in quantity. No evidence was obtained for an autonomous element in the mid‐day maximum in fixation when plants were kept in continuous darkness; a fall in acetylene reduction to an insignificant level 24 hours after darkening was accompanied by a fall in nodule sugars—notably in the amount of sucrose present.

The rate of acetylene reduction by nodulated roots reached a maximum at about 25° C, and, at this temperature, was some six times faster than at 15° C.
THE EFFECT OF CATIONS ON GLUCOSE UTILIZATION BY, AND ON THE GROWTH OF, THE FUNGUS DENDRYPHIELLA SALINA
Authors: ALLAWAY A. E. , JENNINGS D. H.
Published: May 2006

Summary

The effect of sodium and potassium chlorides on glucose uptake by Dendryphiella salina after growth in glucose‐tryptone media of varying cation composition has been studied. The results are explicable in terms of the previous findings on the relationship between glucose uptake and the potassium and sodium content of the mycelium. Other experiments on the effects of potassium and sodium chlorides separately and sodium and calcium chlorides together on growth in a range of glucose concentrations have provided evidence that cations can also influence glucose utilization by providing a source of osmotic pressure within the hyphae alternative to organic solutes.