bluuebunny/crossref_metadata_2025_split huggingface dataset:
ROOT EXUDATION IN COWPEA AND SORGHUM AND THE EFFECT ON SPORE GERMINATION AND GROWTH OF SOME SOIL FUSARIA
Authors: AYOODUNFA V. S. 
Published: May 2006

SUMMARYExudation patterns in cowpea and sorghum seed and seedlings were studied using a filter paper technique. Profuse exudation was observed from cowpea seeds but this decreased considerably 2 days after germination. Root tips of primary, lateral, and adventitious roots were found to be the major sites of exudation but the older parts of seedling roots also exuded significant quantities of amino acids. Exudates from the roots of both species enhanced the germination of conidia of four Fusarium species previously isolated from the rhizosphere and rhizoplane. The germ tubes and some conidia were lysed by cowpea exudate in 48 h. Mycelial growth in liquid culture was enhanced in cowpea root exudate medium but was scanty in sorghum exudate; the presence of antifungal substance was suspected in the latter. The significance of the results obtained in relation to microbial root colonization and pathogenesis is discussed.
THE MEASUREMENT OF TOLERANCE TO EDAPHIC FACTORS BY MEANS OF ROOT GROWTH
Authors: WILKINS D. A. 
Published: May 2006

SUMMARYThe tolerance of plants to toxic metals is frequently measured by comparing rates of root growth in culture solutions with and without the addition of the metal, but many variants of the technique are available. Toxicity is often reduced by the presence of other ions, particularly calcium. Control growth rates may be measured beforehand on the same roots or in parallel on a duplicate set. With a single toxic concentration tolerance is defined as the ratio of the two growth rates; with a range of concentrations the slope of the regression of growth on concentration may be used, but there are some complications with stimulation at low concentrations. Probit analysis may be valuable. There is good evidence that tolerance differences are largely of genetical origin.
ECOLOGICAL PHYSIOLOGY OF THE LICHEN HYPOGYMNIA PHYSODES IV. CARBON ALLOCATION AT LOW TEMPERATURES
Authors: FARRAR J.F. 
Published: May 2006

SUMMARYA simple three‐compartment model is used to test the assertion that lichens show low incorporation of assimilate into structural material. Changing specific activities of three fractions equated with the compartments of the model are followed using carbon‐14. It is concluded that lichens show tight control over the synthesis of structural material.
SEASONAL VARIATION IN THE CAPACITY FOR NITROGENASE ACTIVITY IN THE LICHEN STEREOCAULON PASCHALE
Authors: HUSS‐DANELL KERSTIN 
Published: May 2006

SUMMARYThalli of Stereocaulon paschale (L.) Fr. were collected at approximately monthly intervals during a 13‐month period from a pine forest in northern Sweden. The capacity for nitrogenase activity (C2H2‐reduction) was studied on each collection under standardized, favourable laboratory conditions. Significantly higher capacities were found in thalli collected from bare ground than in thalli collected under snow, but the capacity decreased in autumn close to the snow covering. At snow melt the increase in capacity was rapid.To investigate the decrease in capacity during the autumn, S. paschale was exposed to simulated autumn conditions in the laboratory during 2‐week periods. These simulation experiments indicated that the light regime was of importance for nitrogenase activity. Low irradiance during short days caused a marked decrease in the nitrogenase activity, especially in combination with night temperatures above freezing. Night temperatures below zero, per se, did not reduce nitrogenase activity; instead a tendency to stimulate it was found.
ROOT FORMATION IN CUTTINGS OF APPLE (cv. BRAMLEY'S SEEDLING) IN RELATION TO RINGBARKING AND TO ETIOLATION
Authors: DELARGY J. A. , WRIGHT C. E. 
Published: May 2006

SUMMARYThe effect of excising a cylinder of bark from the base of growing shoots on subsequent root formation in the cuttings was examined in the difficult‐to‐root apple scion variety ‘Bramley's Seedling’. Ringbarking was found to enhance root formation only in etiolated segments of stem and when it was made proximal to the etiolated segment, since root formation took place preferentially distal to the ringbark. A second distal ringbark nullified the promotory influence of a proximal excision. Etiolation, together with proximal ring‐barking, induced root formation in up to 98% of the cuttings.
TOLERANCE OF HOLCUS LANATUS TO LEAD, ZINC AND CADMIUM IN FACTORIAL COMBINATION
Authors: COUGHTREY P. J. , MARTIN M. H. 
Published: May 2006

