bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPARISON OF THE ONION PLANT (ALLIUM CEPA) AND ONION TISSUE CULTURE. II. STIMULATION OF FLAVOUR PRECURSOR SYNTHESIS IN ONION TISSUE CULTURES
Authors: SELBY C. , TURNBULLF A. , COLLIN H. A. 
Published: May 2006

SUMMARYOnion callus was exposed to high concentrations of a number of intermediates involved in the synthesis of S‐trans‐prop‐1‐enyl‐L‐cysteine sulphoxide, the major flavour precursor in the intact onion plant. The intermediates were sodium sulphate, L‐valine, methacrylic acid and S‐(2‐carboxypropyl)‐L‐cysteine. Growth was reduced or totally inhibited at the highest concentration (50 to 100 HIM) Of All the intermediates but, except for methacrylic acid which was inhibitory at all concentrations, a limited growth occurred at the lower concentrations (10 to 20 mM) of the other compounds. The only treatment which caused the callus to produce an onion odour on crushing the tissue was when S‐(2‐carboxypropyl)‐L‐cysteine was incorporated in the culture medium; this result indicated that the callus was capable of the final stages in the synthesis of S‐Jram‐prop‐1‐enyl‐L‐cysteine sulphoxide. The presence of this pathway was confirmed by feeding smaller amounts of L‐cysteine, L‐valine and S‐(2‐carboxy‐propyl)‐L‐cysteine (1 and 3 mM) and separating the amino acids and flavour precursors by t.l.c. electrophoresis. S‐trans‐prop‐1 ‐enyl‐L‐cysteine sulphoxide was found only when S‐(2‐carboxypropyl)‐L‐cysteine was present in the medium. When S‐ethyl and S‐propyl‐L‐cysteine were fed to the callus these compounds were oxidized to their sulphoxides showing that an oxidase system for the S‐alkyl cysteines was present in the callus.
RESPONSE OF CROP PLANTS TO VA MYCORRHIZAL INOCULATION IN AN UNSTERILE INDIAN SOIL
Authors: BAGYARAJ D. J. , MANJUNATH A. 
Published: May 2006

SUMMARYInoculation of three crop plants, viz. cotton, cowpea and finger millet to inoculation with the VA mycorrhizal fungus, Glomus fasciculatus, in an unsterile Indian soil low in available phosphorus significantly increased their root and shoot weights. The phosphorus and zinc content of inoculated plants were higher. Inoculated plants did not differ significantly from uninoculated plants in manganese content.
MITOSIS IN THE ROOT CAP OF ZEA MAYS
Authors: CLOWES F. A. L. 
Published: May 2006

SUMMARYThe rate of mitosis and the probability of the plane of mitosis have been determined for every cell of the cap meristem. of Zea. Overall rates decrease from the central files outwards and from the proximal to the distal tiers. This also applies to transverse divisions, but highest rates in the longitudinal plane occur nearer the periphery of the proximal tier. All the cells show some probability of dividing in both planes and the transition from predominantly transverse divisions at the axis to mostly longitudinal divisions near the periphery is smooth.The meristem is very sensitive to the way the plants are treated not only in the aggregate rate of cell production, but also in the disposition of cell production across the meristem.
LEAF‐CANOPY‐INDUCED SEED DORMANCY IN A GRASSLAND FLORA
Authors: SILVERTOWN JONATHAN 
Published: May 2006

SUMMARYThe germination of 27 species from calcareous grassland was tested in three light treatments in the laboratory: in darkness, under tungsten lamps and under a leaf‐canopy. Germination was significantly lower under a leaf‐canopy than in the dark in 17 species. The phenomena of leaf‐canopy induced dormancy was not associated with the life‐span of species, though there was a weak, negative relationship with seed weight amongst 20 perennials in the sample. It is suggested that the co‐existence of species at high density in calcareous grasslands may, in part, be explained by differences in germination response to fine‐grained variations in the light environment at the soil surface.
THE LATE DEVENSIAN AND FLANDRIAN VEGETATIONAL HISTORY OF CROSE MERE, SHROPSHIRE
Authors: BEALES PETER W. 
Published: May 2006

