bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF HERBICIDES ON THE GROWTH OF SOIL FUNGI
Authors: WILKINSON VALERIE , LUCAS R. L. 
Published: May 2006

SummaryThree methods have been used to investigate the effects of a number of commercial herbicides on the growth of certain soil fungi: measurements of hyphal extension across agar plates; measurements of hyphal extension along sterilized plant material; and manometric techniques. Three points, in particular, emerged from these studies. First, that there was no stimulation of fungal growth. Herbicide interference in growth included suppression of spore germination, inhibition of the rate of linear extension of the mycelia, and abnormalities in growth habit and in patterns of spore production. Secondly, that some herbicides (e.g. linuron and paraquat) were more fungitoxic than others (e.g. MCPA and simazine) to a range of organisms. Thirdly, that there were differences between fungi in their sensitivity to individual herbicides. All three methods have shown consistent differences between fungi in their ability to tolerate paraquat. Trichoderma viride, in particular, has been found to be sensitive to paraquat. The inhibitory effects were observed at concentrations well within the range likely to be experienced in the field.
CELLULOSE AS A CARBON SOURCE FOR ORCHID MYCORRHIZA
Authors: HADLEY G. 
Published: May 2006

SummaryOrchid endophyte fungi are known to utilize cellulose and translocate carbon compounds into protocorms. Evidence is presented which indicates that cellulose is an excellent carbon source for protocorm growth in a variety of orchid‐fungus systems including both temperate and tropical orchids. One per cent cellulose powder as compared with 1% dextrose as a carbon source enhanced the development of protocorms and led to a more sparse, controlled growth of the fungal endophyte and, subsequently, a diminished tendency to parasitism and death of the protocorms. It is not yet known whether cellulose is equally useful for root‐bearing mature orchids but it may be the principal carbon source in nature for orchids in the symbiotic protocorm stage.
THE PHOSPHORUS METABOLISM OF RHIZOPUS STOLONIFER AND CHAETOMIUM SP. WITH RESPECT TO PHOSPHORUS TRANSLOCATION
Authors: LYON A. J. E. , LUCAS R. L. 
Published: May 2006

Summary Rhizopus stolonifer was able to translocate 32phosphorus readily through established hyphae, whereas Chaetomium sp. was unable to do so. When colonies of either species were incubated on KH232PO4 a range of compounds became labelled in the mycelium but a substantial proportion of absorbed 32P was present in the form of orthophosphate in both species. After incubating 32P‐labelled mycelium of Rhizopus stolonifer on unlabelled KH2PO4, the proportion of 32P detected in the form of orthophosphate was unchanged. When mycelium of Chaetomium sp. was treated in this way the proportion of label in the orthophosphate fraction was greatly reduced. Mycelium of Rhizopus stolonifer was able to take up hexose [32P] phosphate intact and subsequently hydrolyse it to orthophosphate. In Chaetomium sp. very little 32P derived from hexose [32P] phosphate appeared as orthophosphate.These results are held to support the view that the ability to translocate phosphorus is associated with rapid turnover of phosphorus compounds.
THE EFFECT OF ABSCISIC ACID ON STEM ELONGATION AND CORRELATIVE INHIBITION
Authors: ARNEY S. E. , MITCHELL D. L. 
Published: May 2006

