bluuebunny/crossref_metadata_2025 huggingface dataset:
FLORAL ENANTIOMORPHY AND THE REPRODUCTIVE SYSTEM OFWACHENDORFIA PANICULATA(HAEMODORACEAE)
Authors: ORNDUFF ROBERT , DULBERGER RIVKA
Published: May 2006

Flowers of the South African genusWachendorfia(Haemodoraceae) are dimorphic. Some individuals in a population produce flowers in which the style and one stamen are deflected to the right and the other two stamens are deflected to the left; other individuals produce flowers with the reverse arrangement of style and stamens. Articifical pollinations ofW. paniculataindicate that it has a weakly developed self‐incompatibility system; intermorph crosses produced more seeds than self‐pollinations or intramorph pollinations. Features of the floral morphology ofW. paniculatasuggest that it is pollinated by a large‐bodied insect, possiblyXylocopa.The dimorphism in the position of anthers and stigmas probably increases the level of intermorph pollination. The low sugar concentration of the nectar, low pollen production per flower, and few flowers per plant also probably result in pollinators visiting more than one plant during their foraging activities, thus reinforcing the floral dimorphism and increasing the opportunities for intermorph pollination.
THE AZOLLA‐ANABAENA AZOLLAE RELATIONSHIP
Authors: PETERS G. A. , TOIA R. E. , RAVEED D. , LEVINE N. J.
Published: May 2006

The nitrogen‐fixing blue‐green alga, Anabaena azollae, occurs as a symbiont in leaf cavities of the water fern, Azolla. Organization and morphological aspects of the association, with emphasis upon the cavity area, were studied by light, transmission, and scanning electron microscopy. Cleared whole mounts, sectioned, and enzymatically digested materials were employed. Leaf cavity formation, including the association of the symbiont and epidermal hairs, is shown during leaf development in A. caroliniana Willd. Enzymatic digestion of the fern leaf tissue provided preparations of algal packets which correspond to the leaf cavity area. The digestion process complemented other approaches in providing insight into the organization of the leaf cavity. Scanning electron microscopy allowed visualization of these packets in three dimensions. The packets are surrounded by a filmy, limiting envelope of unknown composition. The envelope was isolated and shown to remain associated with hairs which protrude into the cavity area. The hairs are multicellular and may be branched or unbranched. When nitrogen fixation by the symbiont is the sole nitrogen source, sections through some cells of hairs in mature leaf cavities exhibit the ultrastructural characteristics of transfer cells. These characteristics are not observed, however, in sections through cells of hairs associated with the early stages of leaf cavity formation in the shoot tip. The potential significance of the envelope and hair cells in the metabolic interaction of the host and symbiont are discussed.
TRANSLOCATION AND TRANSFER OF NUTRIENTS IN VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: COOPER KAREN M. , TINKER P. B.
Published: May 2006

Trifolium repens (white clover) or Allium cepa (onion) infected with the mycorrhizal fungus Glomus mosseae were grown in split‐plate cultures, so that nutrients could be supplied to the external hyphae only. The uptake and translocation of 32P, 65Zn and 35S by hyphae of the fungus was measured.

A lag phase of 2‐3 days in the appearance of 32P in the shoot was caused by a delay in the uptake and translocation of P by the hyphae, rather than in transfer from fungus to host.

The calculated maximum translocation rate of P for onion was 6.4 × 10−16 mole s−1, and the P flux in the hyphae about 2 × 10−10 mole cm−2 s−1. The molar amounts of P, S and Zn translocated were in the ratio of 35:5:1 and the mean fluxes in the ratio of 50:8:1 with clover.
STRUCTURAL RESISTANCES TO MASS TRANSFER IN THE LICHEN XANTHORIA PARIETINA
Authors: COLLINS C. R. , FARRAR J. F.
Published: May 2006

Quantitative morphological data obtained from Xanthoria parietina by light and electron microscopy is related to measurements of photosynthesis rate and estimates of biotrophic ribitol transfer. It is concluded (a) that diffusive CO2 flux into the alga is greatly reduced by the resistance of the fungal cortex, (b) that diffusion can easily account for the mass transfer of ribitol from alga to fungus, and (c) that haustoria have no role in the biotrophic transfer of carbohydrate in lichens.
FRUIT DEVELOPMENT AND WAX BIOSYNTHESIS IN JOJOBA
Authors: BENZIONI ALIZA
Published: May 2006

Simmondsia chinensis (jojoba), a wild desert shrub, is known for its fruit which contains unique wax esters similar in nature to sperm‐whale oil (Yermanos and Duncan, 1976). In this work, the ability of the fruit to synthesize the wax esters has been studied from a very early stage to ripening.
AN ANATOMICAL STUDY OF ROOT INITIATION IN STEM CUTTINGS OF HYBRID LARCH
Authors: JOHN ALLAN
Published: May 2006

The stages in the development of roots in stem cuttings of Hybrid larch have been investigated. Callus develops from a new meristem after the establishment of a cortical vascular system. Roots arise from near the tip of this cortical vascular system and emerge as partially differentiated structures after approximately 42 days.
OCCURRENCE OF HELICAL THICKENINGS IN THE VESSELS OF NEW ZEALAND WOODS
Authors: MEYLAN B. A. , BUTTERFIELD B. G.
Published: May 2006

Helical thickenings were observed on the vessel walls of ninety woods indigenous to New Zealand. They were not observed in a further eighty‐eight species. Four types of thickenings are described: faint striations, light helical thickenings sometimes merging with the vessel wall, prominent helical thickenings and very prominent close helical thickenings. These types are illustrated with scanning electron micrographs.

Although the helical winding orientation was predominantly in the S‐direction, considerable variation was observed in the helical winding angle both between adjacent vessel members of similar dimensions, and also within individual cells.