SUMMARYThe vegetational history of Crose Mere, north Shropshire, is reconstructed by means of pollen analysis, lithostratigraphy and radiocarbon dating. Pollen diagrams from a core representing the Flandrian and Late Devensian are presented. Eleven radiocarbon dates were obtained from the Flandrian and these allowed the estimation of pollen deposition rates from pollen concentrations.The pattern of vegetational changes shows close similarities with those from the lowlands of north‐west England notably the appearance of Pinus sylvestris after Corylus avellana, Ulmus and Quercus in the forest succession. The effects of man on the environment are traced and four main agricultural episodes are distinguished after the ‘elm decline’ at about 5300 B.P.Comparison of pollen percentage and absolute data highlights the problem of interpreting pollen deposition rates from a basin with uneven sedimentation and the possibility of resuspension of freshly deposited sediments.
RELATIVE HARDINESS TO FREEZING OF LAMINAE, ROOTS AND TILLERS OF TALL FESCUE
Authors: PEARCE R. S. 
Published: May 2006

summaryTall fescue (Festuca arundinacea Schreb. cv. S. 170) plants grown in the field and in controlled environments (mainly differing in temperature; photoperiod 12 or 16 h) were divided into laminae, roots and trimmed tillers and these were exposed to frost in a bath. Laminae and tillers hardened as much in some controlled environments as they did in the field (measured in December); a photon flux density of 110 μ mol m−2 s−1 was adequate for this. Generally, growth at low temperatures increased the hardiness of laminae and tillers; roots from plants grown at 16/14°C or at 6/4°C (day/night) were equally hardy. Laminae were hardier when they were taken from plants grown in nutrient depleted soil. The hardiness of the laminae to extension of the period of exposure (from 45 min to 24 h) was not increased by growth in 6/4°C.Hardiness of the different parts of tall fescue was compared using the highest temperature at which significant damage occurred. Laminae from the hardiest plants were hardier than the tillers; on other occasions the hardiness of laminae and tillers was close. Roots (from controlled environments) were less hardy than laminae and tillers. The hardinesses of laminae and tillers were not correlated, partly because the tillers de‐hardened during a prolonged period of growth at 6/4°C; this may have been related to reproductive development. With the exception of the last point, the observations suggest that the relative degree of frost hardening of the different parts might often be related to the likely relative intensity of the frost to which they might be exposed.
MICROBIAL EFFECTS ON THE GERMINATION AND SEEDLING GROWTH OF BARLEY
Authors: HARPER S. H. T. , LYNCH J. M. 
Published: May 2006

SummaryBarley seed was treated with micro‐organisms, or their metabolites and germinated and grown under conditions that in the absence of treatment were known to be favourable for plant development.There was a range of inhibitory and stimulatory effects of micro‐organisms on germination and on the weight and lengths of the roots and coleoptile.There were consistent positive correlations between the lengths of the longest root and of the total root system and between the lengths of the coleoptile and of the total root system.
SODIUM NUTRITION OF PASTURE PLANTS I. TRANSLOCATIGN OF SODIUM AND POTASSIUM IN RELATION TO TRANSPIRATION RATES
Authors: SMITH G. S. , MIDDLETON K. R. , EDMONDS A. S. 
Published: May 2006

ABSTRACTA study of transpiration rates, and of uptake and translocation of sodium and potassium, has supported a previous classification made for certain pasture and fodder species. The plants termed natrophiles were found to have relatively high transpiration rates and to translocate relatively large amounts of absorbed sodium from root systems into leaves. Plants termed natrophobes had lower transpiration rates and translocated less sodium from roots to leaves. In contrast, potassium was readily translocated by both natrophiles and natrophobes; consequently, compared with natrophobes, natrophiles had low K/Na ratios in their leaves. In general, transpiration rate was less associated with absorption of sodium by roots than with translocation of sodium from roots to aerial parts. The practical and ecological implications of these results are discussed.
EFFECT OF POTASSIUM NUTRITION ON LEAF ANATOMY AND NET PHOTOSYNTHESIS OF PHASEOLVS VULGARIS L.
Authors: O'TOOLE J. C. , TREHARNE K. , TURNIPSEED M. , CROOKSTON K. , OZBUN J. 
Published: May 2006

