bluuebunny/crossref_metadata_2025_split huggingface dataset:
FACTORS CONTROLLING STOLON DEVELOPMENT IN THE POTATO PLANT
Authors: KUMAR D. , WAREING P. F. 
Published: May 2006

SummaryThe development of the basal axillary shoots of Solanum andigena as stolons is dependent upon their being subject to apical dominance. Normally, stolons develop only from axillaries located below the soil surface and it is shown that darkness and a moist atmosphere favour stolon emergence. However, all axillaries subject to apical dominance are potentially capable of emerging as stolons, as shown by the fact that maintaining the axillaries of aerial shoots under conditions of darkness and humidity by ‘aerial layering’ results in their emergence as stolons. In rooted stem cuttings, basal axillaries not subject to apical dominance grow as leafy shoots, but if the roots are removed they develop as stolons. Thus, axillary shoots not subject to apical dominance are converted from stolons into leafy shoots by some influence of the roots.Axillaries in the aerial part of the shoot may be stimulated to grow out as stolons by applying gibberellic acid to the stem. The role of indole acetic acid (IAA) in stolon development appears to be related to its effects on apical dominance. It is shown that application of the cytokinins, kinetin and benzylamino purine to the tips of stolons (both natural and experimentally induced) causes them to develop into upwardly directed leafy shoots. The development of an axillary into a leafy shoot or a stolon can be experimentally regulated by manipulation of the levels of applied gibberellin, IAA and cytokinin, stolon development requiring high gibberellin and low cytokinin levels. It is suggested that normal stolon development is regulated by interaction between endogenous hormones, and it is postulated that the apical dominance necessary for stolon development involves the monopolization of cytokinins produced in the roots by the main apex, so that only low cytokinin levels are available to the axillary shoots. The effect of darkness on stolon emergence may be mediated through increased endogenous gibberellin levels.
EFFECTS OF COTYLEDONS, LEAVES AND STEM APEX ON EARLY PERIDERM DEVELOPMENT IN FRAXINUS PENNSYLVANICA SEEDLINGS
Authors: BORGER G. A. , KOZLOWSKI T. T. 
Published: May 2006

SummarySeedlings of Fraxinus pennsylvanica were grown from seed and subjected to various treatments which removed leaves, cotyledons, stem apices or buds at periods up to 35 days after cotyledon emergence. In addition, portions of the stems of several seedlings were kept in darkness during the experiments. Periderm did not form in seedlings from which all foliage was removed as it emerged. Seedlings with any foliage developed periderm, but periderm‐stimulatory substances were not released from foliage until it reached a certain stage of development. Both cotyledons and leaves exported periderm‐stimulatory substances, but leaves appeared to export more. Substances produced in the apical meristem or actively growing buds had no effect on phellogen formation and activity, but appeared to regulate the kind of periderm cells produced, their differentiation, and their anti‐clinical divisions. The stimuli for periderm formation and subsequent development were strongly basipetal and only weakly acropetal. However, darkening the stem below the foliage appeared to moderate the polar transport of periderm‐stimulatory substances. Foliar products increased wound‐periderm formation and were essential for wound‐stimulated formation of normal periderm.
EFFECT OF SELECTION FOR STOMATAL Length AND FREQUENCY ON THEORETICAL STOMATAL RESISTANCE TO DIFFUSION IN LOLIUM PERENNE L.
Authors: WILSON D. 
Published: May 2006

SummaryA population of Lolium perenne L.‘Grasslands Ruanui’ grown in a controlled environment, exhibited much phenotypic variation in stomatal resistance to diffusion (rs) as calculated from stomatal dimensions and frequency. Direct selection for rs was comparatively ineffective and the heritability was low (about 0.22) because of a negative correlation between stomatal length and stomatal frequency. However, selection for frequent and infrequent stomata resulted in a marked correlated genetic shift in the F1 generation toward respectively low and high rs at a given pore opening. Further selection for stomatal frequency did not affect rs and response by frequency itself was much reduced in the F2. Selection for stomatal length had no effect on rsin the F1 but there was a slight reduction in rs in the F2 long stomata selection.
A COMPARISON OF THE UPTAKE OF NITRATE, CHLORIDE AND PHOSPHATE BY EXCISED BEECH MYCORRHIZAS
Authors: SMITH F. A. 
Published: May 2006