Vestures were observed adhering to the helical thickenings in three species.
VARIATION IN BRASSICA OLERACEA L. SUBSP. OLERACEA (WILD CABBAGE) DETECTED BY THE PICRATE TEST
Authors: MITCHELL N. D. , RICHARDS A. J.
Published: May 2006

Variation in response to the Guignard pictate test may be detected within wild British populations of Brassica oleracea L. subsp. oleracea. Plants with the greatest reaction are the least frequent. In different seasons, individuals react differently to the test, possibly in response to temperature fluctuations. In B. oleracea the picrate test is perhaps responding to allyl derivatives of the glucosinolate sinigrin; HCN was not detected.
EFFECT OF ABSCISIC ACID AND BENZYL ADENINE ON THE INORGANIC AND ORGANIC COMPOSITION OF THE DUCKWEED, LEMNA GIBBA L.
Authors: DEKOCK P. C. , VAUGHAN D. , HALL A.
Published: May 2006

The inhibition of growth of Lemna gibba fronds by abscisic acid is accompanied by typical changes in mineral composition such that the ratios of phosphorus to iron and potassium to calcium are lowered compared with normal growing fronds. Benzyl adenine added with abscisic acid tends to reduce these changes and re‐establish growth causing the above ratios to be increased.
MYCORRHIZAL DEPENDENCY OF SEVERAL CITRUS CULTIVARS UNDER THREE NUTRIENT REGIMES
Authors: MENGE J. A. , JOHNSON E. L. V. , PLATT† R. G.
Published: May 2006

Six citrus cultivars were grown with and without the mycorrhizal fungus Glomus fasciculatus under three fertilizer regimes all without phosphorus. The average mycorrhizal dependency (Gerdemann 1975) of Rough lemon and Brazilian sour orange were greater than the mycorrhizal dependecies of Alemow, Troyer citrange, Bessie sweet orange and Trifoliate orange. The mycorrhizal dependency of each cultivar, except Bessie sweet and Trifoliate orange, was substantially altered by at least one of the fertilizer regimes, and therefore the order of mycorrhizal dependency was different at all three fertilizer regimes. On the average, citrus rootstocks exhibited the greatest mycorrhizal dependency with the least fertilization. The average percentage phosphorus in non‐mycorrhizal leaf tissues was inversely correlated with the mycorrhizal dependency of citrus cultivars at the medium fertilizer regime. An inverse correlation was observed between the dry weights of non‐mycorrhizal roots of the citrus cultivars and the mycorrhizal dependency of the citrus cultivars.
INFLUENCE OF BACTERIA IN THE PHYLLOSPHERE OF CAMELINA SATIVA (L.) CRANTZ ON GERMINATION OF LINUM USITATISSIMUM L.
Authors: LOVETT J. V. , SAGAR G. R.
Published: May 2006

In a series of experiments, aqueous washings of the leaves of Camelina sativa (L.) Crantz consistently stimulated the growth in length of radicles of germinating seeds of Linum usitatissimum L. The presence of free‐living nitrogen‐fixing bacteria in the Camelina phyllosphere was necessary for the production of the stimulation.
THE GREEN HYDRA SYMBIOSIS
Authors: JOLLEY ELIZABETH , SMITH D. C.
Published: May 2006

The Chlorella symbiont of the ‘European’ strain of green hydra has been isolated into pure culture using conventional microbiological techniques. The symbiont grew well on Bold's basal medium, indicating that it had no fastidious nutritional requirements. It grew rapidly on liquid media, but very slowly on agar–which may explain why previous authors have failed to isolate it. The ultra structure of the cultured isolate agrees closely with published descriptions of the symbiont. The cultured isolate could also reinfect aposymbiotic hydra, and a cycle of reisolation and reinfection was followed. The cultured isolate lacked the property of maltose excretion normally shown by symbionts, but this property was restored after reinfection. A hypothesis is advanced to explain the induction of maltose synthesis and release by host animal cells.
INHIBITION BY ZINC OF SOLUBLE AND CELL WALL ACID PHOSPHATASES OF ZINC‐TOLERANT AND NON‐TOLERANT CLONES OF ANTHOXANTHUM ODORATUM
Authors: COX R. M. , THURMAN D. A.
Published: May 2006

Inhibitor constants, Ki and K'i for zinc have been determined for a number of soluble and cell‐wall‐bound acid phosphatases of two zinc‐tolerant and two non‐tolerant clones of Anthnxanthum odoratum. The values of Ki for the soluble enzymes of both clones approached infinity which suggested that the inhibition was mainly of an uncompetitive nature. The tolerant clones possessed Ki values for soluble and cell wall enzymes which were significantly higher than the corresponding values for the non‐tolerant clones. K'i values of the cell wall enzymes of tolerant and non‐tolerant clones were not significantly different from one another. It was concluded that non‐tolerant clones possess acid phosphatases which form more stable complexes with zinc than tolerant ones. The relevance of this observation to metal tolerance mechanisms is discussed.
THE EFFECTS OF AIR POLLUTION ON PLANT GROWTH WITH SPECIAL REFERENCE TO SULPHUR DIOXIDE
Authors: CRITTENDEN P. D. , READ D. J.
Published: May 2006

A glasshouse for the study of the effects of ambient levels of air pollution on plant growth is described. Two sealed sub‐sections were force‐ventilated, one received SO2‐polluted ambient air while a second received air that had been passed through an activated carbon filter to remove SO2. Potential diffuse and direct incoming radiation, air temperature and humidity were examined in both chambers in order to determine whether differences in microclimatic factors other than air quality existed between the two ail treatments. Daily mean concentrations of SO2 and suspended particulate matter were measured in the two chambers and outside the glasshouse. During 2 years of continuous monitoring neither pollutant was detected in the filtered air while levels in the unfiltered section were usually below 100 μg m−3SO2 and 50 μg m−3 particulates. Discrepancies between the two chambers in the predicted light conditions and humidity and differences in environmental conditions between the glass enclosures and the open air are discussed critically. The possible occurrence of secondary gaseous pollutants in the unfiltered air in addition to SO2 is also considered.
ENVIRONMENTAL INFLUENCES ON PHOTOSYNTHESIS AND GROWTH IN FRAG ARIA VESCA
Authors: CHABOT BRIAN F.
Published: May 2006