SummaryThe mature length of the second internode (which was undergoing rapid vacuolation at the time of treatment with ABA) was not appreciably affected by doses of ABA below 20 μg per plant although the rate of elongation was depressed for the first 2 days after treatment, the depression being as much as 50% in tall varieties. Doses of ABA in excess of 20 μg not only depressed elongation rate immediately, but resulted in shorter internode length at maturity. Etiolated seedlings showed a stimulation of elongation rate and mature length in the dwarf ‘Meteor’, hut no statistically significant differences in the tall variety ‘The Pilot’ with doses below 20 μg ABA. Higher doses of ABA caused immediate cessation of elongation in vacuolating internodes, but only postponed the onset of vacuolation in younger internodes. Lighted plants also showed this postponement of the onset of vacuolation in the younger internodes at higher doses; in both lighted and etiolated seedlings the normal growth rate was resumed after a delay of between 3 and 7 days.Decapitation reduced elongation rate during the subsequent 48 hours either with or without ABA. In the absence of ABA there was a subsequent recovery in growth rate of the dwarf variety so that the final length of the second internode was the same for both intact and decapitated plants. But decapitation of the tall variety produced a marked reduction in mature length of the second internode, as it did in all ABA treated plants both dwarf and tall, intact and decapitated. The only significant interaction between decapitation and ABA on elongation rate occurred in the tall variety: during the first 24 hours all doses of ABA produced approximately the same big reduction in elongation rate in intact plants but had no statistically significant effect on decapitated plants; during the second day only the higher doses of ABA reduced the elongation rate of intact plants while all three levels produced the same big reduction in elongation rate of the decapitated plants. In the dwarf variety there was no significant interaction between the decapitation and ABA effects. Lateral bud outgrowth in decapitated plants was inhibited by ABA, and 100 μg per plant achieved inhibition comparable to that produced by the apex in intact plants. Hence ABA may possibly be the inhibitory substance demonstrated to be responsible for the phenomena of correlative inhibition.
EFFECTS OF GIBBERELLIC ACID ON INTERNODE GROWTH AND STARCH CONTENTS OF EUCALYPTUS CAMALDULENSIS SEEDLINGS
Authors: BACHELARD E. P. 
Published: May 2006

SummaryEffects of gibberellic acid (1 and 10 μg/plant) on internode extension and cell activity in Eucalyptus camaldulensis seedlings varied with internode position. The relatively small increased extension of lower internodes resulted from cell elongation whereas the progressively increasing growth in upper internodes was caused primarily by cell division. Transverse cell divisions induced by gibberellic acid seemed to require an active apical meristem.Changes in internode diameter growth (increased in lower internodes, decreased in upper) due to gibberellic acid were the result of changes in cell division.The major response to gibberellic acid seems to be an increase in transverse cell divisions and does not seem to be due to competition between meristems for the available food reserves.
RESISTANCE TO WATER FLOW IN SOIL AND PLANT
Authors: ANDREWS ROSALIE E. , NEWMAN E. I. 
Published: May 2006

SummaryTwo experiments described in an earlier paper, on the transpiration rates of root‐pruned and unpruned wheat plants at various soil moisture contents, are discussed with the aid of further data.The matric potential drop across the rhizosphere, and the relative magnitude of the rhizo‐sphere and plant resistances are calculated for the unpruned plants at various soil matric potentials. Even at −15 bars soil matric potential the estimated drop was only 0.02 bar, and the rhizosphere resistance was less than 2% of the plant resistance.The amount of water made available to the plant by root extension was only a small fraction of that lost by transpiration. We suggest that root interception is unlikely to be important in the field, as long as new roots are growing among existing ones.Reasons are considered for the declining influence of root pruning on transpiration as the soil dried. It can be partly explained by the soil resistance remaining very small and by the relationship between transpiration rate and leaf water potential. However, there was evidently some other factor involved, possibly change in plant resistance or influence of root kinins on transpiration rate. The effects of root pruning on transpiration are too complex to provide satisfactory evidence on the magnitude of the rhizosphere resistance, but the experimental results are at any rate in agreement with the calculated prediction that it remained very small.
EFFECT OF LIGHT INTENSITY DURING GROWTH ON LEAF ANATOMY AND SUBSEQUENT LIGHT‐SATURATED PHOTOSYNTHESIS AMONG CONTRASTING LOLIUM GENOTYPES
Authors: WILSON D. , COOPER J. P. 
Published: May 2006