SummaryRates of uptake of nitrate and chloride by excised beech mycorrhizas are much smaller than those of phosphate. With solutions containing 1 mM KCl or KH2PO4, about 45% of the chloride absorbed is found in the fungal sheath, compared with about 85% of the phosphate. The uptake of both chloride and phosphate is increased when the roots are cut into thin slices. The results show that direct uptake of chloride and phosphate into the host cells is limited by diffusion through the sheath, but in the case of chloride the diffusion gradient is not greatly affected by uptake into the sheath. It is suggested that, in the absence of nitrate reduction by the fungus, the processes controlling nitrate uptake and chloride uptake are likely to be similar. Effects of ageing excised mycorrhizas in dilute CaSO4 solutions are discussed.
THE INFLUENCE OF A MATURE LEAF ON XYLEM DIFFERENTIATION
Authors: HESS TAMAR , SACHS T. 
Published: May 2006

SummaryThe general problem studied in this work was the control of the formation of different types of cells from the cambium in ordered spatial arrangements. Young Phaseolus vulgaris plants were used, and the cells which were studied were the vessels and fibres of the secondary xylem. It was possible to control the type of xylem which was formed in the stem by selectively removing leaves of different ages. Many vessels were formed below young leaves while a single mature leaf caused the formation of a large volume of xylem, often more than that formed in an intact plant, and this xylem consisted almost entirely of fibres. Evidence is presented that the stimuli of young and mature leaves differ by at least one component. Quantitative results show that young leaves can be imitated, in terms of the xylem which is formed, by a source of auxin while a mature leaf can be imitated by a combination of auxin and gibberellin.
THE LONGITUDINAL MOBILITY OF GROWTH REGULATORS AND HERBICIDES IN SIEVE TUBES OF WILLOW
Authors: FIELD R. J. , PEEL A. J. 
Published: May 2006

SummaryUsing the dual chambered bark strip system described by Peel et al. (1969), the relative longitudinal mobilities of MCPA, 2,4‐D, 2·4·5‐T, MH, paraquat and TCA in the sieve tubes of willow have been measured. It was possible to measure the quantity of a compound which entered one end of the sieve tube system and to compare this with the mass which moved to the other end of the same system. We have termed the ratio of these two masses the relative mobility.Over a 24‐hr application period, TCA and paraquat had the highest relative mobilities, 2·4‐D and 2·4·5‐T the least. However, the total mass of TCA and paraquat which was moved along the sieve tube system was less than certain of the other compounds, notably MH and MCPA. These differences in relative mobility are thought to be due to variations in the removal of the compounds from the sieve tubes as they are being transported. In experiments of 36‐hour duration in which sieve tube exudate was sampled at 12‐hour intervals, the relative mobility changed with time. After 36 hours the order of relative mobility was different from that after a 24‐hour application time.The relative mobilities of IAA and IAA asp were also studied, either by allowing the IAA asp to be produced by metabolism from applied IAA, or by simultaneous application of 3H‐IAA and 14C‐IAA asp. IAA asp had the greater relative mobility, though the mobility of IAA increased with time to approach that of the IAA asp after a 12‐hour application period.
ENZYMATIC QUANTITATIVE DETERMINATION OF HEXOSES, SINGLY AND IN MIXTURES WITH THEIR OLIGOSACCHARIDES
Authors: ERNST ROBERT , ARDITTI JOSEPH 
Published: May 2006

SummaryQuantitative determinations of a number of naturally occurring D‐hexoses and their oligosaccharides can be accomplished by combinations of enzymatic methods without prior separation of the sugars. These spectrophotometric methods employ readily‐available enzymes and commercial reagents. The procedures are particularly useful for the quantitative analysis of fructofuranosides, such as raffinose or stachyose, in the presence of sucrose, glucose and/or fructose; maltose or lactose mixed with galactose and/or glucose; melibiose in mixtures with raffinose, and other combinations.
SEASONAL VARIATIONS IN THE SECONDARY PHLOEM OF SOME FOREST TREES FROM NIGERIA
Authors: LAWTON JUNE R. 
Published: May 2006