Growth of Fragaria vesca under several conditions of temperature and light was closely related to rates of net photosynthesis calculated for the growing conditions. This suggests that the rate of photosynthetic carbon accumulation is limiting for the overall success of the individual and that metabolic acclimation of net photosynthesis to the environment may be an important adaptation for improving general carbon balance. Growth rate showed differing sensitivity to the five environmental factors investigated; variation in light produced the greatest changes while nutrient levels had little effect. There was good buffering of physiological processes at moderate temperatures with growth reduction pronounced only at temperature extremes.

Under all treatments there was a reduction in the proportion of biomass allocated to reproduction as total biomass accumulation became limited. Temperature treatments shifted reproductive allocation from flowering at low temperatures, to vegetative propagation at higher temperatures. Plants were capable of growing vegetatively under the most limiting conditions without reproducing. It is possible, therefore, that natural limits to distribution may coincide with limits to physiological performance and dispersal rather than to the ability of a population to reproduce itself in place.
FACTORS AFFECTING ABSCISSION IN SPIRODELA OLIGORHIZA (LEMNACEAE)
Authors: WITZTUM A. , KEREN O.
Published: May 2006

Exposure of plants of Spirodela oligorhiza to ultraviolet light results in a high percentage of abscission of daughter colonies. The levels of endogenous ABA and ethylene released in irradiated plants were similar to those of the non‐irradiated controls. Pre‐incubation on IAA very significantly reduced UV‐induced abscission in spite of causing a large release of ethylene.
SCANNING ELECTRON MICROSCOPY OF SURFACE FEATURES OF EUCALYPT MYCORRHIZAS
Authors: SEVIOUR R. J. , HAMILTON D. , CHILVERS G. A.
Published: May 2006

Scanning electron micrographs of surface features are a useful aid for distinguishing mycorrhizas formed by different fungal components. Some of these features raise important questions about mycorrhizal morphogenesis and associated hyphal wall structure.
EFFECTS OF HANDLING AND SURGICAL TREATMENTS ON NITROGENASE ACTIVITY IN ROOT NODULES OF ALNUS GLUTINOSA, WITH SPECIAL REFERENCE TO THE APPLICATION OF INDOLE‐ACETIC ACID
Authors: WHEELER C. T. , CAMERON ELIZABETH M. , GORDON J. C.
Published: May 2006

The possible effects of applied indole‐acetic acid upon nitrogenase activity and respiration in alder nodules could not be distinguished from the effects of the manipulative procedures themselves. The extent to which plants were handled during the acetylene reduction assay had a large inhibitory effect upon the apparent nitrogenase activity of the nodules.
THE ONSET OF NITROGEN FIXATION IN YOUNG ALDER PLANTS AND ITS RELATION TO DIFFERENTIATION IN THE NODULAR ENDOPHYTE
Authors: MIAN SALMA , BOND G.
Published: May 2006

The acetylene assay was used to find how soon nitrogenase activity could be detected in young, nodulating alder plants. Samples taken at intervals initially of 2–3 days were assayed, starting as soon as external signs of nodulation were seen, and continuing for a further 33 days. Squash preparations made from the nodules of the assayed plants were examined microscopically to detect whether there was any relation between nitrogenase activity and the stage of differentiation of the nodule endophyte.

No nitrogenase activity was detected on the first two assay occasions, on which the endophyte was confined to the hyphal stage in all the nodules present. Activity was detected on the subsequent occasions, its onset coinciding with the production of vesicles by the endophyte. Activity rose as the vesicles became more abundant, and in agreement with the limited previous evidence it was concluded that the vesicles, but not the hyphae, are nitrogen‐fixing. The third type of structure produced by the alder endophyte, namely the bacteroid stage, was not detected in the young nodules studied here.

The onset of nitrogenase activity in the nodules preceded by 16 days the increased greening of the leaves signifying the arrival in the shoot of products of nitrogen fixation. Ethylene production per plant increased in exponential manner over the period of the experiment, while ethylene production per unit weight of nodule tissue rose ten‐fold
ANALYSIS OF EFFECTS OF THE BIRD CHERRY‐OAT APHID ON THE GROWTH OF BARLEY: UNRESTRICTED INFESTATION
Authors: MALLOTT P. G. , DAVY A. J.
Published: May 2006

Infestation with the bird cherry‐oat aphid considerably reduced the dry weight yield, the leaf area, the number of tillers and the number of leaves of barley plants. Growth analysis revealed that the major effect of infestation was to reduce unit leaf rate. However, infested plants compensated partially for this by allocating a greater proportion of their dry weight to the production of leaf laminae than did the control plants.

Rates of net photosynthesis in individual, attached leaves were measured using the carbon dioxide exchange method; infested and control plants were found to have very similar rates of photosynthesis. Thus the reduction of unit leaf rate did not result from an effect of photosynthesis. It is suggested that the decreased growth of the barley plants is explicable in terms of cumulative assimilate loss due to aphid feeding.
THE ANT‐PLANTS MYRMECODIA AND HYDNOPHYTUM (RUBIACEAE), AND THE RELATIONSHIPS BETWEEN THEIR MORPHOLOGY, ANT OCCUPANTS, PHYSIOLOGY AND ECOLOGY
Authors: HUXLEY CAMILLA R.
Published: May 2006

The history of investigation of the ant‐plants is briefly reviewed and the external morphology of the plants described. Within Papua New Guinea ant‐plants are abundant in open‐canopied environments and less common but more diverse in rain forest. They also occur terrestrially above 2400 m. Initial tuber development was found to be similar that described by Treub (1883). Later cavities are formed by successive, increasingly complex phellogens. In certain Myrmecodia spp. later cavities are differentiated into regions with distinct surface characteristics, shapes and positions. Cavities in Hydnophytum are simpler in shape but sometimes differentiated in other ways. The anatomy of the cavity surfaces, especially the putative absorption sites ('warts') is described.

