bluuebunny/crossref_metadata_2025_split huggingface dataset:
CARBON DIOXIDE EXCHANGE IN LICHENS: RESISTANCES TO CO2 UPTAKE AT DIFFERENT THALLUS WATER CONTENTS
Authors: SNELGAR W. P. , GREEN T. G. A. , WILKINS A. L. 
Published: May 2006

SUMMARYCarbon dioxide resistance and water content curves are presented for Pseudocyphellaria amphisticta, P. homoeophylla, P. billardierii, P. colensoi, Sticta latifrons and Peltigera dolichorhiza. In all cases the curves are triphasic with a high resistance at low and high water contents and a low resistance at intermediate water contents. The exact water contents at which these changes in resistance occur, and the rate at which the resistance increases at the higher water contents, appear to be species specific. The depressed NAR often found at higher water contents is shown to be caused in part by the increased resistance since it occurs under conditions where there are no changes in respiratory rate. The increase in resistance at higher water contents is suggested to be a result of water on the lower cortex.
VARIABILITY IN THE RESISTANCE OF SODIUM CHLORIDE SALINITY WITHIN RICE (ORYZA SATIVA L.) VARIETIES
Authors: FLOWERS T. J. , YEO A. R. 
Published: May 2006

SUMMARYVarieties of rice differ in their resistance to sodium chloride salinity. Within varieties, which are not homozygous lines, there is very high variability in sodium uptake and in survival under saline conditions by the individual plants. This is in contrast with the relative uniformity in (for example) potassium uptake, dry wt and transpiration rate.There is a negative correlation between sodium (and chloride) accumulation by individual plants and their survival in saline conditions, demonstrating that variability amongst individuals fits the same pattern as has become generalized for varietal differences in glycophyte species. Possible reasons for this variability in sodium and chloride uptake within varieties, and its relevance to selecting salt‐resistant varieties of rice, are discussed.
ANATOMICAL VARIATION ALONG THE LENGTH OF THE ZEA MA YS LEAF IN RELATION TO PHOTOSYNTHESIS
Authors: MIRANDA VALENTINE , BAKER NEIL R. , LONG STEPHEN P. 
Published: May 2006

SUMMARYAnatomical features of the leaf, related to C4 photosynthetic activity, were examined along the length of the second leaf of 7‐day‐old plants grown under a diurnal light regime. Changes of significance to photosynthetic activity were observed in cuticle thickness, stomatal size and frequency, mesophyll anatomy and interveinal distance. Anatomical changes within the basal 3 cm of the leaf were attributable to development. Above this region, variation in some anatomical characteristics, notably stomatal frequency and interveinal distance, could only be attributed to ontogenetic differences between parts of the leaf.
THE SEPARATION, IDENTIFICATION AND QUANTITATIVE DETERMINATION OF PHOTOPIGMENTS FROM THE SIPHONACEOUS MARINE ALGA CODIUM FRAGILE
Authors: BENSON ERICA E. , COBB A. H. 
Published: May 2006

SUMMARYThe photopigments of the Siphonaceous marine alga Codium fragile have been quantitatively determined using thin layer chromatography (TLC). Codium fragile fronds contain a unique spectrum of carotenoids, notable by the absence of β‐carotene, and the presence of a‐ and e‐carotenes, siphonoxanthin, siphonein, neoxanthin and violaxanthin. The carotenes are present in low concentrations whereas siphonoxanthin and its ester siphonein account for as much as 60% of the total carotenoids present. The significance of these findings is discussed in relation to the habitat of this alga.
ULTRASTRUCTURAL AND ULTRACYTOCHEMICAL FEATURES OF A GLOMUS TENUIS MYCORRHIZA
Authors: GIANINAZZI‐PEARSON V. , MORANDI D. , DEXHEIMER J. , GIANINAZZI S. 
Published: May 2006

