bluuebunny/crossref_metadata_2025 huggingface dataset:
AN ASSOCIATION OF PHYTOCHROME WITH THE CHLOROPLAST ENVELOPE MEMBRANES OF SPINACIA OLERACEA L.: A PRELIMINARY OBSERVATION
Authors: HILTON JANET R.
Published: May 2006

The photoreceptor phytochrome has been localized in association with many membrane fractions isolated from etiolated plants. However, the presence of chlorophyll precludes similar measurements in light‐grown plants. Phytochrome has now been measured in chloroplast envelope membrane preparations which, when pure, are completely devoid of chlorophyll.
THE UPTAKE OF METHYLAMMONIUM AND DIMETHYLAMMONIUM BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM
Authors: WRIGHT S.A. , SYRETT P. J.
Published: May 2006

In agreement with previous work with several different organisms, methylammonium uptake by Phaeodactylum is shown to take place by a mediated transport process with Michaelis–Menten kinetics with a Ks of about 35 μM There was no evidence for more than one mediated uptake system. Uptake of methylammonium shows a strong dependence on metabolism. In contrast, uptake of dimethylammonium is by passive diffusion. Uptake of methylammonium, but not that of dimethylammonium, was Na* dependent although the rate of uptake of both compounds was depressed by increasing K+ concentration. Rates of uptake of both compounds increased as a consequence of nitrogen deprivation of the cells and were depressed by addition of low (ca. 2 to 10 μM) concentrations of ammonium, uptake of methylammonium being the more sensitive to ammonium inhibition. It is concluded that methylammonium is probably taken up by an ammonium transport system and that its use allows more detailed study of the characteristics of that system.
ABSCISIC ACID IN THE NODULATED ROOT SYSTEM OF ALNUS GLUTINOSA
Authors: WATTS S. H. , WHEELER C. T. , HILLMAN J. R. , BERRIE A. M. M. , CROZIER A. , MATH V. B.
Published: May 2006

Evidence for the presence of abscisic acid (ABA) in the perennial root nodules of Alnus glutinosa (L.) Gaertn. has been obtained by electron‐capture‐detection gas chromatography (GC–ECD), combined gas‐chromatography mass spectrometry (GC‐MS) and GC‐MS using single‐ion monitoring (GC‐SIM). The free‐ABA content of the nodules was shown by GC‐ECD analysis to fluctuate seasonally over the range 101 to 879 ng g−1 fresh weight. No obvious correlations were found between the amount of ABA detected and rates of nodule growth. However, ABA pools in dormant nodules were up to 25 times higher than in those from actively growing plants.
CHANGES IN CARBOHYDRATES AND NITROGENOUS COMPOUNDS IN THE ROOT NODULES OF ALNUS GLUTINOSA IN RELATION TO DORMANCY
Authors: WHEELER C. T. , WATTS S. H. , HILLMAN J. R.
Published: May 2006

Carbohydrate reserves for overwintering accumulate in the root nodules from late summer and begin to be utilized when leaf fall is virtually complete. It is probable that metabolism of these carbohydrate reserves supports in part the low nitrogenase activity which develops as buds swell and flush in early March, before substantial new photosynthates are translocated to the nodules. Higher rates of photosynthesis as leaves expand, and a reduction in the proportion of photosynthates retained by or translocated to buds as they flush, makes available more photosynthates for translocation to the nodules to support higher nitrogenase activity.

Soluble nitrogenous reserves also accumulate as leaves expand. Ammonia accumulates in the spring during early leaf expansion and could be of importance in repressing nitrogenase synthesis in the endophyte, reducing the demands of the nodule for limited supplies of photosynthates until leaf expansion is more advanced.

Sections of nodules show that the vesicular form of the endophyte largely degenerates during the winter months and new nitrogenase activity probably develops in new vesicles. Nodule meristematic activity recommences about bud burst. Earlier findings have shown high cytokinin activity in the nodules at this time.
INTERACTIONS OF VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTIONS AND HEAVY METALS IN PLANTS
Authors: GILDON A. , TINKER P. B.
Published: May 2006

Leeks were grown on a γ‐irradiated soil selected for its low copper status, in a factorial experiment with additions of phosphorus and copper, and with or without inoculation with Glomus mosseae. There was no response in growth to added phosphorus, but responses to added copper and to inoculation. The results indicate that an infection with mycorrhizal fungi can increase the supply of copper to the host plant, in conditions where increased phosphorus nutrition does not increase dry weight. It is suggested that copper is absorbed and translocated by mycorrhizal hyphae in a manner analogous to that which occurs for phosphorus.
SENSITIVITY OF FOREST PLANT REPRODUCTION TO LONG RANGE TRANSPORTED AIR POLLUTANTS:
Authors: COX R. M.
Published: May 2006

Although some studies have been made of the direct effects of wet deposition of acid on plants, few have examined its effects on plant reproductive processes. Reported here are the relative sensitivities of pollen germination and pollen tube growth from 13 forest species to a range of acidities found in ambient rainfall. In vitro assays indicate that pollen of all species tested was significantly influenced by pH's from 56 to 26. Two‐thirds of the species tested had pollen that was significantly inhibited in germination by pH 30 (1000 μEq H+I−1) whereas few effects were observed at pH 4–6 (25 μEq H+I−1). Broad‐leaved tree pollens were more sensitive to pH than those of conifers, and those of the understorey and ground flora species tested were of intermediate sensitivity. It is of concern that all values of LD50 for pollen germination response to initial culture pH were within the range of acid rain events in eastern Canada. Further research is required into the in vivo responses, to determine if reproduction in plants with sensitive pollen is inhibited by ambient levels of acid deposition.
GROWTH ANALYSIS OF SOYBEAN EXPOSED TO SIMULATED ACID RAIN AND GASEOUS AIR POLLUTANTS
Authors: NORBY R. J. , LUXMOORE R. J.
Published: May 2006

