bluuebunny/crossref_metadata_2025_split huggingface dataset:
EQUATIONAL RELATIONS BETWEEN NUTRIENT QUANTITIES AND CELLULAR GROWTH
Authors: BOSS M. L. 
Published: May 2006

SummaryThe quantities of five nutrients (N, P, K, Mg, Ca) were estimated in enlarging maize root tip cells. When consecutive cell fresh weights were plotted against the total quantity of any one nutrient per cell a parabolic curve resulted which fits the expression: W = kXn, where W is the fresh weight per cell, X the nutrient quantity and n and k are constants. The inference that may be drawn is that, under a defined environment, cell weight and nutrient quantity are related to each other by a constant quantitative factor. Two equations are derived to support the above hypothesis and also to support a related hypothesis that there might exist a quantitative relationship between any one nutrient and all other nutrients in a given cell at any one time.
OBSERVATIONS ON THE FLORAL BIOLOGY OF DIGITALIS SPECIES
Authors: PERCIVAL MARY , MORGAN PATRICIA 
Published: May 2006

SummaryObservations were made on the floral biology of Digitalis amandiana, D. ambigua, D. lanata, D. lutea and D. purpurea. The rhythms of flowering, pollen presentation, stigma opening and nectar secretion were investigated and the amount and concentration of the nectar measured. The flower sizes and insect sizes were compared, and proved that Bombus lucorum workers and queens, and B. agrorum workers and queens, were unable to reach the bottom of the corolla tube of Digitalis lutea. Bombus lucorum chiefly chose this species as nectar seeped along the lower side of the corolla to heights which it could reach (see addendum). The other species had no mechanical barrier to full exploitation of the nectar by B. lucorum and B. agrorum. B. agrorum preferentially worked Digitalis ambigua in early summer and D. lanata later.This paper describes observations made over two seasons, in both natural and glasshouse conditions. The full significance of much of the data cannot yet be evaluated but a tentative assessment of the significance of bee visits for pollination and hybridization is given.
SURFACE ASSOCIATIONS BETWEEN PARTICLES AND THE ENDOPLASMIC RETICULUM IN PROTOPLASMIC STREAMING
Authors: THAINE R. 
Published: May 2006

SummaryProtoplasmic streaming was observed in Tradescantia virginiana staminal hair cells using a bright field oil immersion obective and particle movements were followed in the cytoplasm. By recording and plotting particle positions in every fourth frame of a cine film, different velocities were measured for particles which appeared to follow a common pathway in a transvacuolar strand. From the same kind of analysis, various patterns of particle movement were revealed on the surface of the nucleus.Phase contrast observations of leaf hair cells of Primula obconica and Perilla frutescens showed that the endoplasmic reticulum was particularly well developed in regions of active protoplasmic streaming. Tubules of the endoplasmic reticulum were mainly in parallel orientation, with occasional lateral connections and anastomoses. Groups of parallel, endoplasmic reticulum tubules also appeared to be in continuity with the nucleus and, although these elements approached the nucleus at different angles from the parietal cytoplasm, they were more usually orientated with the long axis of the cell. Particles moved along the endoplasmic reticulum surfaces, sometimes in opposite directions on adjacent tubules, and a dynamic association was observed between the endoplasmic reticulum and mobile particles. This association was well illustrated when endoplasmic reticulum developed in a microscopically undifferentiated region of parietal cytoplasm. As the endoplasmic reticulum developed, the undifferentiated region was apparently transformed and became part of the endoplasmic reticulum. Occasionally, a centre of endoplasmic reticulum development was observed as a compact, complex pattern of tubules which gradually became orientated in a more linear manner as it expanded. This differentiation occurred in association with unusual, concentric, particle movement at the development centre. Finally the endoplasmic reticulum elements formed parallel pathways as commonly seen in actively streaming cytoplasm. These observations are incompatible with current theories of protoplasmic streaming which propose that particles are carried along by the fluid endoplasm or the endoplasmic reticulum. An extension of earlier theories has been made to explain the movement of particles in relation to the activities of the endoplasmic reticulum.Associations of particles and membranes were also observed in cytoplasm of cells involved in the synthesis and transport of organic nutrients. This structural association may be part of a common transport mechanism within parenchyma cells and over long distances in the vascular system.
APICAL DOMINANCE IN FUCUS VESICULOSUS
Authors: MOSS BETTY 
Published: May 2006