SUMMARYThe ultrastructural organization and some cytochemical features (protein and polysaccharide distribution) of the mycorrhiza formed by Glomus tenuis in raspberry roots have been investigated. Certain aspects of the fine mycorrhizal endophyte (smaller hyphae, thinner walls, distinct two‐layered wall structure following the PATAg test for polysaccharides, complete absence of septa) distinguish it from the coarse vesicular–arbuscular mycorrhizal fungi. The modifications occurring in the host‐fungus interface during Glomus tenuis mycorrhiza development are however very similar to those that have been described in several mycorrhizae formed by coarse vesicular‐arbuscular endophytes.
CYTOPLASMIC PHENOLS AND POLYSACCHARIDES IN ECTOMYCORRHIZAL AND NON‐MYCORRHIZAL SHORT ROOTS OF PINE
Authors: PICHÉ YVES , FORTIN J. ANDRE , LAFONTAINE JEAN G. 
Published: May 2006

SUMMARYPinus strobus seedlings were cultivated in growth pouches and inoculated with Pisolithus tinctorius. Semi‐thin sections of mycorrhizal and uninoculated short roots and long roots were stained with toluidine blue and periodic acid Schiff's reagent for phenolic and polysaccharidic intracytoplasmic substances respectively.No obvious difference in intracytoplasmic contents of phenolic substances was observed between ectomycorrhizal and uninoculated short roots. However, the phenolic content of the cortical cells of the long roots was much lower than that of both mycorrhizal and uninoculated short roots.Starch grains were not observed in cortical cells of either mycorrhizal or uninoculated short roots but were abundant both in the cortex and the stele of long roots and in the stele of short roots. The absence of starch synthesis in the cortical cells of potentially ectomycorrhizal short roots should be taken into account when explaining the accumulation of soluble sugars as a prerequisite for ectomycorrhizal formation.
MYCELIAL STRANDS OF PINUS RADIATA D. DON: ULTRASTRUCTURE AND HISTOCHEMISTRY
Authors: FOSTER R. C. 
Published: May 2006

SUMMARYUltrastructural and cytochemical techniques showed that there was a marked difference in the structure and cytochemistry of the hyphae from old and young parts of mycelial strands produced by the mycorrhizas of Pinus radiata D. Don. The older strands were differentiated into an outer region of thick walled hyphae and inner region of thin walled hyphae of two types. Histochemical tests for carbohydrates were used to distinguish between gels produced by the micro‐organisms associated with the strands and those by the fungal hyphae themselves, and to distinguish between the polysaccharides of the mycelial gel and those of the layers in the cell walls of the hyphae. Carbohydrate distribution in and on the strands is discussed in relation to the breakdown of litter and to the stability of soil crumbs under pine forests.
THE UPTAKE OF COPPER BY PLANTS OF MIMULUS GUTTATUS DIFFERING IN GENOTYPE PRIMARILY AT A SINGLE MAJOR COPPER TOLERANCE LOCUS
Authors: MACNAIR M. R. 
Published: May 2006

SUMMARYThe pattern of uptake of copper by plants of Mimulus guttatus that are either homozygous tolerant, homozygous non‐tolerant, or heterozygous tolerant, was compared. Tolerant plants took up more copper, particularly into the roots, and root uptake by the homozygote tolerant was greater than the heterozygote. Plants of all three genotypes took up increasing quantities of copper to their roots until day 7, but no further increase was obtained by day 11. The physiological implication of these results is discussed.
THE EFFECT OF BIPYRIDYL HERBICIDES ON THE LOSS OF NUTRIENTS FROM FUNGI
Authors: SAHID ISMAIL B. , LYON A. J. E. , SMITH S. N. 
Published: May 2006

