bluuebunny/crossref_metadata_2025_split huggingface dataset:
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: HOLLIGAN P. M. , JENNINGS D. H. 
Published: May 2006

SummaryThe incorporation of radioactivity into polyols and carbon dioxide was measured for cultures of Dendryphiella salina incubated in media containing [i‐14C]‐ or [6‐14C]‐glucose, with nitrate, ammonium or glutamate as nitrogen sources.The labelling patterns show that mannitol is synthesized partly via a direct route from substrate glucose and partly from hexose‐phosphate derived from the pentose‐phosphate pathway. Rapid turnover of the mannitol pool and the redistribution of radioactivity caused by the symmetry of the mannitol molecule lead to the synthesis of labelled arabitol from both forms of radioactive glucose. After a 6‐hour incubation period, the proportion of mannitol synthesized via the pentose‐phosphate pathway ranges from 36% in nitrate media to 19% in glutamate media.C1/C6 ratios for yields of 14CO2 also indicate that the activity of the pentose‐phosphate pathway is greatest in the nitrate media and least in the presence of glutamate. Furthermore, there is an increase in the C1/C6 ratio when nitrate or methylene blue is added to cultures in ammonium media.The results are discussed in relation to previous studies of the pentose‐phosphate pathway in fungi containing mannitol.
MORPHOLOGY AND TAXONOMY OF THE OOMYCETES, WITH SPECIAL REFERENCE TO SAPROLEGNIACEAE, LEPTOMITACEAE, AND PYTHIACEAE
Authors: DICK M. W. 
Published: May 2006

SummaryProblems of intraspecific variability and the delimitation of taxa are discussed in relation to the patterns of inheritance in Oomycetes made possible by the combination of a haplobiontic‐B life cycle with multinucleate gametangia.
ENDOGENOUS INORGANIC CARBON SOURCES IN PLANT PHOTOSYNTHESIS
Authors: RAVEN J. A. 
Published: May 2006

SummaryThe biochemical evidence concerning the rate of production of CO2 by dark respiratory pathways in illuminated green plant cells is reviewed.Pyruvate decarboxylation and the TCAC are important sources of biosynthetic intermediates in the light as well as in the dark. The rate of CO2 release required to synthesize these carbon skeletons from pyruvate in the light approaches the rate of dark CO2 production. Oxidative phosphorylation, the second important role of the TCAC in the dark, is supplemented and partly replaced by photophosphorylation in the light, and some sort of ‘physiological uncoupling’ may be required to stop the rate of generation of reductant in the TCAC in the light from exceeding the rate of its consumption in oxidative phosphorylation. The decarboxylations of pyruvate and TCAC metabolism occur, in the light as in the dark, in the mitochondria (except possibly in Acetabularia, where they may also occur in the choroplasts). All the decarboxylations produce unhydrated CO2.The oxidative PPP has no obligatory role to play in carbon skeleton synthesis, and it is supplemented in its dark rôle of NADPH2 synthesis by photoproduction of reductant when the cell is illuminated. Evidence as to whether light stimulates or inhibits the oxidative PPP is contradictory. This pathway occurs in at least some illuminated green cells; the decarboxylation reaction produces unhydrated CO2, and occurs in both the cytoplasm and the chloroplast.The situation with regard to carbon flux through the dark respiration pathways in various groups of plants is considered quantitatively. Even without taking into account the contribution from light‐dependent pathways of CO2 production (photorespiration), it would appear that the absence of net CO2 release to a CO2‐free gas stream in the light in a green cell or tissue cannot entirely be attributed to inhibition of respiration. The absence of CO2 release must also reflect the capacity of the tissue for reassimilation of endogenous CO2.
‘DUAL ISOTHERMS’ FOR THE ABSORPTION OF IONS BY PLANT TISSUES
Authors: BARBER D. A. 
Published: May 2006

SummaryIt has frequently been demonstrated that when plant tissues of the same initial ionic status are transferred to solutions of a sufficiently wide range of concentration, two absorption isotherms are observed. They have been widely interpreted as evidence for the existence of two independent physiological mechanisms for the absorption of nutrients. The experiments here described on the uptake of phosphate and rubidium ions by excised barley roots and discs of beetroot tissue from solutions ranging in concentration between 0.001 and 50.0 mM were conducted by procedures similar to those on which the foregoing conclusions had been reached, except that sterile procedures were used to eliminate any effects of micro‐organisms. The two absorption isotherms were evident under sterile conditions. However, evidence was obtained that only uptake observed at low concentrations (below 0.2–0.5 mM) is attributable to plant metabolism. The isotherm observed over the higher concentration range is accountable to passive diffusion and may thus be regarded as a consequence of the experimental procedures.
THE INFLUENCE OF PHOSPHORUS DEFICIENCY ON THE TRANSPIRATION OF ARCTIUM MINUS BERNH.
Authors: ATKINSON D. , DAVISON A. W. 
Published: May 2006