SummaryThe effect of light intensity during leaf formation on subsequent light‐saturated photosynthesis and its relation to mesophyll and stomatal characteristics, was examined among ten contrasting Lolium genotypes. Photosynthetic activity was recorded at three CO2 concentrations. At approximately 300 ppm CO2 and above, plants of the same mesophyll cell size grown in strong light (0.130 cal/cm2/min) of radiation in the spectral region 400–720 mμ. (1800 ft‐candles) had faster rates of photosynthesis than those grown in relatively weak light (0.021 or 0.056 cal/cm2/ min). At the lowest CO2 concentration there was no effect on photosynthesis of the light intensity at which the plants were grown. The effect of light intensity was not associated with any change in mesophyll structure, but plants grown in weaker light (0.056 cal/cm2/min) had much smaller stomata than those grown in stronger light (0.130 cal/cm2/min). A slight increase in stomatal frequency at the low compared with the high light intensity did not compensate for the reduced stomatal length in terms of total pore space. Differences in apparent photosynthesis in any one light intensity, and between plants from all light intensities at the lowest CO2 concentration, were usually correlated negatively with mesophyll cell size. Effects of the light intensity at which plants were grown on subsequent photosynthesis could be explained in terms of changes in stomatal size.
THE FLORAL BIOLOGY OF THREE SPECIES OF VIOLA
Authors: BEATTIE A. J. 
Published: May 2006

SummaryThe floral biology of Viola riviniana Rchb., V. reichenhachiana Jord. and V. hirta L. is described in detail. The flowers are very complicated morphologically and many changes in the floral organs occur during anthesis. Differences in the flowering periods of the three species were found but comparisons of the length of flower life, the pollen and nectar presentation and the receptivity of the stigmatic surfaces showed few differences between species. Movements of the pedicel and corolla directly affect the outline and colour patterns presented by the flower and these are probably of prime importance in the attraction of insect visitors to these species. All the movements of the floral organs and the changes which they undergo together suggest that anthesis has two distinct phases. The first is characterized by the retention of pollen within the androecium and the second is characterized by the gradual displacement of pollen from the anthers to the petals. Pollination during the flrst phase is effected only by a few insect species which operate the pollination mechanism precisely. By contrast, pollination during the second phase may be effected by a wide variety of insect visitors and is not, therefore, entirely dependent upon the activities of a small number of highly adapted species, as previously supposed. This may be of critial importance to the many species of Viola which are predominantly in‐breeders. In the absence of highly adapted pollinators (which is frequently the case), the second phase of anthesis may be the only opportunity for out‐breeding. The frequency of pollen exchange in the three species is, therefore, partially dependent upon the change in the mode of pollen presentation during anthesis.
SOME ASPECTS OF THE DEVELOPMENT OF MANGO (MANGIFERA INDICA L.) LEAVES
Authors: TAYLOR F. J. 
Published: May 2006

SummaryThe mango is an example of a tree in which all the leaves on a shoot develop simultaneously instead of sequentially. The growth in area of all the leaves in a flush was followed at daily intervals. The dry weight, ash weight, water content, relative turgidity and rigidity of the leaves were measured at weekly intervals for the first 6 weeks of their life. They grew by cell division for the first 7 days after the fall of the bud scales and by cell enlargement over the next 7 days. Between day 7 and day 14 the dry weight per unit leaf area fell, the water content per unit leaf area increased, and the leaf became less rigid, finally hanging limply. After this date these trends were reversed. It is shown that the limpness of the young mature leaves is not due to lack of turgor, but may be correlated with a minimal value of the dry weight per unit leaf area.
THE EFFECT OF NITROGEN SUPPLY ON SOME INDICES OF PLANT‐WATER RELATIONS OF BEANS (PHASEOLUS VULGARIS L.) *
Authors: SHIMSHI DANIEL 
Published: May 2006

SummaryThe effect of nitrogen supply on some indices of plant‐water relations was studied on potted bean plants. When soil moisture was relatively high, the leaves of N‐deficient plants transpired less than those of N‐supplied plants, the transpiration rate being closely associated with the chlorophyll content of the leaves of various ages. In detached leaves which were saturated by floating over distilled water, stomatal width was markedly wider in N‐supplied than in N‐deficient plants. Throughout the available moisture range, the water saturation deficit was higher in N‐supplied leaves. In the dry range of soil moisture, chlorotic leaves transpired more than normal green leaves; N‐deficient plants failed to exhibit a sharp rise in the content of soluble metabolites in the sap, when approaching the wilting range. The content of ‘cell wall materials’ was higher in N‐deficient plants. The relationships between these indices is discussed; it is tentatively concluded that nitrogen deficiency impairs the ability of the plants to adjust their water status to changes in soil moisture by regulation of stomatal transpiration and of sap‐solute concentration.
CONTRIBUTIONS TO THE ECOLOGY OF BRACKEN (PTERIDIUM AQUILINUM)
Authors: WATT A. S. 
Published: May 2006