Greenhouse‐grown soybean plants [Glycine max (L.) Merr. cv. Davis] were exposed to simulated acid rain (pH 2.6 to 5.6) and gaseous air pollutants (SO2+ O3) to determine how effects on short‐term physiological processes are integrated into whole‐plant response. Injury to expanding leaves, characterized by marginal necrosis and leaf deformation, was induced by twice‐weekly exposure to simulated rain of pH 2.6 and to a lesser extent pH 3.4. Growth inhibition resulted only from exposure to rain of pH 2.6, and there were no significant pH x air pollution interactions. Growth analysis from periodic harvests indicated that inhibitory effects of rain of pH 2.6 were mediated through a reduction in leaf area ratio (LAR). The alteration in LAR was not attributable to reduced allocation of dry matter to leaves but to lower specific leaf area caused by leaf deformation. There were no effects of rain pH on unit leaf rate. A second experiment confirmed the lack of growth inhibition from simulated rain with pH > 3.4. Cumulative water use, a measure that integrated aspects of root size, leaf area, and physiology, was remarkably similar in plants exposed to pH 3.4, 4.2, or 5.6 simulated rain. These experiments suggest that vegetative growth of soybeans may be adversely affected by acid rain if pH is low enough to cause physical injury to leaves and loss of photosynthetic area.
GROWTH ANALYSIS OF THE SEEDLINGS OF BALSA, OCHROMA LAGOPUS
Authors: WHITMORE T. C. , WOOL‐KHOON GONG
Published: May 2006

In a glasshouse near Oxford, under conditions similar to a large gap in lowland tropical rain forest, young seedlings of balsa, Ochroma lagopus Swartz, had an estimated unit leaf rate (net assimilation rate) of 33 g m−2 week−1 compared to 44 g m−1 week−1 for Helianthus annuus. The energy conversion efficiency was 05 and 0–6 % of incident radiation 300 to 3000 ran respectively.

Unit leaf rates of woody plants have almost always been found to be lower than those of Helianthus, when both are grown side by side. The lowest rates relative to Helianthus are in Agathis, the only shade‐tolerant genus yet examined.
CARBON FIXATION IN ORCHID AERIAL ROOTS
Authors: GOH C. J. , ARDITTI J. , AVADHANI P. N.
Published: May 2006

Orchid aerial roots contained chlorophylls and were shown to be capable of photosynthesis. 14CO2 feeding in the light showed that the C3 pathway was operating during the day. Aerial roots also exhibited diurnal acidity fluctuations typical of crassulacean acid metabolism (CAM) and malate was the only labelled compound isolated after night 14CO2 feeding. CO2 exchange patterns in aerial roots were consistent with CAM CO., fixation during the night hours. The rate of photosynthetic CO., fixation in the light was much greater than the rate of CAM CO2 fixation in the night. Measurements of CO2 exchange, however, showed little or no net uptake indicating that these roots were not completely autotrophic.
OIDIODENDRON GRISEUM ROBAK: AN ENDOPHYTE OF ERICOID MYCORRHIZA IN VACCINIUM SPP.
Authors: COUTURE M. , FORTIN J. A. , DALPE YOLANDE
Published: May 2006

Osmium tetroxide was used to sterilize the surface of roots of Vaccinium angustifolium and V. corymbosum in order to isolate mycorrhizal fungi. Three isolates of sterile mycelium, all of similar cultural appearance, were obtained from V. angustifolium and were proved capable of forming ericoid mycorrhizas under aseptic conditions. Three isolates were also obtained from V. corymbosum and all formed conidiophores identified as Oidiodendron griseum Robak; they also formed ericoid mycorrhizas under aseptic conditions.
HYPHAL UPTAKE AND TRANSPORT OF NITROGEN FROM TWO 15N‐LABELLED SOURCES BY GLOMUS MOSSEAE, A VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS *
Authors: AMES R. N. , REID C. P. P. , PORTER L. K. , CAMBARDELLA C.
Published: May 2006

Celery (Apium graveolens L.) plants were grown in pots in which the root system was separated from the soil in a side chamber by a fine mesh screen. The side chamber was treated with either an organic (ground plant tissue) or inorganic [(NH4)2SO4] source of 15N. Mycorrhizal (Glomus mosseae) and control (non‐mycorrhizal) plants were exposed to 15N over a period of 30 days (inorganic‐15N) or 88 days (organic‐16N). Mycorrhizal and control plants did not differ in shoot dry weight or shoot P content. Dry weight of root was reduced in the mycorrhiza treatments. Mycorrhizal plants derived significantly (P= 0.01) more 16N, from both N sources, than did control plants. In the inorganic‐N treatment, 15N in mycorrhizal plants was significantly (P= 0.001) and positively correlated with percent mycorrhizal fungal colonization (r= 0.58), number of hyphal crossings (±10 μ diameter) through the mesh into the area of 15N placement (r= 0.76), total length of hyphae per gram of soil (r= 0.74), and length of hyphae of 5 μ diameter in the soil (r= 0.77). No correlations were found between the 16N content of mycorrhizal plants and any parameter in the organic‐N treatment. The 16N content of control plants was not correlated with hyphal length in the outer chamber and there were no hyphal crossings of the size ( 10 μ diameter) which was counted for the mycorrhiza treatments. The presence of the organic matter (ground plant tissue) increased the total length of saprophytic hyphae per gram of soil but decreased the number of vesicular‐arbuscular mycorrhizal fungal hyphae crossing into the area of 16N placement. The mean flux of N through the hyphae of G. mosseae was 7.42 × 10−8 mol N cm−2 s−1 for the inorganic‐N treatment over a 30‐day period, and 1.74 × 10−8 mol N cm−2 s−1 for the organic‐N treatment over an 88‐day period.
PHOSPHORUS ACQUISITION IN FOUR CO‐EXISTING SPECIES FROM MONTANE GRASSLAND
Authors: ATKINSON C. J.
Published: May 2006

Phosphorus acquisition was examined in four co‐existing species from montane grassland. The effect of inorganic phosphate (Pi) concentration on relative growth rate was studied and an attempt was made to determine whether inorganic or organic phosphates are the immediate sources of phosphorus for these plants using assays of Pi uptake kinetics and of root surface phosphatases. These data are also used to assess whether the availability of phosphorus might limit plant growth in this montane grassland.