The ant Iridomyrmex cordatus, which is common in ant‐plants in other regions, is found in ant‐plants in open habitats in Papua New Guinea, but is replaced by I. cf. scrutator in rain forest and above 2000 m. Two fungi, known also from ant‐plants in Java (Miehe, 1911a), occur in the cavities of ant‐plants throughout Papua New Guinea. Arthrocladium sp. Papend. grows on cavity surfaces where ant faecal material is present and the other (an unidentified Monilialine fungus) is parasitic on smooth, clean surfaces. The former is most common and the latter almost confined to Myrmecodia spp. occupied by Iridomyrmex cordatus.

Experiments suggested that both Hydnophytum under artificial conditions and Myrmecodia under field conditions grow better in the presence than absence of Iridomyrmex cordatus and that the stimulus might be that of minerals supplied by the ants. Radioisotopes in both organic and inorganic compounds fed to I. cordatus were deposited preferentially by the ants on the warted cavity surfaces where ant faecal material was present, and were absorbed by the plants. In the discussion it is argued that the plant/ant relationship has had a considerable influence on both the ecology and evolution of the plants, but that this varies in different species.
COMPARATIVE PHYSIOLOGY OF ALBUGO TRAGOPOGONIS‐INFECTED AND PUCCINIA LAGENOPHORAE‐INEECTED PLANTS OF SENECIO SQUALIDUS L.
Authors: WHIPPS J. M. , COOKE R. C.
Published: May 2006

Infections of Senecio squalidus leaves by Puccinia lagenophorae (Uredinales) were characterized by polyol synthesis, development of green islands and deposition of starch within green island tissues. In infections by Albugo tragopogonis (Peronosporales), there was no polyol synthesis, comparable green islands did not develop or developed poorly, and there was extensive and progressive necrosis of host tissues in infected areas. No starch was deposited in infected tissues and there was gradual disappearance of all starch from infected leaves. In both kinds of infection, ethanol‐soluble metabolites accumulated around infected sites but there was no evidence for massive translocation to these sites from the rest of the leaf or plant. The differences between these two kinds of infection are discussed in relation to the biology of biotrophic, pathogenic higher and lower fungi. It is suggested that many lower fungi that infect leaves are hemibiotrophic rather than biotrophic.
THE UPTAKE OF ZINC AND CALCIUM FROM SOLUTION CULTURE BY ZINC‐TOLERANT AND NON‐TOLERANT SILENE MARITIMA WITH. IN RELATION TO CALCIUM SUPPLY
Authors: BAKER A. J. M.
Published: May 2006

Inter‐population variation in the uptake of calcium from solution culture was studied in a range of zinc‐tolerant and non‐tolerant populations of Silene maritima under conditions of high zinc and calcium. The populations exhibited great variability in their patterns of calcium uptake similar to that previously reported for zinc. The effects of variation in calcium supply on yield and calcium and zinc uptake by one zinc‐tolerant and one non‐tolerant population are described. Little difference in yield‐response to calcium was detected between the two populations but they showed major differences in the uptake and accumulation of zinc and calcium and their transport from root to shoot. Total zinc uptake was little affected by increases in calcium level in the tolerant plants but was decreased significantly in the non‐tolerant plants. At the higher calcium levels, total zinc uptake by tolerant plants was also significantly greater than by the non‐tolerant but the populations did not differ in total calcium uptake. Evidence for a reduction in zinc transport in both populations resulting from increased calcium uptake is presented. Marked stimulation of zinc accumulation by the roots of the tolerant population resulting from increases in the external calcium level is interpreted as a possible corollary of zinc tolerance in this tolerant population. The role of calcium in the internal detoxification of zinc is discussed.
ZINC‐PHOSPHORUS INTERACTIONS IN A ZINC‐TOLERANT AND A NON‐TOLERANT POPULATION OF SILENE MARITIMA WITH.
Authors: BAKER A. J. M.
Published: May 2006

Inter‐population variation in the long‐term uptake of phosphorus from solution culture indicated that uptake and transport in some zinc‐tolerant populations of Silene maritima were greater than in non‐tolerant coastal and arctic‐alpine populations. The effects of P and Zn level in the culture solution on yield and uptake of P and Zn by plants of a zinc‐tolerant population exhibiting extreme uptake characteristics and of a non‐tolerant population are described. The tolerant plants were higher‐yielding at low P levels, showed less phosphate response and proved to be more efficient in their P uptake and transport than the non‐tolerant plants. A differential interaction of Zn and P was also detected in the two populations. These features were considered to be of adaptive significance.
THE EFFECTS OF SOWING DENSITY, SALINITY AND SUBSTRATE UPON THE GERMINATION OF SEEDS OF PLANTAGO CORONOPUS L.
Authors: WAITE STEPHEN , HUTCHINGS MICHAEL J.
Published: May 2006

The influence of number of seeds per clump upon germination of Plantago coronopus L. was investigated at different salinity levels on filter paper, sand and soil. These substrates provide both artificial and semi‐natural microenvironments for seed germination.