SummaryThe effect of phosphorus deficiency on the transpiration of Arctium minus was investigated. The transpiration rate of the phosphorus‐deficient plants was lower than that of the controls. This situation was reversed after wilting which depressed the transpiration rate of the control plants. The ratio of light to dark transpiration was higher in the control plants, and covering the abaxial surface of their leaves with petroleum jelly caused a proportionately greater reduction in their rate of transpiration. The leaves of the deficient plants were composed of smaller cells than those of the controls. An examination of leaf surfaces showed that those of the deficient plants were covered by a much denser layer of hairs. It was concluded that the difference in the rate of transpiration was probably connected with stomatal functioning.
IONIC RELATIONSHIPS OF ENTEROMORPHA INTESTINALIS
Authors: BLACK D. R. , WEEKS D. C. 
Published: May 2006

SummaryConcentrations of the major component ions (K, Na and Cl) of sea water and cells of Enteromorpha intestinalis (L.) Link, were determined. Measurements of the electric potential difference across the plasmalemma and the influx and efflux of each ion indicate that K and Cl are actively imported and Na actively exported. Estimates of membrane permeability to the passive diffusive fluxes of these three ions alone have been used to explain the origin of the cell membrane potential. Tracer ion exchange kinetics are taken as showing that the tonoplast is more permeable than the plasmalemma to each ion.
AGEING IN PLANT EMBRYOS II. AGE‐INDUCED DAMAGE AND ITS REPAIR DURING EARLY GERMINATION
Authors: BERJAK PATRICIA , VILLIERS T. A. 
Published: May 2006

SummaryThe rate of ageing of a batch of caryopses of Zea mays was accelerated by placing in a controlled environment of high temperature and humidity. Samples were withdrawn representing a sequence of increasing physiological ageing, and selected stages were subjected to ultrastructural and cytochemical investigation. Membrane aberrations increased with increasing age of the embryos. The damage was seen immediately upon imbibition, but there was much evidence of repair of this damage at later stages of germination. The existence and operation of mechanisms for the repair of such damage are discussed.
CYTOLOGY OF SIEVE ELEMENTS IN MINOR VEINS OF SUGAR BEET LEAVES
Authors: ESAU KATHERINE 
Published: May 2006

SummaryIn view of some questions raised in the literature on assimilate translocation regarding the degree of differentiation of sieve elements in minor veins of Beta vulgaris L. these elements were examined with light and electron microscopes. The sieve elements throughout the minor veins in the sugar beet leaf, including those in the free endings of the veins, have typically differentiated sieve plates, with pores usually lined with callose and containing P‐protein. The sieve plates occur in the end walls and the side walls. The sieve elements are connected with adjacent parenchyma cells (including the companion cells) by branched plasmodesmata. The protoplasts of the sieve elements undergo ontogenetic changes common for these cells in most vascular plants. The one to several sieve elements seen in transection of a minor vein attain maturity before the xylem is completely differentiated. No sieve elements are added after this stage, and the earliest mature sieve elements are not obliterated. The parenchyma cells (including the companion cells) of the phloem are generally several times wider than the sieve elements and constitute the major part of the tissue. However, the width of a parenchyma cell may vary at different levels so that in some sections a given parenchyma cell may not exceed a sieve element in width even if it does so in other sections.
THE ULTRASTRUCTURE OF GUARD CELLS OF PHASEOLUS VULGARIS
Authors: WHATLEY J. M. 
Published: May 2006

SummaryThe ultrastructure of mature guard cells of Phaseolus vulgaris L. grown under continuous light regime showed remarkable stability, remaining constant in appearance under a wide range of conditions of nutrient deficiency. The ultrastructure was quite unlike that of leaf parenchyma cells of normal plants, but had certain characteristics similar to those found in palisade parenchyma cells suffering from magnesium and potassium deficiency.
SOME OBSERVATIONS ON THE EVOLUTION OF POLLEN TYPES IN DICOTYLEDONS
Authors: SPORNE KENNETH R. 
Published: May 2006