Potential uptake rates are unlikely to limit growth via Pi supply. There appears to be no preference for a specific phosphate source for growth with any species examined. Mycorrhizal infection does not appear to be a prerequisite for successful phosphate acquisition in these co‐existing species.
DEVENSIAN LATE‐GLACIAL AND FLANDRIAN VEGETATIONAL HISTORY AT HOCKHAM MERE, NORFOLK, ENGLAND
Authors: BENNETT K. D.
Published: May 2006

The sediment and pollen stratigraphy of a radiocarbon‐dated sequence from a lake on the eastern margin of Breckland is described. The record extends from 12620 to 1620 B.P. From 12620 to 9560 B.P. the vegetation was an open Betula woodland. Movement of sand by wind was one factor keeping the vegetation open. Between 9560 and 9255 B.P. a denser Betula woodland developed, to be replaced by a closed woodland dominated by Corylus avellana, with Pinus sylvestris, Ulmus and Quercus. During this period, Quercus gradually replaced P. sylvestris on the local sandy soils. Corylus avellana remained the woodland dominant until about 7140 B.P., when it was replaced by Tilia cordata. Alnus glutinosa expanded in response to raised water levels at about 6800 B.P., Fraxinus excelsior became an important component of the local woods, also replacing C. avellana. The elm decline occurred in two phases, at 6000 and 4500 B.P. Substantial forest clearance did not begin until about 2500 B.P. The spread of heath vegetation on the Breckland began at about 2250 B.P.
SUBSTRATE FLOW AND UTILIZATION IN THE RHIZOSPHERE OF CEREALS
Authors: WHIPPS J. M. , LYNCH J. M.
Published: May 2006

Wheat and barley plants were grown for 3 weeks with their roots in sterile or non‐sterile sand or irrandiated or non‐irradiated soil and with their shoots in an atmosphere containing 14CO2 at constant specific activity and at approximately atmospheric concentration. The sealed pots were regularly flushed with air and the total quantity of radioactivity lost from the pots as respiratory 14CO2 and the amounts present in the plant rhizoplane, rhizosphere and bulk soil were analysed. Measurements of bacterial numbers allowed calculations of the utilization of the carbon released from the roots of the sand‐grown plants. The relevance of the techniques used and the implications of carbon loss for the plant and associated microorganisms are discussed.
EFFECTS OF LOCALIZED AND OVERALL WATER STRESS ON ASSIMILATE PARTITIONING IN BARLEY BETWEEN SHOOTS, ROOTS AND ROOT EXUDATES
Authors: SHONE M. G. T. , WHIPPS J. M. , FLOOD ANN V.
Published: May 2006

Polyethylene glycol 4000 (PEG) at an osmotic potential of −0.3 MPa had no effect on uptake of 14CO2 and partitioning between shoots and roots in barley. When an osmotic potential of −0.8 MPa was applied to the upper zone of the root system, total 14CO2 uptake and partitioning were unaffected but assimilate accumulated in the tips of nodal roots exposed to PEG. There was a parallel accumulation of soluble sugars. Transport of assimilates to the seminal root system declined. Exudation of soluble, labelled compounds by the roots was markedly diminished. When PEG was supplied to the upper root zone at −0.8 MPa and the lower zone at −0.6 MPa total 14CO2 uptake and assimilate transport declined, but there was still some accumulation of labelled compounds and soluble sugars in the nodal root tips and root exudation was diminished. The results are discussed in relation to assimilate partitioning, growth and osmotic adjustment in nodal roots.
APPLICATION OF SUPERPHOSPHATE TO MYCORRHIZAL PLANTS SITIMULATES SPORULATION OF PHOSPHORUS‐TOLERANT VERSICULAR‐ARBUSCULAR MY CORRHIZAL FUNGI *
Authors: SYLVIA D. M. , SCHENCK N. C.
Published: May 2006

Sporulation of Gigaspora margarita, Glomus clarum, Gl, mosseae and Gi. Heterogama was increased significantly after established pot cultures of bahiagras were drenched with superphosphate. However, sporulation of Gl. Etunicatum, Gl. Macrocarpum and Gi. Gigantean was reduced by the superphosphate drench. Generally, improved sporulation after application of superphosphate was associated with phosphorus (P)‐tolerance of the mycorrhizl fungi. Gigaspora margarita, Gl. Clarum and Gl. Mosseae could colonize roots in soil that had 199 mg kg −1of acid‐extractable P. The other fungi could not colonize roots in this high‐P soil. Removal of shoots, application of herbicide, and stresses from drought and exposure to cold and dark did not affect spore numbers significantly.
ENDOMYCORRHIZAS IN THE GENTIANACEAE
Authors: JACQUELINET‐JEANMOUGIN S. , GIANINAZZI‐PEARSON V.
Published: May 2006

The identity of mycorrhizal fungi in the Gentianaceae was investigated by inoculating Gentiana lutea L. with fungi from orchid, ericoid and vesicular‐arbuscular endomycorrhizas. Results clearly demonstrated that mycorrhizas in G. lutea are formed by vesicular‐arbuscular mycorrhizal fungi but have a very unusual morphology.
THE MYCORRHIZAL ASSOCIATIONS OF SOME AUSTRALIAN ASTERACEAE
Authors: WARCUP J. H. , McGEE P. A.
Published: May 2006

Some 80 species of Australian Asteraceae were examined for their ability to form ectomycorrhizal associations. Twenty‐seven species, all but one belonging to the tribe Inuleae, were found to form both ectomycorrhizas and vesicular‐arbuscular mycorrhizas. Species found to form ectomycorrhizas belong to Angianthus (sensu stricto), Podolepis, Pogonotepis, Waitzea, Helichrysum (pro parte) and Helipterum (pro parte); all are annual or perennial herbs. Four species shown to form ectomycorrhizas gave significant growth responses to inoculation with either an ecto‐or endomycorrhizal fungus in soil low in available phosphate.
RELATIONSHIPS BETWEEN SEED WEIGHT, ASH CONTENT AND SEEDLING GROWTH IN TWENTY‐FOUR SPECIES OF COMPOSITAE
Authors: FENNER M.
Published: May 2006

The relationship between seed weight, embryo weight, ash content and maximum size attained by seedlings dependent on their own food reserves was investigated in 24 species of Compositae.