SUMMARYThe tolerance of Holcus lanatus to lead, zinc and cadmium alone and in combination was studied in a factorial experiment. Cadmium/zinc, lead/cadmium and lead/cadmium/zinc interactions, as measured by their effect on root growth, occurred but were not consistent between the two populations. The population from a contaminated site showed a distinct tolerance to lead, zinc and cadmium in combination, compared to the non‐tolerant population. These results are discussed in relation to the literature of heavy metal tolerance and metal effects on plants.
THE ADDITIVITY OF THE TOXIC EFFECTS OF Cu, Ni AND Zn IN YOUNG BARLEY
Authors: BECKETT P. H. T. , DAVIS R. D. 
Published: May 2006

SUMMARYAs part of a study on the use of young barley plants to monitor accumulations of toxic elements arising from sludge or waste disposal, we have examined the interactions between Cu, Ni and Zn in young barley.We find that Cu has little effect on the amount of Ni or Zn that reaches the shoots or vice versa: Ni uptake is raised by critical levels of Zn; Zn uptake is raised by sub‐critical and critical levels of Ni. These effects are small and may be ignored when monitoring sub‐toxic accumulations. At higher concentrations the interactions are larger and more complex.A significant part of the quantity of any one of these elements that has been translocated to the photosynthesising tissues of the barley test plant, up to a threshold concentration [T]x, is not toxic, alone or in combination with the other two elements. Toxic effects become apparent from a critical tissue concentration [T]c, above which yield decreases in proportion to increases in log [T]. [T]x/[T]c∼ 1/2 – 2/3. Values of [T]x and [T]c are presented.The toxic effects of Cu and Zn appear to be antagonistic (effect less than expected) when the tissue concentrations of both are above their critical levels. Apart from this the toxic effects of the elements above their threshold concentrations are directly additive or slightly less than additive.
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Values are presented for K, k, M and m and the critical values of Ia and Ib.In their general form these results are very similar to those of similar studies on the toxicity of mixed solutions to fish.
HEAVY METALS IN SOILS, VEGETATION DEVELOPMENT AND HEAVY METAL TOLERANCE IN PLANT POPULATIONS FROM METALLIFEROUS AREAS
Authors: SIMON ERIC 
Published: May 2006

SUMMARYThe development of vegetation (mainly the Violetum calaminariae Schwick.) in heavy metal‐contaminated areas depends on the metals mobility in soils and on metal availability for plants. Moreover, the ability of plant populations to evolve metal tolerance is one of the most important characters which determines the structure, density and development of the vegetation in such areas. In this work, metal mobility in soils and availability to plants in both calcareous and non‐calcareous situations were investigated in relation to the development of genetical heavy metal tolerance in plant populations.In soils, exchangeable metals amounts are linearly related to total amounts. Availability of metals for plants depends on soil pH and on organic matter contents. High calcium content in soils reduced lead toxicity more than zinc toxicity and generally reduced metal uptake but some exceptions were found. The structure and the density of the vegetation colonizing calcareous and non‐calcareous places is related to the interaction between lead, zinc and exchangeable non‐toxic cations. A relationship between exchangeable Pb++/Ca++ in soils and the lead tolerance level of plant populations was found. The relation between exchangeable Zn++/Ca++ and zinc tolerance level was not satisfactory.
PROTON CO‐TRANSPORT OF ORGANIC SOLUTES BY PLANT CELLS
Authors: BAKER D. A. 
Published: May 2006

I. SUMMARYThe possible role of proton co‐transport in the uptake of sugars and amino acids by plant cells is discussed. Evidence is presented for sodium or proton co‐transport of organic solutes in animal, bacterial and algal systems and this is discussed in relation to evidence for a similar mechanism operating in the cells of higher plants. It appears that in plant cells an electrogenic proton efflux pump generates a gradient of electrochemical potential for protons which provides energy for the movement of an organic solute‐proton‐carrier complex across the membrane. The large sugar transport associated with the loading of phloem sieve elements is postulated to be driven by a proton co‐transport system and the relation of this loading process to transport and subsequent unloading of the phloem is considered.
STUDIES ON THE NATURALLY OCCURRING GIBBERELLINS IN AONLA (EMBLICA OFFICINALIS GAERTN.) FRUIT
Authors: RAM SANT , RAO T. RAJA 
Published: May 2006

