bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE RESPONSE TO PHOSPHORUS OF SOME ECOLOGICALLY DISTINCT PLANT SPECIES
Authors: RORISON I. H. 
Published: May 2006

SummarySeedlings of four ecologically distinct species were grown in solution cultures containing a range of phosphorus concentrations. Evidence for relationships between their relative growth rates and phosphorus absorption was then considered. Descliampsia flexuosa and Scabiosa columbaria, the two species from edaphically extreme habitats, had slow relative growth rates, but differed in their response to phosphorus. Deschampsia flexuosa grew continuously in concentrations as low as 10−7 M and respontled only slightly to concentrations as high as 10−3 M. Scabiosa columbaria whose response was poor at 10−7 m responded more markedly to 10−3 M at which concentration there was a significant increase of phosphorus in the roots. Rumex acetosa and Urtica dioica, the two ruderal species, had high relative growth rates and differed in their response to phosphorus; Rumex acetoso survived over the whole range; Urtica dioica thrived only at 10−5 M or above. These results, particularly the increase of phosphorus in roots of Scabiosa columbaria, were considered to be of ecological importance.
THE EFFECTS OF FUNGI ON MORPHOGENESIS OF GAMETOPHYTES OF POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M. 
Published: May 2006

SummaryGrowth and development of gametophytes of Polypodium vulgare L. in culture were affected by several fungi. Of those tested the fungus having the greatest effect was Fusarium oxysporum Schlecht ex Fr. When added just before spore germination this fungus delayed the transition from one‐ to two‐dimensional growth of the gametophytes and when added after the transition had occurred it caused a reversion to one‐dimensional growth. Analysis of culture filtrates showed that the detectable volatile substances present in greatest concentration were ethanol and acetaldehyde. Changes in gametophjrte morphology were correlated with changes in the level of ethanol present in the medium and the main effects of the fungus were reproduced by treating gametophytes in uncontaminated cultures with ethanol.
ROOT GROWTH AND DARK FIXATION OF CARBON DIOXIDE IN CALCICOLES AND CALCIFUGES
Authors: LEE J. A. , WOOLHOUSE H. W. 
Published: May 2006

SummaryThe inhibition of root growth by bicarbonate ions has been further investigated by an examination of the process of dark fixation of carbon dioxide by Arrhenatherum elatius and Deschampsia flexuosa. Excised roots incorporated [14C]bicarbonate mostly into malate in 4 hours. Intact plants grown on solutions containing 10 m‐equiv./1 bicarbonate for 24 hours showed large increases in the total acid content of the roots. Malate was increased in both species and citrate also in Arrhenatherum elatius. The increases in total acidity were similar and could be explained solely by the dark fixation of bicarbonate. Seedlings grown on solutions of sodium hydrogen malate showed similar inhibitions to those observed on sodium bicarbonate solutions. Root growth of Deschampsia flexuosa was inhibited throughout a range of malate concentrations (1–20 m‐equiv./l) whereas Arrhenatherum elatius was stimulated at low malate concentrations and only slightly inhibited at 20 m‐equiv/1. The inhibiting action of bicarbonate on the root growth of Deschampsia flexuosa is associated with the increase in malate in the roots by dark fixation. The results are discussed in terms of the organic acid content and metabolism of calcicole and calcifuge species.
ASEXUAL SPORE MORPHOLOGY IN SPECIES OF PIPTOCEPHALIS
Authors: YOUNG T. W. K. 
Published: May 2006

SummaryElectron microscopic observation of surface replicas of the asexual spores of four species of Piptocephalis, reveals that three dry‐spored forms, P. unispora, P. henjaniinii and P. virginiana bear patterns of warts and ridges whilst those of the slime‐spored form P. freseniana, are relatively smooth. The transverse walls of spores of P. virginiana and P. freseniana are rough. Spore scars on the head cell of P. unispora apparently possess a central area which may represent a plug.
A CRITICAL EXAMINATION OF THE USE OF DETACHED EPIDERMIS IN STUDIES OF STOMATAL PHYSIOLOGY
Authors: WILLMER C. M. , MANSFIELD T. A. 
Published: May 2006