SummarySulcate pollen is shown statistically to be positively correlated with four primitive characters. There is some evidence that tricolpate pollen is more primitive than triporate. Polyporate pollen and polycolpate pollen are negatively correlated with two and six primitive characters, respectively, while multiaperturate pollen is negatively correlated with seven primitive characters. Evolution, therefore, has involved a progressive increase in the number of apertures. This conclusion is supported by the fossil record.
ULTRASTRUCTURE AND ION GRADIENTS IN THE SALT GLANDS OF AVICENNIA MARINA (FORSSK.) VIERH.
Authors: SHIMONY CARMELA , FAHN A. , REINHOLD LEONORA 
Published: May 2006

SummaryThe salt gland of Avicennia marina consists of two to four collecting cells, one stalk cell and usually eight secretory cells. The side wall of the stalk cell is completely impregnated with electron‐dense material. An amorphous substance appears between the upper walls of the secretory cells and the cuticle above them. The latter possesses many narrow channels.The ultrastructure of the secretory cells was studied under various conditions. The protoplast is usually dense and poorly vacuolated. The nucleus is relatively large, and the cytoplasm rich in organelles, especially E.R. elements, Golgi bodies and mitochondria. There are many vesicles which appear to be derived from the Golgi bodies and from E.R. cisterns. Elongated vacuole‐like structures, apparently derived from Golgi cisterns, and membranous bands were also observed: it is suggested that both represent different stages of the same structure. In many glands the protoplast appeared to be contracted in one of the secretory cells and the space between it and the cell wall was filled with an amorphous electron‐dense substance.Antimonate precipitation and electron probe analysis were employed to locate ions in the tissues. Both techniques indicated that the salt content of the gland cells was lower than that of the mesophyll. A downhill gradient appeared to exist from cells near the xylem, through the mesophyll to the gland, and was continued through the gland itself. The possible location of ion pumps is discussed in the light of this evidence.
AGEING IN EXCISED ROOTS OF TOMATO
Authors: WESTON GEOFFREY D. 
Published: May 2006

SummaryGlucose pre‐treatment enhances ageing in excised roots of tomato on subsequent sub‐culture in sucrose medium to a much greater extent than pre‐treatment in sucrose or fructose. However, continual sub‐culture in glucose medium causes much less ageing than continual sub‐culture in sucrose or fructose. Sugar concentrations used were such as to preclude effects due to osmotic potential changes. Pre‐treatment in mixtures of glucose and sucrose caused less ageing than glucose alone, but this may be due to the demonstrated reduction in glucose absorption caused by sucrose. A two‐stage system for the development of ageing is proposed and this is discussed in the light of earlier studies on ageing in cultured tomato roots.
UPTAKE OF 32P BY PINUS RADIATA ROOTS INOCULATED WITH SUILLUS LUTEUS AND CENOCOCCUM GRANIFORME FROM DIFFERENT SOURCES OF AVAILABLE PHOSPHATE
Authors: MEJSTŘÍK V. K. , KRAUSE H. H. 
Published: May 2006

SummaryThe efficiency of the mycorrhizal fungi Cenococcum graniforme and Suillus luteus on young seedlings of Pinus radiata for phosphorus uptake from different sources was investigated using 32P. There was a stimulatory effect of mycorrhizas with Suillus luteus on uptake of phosphorus. Cenococcum graniforme had a stimulatory effect on incorporation of 32P only when most of the phosphorus was in organic form. In the other conditions this symbiont had an inhibitory effect. There was a greater accumulation of phosphate in the roots than in the green parts of the seedlings.
POLLEN‐RAIN FROM THE VEGETATION OF NORTH‐WEST INDIA
Authors: SINGH G. , CHOPRA S. K. , SINGH A. B. 
Published: May 2006

SummaryA general survey of the pollen‐rain from the vegetation of north‐west India is described. The survey is based on the study of 114 modern pollen spectra from sixty‐four different sites. It is revealed that with certain qualifications the major aspects of the extant vegetation belts of north‐west India are reflected in the pollen‐rain falling within them. In the territory as a whole, the pollen of herbs dominates that of trees and shrubs except in close proximity to one of the latter. Amongst the woody plant pollen that of shrubs is commonest in the arid belts but tree Pollen asserts itself as rainfall increases. The long‐distance transport of pollen from one region to another does not affect the overall picture of the pollen‐rain to any significant degree except in the areas bordering the Himalayas where pine pollen is over‐represented. Cerealia type pollen usually occurs in areas where there is cereal cultivation but remains unrepresented in the very arid belt which is free of cereal agriculture. The pollen frequencies of Acacia, Prosopis, Zizyphus, Salvadora, Maytenus and the species belonging to Leguminosae, Labiatae and Geraniaceae are Under‐represented. On the other hand 5% pine pollen occurs even as far as 600 km from the source.
FACTORS INFLUENCING THE GROWTH OF THE ROOT SYSTEM OF ETIOLATED SEEDLINGS OF PISUM SATIVUM L.
Authors: MCDAVID C. R. , MARSHALL C. , SAGAR G. R. 
Published: May 2006