SUMMARYThe fruit of aonla (Emblica officinalis) remains at rest without growth for a period of 3 1/2 months after setting and resumes growth thereafter. Studies on endogenous gibberellin activity of the fruit and exogenous applications of gibberellin to the fruit at rest suggest that the inability of the fruit to resume growth immediately after setting is not due to gibberellin deficiency. The fruit, when making rapid growth following its rest, contained six gibberellin‐like factors active in the lettuce hypocotyl test. Five behaved like gibberellins A1, A3, A4, A7 and A9 in paper, thin‐layer and silicic acid: celite column chromatography.
GROWTH OF SUBTERRANEAN CLOVER IN RELATION TO THE FORMATION OF ENDOMYCORRHIZAS BY INTRODUCED AND INDIGENOUS FUNGI IN A FIELD SOIL
Authors: ABBOTT L. K. , ROBSON A. D. 
Published: May 2006

SUMMARYThree vesicular arbuscular (VA) endophytes differed in their ability to increase the growth of subterranean clover when introduced into a freshly collected field soil. Four indigenous endophytes infected the roots in both the control and inoculated treatments. Two of the introduced endophytes, isolates of Glomus monosporus, differed in their ability to increase growth and phosphorus content of subterranean clover. These endophytes were both superior to the third introduced endophyte, G. fasciculatus.Differences in the growth of subterranean clover when limited by phosphorus supply were related to the rate of mycorrhiza development. Inoculation of soil with the three introduced endophytes did not reduce initial infection by the four indigenous endophytes. Mycorrhizas formed by G. monosporus and G. fasciculatus were distinguished from those formed by indigenous endophytes on the basis of morphology.Plants inoculated with isolates of G. monosporus had a greater proportion of their dry weight and phosphorus content in the tops than plants inoculated with G. fasciculatus or the control plants.
ELECTRON MICROSCOPY OF STRUCTURES ON THE ADAXIAL LEAF SURFACES OF CAMELINA SATIVA AND SPINACIA OLERACEA
Authors: LOVETT J. V. , JUNIPER B. E. 
Published: May 2006

SUMMARYObservations of unidentified structures found on adaxial leaf surfaces of two plant species are reported. The observations were made at Bangor in 1977/78 and at Oxford in 1959. The structures are uncommon and, as yet to our knowledge, unreported in the literature.
HETEROCYST DIFFERENTIATION AND POLARITY IN CALOTHRIX
Authors: RAI A. K. , PANDEY K. D. , KASHYAP A. K. 
Published: May 2006

SUMMARYWhen grown in a nitrogen‐free medium Calothrix brevissima West has a basal heterocyst followed by a filament of cells of decreasing size. In a nitrate medium, the alga does not form heterocysts but partial polarity, i.e. tapering of the filaments, remains. In contrast, polarity as well as heterocyst differentiation, is lost on growth in an ammonium medium and the frequent formation of false branches is observed. Following exhaustion of ammonia from the medium, differentiation of heterocysts, each with two distinct polar nodules, begins at semi‐regular intervals along the filaments. Polarity is regained following breakage of the filament adjacent to a heterocyst. The ways in which nutrient limitation and heterocyst differentiation patterns can lead to three different types of false branching in the same alga are discussed.
SUSCEPTIBILITY TO SHADE IN SEEDLINGS OF COLONIZING AND CLOSED TURF SPECIES
Authors: FENNER M. 
Published: May 2006

SUMMARYThe effect of shade on the growth of seedlings of a range of colonizing and closed turf species was investigated by means of a simple experiment. It was found that the colonizing species were, in general, more severely affected by shade than the closed turf species were, both in terms of percentage reduction in dry weight and in terms of percentage reduction in relative growth rate. The relevance of these results to the inability of colonizing species to establish in closed grasslands is discussed.
DIATOM AND POLLEN STUDIES OF A SEDIMENT PROFILE FROM MELYNLLYN, A MOUNTAIN TARN IN SNOWDONIA, NORTH WALES
Authors: WALKER ROSEMARY 
Published: May 2006

SUMMARYCore samples taken from Late Devensian and Flandrian deposits at Melynllyn have been investigated. One profile was sampled at fairly close intervals for diatom and pollen analyses, and a series of radiocarbon dates was obtained. An absolute diatom counting method was used, which enabled the results to be expressed both in terms of annual diatom deposition and as percentages of the diatom sum. The diatom succession indicates that a change from alkaline to circumneutral conditions took place early in the Flandrian period. Diatoms characteristic of acidic, oligotrophic waters have been well established in the tarn from mid Flandrian times to the present day. Pollen analysis serves chiefly as a means of correlating the deposits with those from other sites in the Snowdonia region, although some features of the pollen diagrams are discussed. The data indicate that erosion was accelerated in the drainage basin of the tarn following the decline in Ulmus pollen percentages.
THE SYMPTOMS OF CALCIUM DEFICIENCY IN PLANTS
Authors: SIMON E. W. 
Published: May 2006