SummaryAlthough several workers have published accounts of stomatal studies with detached epidermis, there has not been general agreement as to whether the stomata continue to respond to environmental factors as they do in the intact plant. This paper reports a critical examination of the value of the technique, experiments having been carried out on material from Vida faba and two species of Commelina.The nature of the incubating medium was found to exert a considerable influence on the behaviour of the stomata. In Commelina, the presence of monovalent cations (K+, Na+) stimulated opening, but divalent cations (Ca2+, Mg2+) had an antagonistic effect suppressing opening or even preventing it altogether. In Vicia faba cations exerted less noticeable effects. pH changes affected aperture, but in Commelina the changes were of much smaller magnitude than those induced by the different cations.Factorial experiments were performed to determine the effect of detaching epidermis on the stomatal responses to environmental factors. In Vicia faba the light effect was very apparent on attached epidermis, but on detached epidermis the effect was largely obscured by stomatal opening that occurred in darkness; effects of CO2 concentration were detectable on epidermal strips, particularly in darkness, but were of smaller magnitude than those on attached epidermis. On the other hand, in Commelina, effects of both light and CO2 were of considerable magnitude when strips were immersed in media containing the cations that stimulated opening.The theory that the opening stimulated by monovalent cations is the outcome of their being actively taken up into the guard cells is discussed, and it is concluded that while this might apply to epidermal strips in media, there is inadequate evidence that such a mechanism is responsible for opening in the intact plant; there was no stimulation of opening on attached epidermis when pieces of leaf were immersed in media containing monovalent cations. Attempts are made to explain the difference in behaviour between Vicia faba and Commelina on the basis of the course of ion uptake into the cells of the epidermis; evidence of a possible difference in uptake was obtained from studies of the penetration by neutral red.It is concluded that epidermal strips from both species of Commelina are suitable for studies of stomatal responses to Hght and CO2 so long as they are incubated in a suitable medium. Epidermal strips from V. faba are unsuitable for studies of the light responses, and less satisfactory than Commelina for the responses to CO2.
RANDOMNESS IN THE GENESIS OF PHYLLOTAXIS
Authors: RIJVEN A. H. G. C. 
Published: May 2006

SummaryThis paper attempts to localize the ‘random factor’ at the inception of a spiral phyllotactic pattern, and to discover which other factors may influence leaf initiation at this point.The study shows that the third leaf of Trigonella foenum‐graecum L. can occupy an alternative site, left (L) or right (R) of the first leaf and thereby introduces L‐R asymmetry. The mean divergency angle with the second leaf is about 125°. The positions occupied were, within statistical expectations, equal, but in about 4% of seedlings both the L and R site were occupied resulting in ‘symmetries’. L‐R asymmetry was established independently of the sense of dorsiventrality.In the seed only the first leaf was present and the site of the third leaf not yet determined. Removal of one cotyledon when performed during germination (Day 2 and 3 but not on Day 4), resulted in bias away from the remaining cotyledon. Removal of the distal half of a cotyledon did not affect the L‐R frequency distribution.In immature embryos removal of one cotyledon often resulted in a change of the siting of the second leaf, but toward the remaining cotyledon.In intact seedlings the occupancy of the L or R site was not correlated with differences in weight between the left and right cotyledon, but a rather weak effect of gravity was observed.The effects of applying some phytohormones to a petiole stump in decotylized embryos were investigated. Morphological variants of primordial development were recorded.It is concluded that the ‘random factor’ is of internal origin, close to the apex. Auxins which stimulate primordial development, and other inhibitory substances may play a role in leaf siting.
STOMATAL MOVEMENTS AND RATES OF GASEOUS EXCHANGE IN EXCISED LEAVES OF VICIA FABA
Authors: BALASUBRAMANIAM S. , WILLIS A. J. 
Published: May 2006