SUMMARYApical tips of Fucus vesiculosus L. were grown in sterile sea water. The apical cell region was excised surgically and this resulted in a decreased rate of growth of the segment and the regeneration of new branches. Treatment of cultured tips, whose apical cell region had been excised, with four auxins and two anti‐auxins revealed a striking effect. The latter treatment induced up to three or four times the number of branches regenerated in control experiments. Extraction and chromatographic procedures carried out on apical tips from November to January showed that a mixture of stimulatory and inhibitor)’growth substances was present. It is concluded that growth regulators play a part in determining apical dominance in Fucus.
INCREASES IN THE CAPACITY OF PEA TISSUE TO FORM ACYL‐ASPARTIC ACIDS SPECIFICALLY INDUCED BY AUXINS
Authors: SUDI J. 
Published: May 2006

SummaryA study has been made of the factors which influence the rate of formation of 3‐indoIeacetyl‐L‐aspartate and i‐naphthaleneacetyl‐L‐aspartate when segments of etiolated pea stems are treated with 3‐indolylacetic acid (IAA) and i‐naphthaleneacetic acid (NAA). When the tissue is placed in the auxin solution there is an initial lag in the formation of each conjugate and the maximal capacity is not reached until 6 hours. If the tissue is pretreated with non‐radioactive IAA or NAA for 8–14 hours before transference to radioactive IAA or NAA, the amount of conjugate formed in the next 2 hours is up to six times greater than that formed in tissues receiving no pretreatment. Apparent substrate saturation of the system is reached when the external concentration of IAA and NAA is about 50 and 15 mg/1 respectively.Induction of the formation of IAA aspartate is not a consequence of auxin‐induced extension growth since it also takes place in fully extended segments.The capacities of other auxins to induce the formation of both IAA and NAA aspartateswere assessed. It was established that both conjugates are also induced when the segments are pretreated with 2,4‐dichlorophenoxyacetic acid, 2,3,6‐trichlorobenzoic acid and S‐carboxymethyl‐N, N‐dimethyldithiocarbamate. In contrast, pretreatment with other carboxylic acids such as benzoic acid (which itself can form an aspartate) or transcinnamic acid, 3, 5‐dichlorophenoxy‐acetic acid and α‐2, 4‐dichlorophenoxy‐iso‐butyric acid does not affect the rate of formation of either IAA or NAA aspartate.These findings are interpreted in terms of induced enzyme formation in a system where the capacity for induction is specifically restricted to compounds which have a high auxinic activity. It is also clear that compounds showing a high inductive capacity are not necessarily suitable substrates nor are substrates necessarily capable of induction.
COMPARATIVE PHYSIOLOGICAL STUDIES ON DESCHAMPSIA FLEXUOSA, HOLCUS MOLLIS, ARRHENATHERUM ELATIUS AND KOELERIA GRACILIS IN RELATION TO GROWTH ON CALCAREOUS SOILS
Authors: WOOLHOUSE H. W. 
Published: May 2006

SummaryThe four grasses Deschampsia flexuosa, Holcus mollis, Arrhenatherum elatius and Koeleria gracilis grow on a wide range of soil types under natural conditions. Little is known of the physiological mechanisms by which the different species are adapted to particular soils. In glasshouse experiments all four species grew well on a fertile garden soil but showed varying diminution of growth on a calcareous soil, amounting in the extreme case of Deschampsia flexuosa to near failure, accompanied by chlorosis and severe inhibition of root development. The involvement of bicarbonate is suggested by the severe inhibition of growth of roots of D. flexuosa grown in water culture. Bicarbonate is without effect on the respiration of roots of the four species in short‐term experiments but roots of D. flexuosa showed a much greater rate of 14C‐bicarbonate fixation than the other species.It is suggested that the reduced growth of plants on calcareous soils may often be attributed to effects of bicarbonate on the physiology and growth of the root system leading only in extreme cases to chlorosis of the leaves. The data are discussed in relation to relevant physiological and ecological work. An appendix is added providing calculation of probable bicarbonate concentrations in calcareous soil solutions to provide a basis for the concentrations employed in laboratory studies.
THE PREPARATION AND PROPERTIES OF o‐DIPHENOL: OXYGEN OXIDOREDUCTASE FROM POTATO TUBERS
Authors: ABUKHARMA D. A. , WOOLHOUSE H. W. 
Published: May 2006