SUMMARYAs the symptoms of calcium deficiency develop in plants, there is often a stage in which the tissues are water‐soaked and one involving cell breakdown with loss of turgor (as in internal breakdown of apples). Eventually the tissue may become desiccated yielding a dry, more or less extensive area of necrosis. Two mechanisms are proposed. There is evidence that calcium deficiency renders membranes permeable which would account for a loss of turgor and permit cell fluids to invade intercellular spaces. An alternative situation may develop in soft, succulent fruits, the cells of which burst under hypotonic conditions in vitro. It is suggested that exogenous water may enter a fruit from the atmosphere or (in apple) through the phloem. Such exogenous water in the intercellular spaces of the fruit may cause cells to swell, so cracking the fruit or it may result in a bursting of the cells. A plea is made for further light microscope studies of the development of symptoms of calcium deficiency.
THE EFFECTS OF AIR POLLUTION ON PLANT GROWTH WITH SPECIAL REFERENCE TO SULPHUR DIOXIDE
Authors: CRITTENDEN P. D. , READ D. J. 
Published: May 2006

SUMMARY Lolium perenne L. was grown in a sealed glass chamber force‐ventilated with ambient SO2‐polluted air and the yield compared with that of control plants grown in a second chamber receiving filtered air free of SO2 and suspended participates. Whole plant dry weight of L. perenne cv. S23 grown either on a nutrient‐rich sand culture or an unfertilized field soil was depressed by up to 36% in polluted air containing mean SO2 concentrations of less than 100 μg−3 in. When detailed growth analyses of S23 L. perenne in unfiltered air and of a clone of wild L. perenne previously reported to be resistant to SO2 pollution were compared, there were distinct differences between the two strains in response to SO2‐polluted air but both were less productive in the latter treatment.Sulphur dioxide was strongly implicated as the factor responsible for the reduced dry‐matter production of plants raised in polluted air but there was a poor positive correlation between loss of yield and long term mean SO2 concentration within the unfiltered air chamber. The results are discussed with regard to probable mechanisms of growth inhibition and the possibility that experimental conditions cither enhanced or confounded the effect of SO2 pollution on plant growth.
TOLERANCE OF TREE ROOTS TO WATERLOGGING
Authors: COUTTS M. P. , PHILIPSON J. J. 
Published: May 2006

SUMMARYA study is presented of the growth of rooted cuttings of Lodgepole pine and Sitka spruce into waterlogged soil. Lodgepole pine roots penetrated to depths of 20 cm at 10°C in soil devoid of oxygen, whereas Sitka spruce made only shallow growth into the water‐table. The growth rate of the pine roots decreased with depth below the water‐table and penetration was greater at 10 °C than at 20 °C. Large gas‐filled cavities were found in the stele of the pine roots that penetrated the water‐table but were absent from the spruce. When pine roots were allowed to grow into a water‐table for 2 cm. and were subsequently inundated to a depth of 10 cm, root tip survival was much better than where non‐acclimatized roots were flooded.The results suggest that the deeper penetration of waterlogged soil by Lodgepole pine than Sitka spruce is due to internal oxygen transport in the pine roots; oxygen transport and other possible mechanisms for growth and survival of roots in waterlogged soil are discussed.
THE GROWTH AND NUTRIENT CONTENT OF FESTUCA VIVIPARA (L.) SM. PLANTLETS
Authors: HARMER R. , LEE J. A. 
Published: May 2006

SUMMARYThe nutrient content of Festuca vivipara (L.) Sm. plantlets from a site in the English Lake District were compared with that of seeds of the closely related species, F. ovina L. The almost linear increase in dry weight of plantlets throughout the growing season was associated with an increase in their mineral nutrient content derived from the parent plant. Their amino acid and soluble carbohydrate content also increased markedly with size. The relatively high levels of free amino acids and soluble carbohydrates in viable plant‐lets contrasts with the generally low levels of these compounds usually found in mature seed of grasses. Viable plantlets contained three to four times the nutrient content of F. ovina seeds resulting principally from the larger dry weight of the plantlets. The growth and survival of plantlets is discussed in relation to the success of vivipary as a method of reproduction in arctic‐alpine environments.
GROWTH OF ISOLATED EMBRYONIC AXES FROM DORMANT SEEDS OF HAZEL (CORYLUS AVELLANA L.)
Authors: JARVIS B. C. , WILSON D. A. , FOWLER M. W. 
Published: May 2006