On all substrates, germination was positively dependent on clump density and seeds in clumps had a higher tolerance of salinity as reflected in higher germination percentages. Final percentage germination for a given clump size and salinity level depended upon substrate, being far higher on filter paper and sand than on soil, whilst the time required to reach final germination also increased in that order. The possible ecological significance of density‐dependent seed germination is discussed.
RE‐ORGANIZATION OF FINE STRUCTURE DURING REHYDRATION OF DESICCATED LEAVES OF XEROPHYTA VILLOSA
Authors: HALLAM N. D. , GAFF D. F.
Published: May 2006

Air‐dry viable leaves of Xerophyta villosa, fixed in non‐aqueous fixatives, show disorganization of the cytoplasm and loss of cristae, grana and thylakoids, but retention of intact double membranes around plastids and of intact nuclei. Some reorganization of cell fine structure takes place while the leaves are rehydrating: cristae reappear in the mitochondria and numerous spherical vesicles in the plastids first swell, flatten to discs, and associate at their rims to form the thylakoid system and, following full rehydration, grana. Reformation of starch grains in the rehydrated tissue appears to precede the renewal of net photosynthesis.
A PLOTTER FOR PLANT POPULATION STUDIES
Authors: CULLEN J. M. , WEISS P. W. , WEARNE G. R.
Published: May 2006

A simple plotter utilizing rectangular coordinates is described for use in following populations of known individual plants over periods of time. Each plant is positioned by two coordinates determined by reference to a metal bar and a shorter arm, each graduated in mm and held at right angles to each other in the horizontal plane. The arm moves along the bar and is adjustable for height. The bar rotates about its longitudinal axis thus allowing the arm to swing to an upright position to avoid vertical obstructions. The plotter copes readily with tall vegetation and difficult terrain, is easily transported and installed, and has been used successfully to plot individual plants of Chondrilla juncea L. and Emex australis Steinh.
THE PALAEOBOTANY OF INTERGLACIAL DEPOSITS AT SUGWORTH, BERKSHIRE
Authors: GIBBARD P. L. , PETTIT M.
Published: May 2006

Interglacial deposits in a river channel‐fill sequence at Sugworth, Oxfordshire contain a rich flora indicating a late Cromerian (Cr IIIb) age. Analyses of pollen and macroscopic plant remains indicate uniform vegetational conditions throughout the period of deposition, with mixed deciduous‐coniferous woodland in the valley, and alder fen carr bordering the river. On the immediate floodplain and point bar the various wet areas supported several herb communities. New interglacial records for several plant taxa are discussed, in particular Cyperus michelianus and C. fuscus.
PRESENCE OF 14C ACTIVITY IN ROOT EXUDATES AND GUTTATION FLUID FROM AGROPYRON REPENS TREATED WITH 14C‐LABELLED GLYPHOSATE
Authors: COUPLAND D. , CASELEY J. C.
Published: May 2006

Summary

The herbicide, N‐phosphonomethyl glycine (glyphosate), is readily absorbed by the foliage and translocated in the phloem of Agropyron repent (L.) Beauv. The roots and rhizomes were active sinks and, 8 days following herbicide treatment, 14C accumulated at the rhizome nodes, especially at the apical buds. Appreciable amounts of [14C]glyphosate were exuded from intact roots into surrounding solutions but very low levels occurred in the guttation drops collected from the leaf tips. Some implications of the work are discussed.
SALT‐INDUCED LOSS OF POTASSIUM FROM PLANT ROOTS
Authors: NASSERY H.
Published: May 2006

Summary

The loss of K+ from excised barley, wheat, chick pea and bean roots was measured in the absence or presence of different concentrations of NaCl and mannitol. In the presence of 50 mM Ca2+, the threshhold NaCl concentration for induction of K+ loss was 160 mM for barley, wheat and chick pea and 140 mm for bean. Mannitol iso‐osmotic to 160 mM NaCl did not induce K+ loss from barley, wheat or chick pea roots indicating that the induction of K+ loss was a salt‐induced and not an osmotic injury. The preventive effect of various concentrations of CaCl2 and MgCl2 on salt‐induced K+loss indicated that the protective effect of Ca2+was specific. Although 50 mM Ca8+ was sufficient, concentrations up to 40 mM may be more effective. The measurement of salt‐induced K+ loss appears to be a quick and reliable method of estimating the degree of salt resistance in plants.
SEASONAL AND EDAPHIC VARIATION IN VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION OF GRASSES BY GLOMUS TENUIS
Authors: RABATIN SUSAN C.
Published: May 2006

Summary

Seasonal differences in percentage length of gramineous host root infected with Glomus tennis were measured in three field sites in Pennsylvania, U.S.A. Highest G. tennis infection levels were generally found in the spring in very phosphorus‐deficient soils low in moisture. In roots sampled from soils with a high spring soil‐moisture content, fine endophyte infection increased to a maximum later in the growing season. A higher percentage frequency of fine endophyte infection on fine grass feeder roots in spring is taken as evidence for the hypothesis that G. tenuis is a vesicular–arbuscular mycorrhizal fungus particularly adapted to penetrating host roots during brief seasonal fluxes of phosphorus availability. The implications of these data are discussed in relation to mechanisms in grasses which adapt them to nutrient stress.
EFFECT OF WATER STRESS ON PHOSPHORUS UPTAKE BY MYCORRHIZAS OF PINUS RADIATA
Authors: REID C. P. P. , BOWEN G. D.
Published: May 2006

Summary

The uptake of 32P by excised non‐mycorrhizal and mycorrhizal roots of Pinus radiata was examined in solutions adjusted with polyethylene glycol 4000 to water potentials of 0, 005, 01, 0.3, 0.6 and 1.2 negative MPa. Solutions contained 5 μm KH2PO4 and 0.5 mM CaSO4. Uptake of phosphate was little affected by water potential in either mycorrhizal or non‐mycorrhizal roots. Changes in water potential also caused no appreciable change in its efflux from mycorrhizal roots, suggesting little effect on permeability to phosphate. Uptake of phosphate, when based on surface area of the roots, was similar for both mycorrhizal and non‐mycorrhizal roots, but was less for non‐mycorrhizal roots when based on fresh wt.