The fraction of total seed weight contributed by the seed coat increased with seed weight from 15 % in Erigeron canadensis to 61 % in Tragopogon pratensis. Seedling weight was proportional to embryo weight raised to the power of 2/3. That is, the larger the embryo the less carbon it assimilated per unit weight of embryo. The relative growth rate of the seedlings during the first 3 weeks was inversely proportional to In embryo weight. The root weight ratios of the seedlings were inversely proportional to In embryo weight. The ash content of the seeds was negatively correlated with their weight but absolute mineral content per seed was directly proportional to maximum seedling size attained, regardless of seed size.

It is postulated that the relatively larger seed coats of big seeds are a defence against increased risk of predation. The ash contents and root weight ratios of the seedlings suggest that the growth of small seedlings is limited by soil nutrients and that of large seedlings by light.
EFFECT OF ETHYLENE ON GIBBERELLIC ACID‐I NDUCED PROTEASE ACTIVITY IN WHEAT ALEURONE LAYERS *
Authors: VARTY K. , ARREGUIN L. B. , MÜGGENBURG R MA. I. , MIJANGOS M. J. L. , TREJO B. A.
Published: May 2006

Ethylene‐stimulated gibberellic acid‐induced protease synthesis in isolated wheat aleurone layers (Triticum aestivum L.) by about 60%. Ethylene did not change the isoelectric focusing pattern of protease isoenzymes, indicating that the hormone promoted only quantitative changes in protease synthesis rather than activating genes for different proteolytic enzymes. The pH optimum and Km of the enzyme with respect to N,N'‐dimethylhaemoglobin were 3.5 and 0.102% respectively. The purified protease consisted of a single polypeptide with a molecular weight of 43 700 daltons. These physical characteristics of gibberellic acid‐induced protease were unaffected by ethylene.
VEGETATION AND SOIL FACTORS ON A HEAVY METAL MINE SPOIL HEAP
Authors: THOMPSON JILL , PROCTOR J.
Published: May 2006

The vegetation of a small Scottish metal‐mine spoil heap was sampled by means of 70 0.25‐m2 quadrats and classified into three groups. The most common species were Agrostis capillaris and Festuca rubra which were important constituents of all three groups. Soil samples were collected from each quadrat and analysed for pH, loss‐on‐ignition, heavy metal and nutrient elements in the soil solution and for several physical properties. The mine spoil was physically and chemically heterogenous with many of the soil solution samples having potentially toxic concentrations of copper, lead and zinc. The vegetation data were ordinated: axis 1 of the ordination was significantly correlated (positively) with all three heavy metal concentrations, silt and sand, and (negatively) with loss‐on‐ignition and potassium concentration; axis 2 was significantly negatively correlated with pH and calcium, nitrate and phosphate concentrations. Consideration of this ordination and comparisons between soil parameters associated with each of the three vegetation groups and with non‐vegetated quadrats, suggest that lead and zinc may be the major determining factors of the spoil‐heap vegetation. Low nutrients (except phosphate) and in some cases adverse soil physical factors might be important also. The apparently small influence of copper is discussed. Above‐ground parts of five plant species were collected from the mine spoil and were shown often to have high heavy metal concentrations which differed between species. Finally we discuss some implications of interspecific differences in metal‐mine occurrence within the genera Agrostis and Festuca.
EFFECTS OF CYCLOHEXIMIDE AND CHLORAMPHENICOL ON CHLOROPLAST REPLICATION IN SYNCHRONOUSLY DIVIDING CULTURED CELLS OF EUGLENA GRACILIS
Authors: HASHIMOTO HARUKI , MURAKAMI SATORU
Published: May 2006

Summary

Chloroplast replication and division of Euglena gracilis Z cells cultured synchronoulsy under a diurnal light–dark regime (14:10h light: dark) proceeded in the dark period and were completely inhibited by 5 μg ml1 cycloheximide (CHI) added during the dark period. In the presence of 2 μg ml−1 CHI, chloroplast replication slowed but could be accomplished by the end of a prolonged 24 h dark period, while both the cell and nuclear division were completely inhibited. Chloroplast replication in the presence of 2 μg ml1 CHI was completely inhibited if the dark period was replaced by a light period. Chloramphenicol (CAP) (1 to 2 mg ml−1) slightly inhibited chloroplast replication while accumulation of chlorophyll and total cellular protein were considerably reduced. From the results presented it is concluded that chloroplast replication in synchronously cultured cells of Euglena gracilis is dependent on cytoplasmic protein synthesis that takes place during the dark period rather than chloroplastic protein synthesis, and that a putative protein(s) involved in chloroplast replication is inactivated by light.
DIFFERENTIAL STARCH DEPOSITION: A ‘MEMORY’ HYPOTHESIS FOR NOCTURNAL LEAF MOVEMENTS IN THE SUN‐TRACKING SPECIES LAVATERA CRETICA L.
Authors: FISHER F. J. F. , FISHER P. M.
Published: May 2006