SummaryThe variation in height and density of the fronds in the hinterland of area D is confirmed as stages in the development of bracken from the pioneer to the mature phase. Factors affecting its rate are winter and spring frost and rainfall. In the absence of interference there would appear to be no degenerate phase such as has been described as part of a natural cycle of change in the hinterland of area E.By the use of thatch and cage development is expedited but later reactions ensue affecting the number of fronds, their height, spindliness and depth of origin such as are found in the degenerate phase in area E. Thatch and cage induce degeneration in area D and probably accentuate it in area E.The mechanism of degeneration requires detailed investigation but it would appear to involve the change from a community (mature phase) in area D where the old shoots are dispersed singly or at most in small groups in an uneven‐aged population to one in which they are aggregated in larger more or less even‐aged patches such as are found in area E.In the contrast between the hinterlands of area D and area E as well as in phasic development, litter, its amount and kind, emerges as important. Burning removes this litter and its influence on bracken in different phases, leading in some to retrogression and even local extinction, in others to rejuvenation, is discussed.
SOME ECONOMIC IMPLICATIONS OF THE TAXONOMY OF LABIATAE ESSENTIAL OILS AND RUSTS
Authors: EL‐GAZZAR A. , WATSON L. 
Published: May 2006

SummaryEssential oils extracted from twenty‐two genera of Labiatae have been examined by gas‐liquid chromatography. The results support the taxonomic suggestion that there are two major series of genera: the one (GROUP B, El‐Gazzar & Watson 1970) oil‐rich, the other appearing to be oil‐poor. Records of susceptibility to Puccinia menthae Pers. are nearly confined to the oil‐rich group, but within this assemblage certain minor groupings of important genera may be resistant. Attention is drawn to commercial possibilities among large GROUP B genera (e.g. Hyptis, Plectranthus; as yet exploited hardly or not at all) known to be oil‐rich and possibly resistant to Rusts including Puccinia menthae.
ABSORPTION OF POLYETHYLENE GLYCOLS BY PLANTS AND THEIR EFFECTS ON PLANT GROWTH
Authors: LAWLOR D. W. 
Published: May 2006

SummaryA study was made of polyethylene glycols (PEG) as osmotica to decrease the water potential of culture solutions for studies of higher plant response to water stress. Analysis of possible inorganic impurities in commercial PEG and comparison of the growth of maize in solutions purified by gel filtration or unpurified, suggest that impurities are not responsible for the toxic effects reported.PEG in leaves was estimated by Hyden's method and with [14C]‐labelled PEG 4000. Over 90 % of the higher molecular weight PEG was recovered from maize and bean leaves but less from cotton and tulip tree. PEG of 1000 molecular weight or larger entered plants slowly, about 1 mg/g fresh weight of leaf per week, but mechanically damaged roots or those subjected to low water potentials permitted entry. PEG decreased transpiration and water potential and caused the leaves to die. PEG 200 and mannitol entered plants with undamaged roots but the effects on leaves were unlike the higher molecular weight PEGs.Low and high molecular weight PEG and mannitol affected respiration to the same extent and comparison with non‐ionic detergents showed that the detergent properties of PEG were not responsible for the toxicity.Autoradiography showed that PEG 4000 accumulated initially in the margins of leaves and became distributed in the mesophyll except along the veins.PEG of higher molecular weight is considered to cause blockage of the pathway of water movement, reducing water absorption and causing desiccation of the plant.
FURTHER OBSERVATIONS OF CATION‐STIMULATED STOMATAL OPENING IN ISOLATED EPIDERMIS
Authors: WILLMER C. M. , MANSFIELD T. A. 
Published: May 2006