It is thus considered that changes in soil water potential per se may have little impact on absorption processes by mycorrhizal and non‐mycorrhizal roots. However, effective penetration of soil by mycelial strands and hyphae from ectomycorrhizas may be important in offsetting lowered transfer of ions to roots under low soil moisture conditions.
TOLERANCE OF ANDROPOGON SCOPARIUS TO COPPER AND ZINC
Authors: EHINGER L. H. , PARKER G. R.
Published: May 2006

Summary

The glass, Andropogon scoparius, from two sites in northwestern Indiana was tested hydro‐ponically for tolerance to zinc and copper. Plants from both sites showed a continuum of response to zinc, spanning the range of inhibition to enhancement of root growth. The urban plants were unaffected by 0.025 p.p.m. copper, whereas the rural plants were adversely affected at this level. The rural plants exhibited greater root growth than the urban plants at 0.1 p.p.m. copper. At 0.025 and 0.05 p.p.m. copper, the urban plants exhibited the greater root growth. At 0.075 and 0.l p.p.m. copper, the plants from both sites exhibited the same root growth. It was concluded that the urban site plants possess tolerance to low (0.025 p.p.m.) copper levels.
THE ROLE OF METAL‐ION BINDING IN MODIFYING THE TOXIC EFFECTS OF SULPHUR DIOXIDE ON THE LICHEN UMBILICARIA MUHLENBERGII
Authors: NIEBOER E. , RICHARDSON D. H. S. , LAVOIE P. , PADOVAN D.
Published: May 2006

Summary

K+ efflux from Umbilicaria muhlenbergii was not affected following the uptake of known amounts (< 20 μmol g‐1) of Ca2+, Mg2+, Sr2+ and Zn2+, but was increased in the cases of Cu2+ and Pb2+. In a number of samples that had taken up increasing amounts of Cu2+, a discontinuity in K+ release during metal incubation correlated with a decrease in subsequent 14C fixation. Some of the binding sites associated with the first phase of Cu2+ uptake (up to 12 μmol g‐1) are interpreted to occur near, on or within the algal cells. The larger K+ loss associated with higher Cu2+ uptake levels indicated that a component of the second Cu2+ uptake phase involved binding at or penetration of the fungal membranes. The uptake of Sr2+, Ni2+ and Zn2+ conferred some protection to samples subsequently exposed to 75 p.p.m. aqueous SO2 for 1 h, while Mg2+, and Ca2+ had no effect. The combined effects of Cu2+ uptake and SOS exposure (and also Pb2+ and SO8) were approximately cumulative. Finally, the results are explained by reference to a classification that separates metal ions into three chemically and biologically significant categories. It is concluded that class A metal ions (those with a preference for ionic interactions) and borderline metal ions with class A character tend to protect lichens against SO2 damage, while borderline metal ions with class B character (a preference for covalent interactions) have the opposite effect.
THE ROLE OF METAL‐ION BINDING IN MODIFYING THE TOXIC EFFECTS OF SULPHUR DIOXIDE ON THE LICHEN UMBILICARIA MUHLENBERGII
Authors: RICHARDSON D. H. S. , NIEBOER E. , LAVOIE P. , PADOVAN D.
Published: May 2006

Summary

Total 14C fixation in Umbilicaria muhlenbergii was not significantly affected at levels near the capacity of the first binding site (c. 12 μmol g‐1) of class A metal ions or borderline metal ions with class A characteristics: i.e. Sr2+, Mg2+, Ca2+, Ni2+, and Zn2+. Although both Cu2+ and Pb2+ are borderline ions with significant class B character, only Cu2+ greatly reduced fixation. However Ni2+ and Pb2+, as well as Cu2+, induced increased photosynthate release from lichen samples. Protection against damage due to SO2 exposure was rendered by the uptake of class A ions and even borderline ions except those normally accumulated intracellularly (Mg2+, Zn2+) or possessing the capacity to penetrate cells readily (Cu2+). Of the borderline ions tested, Pb2+, Cu2+ and Ni2+, as well as SO2, induced changes resulting in the incorporation of less 14C into ribitol and more into sucrose and other sugars during photosynthesis by the lichen samples. The presence of the class A ion Ca2+ caused a shift in the opposite direction. The presence of Ca2+, Ni2+, Pb2+, but not Cu2+, on the lichen tended to inhibit the large SO2‐induced shift away from ribitol production. The threshold levels of various metals reported from field studies to result in visible damage are discussed in terms of the observed photosynthetic perturbations, K2+ leakage and factors determining metal uptake by lichens. Finally, the ecological significance of the ability of Ca2+ to protect lichens against the damaging effects of air pollution is discussed.
PATHWAYS OF PLASTID DIFFERENTIATION IN SPIRODELA OLIGORRHIZA
Authors: PORATH D.
Published: May 2006

Summary

In light‐grown Spirodela oligorrhiza, a duckweed, chloroplasts complete differentiation in 2·5 days. When young green fronds are transferred to the dark, their plastids undergo ultrastructural changes that are retrogressive. Prolamellar bodies appear in the intergranal spaces within 12 to 18 h, while well‐developed amyloplasts can be seen after 11 days. Mature green fronds maintained in the dark for up to 3 months remain unchanged. The results are discussed in the context of monotropic and reversible pathways of plastid differentiation in higher plants.
CELL DOUBLING TIME IN THE APICAL MM OF ELONGATING LATERAL ROOTS OF VICIA FABA L.
Authors: THOMPSON A. , MacLEOD R. D.
Published: May 2006