Summary

Oblique illumination of the lamina of Lavatera cretica produces asymmetrical deposits of starch as a function of light‐shadow patterns owing to surface irregularities. Asymmetrical deposits, produced immediately after sunrise each day, are believed stored until shortly before the next sunrise. During daytime tracking, deposits are evenly symmetrical. Overnight conversion of these even deposits is believed to continue for most of the night. Shortly before sunrise, however, only residual asymmetrical deposits remain to be converted. Resulting solute asymmetries in the translocation stream are believed to trigger turgor gradients in the pulvinus, so producing anticipatory movements just before dawn. Pre‐dawn movements thus actually repeat those accompanying the previous post‐dawn oblique lighting. Changing solute gradients across the pulvinar phloem, originating from shifts in sunlight direction, are cited as the probable cause of normal tracking adjustments.
COMPARISON OF NUTRIENT SOLUTIONS FOR GROWTH OF PLANTS IN SAND CULTURE
Authors: SMITH G. S. , JOHNSTON C. M. , CORNFORTH I. S.
Published: May 2006

Summary

A comparison of eight different nutrient solutions showed large differences in ability to support growth of maize, ryegrass and white clover in silica sand. Plants grown with the Ruakura solution, a solution especially designed for pasture species, consistently outyielded those grown with the other nutrient solutions. Insufficient iron was a major cause of poor growth with many of the solutions, particularly for maize. However, where deficiencies of iron were corrected, growth differences, although smaller, still persisted among the nutrient solutions. Results of tissue analysis and measurements of the solution surrounding the roots showed a considerable number of individual factors which were likely to be yield limiting.
EVIDENCE FOR THE ABSENCE OF CHROMOSOME DIFFERENTIATION IN POPULATIONS OF SILENE MARITIMA WITH. GROWING ON HEAVY‐METAL‐CONTAMINATED SITES
Authors: COBON ANDREA M. , MURRAY B. G.
Published: May 2006

Summary

Silene maritima, a species that grows on coastal shingle and heavy‐metal‐contaminated mine spoils, was investigated to see whether these populations show any chromosomal differentiation. Karyotype studies do not reveal any difference between populations from metal‐free and metal‐contaminated habitats. Similarly, studies on the meiotic behaviour and pollen fertility of F1 hybrids between plants from the two types of habitat show no indication of chromosome change accompanying the evolution of metal tolerance.
A FURTHER POLLEN ANALYTICAL STUDY OF THE BLACKLANE PEAT SECTION ON DARTMOOR, ENGLAND
Authors: Simmons I. G. , Rand J. I. , Crabtree K.
Published: May 2006

Summary

The Blacklane Brook profile, first published in 1964, has been re‐examined and given firm dating in the light of the archaeological and fossil tree‐line interest that the profile has generated. A much fuller record of the open vegetation of Flandrian I is presented, and many new pollen types for the site are indicated. The recession phase noted in 1964 is found in this profile also and is dated to begin ca. 7760 BP. It is thus placed well within the Mesolithic cultural period. The resolution of the pollen diagram and the difficulties of interpretation of upland sites do not make it possible to make firm statements about the location of the tree‐line at different periods.
LEAF STOMATAL DENSITY AND DIFFUSIVE CONDUCTANCE IN THREE AMPHISTOMATOUS HYBRID POPLAR CULTIVARS
Authors: REICH PETER B.
Published: May 2006

Summary

Stomatal density and diffusive conductance were characterized for both leaf surfaces in three amphistomatous hybrid cultivars of poplar. Consistent differences in stomatal density were observed between cultivars and between leaf surfaces within a cultivar. Mean stomatal density in the three cultivars ranged from 150 to 330 stomata mm−2 for abaxial leaf surfaces and from 75 to 100 stomata mm−2 for adaxial surfaces. The density of stomata on the abaxial versus adaxial surface was related to the spatial orientation of leaves with respect to the horizon and this stomatal ratio ranged from 1–4 to 4–0 in the three clones. Also, stomatal density was greater in leaves at higher rather than lower nodal positions.

Differences in diffusive conductance between cultivars and leaf surfaces were observed on intact and detached leaves in the light and dark. Within each cultivar mean abaxial conductance (Kab) was greater than adaxial conductance (Kad). Mean conductances in the light for the three cultivars ranged from 0–22 to 0–62 cm s−1 for abaxial, and from 0–15 to 0–17 cm s−1 for adaxial surfaces, and in the dark they were between 0.06 and 0.26 cm s−1 for abaxial, and from 0–04 to 0–06 for adaxial surfaces. The differences in conductance between cultivars and between leaf surfaces were correlated with their respective stomatal densities. Stomatal response to light and to leaf excision also varied between cultivars and between the two leaf surfaces.
BISULPHITE‐INDUCED PIGMENT DAMAGE IN THE BLUE‐GREEN ALGA NOSTOC CALCICOLA BRÉB.
Authors: SINGH S. P. , SINGH R. P.
Published: May 2006

Summary

Damage to photosynthetic pigments is a useful criterion for assessing damage to aquatic plants exposed to bisulphite. The bisulphite‐induced damage to Chi a, carotenes and phycobilins in cells of Nostoc calcicola was dependent on both concentration and pH. Carotenes seemed most resistant to bisulphite, while phycocyanin was severely damaged even at extremely low levels of bisulphite. Higher bisulphite levels could be tolerated when the pH was initially adjusted to pH 8.0. The short‐term experiments revealed a shifting of the Chi α peak from 430 to 410 nm. The possible mechanisms leading to bisulphite‐induced pigment damage are discussed.
COBALT AND NITROGEN FIXATION IN LUPINUS ANGUSTIFOLIUS L.
Authors: DILWORTH M. J. , BISSELING T.
Published: May 2006

Summary

Bacteroids from cobalt‐deficient root nodules of Lupinus angustifolius L. cv. Unicrop were isolated and assayed for products of the cobalamin‐dependent enzymes methionine synthetase, ribonucleotide reductase and methylmalonyl‐CoA mutase.

Since bacteroids from lupin nodules did not show propionate‐dependent O2 uptake, it was not possible to assess whether in vivo action of methylmalonyl‐CoA mutase was affected, although it appears unlikely to be of major significance.