SUMMARYThe growth of the root system of dark grown dwarf‐pea seedlings ceases 10–12 days after germination, even though cotyledonary reserves continue to be used for shoot growth. The cessation of root growth was not due to competition between shoot and root for cotyledonary reserves, but appeared to be the result of a depletion of essential factors which are normally supplied to the root by the light‐grown shoot. These factors included auxin, the B vitamins (thiamine and nicotinic acid) and adenine. Application of IAA in lanolin to the cut stumps of de‐shooted seedlings plus a supply of thiamine, nicotinic acid and adenine in the culture solution substituted to some extent for an illuminated shoot.
AN IMPROVED BIO‐ASSAY FOR ABSCISIC ACID AND OTHER ANTITRANSPIRANTS
Authors: OGUNKANMI A. B. , TUCKER D. J. , MANSFIELD T. A. 
Published: May 2006

SUMMARYA greatly improved method is described for the bio‐assay of abscisic acid (ABA) and other compounds that possess ‘antitranspirant’ activity. As in the previous method, the stomatal responses are observed on pieces of isolated epidermis of Commelina communis immersed in small volumes of solution containing the compounds to be assayed. In new media, it is now possible to obtain linear responses to ABA concentrations over the range 10‐4‐10‐8 M in PIPES buffer at pH 6.8, and over the range 10‐7‐10‐10 M in citrate buffer at pH 5.5. In citrate buffer, it is possible to detect as little as 26 pg of ABA. In both media, the assay is unaffected by the presence of six other growth regulators (auxin, gibberellic acid, kinetin, coumarin, xanthinin and scopoletin) but the stomata closed partially in response to 10‐3 M chlorogenic acid.
GROWTH AND WATER ABSORPTION OF WHEAT WITH PARTS OF THE ROOTS AT DIFFERENT WATER POTENTIALS
Authors: LAWLOR D. W. 
Published: May 2006

SUMMARYThe growth and water transport of wheat plants was measured with the root system divided into two equal parts and grown in solutions of different osmotic potential. Growth of roots decreased with decrease in osmotic potential and stopped at ‐10 bar, but solutions of high osmotic potential, available to part of the root system, did not significantly influence the growth of the other part of the root system when the osmotic potential was small. However, it did allow greater growth of leaves and faster transpiration rates, because plant water potential was not greatly decreased. The rate of water transport slowed with decreasing osmotic potential but with part of the root system under stress absorption from solutions of high potential increased. The resistance of the parts of the root system and plant increased, approximately logarithmically, with decreasing leaf water potential from ‐4 to ‐17 bar. Roots are influenced by the potential of water at their surface, but a decrease in water absorption by part of the root is compensated for by an increase in water absorption by other roots.
HYDROPHILIC GROWTH INHIBITORS FROM LAMINARIA AND ASCOPHYLLUM
Authors: HUSSAIN A. , BONEY A. D. 
Published: May 2006

SUMMARYWater‐soluble compounds isolated from Laminaria digitata and Ascophyllum nodosum caused marked inhibition of lettuce hypocotyl growth. GLC analysis of these substances showed, in one case, properties similar to ABA (abscisic acid) but definite information on this must be deferred until the chemical nature of the seaweed compound is verified. The possible role of these compounds in seaweed growth and their possible significance as ectocrines in the sea, are discussed.
DEVELOPMENT OF CHLOROPLASTS FROM AMYLOPLASTS IN POTATO TUBER DISCS
Authors: ANSTIS P. J. P. , NORTHCOTE D. H. 
Published: May 2006