SUMMARYA medium of sucrose and inorganic salts permits development of isolated embryonic axes of hazel into leafy seedlings. Gibberellic acid stimulates the early growth of excised axes in this medium and with sucrose alone. In the longer term, GA3 leads to less root growth, increased shoot growth (but an overall reduction in seedling length) and a poor leaf development. Abscisic acid markedly inhibits extension of isolated axes irrespective of the presence of gibberellic acid.
DETECTION AND ESTIMATION OF POLYPHOSPHATE IN VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: CALLOW J. A. , CAPACCIO L. C. M. , PARISH G. , TINKER P. B. 
Published: May 2006

ABSTRACTPolyphosphates have been extracted from onion roots infected with Glomus mosseae by the technique of phenol‐detergent extraction. The polyphosphate was separated from RNA and DNA and characterized by the technique of polyacrylamide gel electrophoresis. On gels stained with Toluidine Blue, the blue‐purple nucleic acid bands (β‐metachromatic) could be readily distinguished from the pink (γ‐metachromatic) polyphosphate band, which ran faster than tRNA, and was coincident with synthetic, marker polyphosphate of chain length 200 ±10. By excising stained gel bands, dry‐ashing and P determination, and by enzymic hydrolysis, the presence of condensed orthophosphate in this band has been confirmed. Polyphosphates could not be detected in uninfected roots and the content in infected roots increases several‐fold when plants are supplied with orthophosphate 24 h before extraction. By calculation it has been shown that the polyphosphate forms a substantial proportion (40%) of the total P present in the fungal component of mycorrhizal roots, and that this concentration is sufficient to support the proposed phosphorus translocation.
LIPID PHYSIOLOGY OF VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: COOPER KAREN M. , LOSEL DOROTHY M. 
Published: May 2006

SUMMARYA microscopic and biochemical comparison was made of the distribution, quantity and composition of lipid in roots of onion, clover and ryegrass infected with the VA mycorrhizal fungus, Glomus mosseae, in uninfected roots and in the external mycelium from infected, aseptically grown onion roots. Abundant oil‐droplets were observed in the internal and external fungal mycelium, in the vesicles and chlamydospores, and adjacent to the appressoria at entry points. Mycorrhizal roots contained significantly more total lipid than uninfected roots. In estimations of separated lipid classes, the mycorrhizal roots consistently showed higher levels of triglyceride than non‐inycorrhizal roots. External mycelium contained high levels of neutral lipids, especially triglyceride, diglyceride and free fatty acids. Compared with uninfected roots, mycorrhizal onion roots contained higher levels of diphosphatidyl glycerol, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidy) choline, phosphatidyl glycerol, phosphatidic acid and phosphatidyl inositol. With the exception of phosphatidyl inositol and phosphatidic acid, these were all prominent components of G. mosseae mycelium.
UNUSUAL REPRODUCTIVE STRUCTURES IN SYRINGODERMA ABYSSICOLA (S. & G.) LEVRING*
Authors: WALKER DAVID C. , HENRY ERIC C. 
Published: May 2006

SUMMARYReproductive structures of Syringoderma abyssicola (S. & G.) Levring are unique. They begin development as normal unilocular sporangia. However, the initial products of cytokinesis develop a cell wall, but not as in plurilocular sporangia. Some of these walled cells may in turn divide to produce a tetrad of naked flagellate cells. This is in contrast to other members of the Dictyotales, the order in which S. abyssicola is currently placed.
PHYSIOLOGICAL ECOLOGY OF THE MARINE ALGA ACROCYSTIS NANA
Authors: MNTANGI M. J. , FARRAR J. F. 
Published: May 2006

SUMMARY Acrocystis nana is a tropical and subtropical red alga confined to areas of the shore emersed for between 3 and 9 h per tide. In the laboratory, it becomes unhealthy if immersed constantly but retains its original weight if dried for 3 h out of each 24 h and is aerated during the immersion period. Weight loss in various regimes in the light and in the dark is largely confined to material soluble in 0.1 N HC1 and is greatest from an 80% ethanol‐soluble fraction tentatively identified as floridoside. The thalli contain an extracellular sap with an ionic composition distinct from seawater. Results are discussed in relation to the zonation of A. nana on the shore and the concept of physiological buffering.