SummaryMeasurements of apparent osmotic pressures of guard cells in isolated epidermis of Commelina communis indicate a considerable rise (up to 26.3 bars) when K+ ions are added to the incubation medium. This rise in apparent osmotic pressure appears to be the major cause of the stomatal opening that is stimulated by K+ ions, but reduction in turgor of the epidermal cells, owing to the solutes in the incubation medium, may also contribute to the wide stomatal apertures. Histochemical tests on epidermis taken from leaves with stomata that were closed in darkness, or that were open in light, suggest that K+ accumulates in guard cells when stomata open in response to light. No movements of K+ or Na+ from epidermis to mesophyll could be detected and it is concluded that ion movements associated with changes in guard cell turgor are probably confined to the epidermis in C. communis. Ion uptake (indicated by 86Rb and 24Na) into epidermis was stimulated by light but not by a reduction in CO2 concentration, whereas stomatal apertures were affected by these environmental factors to approximately the same extent. It is tentatively concluded that active transport of monovalent cations into guard cells might explain the CO2‐independent light responses of stomata, but not their light‐independent CO2 responses.
EFFECTS OF SIMULATED DROUGHT ON SHOOT DEVELOPMENT IN LIRIODENDRON SEEDLINGS
Authors: DOLEY D. 
Published: May 2006

SummaryShoot extension, leaf growth, xylem radial growth, and xylem structure in i‐year old Liriodendron tulipifera L. seedlings maintained in a growth chamber were affected more by reduction of atmospheric relative humidity from about 95 to about 45% than by simultaneous reduction of the root medium water potential (Ψsoi) from – 0.4 to about –11 bars. For plants subjected to the same minimum Ψsol, the rate of change of Ψsol during the imposition and relief of simulated drought had no apparent effect on growth. Xylem formed near the stem base during a period of simulated drought resembled that characteristic of the terminal stage of seasonal growth under normal conditions; vessel elements, fibres and ray parenchyma cells were narrower in the radial direction, vascular rays increased in width, and more vertical parenchyma was evident than under conditions of rapid growth. The differences between the structure of xylem formed at high and low plant water potentials diminished towards the apex of the stem, and it is suggested that these differences may be due chiefly to an impairment of synthesis and translocation of growth factors.
CHANGE OF APPARENT WEIGHT OF PLANT TISSUES IN SOLUTIONS
Authors: BRIGGS G. E. 
Published: May 2006

SummaryThe effect of changes in the vacuole of the amounts of solute and of water, and of the turgor pressure, on the apparent weight of a cell and of a piece of tissue is considered. The permeability of cells in the root of carrot is estimated from the change in apparent weight of discs suspended in a solution of KNO3. The permeability to urea is estimated from the change in apparent weight in water after discs had equilibrated with a solution of urea. The dimensions of permeability to water and solute, and the effect of flow of water on the apparent permeability to solute, are considered. The change in apparent weight is used to measure the relatively slow uptake of cane sugar from dilute solutions of this substance. The uptake is not due to passive diffusion and the sugar absorbed appears to be osmotically active. From measurements of carbon dioxide produced and chloride ions absorbed from 0.01 M KC1 the change in apparent weight in water and change in osmotic pressure of the vacuolar sap are estimated. These are compared with the observed changes in apparent weight and changes in osmotic pressure deduced from the change in the relation between the vacuolar volume and the concentration of KC1 with which it is in equilibrium.
THE SUBCELLUAR DISTRIBUTION OF ZINC AND COPPER WITHIN THE ROOTS OF METAL‐TOLERANT CLONES OF AGROSTIS TENUIS SIBTH.
Authors: TURNER R. G. 
Published: May 2006

SummaryHeavy metal tolerance in the common bent grass Agrostis tennis Sibth. was investigated by comparing the zinc and copper distribution within the roots of metal‐tolerant and non‐tolerant clones. Analysis of root subcellular fractions showed the importance of the cell wall fraction in metal binding in root cells of metal‐tolerant A. tenuis. At normal nutrient levels the root cell wall from metal‐tolerant clones contained more copper and zinc than did non‐tolerant material. High levels of metal nutrition demonstrated the accumulating power of this fraction. Alterations in the nutrient level of one heavy metal did not influence the distribution of the other metal studied. The importance of metal accumulation by the cell wall fraction is discussed and it is proposed that it is an important site in the mechanism of heavy metal tolerance in A. tenuis.