SummaryParaquat and diquat cause rapid loss of potassium and phosphate from Aspergillus niger, Penicillium frequentans, Mucor hiemalis and Zygorrhynchus heterogamus. The rate of loss is greater at higher concentrations of herbicide, particularly from Zygorrhynchus and Mucor. A brief incubation in paraquat or diquat is followed by sustained loss of potassium when colonies of the four species are transferred to water. Sodium azide also stimulates loss of potassium but thisceases when colonies are transferred to water. Paraquat enhances the level of malondialdehyde, a breakdown product of membrane fatty acids, in Zygorrhynchus and Mucor. These results are discussed with reference to the possible mode of action of bipyridyl herbicides in fungi.
VARIATIONS IN ENZYME ACTIVITY DURING PERIODIC FRUITING OF AGARICUS BISPORUS
Authors: HAMMOND J. B. W. 
Published: May 2006

SummaryGlucose‐6‐phosphate dehydrogenase (G6PD), glucosephosphate isomerase (GPI) and mannitol dehydrogenase (MD) were assayed in sporophores harvested at stages 1 (pin) and 2 (button) of development throughout several fruiting cycles. Higher G6PD specific activity was consistently found in stage 1 and 2 sporophores harvested between periods of maximum stage 2 production (flushes). There was minimum G6PD activity during the flushes. At stage 1 the range of variation was greater and the timing of the peaks in the flush cycle more uniform than in stage 2 sporophores. GPI and MD activities also varied with flushing, but showed a less consistent pattern than G6PD. MD normally exhibited greatest activity in stage 1 and 2 sporophores between flushes. GPI activity was higher between flushes in stage 1 sporophores, and during flushes at stage 2.Mannitol and trehalose were highest in stage 1 sporophores harvested between flushes. The results are discussed in relation to the mechanism of flushing.
INTRACLONAL VARIATION AND COMPETITION IN RANUNCULUS RE PENS
Authors: DOUST LESLEY LOVETT 
Published: May 2006

SummaryExperiments were performed to study sources of variation between ramets of a clone, and differences in growth form between plants from two locally specialized populations of Ranunculus repens in a woodland and a grassland site. In one experiment, ramets were taken from different positions along each of five primary branches of clones. For both populations variability in growth parameters of ramets of each clone was attributed to the position of a ramet within a branch, and not to any differences between branches of a clone.In clones which are made up of several interconnected ramets, these ramets may: (1) compete with each other for light and other resources; and (2) supply each other with resources. In clones where connections have been lost only (1) above, will pertain. In a second experiment clonal material selected from the two populations was grown in flats under conditions of high ramet densities. For each clone, in half of the replicates, stolon connections between ramets were severed; in the other half stolons were left intact. In clones originating from the grassland population, ramets of the same genotype accumulated significantly more total dry wt and had more above‐ground biomass when they were interconnected than if stolons had been cut. In clones from the woodland population, total dry wt was not significantly altered. In plants from both populations, after connections were cut, the distribution of dry matter to various plant organs was significantly altered (plants distributed more dry matter to inflorescences and ramet caudices, and less to stolons). The pattern of proportionate allocation of dry matter suggested that below‐ground competition was more intense when stolons had been severed.Growth form and the response to intraclonal competition are discussed in terms of local specialization in the woodland and grassland sites.
RESISTANCES TO CARBON DIOXIDE FIXATION IN FOUR SUBMERGED FRESHWATER MACROPHYTES
Authors: BLACK M. A. , MABERLY S. C. , SPENCE D. H. N. 
Published: May 2006