SummaryLow levels of potassium (K+) nutrition resulted in a decrease in dry wt of leaves, stems and roots of two contrasting bean cultivars, Michelite (M‐62) and Redkote (RK). A decrease in eel! size and compaction of cells per unit area, resulting in decreased leaf thickness, and degradation of chloroplasts, and loss of cell wall integrity accompanied the decrease in percent K+ of leaf tissue.Net photosynthesis rate decreased below a threshold level of about 1% K+ in the leaf tissue with corresponding nutrient solution levels of between 1·2 and 0·3 mequiv. K+1‐1. Below this critical level, both stomatal and mesophyll diffusion resistances to CO2 increased markedly. Varietal differences for these responses suggests differences in efficient utilization of the element rather than differential ability to absorb K+.
TRANSLOCATION AND TRANSFER OF NUTRIENTS IN VESICULAR‐ARBUSCULAR MYCORRHIZAS. III. POLYPHOSPHATE GRANULES AND PHOSPHORUS TRANSLOCATION
Authors: COX G. , MORAN K. J. , SANDERS F. , NOCKOLDS C. , TINKER P. B. 
Published: May 2006

SummaryX‐ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm‐3) of cytochemically‐demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high‐voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra‐matrical mycelium in soil measured in the light microscope were around 12·6 cm h‐1. From these data a flux rate of about 2·7 × 10‐8 mol P cm‐2 s‐1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: MACFARLANE J. D. , KERSHAW K. A. 
Published: May 2006

SummaryData are presented which fully corroborate previous provisional findings that two populations of Peltigera canina differ quite markedly, when air‐dry, in their response to heat stress. In addition, observations upon a number of other species are described, and it was shown that thallus temperatures as low as 25 °C can severely stress Peltigera scabrosa.The design of the stress treatment paralleled naturally occurring stress periods and temperature levels found under summer field conditions. Stress effects were assessed by monitoring nitrogenase activity, net photosynthetic rates and respiration rates. The mycobiont usually has a much greater tolerance of thermal stress than the algal component, so that net photosynthetic rates of the lichens are seriously impaired whilst concurrent respiration rates can be fully maintained. This probably accounts for the extreme temperatures required by previous workers to induce a stress effect when this was defined solely by a reduction of respiration rates.The significance of these findings is discussed in relation to the ecology and geographical distribution of lichens.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS X. LIGHT AS AN ECOLOGICAL FACTOR
Authors: KERSHAW K. A. , MACFARLANE J. D. 
Published: May 2006

SummaryLittle attention has been paid to the potential importance of light in the ecology of lichens. Data is presented which shows that Peltigera canina var. praetextata from a woodland floor can rapidly acclimate to low or high light levels and thus maintain a given level of photosynthesis irrespective of the leaf canopy status. This photosynthetic adjustment takes place naturally in the field during leaf fall in October. P. scabrosa shows a similar response to low light and furthermore, acclimation to low levels of illumination can readily take place in air‐dry material. In contrast populations of Peltigera aphthosa collected from the dense shade of spruce in northern Ontario are extremely sensitive to quite modest levels of ‘high’ light, with pronounced damage occurring under 350 μE m‐3 8‐1 illumination. Contrasting populations of P. aphthosa collected from open habitats are not affected by this level of illumination.The maintenance of the correct day length during air‐dry storage is also very important since a rapid alteration of daylength produces a marked although temporary photosynthetic decline. On the other hand continuous daylight induces a rapid and continuous decline of photosynthesis probably leading eventually to the death of the phycobiont.
THE LOCATION AND SIZE OF THE EXTENSION ZONE OF EMERGING WHEAT LEAVES
Authors: KEMP D. R. 
Published: May 2006

SummaryThe length of the extension zone (LEZ) of emerging wheat leaves varied with the stage of leaf development and between leaves with the length of the encircling sheath (LES). The ratio LEZ/LES varied from 0·60 when the leaf tip emerged from the encircling sheath to 0·35 when the ligule emerged. The relationship between LEZ/LES and an index of leaf development (DI), defined as the sheath length of the growing leaf relative to LES, was: LEZ/LES= 0·632 exp (‐0.622.DI); (r= 0.91). 14C incorporation studies supported the measurement of extension zone location and length.There appeared to be a small zone of non‐expanding tissue, within the extension zone, around the ligule, but it was not a major discontinuity within the whole extension zone. The relative extension rate of the extension zone declined by only 50 % from leaf tip to ligule emergence whereas the relative extension rate of the whole leaf declined by 90 % over the same interval.There was little variation in protein and carbohydrate concentrations around the upper limit of the extension zone in emerging leaves. For studies of leaf growth in wheat where it is not possible to measure LEZ, harvesting the lower 50 % of the enclosed part of an emerging leaf would adequately sample the extension zone.
THE EFFECT OF INORGANIC NITROGEN ON THE MAJOR ENZYMES OF AMMONIUM ASSIMILATION IN GRASSLAND PLANTS
Authors: TAYLOR A. A. , HAVILL D. C. 
Published: May 2006