Cobalt deficiency decreased the DNA content per bacteroid in crown nodules, but not in later‐formed lateral nodules. The percentage of amino‐acid nitrogen accounted for by methionine was also lowered in bacteroids from crown nodules but not lateral nodules.
FLUXES OF PHOSPHORUS IN LEAVES OF BARLEY INFECTED WITH BROWN RUST
Authors: AHMAD I. , FARRAR J. F. , WHITBREAD R.
Published: May 2006

Summary

The movement of 32P, fractionation of 32P and unlabelled phosphorus, and efflux of 32P from leaf discs, in control and brown‐rust infected first leaf blades of barley are described for the day of sporulation, 7 d after infection. It is shown that P retranslocation is greatly reduced by disease, that the concentration of P in the infected leaf blade increases greatly and that the increase is probably largely in the fungus, and partly in the form of polyphosphate. The P content of fungal spores is derived largely from P currently entering the leaf in the xylem. The data are used to derive P budgets for control and infected leaf‐blades, and the significance of P to the diseased state is discussed.
OBSERVATIONS ON DRECHSLERA LEAF SPOT ON LOLIUM PERENNE AFFECTED BY CADMIUM
Authors: SCHOLES J. D. , SHATTOCK R. C.
Published: May 2006

Summary

Chlorotic patches in a three year old ley of Lolium perenne L. were associated with high concentrations of cadmium, lead and zinc in the soil. L. perenne in these patches was severely affected by Drechslera leaf spot. When cadmium at 10 to 25 μg cm−3 was added to plants grown in solution culture, or in soil as simulated swards, levels of disease resulting from inoculation were up to 10 times greater than on plants grown in cadmium‐free solution or soil. Cadmium reduced the dry weight of roots and especially shoots in both inoculated and uninoculated plants and accumulated in root and shoot tissues. Cadmium uptake decreased the uptake of potassium.
THE RESPONSE OF BARLEY LEAF EPIDERMAL CELLS TO INFECTION BY SEPTORIA NODORUM
Authors: KEON J. P. R. , HARGREAVES J. A.
Published: May 2006

Summary

The inability of Septoria nodorum Berk, to penetrate barley leaves was associated with the development of papillae beneath penetration sites and a modification to the structure of the cell wall surrounding papillae. Penetration hyphae did not progress further than the outer cellulose layers of the wall.

Reaction sites (papillae and modified cell walls) were isolated using cellulase. Modified cell walls were resistant to cellulase and did not react with zinc chlor‐iodide, indicating that the cellulose microfibrils were protected from both the enzyme and the stain. Material deposited in the interfibrillar spaces appeared to be responsible for this protection. Callose could not be detected in papillae; however, this may have also been due to encrusting substances which prevented callose reacting with aniline blue. The material deposited within papillae appeared to be similar to that deposited in cell walls. Lignin could not be detected in reaction sites. Intense staining with Coomassie brilliant blue R250 and periodic acid Schiff's reagent suggested that both proteins and carbohydrates were deposited in these structures. The possibility that these deposits were glycoproteins is discussed.
THE INFLUENCE OF LIGHT AND POTASSIUM NITRATE ON THE DORMANCY AND GERMINATION OF AVENAFATUA L. (WILDOAT) SEED AND ITS ECOLOGICAL SIGNIFICANCE
Authors: HILTON JANET R.
Published: May 2006

Summary

It has been suggested that applications of nitrogen‐containing fertilizers can stimulate the germination of dormant Avena fatua L. seed in the field and may be used to reduce numbers of seeds in the soil. However, it is not clear whether a subsequent cultivation imposing a light treatment on a proportion of the buried seeds is also necessary. To study this question potassium nitrate (KNO3) was applied to dormant seed of A. fatua in darkness and in light under controlled laboratory conditions. Potassium nitrate had very little effect on germination in darkness but concentrations of 2 × 10−4, 2 × 10−3 and 2 × 10−2 M stimulated germination in the light. The degree of stimulation by light was related to the proportion of phytochrome that was maintained as Pfr, the physiologically active form. In the presence of 2 × 10−1 M KNO3 no germination occurred either in light or in darkness.
ANION ACCUMULATION BY LICHENS
Authors: NIEBOER E. , PADOVAN D. , LAVOIE P. , RICHARDSON D. H. S.
Published: May 2006

Summary

Phosphate and sulphite competed effectively with arsenate when samples of Umbilicaria muhlen‐bergii (Ach.) Tuck, were incubated in arsenate solutions in the presence of increasing concentrations of the second anion. Equimolar amounts of phosphate had no effect on arsenate uptake while an 100‐fold excess of the former caused almost complete cessation of arsenate uptake. By contrast, sulphate enhanced arsenate uptake by lichen samples while acetate had no effect.

In experiments on phosphate‐arsenate competition it was possible, by regarding the latter as an inhibitor, to evaluate the kinetics of phosphate uptake in If. muhlenbergii. The Km of 660 μM and the Vmax. of 0.059 μmol min−1 indicated that the lichen took up some ten times more arsenate than phosphate per unit time. Studies of photosynthetic fixation of 14C revealed that a reduction in photosynthesis was related to the amount of arsenate accumulated. Conditions which enhanced arsenate uptake (e.g. stimulation by sulphate) resulted in greater photosynthetic inhibition, while those that reduced uptake (e.g. inhibition by phosphate) had an ameliorating effect. The ecological implications of these results are discussed.
FURTHER ANALYSIS OF THE IN VITRO PHYTOCHROME MEDIATION OF THE AMOUNT OF GIBBERELLIN‐LIKE SUBSTANCES IN ETIOPLAST‐ENRICHED SUSPENSIONS ISOLATED FROM HORDEUM VULGARE L. LEAVES
Authors: HILTON JANET R.
Published: May 2006

Summary

Gibberellin‐like substances were extracted from light‐treated etioplasts to test the hypothesis that phytochrome controls their efflux. Results obtained using sucrose density centrifugation showed that phytochrome mediates a change in the extractability of gibberellins and does not mediate changes in the permeability of the etioplast envelope membrane with respect to gibberellins, as previously proposed.
EXAMINATION OF THE CUTICULAR SURFACES OF FRESH DELICATE LEAVES AND PETALS WITH A SCANNING ELECTRON MICROSCOPE: A CONTROL FOR ARTEFACTS
Authors: EVELING D. W.
Published: May 2006

Summary

The cuticle surfaces of fresh, uncoated petals of Nicotiana alata Link & Otto and leave of Phaseolus coccineus L., Coleus blumei Benth. and Dactylis glomerata L. were examined in a canning electron microscope using a range of accelerating voltages, beam currents and recording scan times. The best micrographs of undamaged and unwrinkled cuticles, taken at magnifications ranging from 500 to 5000. were‐obtained using an accelerating voltage of 10kV, a low beam current and a recording scan time of 40 s. Fixation of the cuticles with osmium tetroxide vapour neither reduced charging nor improved preservation.