SummaryAn o‐diphenol: oxygen oxidoreductase (E.C. 1.10.3.1) has been purified from potato tubers. The enzyme shows a similar affinity for a range of substrates although the affinity is highest for chlorogenic acid, which occurs naturally in potato tubers. The affinity for oxygen is relatively low (Km= 2.23 × 10−4 m).The pattern of activity over a range of pH values varied considerably with different substrates. Ultracentrifuge studies and agar gel electrophoresis suggest the preparation is relatively pure although throughout purification the preparation showed an increasing cresolase as well as o‐diphenoloxidase activity.It is suggested that the cresolase activity is a normal component of the enzyme activity which may well be of importance in vivo. The high potency of a number of inhibitors including the copper‐specific 3:4 dichlorophenyl serine suggests that this metal is an integral part of the prosthetic group.
THE BASIC ACTION OF GIBBERELLIC ACID IN ELONGATION OF ‘METEOR’ PEA STEMS
Authors: ARNEY S. E. , MANCINELLI P. 
Published: May 2006

SummaryThe published evidence on the histological action of gibberellins does not favour the widespread belief that the primary action of gibberellic acid (GA) in stem growth is on cell elongation. Histological evidence from Meteor pea internodes shows that the main effect of GA is to stimulate cell division; and even when applied to internodes which have passed into the vacuolation phase of growth GA often re‐activates cell division. Mitotic activity in the apical meristem of Meteor pea stems is also stimulated by GA. The experimental results suggest that the primary effect of GA on caulescent plants, as on rosette plants, is to increase mitotic activity in apical and sub‐apical meristems; the cell elongation effect of GA may well be a derivative of the increased mitotic activity, possibly through an increased production of auxin in the meristematic region.
RELATIONSHIP BETWEEN ROOT GROWTH OF FLAX (LINUM USITATISSIMUM) AND SOIL WATER POTENTIAL
Authors: NEWMAN E. I. 
Published: May 2006

SummaryFlax plants were grown in vertical cylinders of soil contained in polyethylene tubing. Root growth was estimated from the number of roots crossing vertical and horizontal lines on the tube surface. After the plants were 29 days old, some of the soil cylinders received no more water, and root growth and soil water content in each 10 cm layer of soil were determined at 2‐day intervals. When a graph of root growth against soil water potential is plotted, points from each 10 cm layer fall approximately on the same concave curve. A marked reduction in root growth first occurred at — 7 bars total water potential. At — 15 bars, root growth was 20% or less of the rate before drying, but some root growth occurred in soil drier than — 20 bars. The results suggest that root growth in each layer was not influenced by water potential elsewhere in the plant.
A POROMETER FOR USE IN THE FIELD
Authors: WEATHERLEY P. E. 
Published: May 2006

SummaryA falling mercury plug draws air through a leaf cup in series with a standard capillary resistance bridged by a mercury manometer. Readings on the manometer correspond to leaf conductances. Thus no timing is necessary. The cup is a short length of latex rubber tubing (mternal diameter 2·5 mm) held in position by a light clip. The apparatus can be held and operated in one hand leaving the other free to manipulate the porometer chp. No levelling is necessary. The poro‐meter is contained in a case 24 × 6 × 3 cm and is easily portable. Using the apparatus itself, capillaries are readily standardized in units of conductance expressed in terms of rate of flow of air through the capillary per unit pressure difference (mm3/min/rnm Hg). Using a 2·5 mm cup the highest stomatal conductances measured were around 200 units. Three standard capillaries are incorporated in the porometer allowing approximately a 500‐fold change in leaf conductances to be covered.The performance of the instrument on Sambucus nigra, Vaccinium vitis‐idaea and Poa annua is demonstrated and some of its advantages and weaknesses discussed.
STUDIES ON OXYGEN TRANSPORT THROUGH MUSTARD SEEDLINGS (SINAPIS ALBA L.)
Authors: GREENWOOD D. J. 
Published: May 2006