Summary

Cell doubling time was determined in several ways in the apical mm of newly emerged, 0·2, 1 and 4 cm long lateral roots of Vicia faba L. and in every case it tended to decrease with increase in root length. Similar values were obtained in the roots of each length investigated when cell doubling time was calculated from the rate of passage of cells into the period of DNA synthesis (S) in both control and colchicine treated roots and from the rate of accumulation of cells in metaphase in the presence of colchicine, assuming cell number increased exponentially, i.e. colchicine had not affected the rate of entry of cells into mitosis or S during the 3 to 6 h period over which measurements were taken. A discrepancy was found, however, between the values determined for cell doubling time obtained from these rates and those calculated on the basis of the method devised by Evans and his co‐workers (Evans, Neary and Tonkinson, 1957). Possible reasons for such a discrepancy are discussed.
THE EFFECTS OF AIR POLLUTION ON PLANT GROWTH WITH SPECIAL REFERENCE TO SULPHUR DIOXIDE. III. GROWTH STUDIES WITH LOLIUM MULTIFLORUM LAM. AND DACTYLIS GLOMERATA L.
Authors: CRITTENDEN P. D. , READ D. J.
Published: May 2006

Summary

Lolium multiflorum cv. S22 and Dactylis glomerata cv. S143 were grown in a sealed glass chamber, force‐ventilated with ambient SO2‐polluted air and the yields compared with those of control plants grown in a second chamber receiving filtered air, free of SO2 and particulates. Shoot dry weight of both species was reduced by 30 to 40 % after 8 to 10 weeks in unfiltered air containing mean SO2 concentrations of 50 to 90 μg m−3, growth reductions being readily detectable after 3 weeks from transplanting seedlings to the chambers. The productivity of L. multiflorum was only marginally depressed (c. 10 %) by late summer SO2 levels in the range 10 to 50 μg m−3. It is suggested that grass plants may be particularly susceptible to SO2 pollution during the early growth phase following germination when aerodynamic resistance is low and relative growth rate maximal. The possibility that environmental factors other than SO2 pollution contributed to the inhibitory effect of the unfiltered air treatment is discussed.
TOLERANCE AND TOXICITY OF COBALT, COPPER, NICKEL AND ZINC IN CLONES OF AGROSTIS GIGANTEA
Authors: HOGAN GARY D. , RAUSER WILFRIED E.
Published: May 2006

Summary

Three clones of Agrostis gigantea were evaluated for their tolerance to cobalt, copper, nickel and zinc. Of the clones originating from a mine waste site in Sudbury, Ontario, one showed tolerance to copper, cobalt, and nickel, the other only to nickel. Neither of these clones showed tolerance to zinc. A clone from a seed supply house lacked tolerance to any of the metals tested. Copper was most toxic to A. gigantea, followed by nickel, cobalt and zinc.
THE BIOLOGY OF AMBROSIA TRIFIDA L.
Authors: Abul‐Fatih H. A. , Bazzaz F. A.
Published: May 2006

Summary

Ambrosia trifida L. is an annual plant found in repeatedly disturbed ground in the midwestern and eastern United States. When present, it dominates the community, producing most of the plant biomass and suppressing all associated species. When A. trifida was selectively removed in field plots early in the growing season, the biomass of the remaining species, their density and species diversity increased but the biomass of the community decreased. With A. trifida the total standing above‐ground plant biomass of the other species was 43.7 gm‐2, their density was 86 plants m−2 and the species diversity was 0.21. Without A. trifida the corresponding values were 666 g m −2, 584 plants m−2, and 1.64. Total above‐ground biomass of the community was 1640 with and 666g m−2 without A. trifida. Ambrosia trifida produced 97 % of the plant biomass. The negative correlation between biomass and diversity was undoubtedly caused by the strong dominance and high production of A. trifida. This species may be considered an ‘organizer’ or ‘keystone’ species which controls the properties of some annual communities in disturbed ground.
THE BIOLOGY OF AMBROSIA TRIFIDA L.
Authors: ABUL‐FATIH H. A. , BAZZAZ F. A. , HUNT R.
Published: May 2006

Summary

Ambrosia trifida plants were grown in monocultures in the field at five densities ranging from 4 to 500 plants m−2. Plant growth, productivity, biomass allocation, plant architecture, and seed predation were studied in repeated harvests. Plant growth was very plastic and the weight of individual plants was greatly influenced by density. Mean dry weight per plant varied from 11 g in the highest density to 320 g in the lowest density. At the final harvest in September the plants had lost up to 34% of their biomass through senescence of lower leaves. Above ground biomass production was extremely high and averaged from 1590 g m−2 in the lowest density to 3058 g m−2 in the highest density. Leaf area index was very high especially at high densities.

The relationship between plant height and density was complex and some individuals in the intermediate density were more than 3 m tall. Reproductive ratios, the weight of reproductive materials/shoot biomass, generally declined with increasing density and were significantly higher when the weight of the male flowers was added to the weight of seed. With time a pronounced decline in leaf area ratio occurred in all densities. There was no significant effect of density on unit leaf rate. The plants were able to discard their lower unproductive leaves in dense plots and effectively raised their canopy further up the stem. But this left much unproductive stem structure below and leaf area ratio and relative growth rate declined. Plants in high densities were single stemmed while those in the lowest density were much branched.