The examination of the fresh uncoated cuticles proved an acceptable check or control for other methods used to prepare the auricles for scanning elecrron microscopy.
A MATHEMATICAL DESCRIPTION OF THE EFFECT OF RESATURATION ON NET PHOTOSYNTHESIS IN THE LICHEN, PARMELIA PRAESIGNIS NYL.
Authors: LINK S. O. , NASH T. H.
Published: May 2006

Summary

Resaturation respiration occurs in Parmelia praesignis Nyl., although it is not strongly developed as in other lichens. Less than 2 h was required for full recovery of photosynthetic ability after having been dry for at least 5 weeks. After three daily, 4 h soaking periods the time for recovery was reduced to 11 min. The resaturation phenomenon is mathematically described for the first time as a negative exponential from which parameters can be derived for maximal net photosynthetic rate, maximal velocity and the velocity at the half‐time for recovery. Net photosynthetic rate was independent of the period of drought. The velocity at the half‐time for recovery increased by 81% after one soaking period and by 990% after two.
CRASSULACEAN ACID METABOLISM IN YOUNG ORCHID LEAVES
Authors: GOH C. J. , WARA‐ASWAPATI O. , AVADHANI P. N.
Published: May 2006

Summary

Acidity fluctuations typical of Crassulacean acid metabolism (CAM) were observed in both young and mature leaves of a succulent orchid hybrid Arachnis Maggie Oei. The maximum level of acidity in young leaves was only half the peak value in the mature leaves. The stomatal rhythm and CO2 gaseous exchange of mature leaves exhibited CAM characteristics, whereas young leaves showed typical non‐CAM behaviour with low stomatal resistance and a net CO2 uptake during the day, high resistance and a net CO2 output during the night. The stomatal movement of both young and mature leaves was regulated by the internal CO2 concentration of sub‐stomatal chamber.
SUCROSE ACCUMULATION AND THE INITIATION OF FRUCTAN BIOSYNTHESIS IN LOLIUM TEMULENTUM L.
Authors: POLLOCK C. J.
Published: May 2006

Summary

Plants of Lolium temulentum L. grown at 20 °C were transferred to 5 °C at the beginning of the light period. Sucrose accumulation was much more marked at low temperatures, with increases in rate detectable about 1 h following transfer. Exposure to low temperature over 7 d resulted in appearance of fructan, initially as oligosaccharides, and eventually as polymers of higher molecular weight. Sucrose accumulation was most marked in the blades of mature leaves, whereas the accumulation of fructan was maximal in the meristernatic regions of developing leaves. Chilling also led to a rise in activity of sucrose: sucrose fructosyltransferase, the first enzyme specifically involved in the biosynthesis of fructans. This activity was also higher in leaf meristems than in other regions of the plant.
COMPUTER CONSTRUCTION AND TYPESETTING OF IDENTIFICATION KEYS
Authors: PAYNE R.W.
Published: May 2006

Summary

The ability to produce computer files containing keys, together with the commands necessary to typeset them directly from the program that constructs them, greatly simplifies the production of high quality identification keys.
SODIUM TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK
Authors: RITCHIE R. J. , LARKUM A. W. D.
Published: May 2006

Summary

Sodium transport was studied in the marine euryhaline alga,Enteromorpha intestinalisin seawater (465 mM Na+and in low salinity medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cr, 20.4 mM Na+, 0.5 mM K+]. The intracellular Na+concentration ([Na+1]) ofE. intestinaliswas so low that it was difficult to detect using chemical and22Na+methods. Consequently, intracellular Na+fluxes were also difficult to measure. Most of the Na+of theEnteromorphatissue was bound to the fixed negative charges of the cell wall and this binding has, in previous studies, led to great overestimates of the intracellular Na+of this plant‐Data of22Na+labelling gave lower estimates of the Na+1] than a rinsing technique using isotonic Ca(NO3)2. The overall mean [Na+1] of seawater plants was only 5.5 ± 1.4 mM, with a value of 0.623 ± 0.163 mM Na+in ACBSW plants. With one exception, all the seawater22Na+experiments indicated a single intracellular exchange phase, i.e. a separate vacuolar phase could not be detected. The data on plants grown at low salinity could be interpreted as having either a single intracellular phase or two intracellular phases because of the problem of cell wall Na+exchange. No significant difference was found in total22Na+uptake or exchange fluxes in the light and dark in seawater‐grown plants but there may have been a light effect on low salinity plants. The Na+flux inEnteromorphaplants in seawater was about 3 nmol m−2s−1and in low salinity plants was about 0.2 nmol m−2s−1.