SummaryDiscs (0·6 cm diameter) from submerged leaves of Potamogeton lucens L., P. perfoliatus L., P. polygonifolius Pourr. and P. praelongus Wulff were allowed to photosynthesize in well stirred conditions at pH 4·3, 20 °C, and a saturating light intensity of 120 W m−2 (400 to 700 nm) in a range of free CO2 concentrations for 1 h, and the rates were calculated from 14CO2 uptake. Total resistance (1/k+ 1/P) was calculated from these data, using a modification of Fick's first law. 1/k+ 1/P was found to vary between 3·7 × 104 and 5·9 × 104 s cm−1 in the four species. The internal diffusive resistance (l/D) only made up 2·6 to 4·3 % of this total. Estimates were made of the proportions of 1/k (the chemical resistance), 1/P (the diffusive resistance) and δ/D (the boundary layer diffusive resistance) to the total resistance over a range of possible values for the concentration of CO2 at the site of carboxylation: 1/P was always greater than 1/k, and δ/D was always the single largest resistance. The average boundary layer thickness for the leaf discs was calculated as 340 μm; for whole leaves of these species, also well stirred, the boundary layer thickness was estimated to range between 440 and 1090 μm. The ecological significance of the boundary layer to freshwater macrophytes in standing waters is discussed.
VARIATION IN NITRATE REDUCTASE ACTIVITY BETWEEN AGROSTIS SPECIES AND ECOTYPES
Authors: OSBORNE B. A. , WHITTINGTON W. J. 
Published: May 2006

SummaryIt was shown that nitrate reductase activity varied between species of Agrostis. Lower values were found in A. setacea and A. stolonifera and higher but variable values occurred in A. tenuis and A. canina. The hypothesis that species or ecotypes within species might have nitrate reductase activities related to soil nitrate or applied fertilizers was examined, but no clear relationship was found. Consideration is given to the difficulties inherent in establishing such correlations. As in current published evidence the relationship between dry matter production and nitrate reductase was often found to be negative rather than positive as might have been expected.
PEROXIDASE ACTIVITY IN GRASS‐DWARF SELECTION LINES IN SPRING WHEAT (TRITICUM AESTIVUM L.)
Authors: MOORE K. , CUBITT I. R. 
Published: May 2006

SummaryGrass‐dwarf and normal genotypes have similar peroxidase levels when grown at 26°C. Higher levels of peroxidase activity were found in grass‐dwarf lines induced to remain vegetative at low temperatures of 15°C than in the same lines grown at 26°C which is adequate for reproductive development. Peroxidase activity was greatest at 15°C in Type I grass‐dwarf genotypes and progressively lower in Type II, Type III and normal parental genotypes after 7 weeks’ growth. This promises a quantitative method for distinguishing different types of grass‐dwarf genotypes at an early stage of growth.Heating the shoot apical meristem of grass‐dwarf genotypes to 26°C induced reproductive development and reduced peroxidase activity below that in unheated vegetative grass‐dwarf plants.
CELLULAR ORGANELLES AND CELL‐WALL FORMATION IN FIBRES FROM THE FLOWERING STEM OF LOLIUM TEMULENTUM L.
Authors: JUNIPER B. E. , LAWTON JUNE R. , HARRIS P. J. 
Published: May 2006

SummaryThe structure of the thick wall of lignified fibre cells from the flowering stem of Lolium temulentum L. is described. The formation of wall layers is related to the period of cell elongation and to the presence or absence and state of development of organelles which are possibly involved in the formation of the cell wall.It is suggested that while the fibre cells are still elongating, rough endoplasmic reticulum (RER) and dictyosomes associated with small, electron transparent vesicles are involved in the formation of the cell wall, whereas in fibre cells which are nearing the end of elongation, and those which have stopped elongating, it is suggested that microtubules, lomasomes and dictyosomes associated with large electron transparent vesicles and small vesicles with electron dense cores are involved.The nomenclature for labelling wall layers as primary or secondary is discussed.
THE ASSESSMENT OF NITROGEN FIXATION AND THROUGHPUT BY LICHENS
Authors: MILLBANK J. W. , OLSEN J. D. 
Published: May 2006