SUMMARYWhite potato tuber tissues (Solarium tuberosum, vars. King Edward and Craigs Royal), contained carotenoids but did not contain either protochlorophyll or chlorophyll. On illumination of tuber discs, the accumulation of chlorophyll a and chlorophyll b began simultaneously after 19 hours and continued for 3 weeks. This greening process was associated with a synthesis of galactolipids.Light of intensity 750 1× was sufficient to induce maximum greening and to cause greening throughout the disc. Blue light was more effective than orange or green light.Chlorophyll accumulation in tuber discs was inhibited by cycloheximide, chloramphenicol, lincomycin, δ‐aminolaevulinic acid, benzyladenine, and high concentrations of sodium arsenate and potassium cyanide. It was unaffected by 2,4‐D, laevulinic acid and malonic acid. When green discs were returned to darkness, the total chlorophyll content remained constant over a period of 7 days but the ratio of chlorophyll a to chlorophyll b decreased.These results are discussed in terms of the control mechanisms and differentiation processes involved in the development of chloroplasts from amyloplasts.
NITROGEN METABOLISM OF HALOPHYTES II. NITRATE AVAILABILITY AND UTILIZATION
Authors: STEWART G. R. , LEE J. A. , OREBAMJO T. O. 
Published: May 2006

SUMMARYThe availability and utilization of nitrate by salt‐marsh plants has been studied. All the species examined are able to assimilate nitrate, which appears to be the most important form of nitrogen available on the marsh. Species, from the strand line and lower marsh have higher nitrogen contents and nitrate reductase levels, than those from the upper marsh. Competition between species for nitrate is more important in the upper than lower marsh, because of low nitrate supply. Species such as Armeria maritima, Glaux maritima, Limonium vulgare and Triglochin maritima are able to compete more effectively for nitrate in the upper marsh than Puccinellia maritima, Salicornia europaea, Suaeda maritima, Spergularia media and Spartina×anglica. The results indicate there is an increase in nitrogen supply down the marsh, which may be associated with the input of nitrate during tidal innundation.
THE INFLUENCE OF LIGHT AND WATER DEFICIT UPON DIFFUSIVE RESISTANCE OF LEAVES OF VICIA FABA L.
Authors: KASSAM A. H. 
Published: May 2006

SUMMARYThe resistance of the upper (ru) and lower (r1,) surface of the leaf to diffusion of water vapour in Vicia faba was influenced differently by light and water deficit. ru saturated at about 100 Wm‐2 while r1, saturated at about 13 Wm‐2. At a given light intensity r1, was always smaller than r1. The difference in the density of stomata between the two surfaces of the leaf alone does not explain the magnitude of the difference between ru and r1, for V. faba and other species. Impressions of the stomata of the two surfaces at different light intensities indicated that the stomata on the lower surface were more widely open than those of the upper surface.When stomatal response to light was not saturated, increase in leaf‐water deficit was accompanied by increase in ra and r1. Under saturating light intensities however r1, increase in leaf‐water deficit did not affect ru and r1, until leaves were flaccid and pressure potential close to zero; although the stomata on the upper surface closed at slightly higher water potentials than those of the lower surface. A dry treatment lasting 2 days, at the end of which the leaf was flaccid, affected the subsequent performance of the stomata while the leaf‐water deficit had been eliminated. This after‐effect was much greater on ru than on r1, and a complete recovery of the stomata on the upper surface took more than 2 days.Larger differences between ru and r1, values are associated with larger lower to upper stomatal density ratios in a number of species. However r1, the ratios of ru/r1, are much larger than the corresponding stomatal density ratios. It appears that in V. faba, and in a number of other species, the stomata of the lower surface are more widely open that those of the upper surface either at equal light intensity or when leaves are illuminated from above.
COMMENTS ON THE USE OF REGRESSION ANALYSIS FOR THE STUDY OF PLANT GROWTH
Authors: NICHOLLS A. O. , CALDER D. M. 
Published: May 2006

SUMMARYThe adaptations of plants to environment can take many morphological and physiological forms. The rate at which new plant material is accumulated is an integrated measure of plant response to environment and is a useful character when comparing either genetic differences between populations or effects of different environmental conditions on populations.Several approaches have been made to the study of quantitative plant growth. With frequent harvesting, regression analysis provides a powerful tool in describing the relationship of total weight with time. In this paper we have adopted procedures outlined by Draper and Smith (1966) and applied regression analysis to two sets of data from our programme on Atriplex. These demonstrate ways in which appropriate polynomial regression equations can be objectively applied to the total weight‐time relationship. Implications of fitting an inappropriate regression equation and the problems of extrapolation are also discussed.
LINKS BETWEEN ROOTS BY HYPHAE OF VESICULAR–ARBUSCULAR MYCORRHIZAS
Authors: HEAP ALISON J. , NEWMAN E.I. 
Published: May 2006

SUMMARYUsing a buried slide technique, hyphal connections are shown to exist between different roots on one plant, Lolium perenne L., and also between two roots of different species L. perenne and Plantago lanceolata L. These two species are commonly found together in permanent pasture.