Sodium inEnteromorphais far from electrochemical equilibrium (more than –100 mV) in plants in both seawater and ACBSW medium so that Na+is actively excluded from the cells. The plasmalemma has a very low Na+permeability (seawater, 3 pm s−1; ACBSW plants, either 3 or 100 pm s−1depending on which compartmentation model is accepted).
EFFECT OF EDTA ON ENDOGENOUS MANGANESE DURING INDOLEACETIC ACID‐INDUCED GROWTH OF A VENA COLEOPTILE SEGMENTS
Authors: KRISHNA T. MOHAN , BHARTI SUDHAKAR
Published: May 2006

Summary

The effect of ethylenediamine tetracetic acid (EDTA) on endogenous Mn2+ was studied by electron spin resonance (ESR) spectroscopy during indoleacetic acid (IAA)‐induced growth of Avena coleoptile segments. An enhancement in the concentration of endogenous Mn2+ was recorded in coleoptile segments treated with low concentrations (1 × 10−6 M) of EDTA or ethyleneglycol‐bis‐(β‐aminoethylether) N, N″‐tetracetic acid (EGTA ‐ 1 × 10−6 to 1 × 10−5 M), while at higher concentrations both EDTA and EGTA appeared to chelate Mn2+. An intermediate concentration of EDTA (5 × 10−5 M) interacted with IAA in enhancing the growth, while both lower (1 × 10−6M) and higher (5 × 10−6M) concentrations inhibited IAA‐induced growth. Inhibition of IAA‐induced growth at higher concentrations of EDTA was reversed by exogenous Mn2+. Concentration of endogenous Mn2+ declined further when IAA was present along with different concentrations of EDTA, except in coleoptile segments treated with 5 × 10−4 M EDTA. The data suggest that endogenous Mn2+ is essential for IAA‐induced growth and that a precise balance of free to bound/complexed Mn2+ may be involved in IAA action.
OBSERVATIONS ON FREE‐LIVING TREBOUXIA DE PUYMALYAND PSEUDOTREBOUXIA ARCHIBALD, AND EVIDENCE THAT BOTH SYMBIONTS FROM XANTHORIA PARIETINA (L.) TH. FR. CAN BE FOUND FREE‐LIVING IN NATURE
Authors: BUBRICK P. , GALUN MARGALITH , FRENSDORFF A.
Published: May 2006

Summary

The presence of free‐living Trebouxia and/or Pseudotrebouxia is documented. Several free‐living phycobionts were brought into culture and compared to the cultured Xanthoria parietina phycobiont. With the aid of both morphological and immunological criteria, we provide evidence that both the mycobiont and phycobiont of X. parietina can be found free‐living in nature. The potential for resynthesis between bionts under natural conditions is discussed.
LONGEVITY AND PRODUCTIVITY OF LEAVES OF A CULTIVATED ANNUAL, GLYCINEMAX MERRILL
Authors: MIYAJI KEN‐ICHI
Published: May 2006

Summary

To understand the structure and dynamics of the leaf population composing a canopy, a life table analysis using rates of leaf emergence, mortality and dry matter production was applied to the foliage of soybean plants grown at three densities and sown at three times.

The mean leaf longevity differed greatly depending on the time of sowing, but in the early sown plants little difference was found among the leaves of lower and middle layers of the canopy in spite of the wide difference in the irradiance of the layers.

The rate of net photosynthesis of upper leaves in full daylight tended to decline gradually owing to senescence in leaves older than 20 d. That of lower‐layer leaves, in very dark conditions, decreased very rapidly owing to both shading and senescence. Analyses of the survivorship curves and the time trends of net photosynthetic rates showed that lower leaves in densely planted populations survived for quite a long time after they had lost the ability to produce additional dry matter.

The rate of canopy net photosynthesis tended to follow a saturation curve with the increase in the leaf area index of whole canopy. There was no optimum leaf area index that maximized canopy photosynthetic rate.
IRON REQUIREMENTS OF C3 AND C4 PLANTS
Authors: SMITH G. S. , CORNFORTH S. , HENDERSON H. V.
Published: May 2006

Summary

Plants having the C4, photosynthetic pathway required higher concentrations of iron in the nutrient solution for maximum growth when grown in sand culture than those with the C3 pathway. There were only small differences among species in the concentration of iron required in the leaves to achieve near maximum dry matter yield. This suggests that C3 and C4 plants differ in their ability to absorb iron from the root zone. Higher concentrations of iron were required in the nutrient solution for maximum growth of both the C3 and C4 plants when nitrate, rather than ammonium nitrate, was the sole source of nitrogen. It seems likely that when nitrate was used, there was a decrease in availability of iron to the plant as a result of the increased alkalinity in the root zone. By contrast, the root zone was acidified when ammonium nitrate was applied. Iron concentrations greater than 2 to 5 μg Fe ml−1 in the nutrient solution reduced the dry matter yields of a number of plants grown with ammonium nitrate as the nitrogen source, probably because of a decrease in the absorption of phosphorus by the roots.
OBTAINING A STERILIZED SOIL FOR THE GROWTH OF ONOCLEA GAMETOPHYTES
Authors: RUBIN GAIL , PAOLILLO D. J.
Published: May 2006

Summary

Autoclaved soils totally inhibited germination of spores of the fern, Onoclea sensibilis. Gamma‐irradiated soil sometimes allowed germination and growth, whereas germination and growth on ashed soil was entirely reproducible. All methods of sterilization produced sterile soil, but only ashing produced a medium acceptable for use in other experiments. Experiments with mineral solutions suggest that the failure of sterilized soil to support germination is due to toxic compounds rather than nutrient deficiency. Ashing the toxic soils removed the inhibitory compounds, which seemed to be related to the breakdown of organic matter during sterilization by autoclaving and gamma irradiation. On gamma‐irradiated soil, germination was promoted by removal of ethylene from the atmosphere around the spores, but subsequent growth failed, probably due to other inhibitors formed in the soil during irradiation.
STUDIES ON NITRATE REDUCTASE IN BRITISH ANGIOSPERMS
Authors: HIPKIN C. R. , Al GHARBI A. , ROBERTSON K. P.
Published: May 2006

Summary

In vivo nitrate reductase (NR) activity was measured in the leaves of plants from woodland, wooland‐edge and open (ruderal) communities. Nitrate reductase activity was highest in the youngest fully‐expanded leaves of all plants sampled. Nitrate reductase activity in populations from woodland and woodland‐edge increased after feeding with nitrate; feeding with Mo had no significant effect. During the day NR activity in plants from each community increased to a maximum near the middle of the photoperiod and then decreased. These daily changes are discussed in terms of the possible regulatory roles of light and the transport of nitrate to the shoot.