SummaryAn apparatus is described for simulating the natural environmental conditions relating to large thallose lichens, to enable their rates of nitrogen fixation to be estimated using 16N2 enriched nitrogen gas. Daylength, temperature, light intensity, thallus moisture and carbon dioxide concentration can be controlled and seasonal conditions can be reproduced. The rate of long term 15N2 incorporation can be compared with that of acetylene reduction measured over short periods and the relationship established. Details of materials and suppliers are given.
THE EFFECT OF SIMULATED ACID RAIN ON TWO POPULATIONS OF SENECIO VULGARIS L.
Authors: HODGKIN S. E. , BRIGGS D. 
Published: May 2006

SummaryThe effect of simulated acid rain on two populations of Senecio vulgaris was studied. Evidence suggests that the population from a relatively unpolluted area of the British Isles was more sensitive to applied dilute sulphuric acid than a population from east England, where a higher level of air pollution is likely. In making a cautious interpretation of our results, we point out that further studies are necessary before the hypothesis, that ecotypic differentiation occurs in response to acid rain, can be accepted.
EVOLUTION OF UNILATERAL INCOMPATIBILITY IN FLOWERING PLANTS: FURTHER EVIDENCE IN FAVOUR OF TWIN SPECIFICITIES CONTROLLING INTRA‐AND INTERSPECIFIC INCOMPATIBILITY
Authors: PANDEY K. K. 
Published: May 2006

SummaryThe breeding system in Nicotiana glauca is unique in that the species comprises mainly self‐compatible (S.C.) green‐flowered plants but also includes rare self‐incompatible (S.I.) red‐flowered races. The S.C. plants of Nicotiana glauca show unilateral interspecific incompatibility with other S.I. species of Nicotiana, a widely occurring characteristic normally associated with S.C. species with relatively long‐established self‐compatibility.The present study of S.I. and S.C. strains of Nicotiana glauca showed that the ♀ S.I. × S.C. ♂ type of unilateral incompatibility (U.I.) occurs within this species, and the U.I. is a function of the S alleles. Of the nine SI alleles studied seven, when present in the homozygous state in the style, made that style reject Sc (Nicotiana glauca) pollen whereas two alleles allowed styles to accept this pollen. Similar polymorphism at the Nicotiana glauca S locus was also found in relation to Sf pollen from the S.C. species Nicotiana langsdorffii. Sl alleles in Nicotiana glauca were classified differently for the polymorphisms in relation to Sc and Sf pollen.The results show that the Sc allele is sporophytically determined causing allelic interaction in the pollen and style. Dominance, co‐dominance and competitive interaction were observed. In contrast the St allele of Nicotiana langsdorffii is gametophytically determined, stylar alleles always showing independent action.Within the same species Nicotiana glauca, there is both gametophytic and sporophytic determination of 5 alleles. Whereas in species with sporophytic self‐incompatibility allelic interaction is predetermined in the pollen and style, in this case allelic interaction is not determined until after pollen/stigma contact and is complementary.The occurrence within the same species of (1) the unilateral S.I. × S.C. type of incompatibility, (2) both gametophytic and sporophytic determination, (3) late determination of allelic interaction after pollen/stigma contact, and (4) competitive interaction of 5 alleles, is all explained on the basis of the author's theory of ‘twin specificities’ controlling intra‐and interspecific incompatibility in flowering plants.Wider implications of the theory are discussed. Early evolution of specificity determination in prokaryotes provided a basis for cell to cell interaction that eventually led, on the one hand, to evolution of sex and genetic recombination systems and, on the other, to mechanisms for infection/disease protection, and graft‐incompatibility control. These phenomena are evident in both plant and animal kingdoms.
DIFFERENCES IN FRUCTAN CONTENT AND SYNTHESIS IN SOME ALLIUM SPECIES
Authors: DARBYSHIRE B. , HENRY R. J. 
Published: May 2006