SummaryThe entry of oxygen into various organs and the transport of oxygen through plant tissues was studied. Seedlings had their roots embedded in agar‐gel to exclude oxygen. The gas atmosphere around a part of the plant was changed from nitrogen to oxygen and the subsequent increase in oxygen concentration at a point on the root surface was measured. Changing the atmosphere around the stems and leaves induced rises in oxygen concentrations throughout the length of the roots to the root tips. An equation derived by assuming that transport was by gaseous diffusion and was large in comparison with metabolic uptake, fitted the increases in oxygen concentration at points on the roots within 3 cm of the stems, but not at the root tips. The discrepancy was accounted for by the greater value of metabolic uptake relative to oxygen transport at the root tips than near the stems. Thus all the results were consistent with oxygen diffusing through gas spaces within the plants.Removing all the leaves restricted the entry of oxygen into the aerial portions of the plants, but the extent to which it did so was reduced by subjecting the seedlings to water stress and was less with old than with young seedlings. Excising the leaves was considered to release cell sap which blocked the gas channels.Exposure of either the stem or a segment of root to oxygen resulted in a small amount of oxygen being transported along the roots.Oxygen transport from the aerial portions of the plant to a point on the roots, 1–2 cm from the hase of the stems, was almost independent of (a) the aeration conditions of the growth media; (b) the mechanical impedence to root growth offered by the media; (c) root length; (d) shoot length; (e) age of plant.
SHADE TOLERANCE IN TREE SEEDLINGS
Authors: LOACH K. 
Published: May 2006

SummarySeedlings of five tree species of different shade tolerance were raised in full daylight and in three degrees of shade. Leaf chlorophyll content, the rate of respiration in darkness at 30°C and photosynthesis rates at 30°C over a range of light intensities, were measured in each case. The initial slope of the curve, relating photosynthesis rate and light intensity, provides a measure of the capacity of the photochemical system of the leaves and was usually steeper in shade grown leaves than in sun leaves. Thus all species showed a degree of adaptation to shade conditions, but, surprisingly, leaves of the shade tolerant species had slightly less steep slopes than the intolerant species. This was offset by a considerably lower rate of leaf respiration and a lower light compensation point in the tolerant species, so that considered over a range of varying low light intensities, the net photosynthesis would probably be similar in both groups. Moreover, whilst leaves of the tolerant species tended to show reduced respiratory activity when grown in shade, this was less evident in the intolerant species. The differences in rates of respiration may he the most important determinants of success or failure in woodland shade, where the plant may spend many more hours below than above the light compensation point.
THE RELATION BETWEEN HOST AND ENDOPHYTE IN ORCHID MYCORRHIZA
Authors: HARVAIS G. , HADLEY G. 
Published: May 2006

SummaryExtensive isolation of root endophytes from Orchis (Daciylorchis) purpurella and other British orchids yielded a variety of strains of Rhizoctonia and of other fungi. R. repens, a common orchid endophyte, occurred in several host species and habitats. R. solani was uncommon, being obtained only from Orchis purpurella and Coeloglossum viride in certain situations. Most Rhizoctonia strains were obtained from only one plant and one habitat and the evidence indicated that there was no specificity between host and endophyte.In symbiosis tests isolates from roots generally infected the protocorms but did not always stimulate the growth of the species from which they originated. Four strains of R. solani isolated from soil were stimulatory to Orchis purpurella protocorms. Of four Rhizoctonia solani strains pathogenic on crop hosts, two stimulated protocorm growth and one was parasitic. It is suggested that the occurrence of a strain as a root endophyte may largely be a reflection of its distribution and of the factors affecting its growth in the soil.
HEMIPARASITIC NUTRITION IN ANGIOSPERMS
Authors: GOVIER R. N. , NELSON M. DENISE , PATE J. S. 
Published: May 2006