SummaryThe appearance of the phloem is described for the trees Albizia adianthifolia, Bombax buono‐pozense, Antiaris africana, Holarrhena floribunda, Ricinodendron heudelotii, Sterculia tragantha, and Tectona grandis. Measurements of the percentage sieve tube area, the sieve tube number per unit and the diameters of the sieve tubes have been made throughout one year. Changes in structure and composition of the phloem occurred in different ways in the several species at different times of the year. Increase in length of sieve tube elements with age was found in four of the species. In the three species with compound oblique sieve plates the pores were less than μm diameter, and the percentage sieve tube area was lower than that of the trees with phloem with simple sieve plates. The variety of phloem structure and the quantitative changes in phloem dimensions are discussed; the need for thorough investigation of phloem structure for each species as a prelude to physiological studies of the phloem is emphasized.
AN ASSESSMENT OF INTER‐SPECIFIC RELATIONSHIPS IN EQUISETUM SUBGENUS EQUISETUM
Authors: PAGE C. N. 
Published: May 2006

SummaryThe use of the scanning electron microscope to survey the surface relief of Equisetum reveals with clarity the existence of hitherto little known fine surface features. These patterns of sculpturing are characteristic and distinct from species to species, and form a valuable basis on which to construct taxonomic and phylogenetic ideas independently of the features of habit and gross morphology used currently but known to be highly variable. A new taxonomic layout for the species of subgenus Equisetum is suggested on this evidence, and the interrelationships and evolution of the species concerned are considered.
THE EFFECT OF ABSCISIC ACID ON STOMATAL BEHAVIOUR IN FLACCA, A WILTY MUTANT OF TOMATO, IN DARKNESS
Authors: TAL M. , IMBER DOROT 
Published: May 2006

SummaryYoung plants of the wilty tomato mutant, flacca, in which the stomata resist closure, were sprayed with abscisic acid eight times over a period of 24 hours in light and darkness. The hormone induced closure of stomata similarly in leaves treated either in light or in darkness. Abscisic acid does not appear to induce stomatal closure in darkness by increasing the internal CO2 concentration in the leaf, since this concentration should already be very high in darkness. A considerable and rapid decrease of CO2 assimilation and increase of CO2 evolution were demonstrated in mutant as well as in normal plants transferred from light to darkness.
THE CONTROL OF GERMINATION IN STACHYS ALPINA (L.)
Authors: PINFIELD N. J. , MARTIN M. H. , STOBART A. K. 
Published: May 2006

SummarySeeds of Stachys alpina are dormant, but can be induced to germinate either by treatment with gibberellin or by the removal or perforation of the integuments. Incubation of intact seeds and seeds with punctured integuments in increased oxygen tensions failed to stimulate germination above that observed in air, while after‐ripening in dry storage, incubation in continuous illumination and exposure to alternating temperatures were not effective in inducing germination of intact seeds. However, chilling treatments of up to 20 weeks' duration resulted in 20–30% germination. The significance of the response to gibberellin and of the role of the integuments in controlling dormancy are discussed.
OESTROGENS IN THE LONG‐DAY PLANTS HYOSCYAMUS NIGER AND SALVIA SPLENDENS GROWN UNDER INDUCTIVE AND NON‐INDUCTIVE LIGHT CONDITIONS
Authors: KOPCEWICZ JAN 
Published: May 2006

SummaryAn increased biosynthesis of oestrogen‐like substances occurs in plants growing under inductive photoperiods. Oestrogens appear at the time of flower bud formation and reach a maximum at the time of flower development. Three oestrogen‐like substances were found in extracts from flowering plants of both Hyoscyamus niger L. and Salvia splendens Sellow. These substances differed both from one another and from the standard substances they were compared with except that one substance in Hyoscyamus may be oestrone.
CYANIDE SENSITIVITY OF RESPIRATION DURING AGEING OF ARUM SPADIX SLICES
Authors: WEDDING R. T. , MCCREADY C. C. , HARLEY J. L. 
Published: May 2006