SUMMARYNaturally occurring grassland plants possess the enzymic potential for assimilation of ammonium via the glutamate dehydrogenase and glutamine synthetase/glutamate synthase pathways. In the majority of species, high exogenous ammonium concentrations enhanced the levels of root and shoot GDH and reduced the levels of root glutamine synthetase. However, the enzyme response to increasing nitrate or ammonium availability was relatively small and suggested that these species are not adapted for major changes in the form or availability of nitrogen.
A FIELD SURVEY OF MYCORRHIZAL ASSOCIATIONS IN FERNS OF PAKISTAN
Authors: IQBAL S. H. , YOUSAF M. , YOUNUS M. 
Published: May 2006

SUMMARYRoots of the ferns examined in this investigation were constantly mycorrhizal. A mixture of several endophytes infecting a root system was a usual feature of them. Vesicular‐arbuscular endophytes predominated over endophytes with a septate mycelium. Ectomycorrhizal fungi with a septate mycelium bearing clamp‐connections ran longitudinally inside the cortex and occasionally these hyphae formed a mantle on the outside of the roots. A displacement of endotrophic mycorrhizas by ectomycorrhizal fungi occurred in Adiantum vemistum D. Don when growing under pine forest. Heavy arbuscular and vesicular infections occurred throughout the period of investigation. Several spore types were present in each rhizosphere.
INFLUENCE OF PHOSPHATE SOURCE ON VESICULAR‐ARBUSCULAR MYCORRHIZAE OF BOUTELOUA GRACILIS
Authors: ALLEN MICHAEL F. , SEXTON JAMES C. , Jr MOORE THOMAS S. , CHRISTENSEN MARTHA 
Published: May 2006

SUMMARYNon‐mycorrhizal and vesicular‐arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus were grown in defined media containing different phosphate sources and compared with respect to phosphate content and form, biomass, chlorophyll concentration, and root phosphatase activity. The phosphate sources were sodium monobasic phosphate, a mixture of sodium monobasic phosphate and calcium phytate, and calcium phytate. Inositol and inositol plus calcium were added to the sodium phosphate medium as additional treatments. Mycorrhizal infection was highest in roots of plants grown in the presence of phytate (75%). Lower root infection levels were noted in plants from the sodium phosphate (19%) and mixed phosphate (22%) media. No penetration by fungi occurred in plants from the sodium phosphate plus inositol or inositol and calcium media. Dry wts of non‐mycorrhizal plants were highest when grown in media containing phytate and sodium phosphate plus inositol and calcium followed in decreasing order by sodium phosphate plus inositol, mixed phosphates, and sodium phosphate. Mycorrhizal infection increased leaf dry wt in plants from the sodium phosphate medium and root dry wt from the phytate medium. Phosphate concentrations in the plants were highest when grown in mixed phosphate medium followed by sodium phosphate and phytate. Mycorrhizal infection always increased significantly leaf phosphate concentrations but increased root phosphate concentrations only in the phytate medium. Phosphates were found predominantly as organically‐bound compounds in leaves of mycorrhizal plants whereas in leaves of non‐mycorrhizal plants, most of the phosphate was inorganic. Chlorophyll concentrations increased significantly with mycorrhizal infection with no change in a/b ratios. Mycorrhizal plants grown in the phytate medium had substantially higher alkaline phosphatase activity than did non‐mycorrhizal plants; acid phosphatase activity was not affected by mycorrhizal condition.These results suggest that form of the phosphate in the root environment influences mycorrhizal establishment and effect of mycorrhizae on plant growth.
THE UPTAKE OF 2‐OXOGLUTARATE AND PYRUVATE BY ISOLATED PEA CHLOROPLASTS
Authors: PROUDLOVE M. O. , THURMAN D. A. 
Published: May 2006

SUMMARYThe uptake of 2‐oxoglutarate and pyruvate by intact, isolated pea chloroplasts has been studied by centrifugal filtration. Inhibition of 2‐oxoglutarate transport by malate, fumarate, oxaloacetate and glutamate suggested that a dicarboxylate carrier is operating. This carrier is substrate saturated at approximately 1 mM and shows a Vmax of 32 μmol (mg chlorophyll)‐1 h‐1 and has a Km of 0·19 mM. Pyruvate enters pea chloroplasts mainly by diffusion, but at low external concentrations of the keto‐acid uptake may be carrier mediated with a Vmax of 6·5 μmol (mg chlorophyll)‐1 h‐1 and a Km of 0·33 mM. A number of compounds related to pyruvate, and also α‐cyano‐4‐hydroxycinnamic acid, failed to inhibit pyruvate movement.
NITRATE AVAILABILITY UNDER LOW IRRADIANCE AND ITS EFFECT ON NITRATE REDUCTASE ACTIVITY
Authors: UDAYAKUMAR M. , DEVENDRA R. , REDDY V. SREENIVASA , SASTRY K. S. KRISHNA 
Published: May 2006