SUMMARYIn Allium cepa (cv. Creamgold), A. cepa (cv. Bunching Onion), A. porrum (leek) and A. sativum (garlic), fructans were the only nonstructural carbohydrates detected apart from glucose, fructose and sucrose. No starch or members of the raffinose series of oligosaccharides were detected. Both cultivars of A. cepa, and A. porrum had fructan polymers of the same length. The maximum DP (degree of polymerization) detected was 12. However, maximum carbohydrate concentration occurred in DP5 for A. cepa (cv. Bunching Onion) and DP12 for A. porrum. A. sativum was different from the other species in that larger polymers were present, reaching a DP of 50. The trisaccharides, 1F‐fructosylsucrose and 6G‐fructosylsucrose were found in all species. A. cepa and A. sativum contained similar fructan: fructan frutosyltransferases. Enzymes from both plants transferred fructosyl residues from trisaccharide to form tetrasaccharide and sucrose as the major products. This self‐transfer predominated even in the presence of higher molecular weight acceptor molecules.
INFLUENCE OF WATER AND SALT STRESS ON WATER RELATIONSHIPS AND CARBON DIOXIDE EXCHANGE OF TOP AND ROOTS IN BEANS
Authors: JENSEN C. R. 
Published: May 2006

SUMMARYWhen low‐salt plants, grown in nutrient solution, were exposed to osmotic potentials in the root medium (πs)* of minus 2.7 and minus 4.7 bar due to the addition of KNO3, osmotic adjustment occurred. The leaf osmotic potential (π1,) decreased, leaf turgor potential (Ψp) and leaf water content (W) were maintained, no wilting took place, stomatal conductance (g) was partially regained and net photosynthesis was only moderately depressed.When low‐salt plants were exposed to πs of minus 2.7 and minus 4.7 bar due to the addition of PEG 1500, no adjustment to water stress was observed. Ψp decreased, the leaves became dehydrated and a high percentage wilted. Stomatal conductance, net photosynthesis, top dark respiration and root respiration were depressed. NO3‐uptake ceased completely at minus 4.7 bar.When low‐salt plants were exposed to πs of minus 4.7 bar, due to both PEG (minus 2 bar) and KNO3 (minus 2 bar), osmotic adjustment took place; π1 decreased, Ψp, W, g, net photosynthesis, top dark respiration and root respiration recovered to some extent, but the proportion of wilted leaves was high.When medium‐ and high‐salt plants, osmotically adjusted to πs of minus 2.7 and minus 4.7 bar due to KNO3 were exposed to water stress due to PEG (minus 2 and minus 4 bar), (Ψp and W were maintained, none or few leaves wilted and g was depressed less than in low‐salt plants. These responses are attributed to influence of pre‐osmotic adjustment on turgor maintenance and hydration of the plant.It is concluded that osmotic adjustment by inorganic solute uptake, before or during exposure to water and salt stress, can reduce the severe effects of low water potentials in the root medium.
PHYSIOLOGICAL ASPECTS OF RAINFOREST REGENERATION
Authors: CHANDLER GRAEME 
Published: May 2006

SUMMARY Syzygium floribundum, a rainforest climax species and Solarium mauritianum, a rainforest pioneer, were raised in sand cultures containing NO3− or NH4+ under various shade regimes. Optimum growth of Syzygium occurred with NH4+ and of Solatium with NO3−. Ammonium appeared toxic for Solatium at low light intensity.Shoot‐root ratios of Syzygium were remarkably constant irrespective of light intensity but ammonium promoted greater leaf production. Conversely, Solatium shoot‐root ratios were not affected by nutrients but increased dramatically at low light intensity.Leaves of Syzygium exhibited high levels of glutamate dehydrogenase (GDH) activity which decreased with increasing light intensity. Roots of Syzygium exhibited low GDH activity. This, together with high glutamine synthetase (GS) activity in the roots, suggests that GS is the main ammonium assimilating enzyme in the roots of Syzygium. GDH and GS are both active in the leaves of this species. High GDH and low GS activity in both leaves and roots of Solatium suggests that GDH is the main NH4+ assimilating enzyme in this species.