SummarySlices of the sterile spadix of Arum may show variable responses ranging from inhibition to stimulation of respiration when exposed to cyanide. Some of the factors responsible for this variation in response were determined to be: (1) age of the spadix‐more mature spadices tend to be unaffected or stimulated by cyanide as opposed to very young spadices, which are inhibited; (2) thickness of the slice made from the spadix‐thin (c. 60 μm) slices are stimulated by 2.5 mM KCN while thick (>200 μm) slices are inhibited; (3) ageing of slices in aerated water‐this response is complex, with slices c. 100 μm thick freshly cut from spadices of intermediate maturity being stimulated by cyanide initially. During the following 24 hours, however, the respiration of the slices is inhibited by cyanide, but from 2–5 days after slicing the spadix slices reach a plateau of stimulation where rates may be almost doubled by cyanide. This is followed by a decline after 8 days' ageing to a situation in which respiration is unaffected by cyanide.An inhibitor of cyanide‐resistant respiration, m‐chlorobenzhydroxamic acid, strongly inhibits spadix respiration, with a Kl similar to that of KCN. The effect of this inhibitor is additive to that of cyanide and in appropriate conditions, the two inhibitors together will completely inhibit Arum spadix respiration.
EFFECTS OF WATER STRESS ON GROWTH AND NITROGEN‐FIXING ACTIVITY OF TRIFOLIUM REPENS
Authors: ENGIN MUJGAN , SPRENT JANET I. 
Published: May 2006

SummaryThe growth and nitrogen fixation of Trifolium repens have been investigated during the imposition of and recovery from different levels of water stress. Growth (measured as fresh and dry weight of roots and shoots, shoot length and nitrogen content) and nitrogen fixation (per plant and per unit weight of nodule) were depressed by application of water stress. The ability of plants to recover and the time taken for recovery were both related to the duration of the stress period. Meristematic activity in nodules was resumed after watering, making clover nodules more resistant to stress than plants, such as soybean, with spherical nodules.Nitrogen fixation, estimated by the acetylene reduction technique, was compared with the total nitrogen content of plants. Differences between the estimated and actual nitrogen content varied with age and degree of water stress.
SULPHUR DIOXIDE: ITS EFFECT ON PHOTO‐SYNTHETIC 14C FIXATION IN LICHENS AND SUGGESTED MECHANISMS OF PHYTOTOXICITY
Authors: PUCKETT K. J. , NIEBOER E. , FLORA W. P. , RICHARDSON D. H. S. 
Published: May 2006

SummaryThe toxicity to lichens of dissolved sulphur dioxide (as measured by net photosynthetic 14C fixation) was studied as a function of pH and is linked with the oxidation‐reduction properties of sulphur dioxide. An examination of pigments from lichens and spinach exposed to aqueous sulphur dioxide in vivo and in vitro suggests that the increased toxicity observed at low pH values is associated in part with the destruction of chlorophyll by an irreversible oxidation process.
INDUCTION OF NITRATE REDUCTASE IN LEAVES OF BARLEY IN THE DARK
Authors: ROTH‐BEJERANO NURITH , LIPS S. HERMAN 
Published: May 2006

SUMMARYThe induction of nitrate reductase activity in barley leaves normally requires light in addition to nitrate. However, nitrate reductase activity was induced in darkness in detached etiolated leaves when these were incubated with nitrate and glycollate. Other effective carbon compounds were sucrose, glucose or phosphoglyceric acid. Acetate, pyruvate or succinate was ineffective. Sodium bisulphite inhibited the stimulatory effect of glycollate or sucrose on enzyme induction. It is suggested that the induction of nitrate reductase requires the concomitant reduction of nitrate and that the NADH required for the reduction is derived from the metabolism of glycollate.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA IV. ACETATE ASSIMILATION
Authors: HOLLIGAN P. M. , JENNINGS D. H. 
Published: May 2006

SUMMARYBoth mannitol and arabitol are synthesized by Dendryphiella salina when acetate is supplied as the sole carbon source. As in media containing glucose, there is a rapid turnover of the hexitol. Addition of glucose to the medium inhibits acetate uptake and leads to marked increases in yields of residual dry weight of fungus and respiratory carbon dioxide.
THE EFFECT OF GIBBERELLIC ACID, KINETIN AND INDOLYLACETIC ACID ON THE LATERAL MOVEMENT OF LABELLED PLANT GROWTH REGULATORS IN WILLOW STEMS
Authors: FIELD R. J. 
Published: May 2006

SUMMARYUsing willow stem segments it has been possible to show that the presence of gibberellic acid in the xylem can influence the lateral mobility of radioactive indolylacetic acid and its principal metabolite, indoleacetylaspartic acid. The extent of the lateral movement of indolylacetic acid depends on the concentration of endogenous gibberellin in the xylem, and movement may be increased by exogenous gibberellin applications to the xylem. The mechanism controlling the lateral movement of 2, 4‐dichlorophenoxyacetic acid and 2, 4, 5‐trichlorophenoxyacetic acid appeared to be somewhat different and there was no positive movement towards gibberellin.These results are discussed in relation to previous experimentation on the interaction of plant growth regulators during transport. It is suggested that gibberellins may influence cell membranes and this may account for their effects on the transport of indolylacetic acid.
ASPARAGINE ACCUMULATION IN GENETICALLY CHLOROTIC TISSUE
Authors: LAND J. B. , NORTON G. 
Published: May 2006