SummarySimultaneous measurements of leaf resistance to gaseous flow, rate of transpiration and rate of carbon dioxide exchange were made with the main object of investigating the effects of severing the petiole on stomatal movements and gaseous exchange of leaves of Vicia faba of differing initial water content.Extensive stomatal changes occurred on cutting the petioles of illuminated leaves in air. The magnitude and direction of the stomatal movements were strongly influenced by the water relations of the leaf at the time of excision. When the water deficit was small there was a substantial temporary stomiatal opening and corresponding temporary increases in rates of transpiration and photosynthesis. In leaves of moderate water deficit the stomatal opening on leaf excision was much less pronounced and, in leaves under severe water stress at he time of cutting, there was little evidence of any immediate stomatal response. Preliminary stomatal opening and a temporary increase in transpiration rate were also observed in leaves excised in air from plants kept in darkness. In experiments in which the illuminated leaves were severed under water, however, a temporary increase of leaf resistance to gaseous flow was found on leaf excision, and associated declines in rates of transpiration and of photosynthesis.The changes in transpiration rate resulting from leaf severance are clearly associated with stomatal behaviour, and there is evidence of close stomatal control, under these conditions, of rates of transpiration and of photosynthesis. The phenomena involved in leaf excision both in air and under water are discussed and stomatal behaviour shown to depend to a considerable extent on the water relations of the leaf; stomatal movements are interpreted largely in terms of differential turgor changes in the guard cells and neighbouring epidermal cells.
MORPHOLOGY AND TAXONOMY OF THE OOMYCETES, WITH SPECIAL REFERENCE TO SAPROLEGNIACEAE, LEPTOMITACEAE AND PYTHIACEAE
Authors: DICK M. W. 
Published: May 2006

SummaryThe morphology of sexual reproduction is reviewed and the importance of developmental stages is considered. Particular attention is drawn to the taxonomie significance of the size, wall structure and protoplasmic organization of the oospore.
FACTORS CONDITIONING DEVELOPMENT OF SEXUAL AND APOGAMOUS RACES OF PHASCUM CUSPIDATUM HEDW.
Authors: HUGHES J. G. 
Published: May 2006

SummaryThe effect of the intensity and composition of daylight and fluorescent light on vegetative growth and reproduction of the haploid sexual and diploid apogamous races of Phascum cuspidatum Hedw. has been investigated, using leaf number as an index of vegetative growth. Sown together in daylight at different seasons, both races proved to be summer annuals. In both races it was shown that leaf number is not conditioned by light intensity and that vegetative growth was prolonged in fluorescent light. The frequency of the vegetative development of sporangia in the diploid apogamous race was found to be low in daylight. Reduction in leaf number under coloured filters was not accompanied by increased development of sporangia; but under yellow‐filtered fluorescent light the frequency of sporangial development is greatly increased.The low fertility of the diploid apogamous race of this and other species is discussed, and it is proposed that alternation of generations in mosses is based in part on a mechanism which ensures that neither sporophyte nor gametophyte alone can form sporangia.
THE OCCURRENCE OF SOUTHERN, STEPPE AND HALOPHYTE ELEMENTS IN WEICHSELIAN (LAST‐GLACIAL) FLORAS FROM SOUTHERN BRITAIN
Authors: BELL FRANCES G. 
Published: May 2006

SummaryThe southern element in Full‐glacial floras is thought to be primary except for a small number of derived species. The presence of southern plants in conjunction with northern and montane species is explained as the result of the special climate and advantageous open‐ground conditions of the Full‐glacial. A physiognomically steppe‐like vegetation may be recognized as part of the assemblages. The presence of halophytes is related to saline soils, probably developed over permafrost.
AUXIN, ETHYLENE AND KINETIN IN A CARRIER‐PROTEIN MODEL SYSTEM FOR THE POLAR TRANSPORT OF AUXINS IN PETIOLE SEGMENTS OF PHASEOLUS VULGARIS
Authors: OSBORNE DAPHNE J. , MULLINS MICHAEL G. 
Published: May 2006

SummaryThe capacity of bean petiole segments to transport 14C‐indole‐3‐acetic acid decreases to approximately half within 5 hours of excision and to less than one‐tenth after 10 hours. Exposure of the segments to ethylene enhances this loss in capacity, but pretreatment with an auxin completely protects the transport system from both the natural and ethylene‐induced fall. A decrease in synthesis of protein accompanies the natural loss of transport capacity, and treatments with auxin or kinetin which retain synthesis also retain transport. Only auxin treatments protect against the effects of ethylene. To correlate these results, a theoretical model for polar transport is developed in which it is proposed that auxin molecules are bound to a specific carrier protein sited at the plasmalemma. Transport capacity could be regulated by the rate of synthesis of the carrier protein, with a secondary regulation of the activity of the carrier by the binding of either auxin or ethylene molecules to specific sites on the protein.
GIBBERELLIN‐STIMULATED NUCLEIC ACID METABOLISM IN THE COTYLEDONS AND EMBRYONIC AXES OF CORYLUS AVELLANA (L.) SEEDS
Authors: PINFIELD N. J. , STOBART A. K. 
Published: May 2006