The presence in dense stands of tall and short plants created a bimodal distribution of leaf area and seed weight. Most seed biomass was located in the upper canopy of low density plants. The percentage of plants producing male flowers decreased with increasing density and, in the highest density, with decreasing height in the canopy. The shorter plants, without male flowers, had a higher reproductive ratio. They invested their reproductive energy into seed. Insects damaged many seeds and the percentage of damaged seeds per plant declined with increasing density. Furthermore in the population of highest density seed predation was higher in the ‘apparent’ tall plants than in less apparent short plants.
ALLEVIATION OF WATERLOGGING DAMAGE TO YOUNG BARLEY PLANTS BY APPLICATION OF NITRATE AND A SYNTHETIC CYTOKININ, AND COMPARISON BETWEEN THE EFFECTS OF WATERLOGGING, NITROGEN DEFICIENCY AND ROOT EXCISION
Authors: DREW M. C. , SISWORO E. J. , SAKER L. R.
Published: May 2006

Summary

A study was made of the effects of either 6‐benzylaminopuiine (BAP), a synthetic cytokinin, or calcium nitrate on the response of the shoots of 13‐day‐old barley plants to soil waterlogging. Spraying leaves daily with BAP resulted in small improvements in leaf extension and retarded the premature loss of chlorophyll in the older leaves after 7 days waterlogging, but the rates of accumulation of dry matter and inorganic nutrients in shoots were reduced to the same extent as in unsprayed plants. After a further 7 days waterlogging, during which spraying was discontinued, plants treated with BAP were no longer appreciably different from untreated ones.

When calcium nitrate was added daily to the surface of the waterlogged soil, no symptoms of waterlogging damage appeared. Leaf extension, shoot weight, emergence of tillers, chlorophyll concentrations and the accumulation of inorganic nutrients in shoots were similar to those in plants in non‐waterlogged soil after 7 and 14 days. The effect was dependent on the presence of a narrow zone of aerated soil close to the surface, in which root growth and function could continue.

When plants were grown for 13 days in aerated nutrient solution, and then transferred to solutions lacking nitrate, the development of leaf chlorosis, the decrease in the concentration of nitrogen in the shoots and their retarded accumulation of dry matter were all similar to that caused by waterlogging. The premature loss of chlorophyll in the older leaves was retarded by spraying with BAP. Chlorosis of the older leaves could also be promoted in plants in aerated nutrient solution by excising part of the root system.

Mechanisms by which BAP and calcium nitrate alleviate symptoms of waterlogging damage, and the significance of nitrogen deficiency and root excision in relation to waterlogging damage, are discussed.
THE DIFFERENTIAL TEMPERATURE RESPONSES OF THE GROWTH OF CERTAIN PLANT SPECIES FROM DIFFERENT ALTITUDES. I. GROWTH ANALYSIS OF PHLEUM ALPINUM L., P. BERTOLONII D. C., SESLERIA ALBICANS KIT. AND DACTYLIS GLOERATA L.
Authors: WOODWARD F. I.
Published: May 2006

Summary

The growth rates of Dactylis glomerata L. and Phleum bertolomii D.C., which ale essentially lowland species in Britain, show a large response to an increase in day temperature from 10 to 20 ° C. while those of Sesleria albicans Kit. which occurs from sea‐level to 900 m, and Phleum alpinum L. (600 to 1200 m) show little response.

These differences can be attributed to the greater leaf‐area ratio, and to the increased rates of both leaf‐initiation and leaf‐expansion of the lowland species at higher temperatures. Net assimilation rates are scarcely affected by temperature. The differences are therefore due to morphogenetic effects and not to differences in the rates of physiological processes.
THE DIFFERENTIAL TEMPERATURE RESPONSES OF THE GROWTH OF CERTAIN PLANT SPECIES FROM DIFFERENT ALTITUDES. II. ANALYSES OF THE CONTROL AND MORPHOLOGY OF LEAF EXTENSION AND SPECIFIC LEAF AREA OF PHLEVM BERTOLONII D.C. AND P. ALPINUM L.
Authors: WOODWARD F. I.
Published: May 2006

Summary

Independent temperature control of separate organs of seedling plants of Phleum bertolonii and P. alpinum indicates that the temperature of the first leaf and coleoptile exert the dominant temperature control of specific leaf area (SLA).

Rates of leaf extension in the upland species P. alpinum are slower than in the lowland species P. bertolonii. This difference is related in the main to the significantly greater number of cell generations involved in the expansion of the leaf and not to the cell generation time, which does not differ between the species. Experiments with the growth of callus cultures suggest that interspecific differences in the potential for cell growth do not account for the observed differences in leaf extension.

In both species the response of SLA to temperature is mainly a consequence of its influence on cell diameter. As a result it is the temperature in the region of cell expansion, within the leaf sheath, that will control SLA.
EFFECT OF HEAT TREATMENT AND THREE PESTICIDES UPON THE GROWTH AND REPRODUCTION OF THE MYCORRHIZAL FUNGUS GLOMUS FASCICULATUS
Authors: MENGE J. A. , JOHNSON E. L. V. , MINASSIAN V.
Published: May 2006

Summary

The effects of several heat treatments, a nematicide (DBCP) and two fungicides (ethazole and PCNB) on survival, infection, and sporulation by the mycorrhizal fungus Glomus fasciculatus, were examined. Inocula of G. fasciculatus were killed when exposed for 10 min at 52·5 °C, but not when exposed to 51·5 °C. Although inocula of G. fasciculatus survived a 10 min soaking in PCNB at several concentrations, infection and sporulation on Sudan grass were consistently inhibited by soil drenches with this fungicide. Soil drenches of DBCP (20μg ml−1 H2O) or ethazole (50 μg ml−1 H2O) applied at the time of inoculation with G. fasciculatus did not significantly affect infection and sporulation by the fungus on Sudan grass. However, soil drenches with DBCP (15 to 20 μg ml−1 H2O) and ethazole (10 to 40 μg ml−1 H2O) applied 30 to 60 days after inoculation significantly increased infection and sporulation by G. fasciculatus. All data indicate that the pesticides DBCP and ethazole could be used to reduce contamination and to increase the quantity of inoculum of G. fasciculatus.