SUMMARYLeaf nitrate reductase (EC 1.6.6.1, NADH: nitrate oxidoreductase) (NR) activity decreased on exposure to low irradiance and the decrease was dependent upon duration of exposure. The observed decrease was associated with a decrease in the rate of xylem exudation and nitrate concentration resulting in lesser supply of nitrate to the tops. Continuous nitrate supply to excised leaves in shade or even in the dark resulted in a high NR activity, suggesting that lack of reducing power was not the main cause for lower NR activity. Further, when excised leaves were deprived of nitrate, even in light, NR activity decreased with time. In leaves with their petioles dipped in water, the NR activity decreased and on retransfer to KNO3 within 105 min the activity increased, suggesting that continuous nitrate supply was essential for maintaining high NR activity.
MYCORRHIZAL INFECTION AND GROWTH OF TRIFOLIUM SUBTERRANEUM: USE OF STERILIZED SOIL AS A CONTROL TREATMENT
Authors: SMITH F. A. , SMITH S. E. 
Published: May 2006

SUMMARYEffects of mycorrhizal infection on the growth of Trifolium subterraneum have been studied by comparing plants grown in sterilized soil/sand mixtures with plants grown in untreated soil/sand mixtures. The original soil contained a high level of endomycorrhizal inoculum. The aim was to consider whether this approach is valid, bearing in mind the possible effects of sterilization (γ‐irradiation or autoclaving) on soil properties. Plants in the untreated soil/sand mixtures became significantly larger than plants in the sterilized soil/sand mixtures about 4 weeks after planting. This response was associated with rapid infection by vesicular‐arbuscular mycorrhizal fungi; it still occurred when nitrate replaced N2 as the nitrogen source for the plants. Addition of soluble phosphate enhanced the growth of the non‐mycorrhizal plants to a level similar to that of the mycorrhizal plants. Mixing sterilized and untreated soil did not depress mycorrhizal infection or growth. These results indicate that the growth difference was a classic mycorrhizal response, and did not reflect toxic effects of soil sterilization. The growth of Brassica oleracea (broccoli), which does not form mycorrhizas, was better on sterilized soil.
TECHNIQUES FOR STUDYING THE INFECTION OF PLANTS BY VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI UNDER AXENIC CONDITIONS
Authors: HEPPER CHRISTINE M. 
Published: May 2006

SUMMARYMethods of growing axenic seedlings infected by vesicular arbuscular mycorrhizal fungi are described, using agar, paper or glass as a support. Two of the techniques are particularly suitable for studying the interaction between the fungus and the host plant, for example the germination of the spore inoculum, hyphal growth around the roots before the symbiosis has been initiated and the early stages of root penetration.
THE RELATIONSHIP BETWEEN PHOSPHATE ABSORPTION AND OXYGEN UPTAKE IN EXCISED BEECH MYCORRHIZAS
Authors: HARLEY J. L. , McCREADY C. C. 
Published: May 2006

SUMMARYWhen mycorrhizal rootlets of beech are aged for several days in water, their respiration rate falls. If phosphate is applied, the respiratory rate rises and the rise in oxygen consumption is proportional to phosphate uptake in replicate samples aged for equivalent times. The ratio of μg‐atom phosphorus to μg‐atom oxygen absorbed is usually around or just below unity, but it varies with the state of the tissues to values as low as 0·28. High values of this ratio in the later state of ageing may be spurious because, in senescent mycorrhizas, phosphate penetrates non‐metabolically. High values in fresh mycorrhizas occur because the rate of phosphate‐induced oxygen uptake is low but it rises faster than that of phosphate uptake in the early stages of ageing. The conclusion is drawn that the processes of phosphate absorption and polyphosphate formation are often 20 to 30% efficient with respect to respiratory oxidative phosphorylation. The linear relationship of total oxygen consumption to phosphate absorption observed in fresh mycorrhizas is due to the pre‐emption of a portion of total phosphorylation by polyphosphate production.