SummaryGibberellin treatment of intact hazel seeds stimulated 14C incorporation from [8‐14C] adenine into RNA and DNA of both cotyledons and embryonic axes compared with the corresponding water controls. This stimulation was apparent in the embryonic axes after only 12 hours treatment, but was not detected in the cotyledons until after 48 hours gibberellin treatment. The 14C incorporation into nucleic acids of cotyledons isolated from air‐dry seeds was also shown to be stimulated by gibbereliin treatment. It is concluded that the first effect of gibberellin on the intact hazel seed is on the embryonic axis, but that a second response occurs in the cotyledons, which is to some extent independent of the embryonic axis. It is suggested that the results for the cotyledons represent gibberellin‐stimulated nucleic acid synthesis, including the formation of specific mRNA required for the production of enzymes concerned with reserve lipid mobilization.
A STUDY OF THE ROOT SYSTEM OF BARLEY
Authors: HACKETT C. 
Published: May 2006

SummaryRelationships between the number, length, surface area, volume and dry weight of the root members of two varieties of barley (Hordeum vulgare L. vars Maris Badger and Proctor) were examined over the first 4 weeks of growth in water culture. Plants given a complete nutrient supply were compared with plants deficient in potassium or phosphorus.Although there were large effects of age, variety and nutrition on all the root dimensions, relationships between the dimensions varied comparatively little. In consequence, effects of age, variety and nutrition on the rate of nutrient uptake per unit of root were qualitatively similar whichever dimension of the root system was considered.It is shown by reference to descriptions of root systems published elsewhere that constancy in relationships between root dimensions occurs in solid media also. This property of root systems, which appears to result quite straightforwardly from the contrasting morphological characteristics of root axes and laterals, may help to simplify some aspects of the study of nutrient absorption by roots.
STUDIES ON THE METABOLISM OF EUCALYPTUS OBLIQUA
Authors: CARRODUS B. B. 
Published: May 2006

SummaryBoth ammonia and nitrate are available forms of nitrogen for uninfected roots of Eucalyptus obliqua. Glutamine and glutamate increase in quantity when ammonia is absorbed from solution. The effect of temperature on uptake of ammonia is complex. External sources of carbon skeletons do not stimulate the uptake of ammonia from solution. Uptake of ammonia is insensitive to the presence of DNP and KCN, although glycolysis is inhibited by these compounds.
SIMPLE AUTOMATIC SCANNING AND RECORDING SYSTEM FOR THE MEASUREMENT OF WATER POTENTIALS WITH DROPLET THERMOCOUPLE PSYCHROMETERS
Authors: BARRS H. D. 
Published: May 2006

SummaryA simple, automatic scanning and recording system designed specifically to receive the output from up to twenty‐five droplet thermocouple psychrometers is described. Essential components are a solenoid‐operated, low‐level switch, a high grade preamplifier and a potentiometric chart recorder capable of remote operation. Chart traces show noise level is low even on a 10 μV range. Provision is made to correct psychrometer readings for temperature effects due to heat of respiration. Statistical comparison of psychrometer calibrations obtained with this system and with manual switching into a reflecting galvanometer show the former system is at least as accurate as the latter. Parallel leaf water potential measurements made with the two systems agreed closely.
A NOTE ON THE MEASUREMENT OF STOMATAL APERTURE
Authors: LESHEM Y. , THAINE R. 
Published: May 2006