SummaryPlants of the hemiparasite Odontites verna (red bartsia) benefited markedly through association with barley (Hordeum vulgare L.) or white clover (Trifolium repens L.). Benefit commenced after the establishment of haustorial connections on the roots of a host.Compounds containing labelled carbon moved through haustoria into the hemiparasite following feeding of [14C]urea or 14C‐labelled carbon dioxide to shoots of a range of host species. The reverse movement from hemiparasite to host was of a very small proportion although the hemiparasite was clearly capable of transferring assimilates from its leaves to all parts of its root system.A bleeding sap technique was used to study the common metabolites released from the roots of Odontites, barley and white clover and to determine those organic compounds involved in transfer from each host to the hemiparasite. After a short exposure of the host shoot to 14CO2, it was possible to recover labelled amides, amino acids, organic acids and sugars in sap exuding from the cut root stumps of host and hemiparasite, and in the ethanol‐soluble fractions of host roots and hemiparasite tissues. Labelled sucrose was not detected in the bleeding sap or tissues of the hemiparasite although it was the main labelled compound to be translocated to the host root. The hemiparasite root appeared to metabolize a proportion of the assimilates that it received from a host plant. Odontites grown alone was capable of a limited rate of synthesis of amino acids in its own roots. When grown in association with a suitable host, assimilation of nitrate by roots of the hemiparasite was supplemented by absorption of amides, amino acids and other metabolites elaborated in the host. The spectra of compounds entering the hemiparasite varied greatly with the host species, these differences being reflected in the composition of the pool of soluble compounds in the mature hemiparasite.
PHELLOGEN ACTIVITY IN ROBINIA PSEUDACACIA L.
Authors: WAISEL Y. , LIPHSCHITZ NILI , ARZEE TOVA 
Published: May 2006

SummaryPhellogen activity in Robinia pseudacacia and some of the factors controlling it were investigated. A highly active phellogen is characterized by the production of large thin‐walled phellem cells. A layer of flat, thick‐walled phellem cells next to the phellogen characterizes an inactive meristem. The annual rhythm of phellogen activity of Robinia trees grown outdoors reveals that the phellogen is active twice a year, while under the same conditions the cambium is active once a year only. Under controlled conditions of temperature and day‐length the phellogen was found to be active mainly under combinations of short day and high temperature or long day and low temperature.
STUDIES ON THE TRANSPORT OF OXYGEN THROUGH THE STEMS AND ROOTS OF VEGETABLE SEEDLINGS
Authors: GREENWOOD D. J. 
Published: May 2006

SummaryExperiments were carried out to determine whether oxygen could enter the leaves of vegetable seedlings and be transported through the tissues to the roots. The technique involved embedding seedlings in agar/potassium phosphate gel to exclude oxygen; the atmosphere around the leaves was varied and oxygen concentrations were measured at points on the root surface 0.5–2.0 cm from the junction of stem and root system. When the gas around the leaves was changed from nitrogen to oxygen, the oxygen concentration at the root surfaces increased rapidly. The rates of increase agreed approximately with those calculated by assuming that the plants contained continuous non‐tortuous gas‐filled channels, the view that diffusion through these channels was the means by which oxygen was transported through the plant, and that the gas channels were within about 12 μ of the root surfaces.Experiments were also carried out to determine whether the roots of seedlings could grow in oxygen‐free media. Seedlings were grown in an atmosphere of air with their roots in columns of agar‐gel containing yeast and glucose. Depending on the amount of yeast and glucose in the gel, the oxygen concentration fell to zero at depths of between 0.5 and 2.0 cm from the gel surface. Seedling roots rapidly penetrated oxygen‐free zones in the gel but the extent of penetration appeared to be unrelated to the depth of zero oxygen concentration.A similar pattern of results was obtained with seedlings of twelve different species and it was concluded that the stems and roots of most seedlings contain continuous, non‐tortuous gas channels through which oxygen diffused. When the plants were grown under anaerobic conditions such diffusion could satisfy all the roots’requirements for oxygen.
MICROFIBRILS IN THE LORICA OF THE FRESHWATER ALGA DINOBRYON
Authors: KARIM A. G. A. , ROUND F. E. 
Published: May 2006

SummaryThe presence of very fine microfibrils in the lorica of species of Dinobryon has been revealed by electron‐microscope examination of shadowed material. No indication of scales or annular components in the lorica, such as have been recorded by earlier workers using the light microscope, can be detected.