SummaryCellulose acetate replicas were made from silicone rubber impressions of the abaxial surfaces of perennial ryegrass leaves. Apertures between 1 μ and 4 μ (mean 2 μ) were measured in replicas from leaves which had been exposed to conditions expected to close the stomata. This discrepancy is explained by observations of the ventral walls of guard cells in transverse sections of stomata, and by Araldite impressions of the cut ends of ryegrass leaves. These show that when a stoma is closed the ventral walls make contact below the paradermal walls of the guard cells and consequently a small depression is left between the cells. These depressions are similar in width to the apparent apertures in the cellulose replicas which may be wrongly interpreted as slightly open stomata. In some species the silicone impression method is incapable of giving an accurate measurement of stomatal aperture. Consequently, in attempts to relate such measurements to stomatal function or rate of transpiration it should be established that small apertures shown in cellulose acetate replicas are not the result of depressions between the external surfaces of guard cells in closed stomata.
EFFECT OF TEMPERATURE 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 temperature during growth of ten Lolium genotypes from contrasting populations on subsequent light‐saturated photosynthesis and on leaf mesophyll and stomatal characteristics was examined. Most genotypes grown at 9° and 15° C had faster rates of photosynthesis at 15° than those grown at 21° C. Photosynthetic activity at 21° C was also greater when plants were grown at 15° Compared with 21° C. This temperature effect was not associated with changes in the observed mesophyll or stomatal characteristics. Plants grown at 21° usually had smaller mesophyll cells than those grown at 15° C. Among plants grown at 9° and 15° C, and among those grown at 21° C, light‐saturated photosynthesis was negatively correlated with mesophyll cell size.
NOTE ON THE CYTOLOGY OF AN F1 HYBRID BETWEEN SILENE DICLINIS (LAG.) M. LAINZ AND S. HEUFFELII SÓO
Authors: MORISSET PIERRE , BOZMAN GABRIELLE V. 
Published: May 2006

SummaryThis paper describes the meiotic cytology of an artificial F1 hybrid (2n= 24) between Silene diclinis (Lag.) M. Lainz (2n= 24) from Spain and S. heuffelii Sóo (2n= 24) from Rumania.The hybrid was intermediate between the two parents in most of its morphological characters. It had a pollen fertility of 31%. At meiosis, it formed bivalents except for an association of three or four chromosomes which revealed the presence of an heterozygous reciprocal translocation. The extent of pairing showed that the chromosomes of S. diclinis are homologous with those of S. heuffelii. Anaphase bridges occurred at both meiotic divisions; this phenomenon is discussed and interpreted as the result of spontaneous chromosome breakage. This breakage is tentatively explained as a consequence of minute structural differences between paired chromosomes.It is suggested that spontaneous chromosome breakage at meiosis may be a common but overlooked effect of diclinis in plants.
LIME CHLOROSIS IN SEEDLING ESTABLISHMENT ON CALCAREOUS SOILS
Authors: HUTCHINSON T. C. 
Published: May 2006

SummaryA comparison has been made amongst a number of species as to the ability of green and chlorotic foliage to fully reverse induced leaf water‐deficits. In all cases it was found that chlorosis conferred a reduction in the ability of the affected leaf to resaturate, compared with green leaves of the same species. Three distinct patterns of behaviour of chlorotic leaves were found in this respect. Permanent damage was caused by leaf water‐deficits as low as 10% in some species, whilst chlorotic leaves of others could withstand 60% water‐deficits before irreversible damage was detected. Green foliage of chlorosis‐resistant species were able to tolerate deficits of from 60 to 85% before resaturation ability was impaired. The ecological implications of these findings are considered, with respect to the establishment and survival of chlorosis‐resistant and susceptible seedlings on calcareous soils subject to periodic droughts.
DIFFERENTIATION OF RESPONSE TO CALCIUM WITHIN THE SPECIES FESTUCA OVINA L., USING ETHYLENEDIAMINE TETRAACETIC ACID
Authors: URQUHART C. 
Published: May 2006

SummaryA method was described by which differentiation of response to calcium within plant species could be rapidly detected. Festuca ovina tillers were used as the experimental material, and the method consisted of measuring root extension‐growth in 10−3m disodium ethylenediamine tetraacetic acid (Na2‐EDTA). A significant correlation (r=−0.86) was obtained between root growth in Na2‐EDTA and the calcium content of soil from the plants' natural habitats. The action of Na2‐EDTA on plant tissue was discussed and it was concluded that calcium deficiency was induced.
CHANGE OF APPARENT WEIGHT OF PLANT TISSUES IN SOLUTIONS
Authors: BLYTH D. F. , BRIGGS G. E. 
Published: May 2006

SummaryThe volume in carrot tissue apparently not penetrated, AOV, by a plasmolysing solution of cane sugar, potassium nitrate, potassium chloride or calcium chloride is a linear function of the reciprocal of the osmotic pressure of the solution over the range of the concentration used. This AOV, which includes the solids in the cell walls, is practically independent of the nature of the electrolytes but appears to be greater for cane sugar. There is no clear evidence for any active transport of water into the vacuoles of the cells.