SUMMARYSoluble amino acid analyses of the green and chlorotic areas of several variegated plants generally showed that amino acids accumulated in the chlorotic tissues. Asparagine levels were consistently and conspicuously higher in the chlorotic areas. This pattern is discussed in the context of other physiological chloroses.
PROSTELAR AUTOLYSIS: A FURTHER EXAMPLE OF A PROGRAMMED SENESCENCE
Authors: BERJAK PATRICIA , LAWTON JUNE R. 
Published: May 2006

SUMMARYA pattern of degeneration, which terminates in total autolysis of the cells concerned, is described for certain stelar cells (termed prostelar cells) in young regions of the root in cress. The early senescence of these cells is characterized by extensive cytolysome formation, while final autolysis follows tonoplast dissolution. Degenerated prostelar cells are soon replaced by differentiating cambial derivatives.It is suggested that the sequence of events which occurs during the degeneration of these cells is under genetic control and the possibility of genetic programmes controlling certain senescence processes in plants is considered. These observations are discussed in the light of generally held concepts of plant anatomy.
THE DISPERSAL EFFECTIVENESS OF THE ACHENE–PAPPUS UNITS OF SELECTED COMPOSITAE IN STEADY WINDS WITH CONVECTION
Authors: SHELDON J. C. , BURROWS F. M. 
Published: May 2006

SUMMARYThe role of the involucral bracts of the Compositae capitulum in fruit dispersal, the behaviour of the pappus of composite fruits to changes in humidity, and the presentation of the achene‐pappus units for wind dispersal, are briefly reviewed. Arguments put forward in the literature for and against the effectiveness of the pappus in facilitating wind dispersal are presented. A method is described for comparing the dispersal efficiency of achene‐pappus units of selected composites. The computed trajectories for fruits of selected species under the independent effects of wind speed and plant height, wind speed and boundary layer, and the combination of these with convection velocity are given.It is shown that the efficiency of dispersal is determined more by the fine details of the pappus geometry, which directly affects its aerodynamic properties, than by the size ratio of pappus to achene. Under steady horizontal winds, increased height of fruit release increases dispersal distance. Reported patterns of wind dispersal are discussed in terms of air movement, flight path interference by neighbouring plants and, for some species, the fruit dissemination mechanism.While increased wind velocities increase the trajectory distance, dispersal of many composites is hampered by the pappus response to humidity. Increased dispersal distances are given by steady convection currents, whereas turbulence may either curtail or prolong transportation.The apparent inefficiency of wind dispersal reported under field conditions is explained by the combined effects of these various environmental factors upon the dispersal units during the period of dissemination.
A COMPARISON OF DEVELOPMENT OF PUCCINIA HORDEI OTTH. ON NORMAL AND SLOW RUSTING VARIETIES OF BARLEY (HORDEUM VULGARE L.) USING ANALYSES OF FUNGAL CHITIN AND MANNAN
Authors: WHIPPS J. M. , CLIFFORD B. C. , RODERICK H. W. , LEWIS D. H. 
Published: May 2006

SUMMARYThe growth and development of Puccinia hordei Otth. race F on leaves 3 and 5 of barley varieties Gold and Peruvian, normal and slow rusters respectively, were compared using histological and biochemical techniques. Assays of chitin and mannan contents agreed well with histological observations of infection and were linearly related to each other. The use of these and other compounds as indices of fungal growth is discussed.
NITRATE‐NITROGEN ASSIMILATION IN THE LEAVES OF HELIANTHUS ANNUUS L.
Authors: KAISER J. J. , LEWIS O. A. M. 
Published: May 2006

SUMMARYXylem sap analyses of 5‐week‐old plants of Helianthus annuus L. fed at high and low nitrate concentrations show that between 77 and 94 % of the nitrogen conveyed to the leaf by the xylem is in the form of nitrate, present at up to 300 % of its concentration in the feeding solution, thus confirming nitrate as the major nitrogen source of leaves of this species when its roots are nitrate fed. Organic nitrogen is mainly in the form of glutamine.The pathways of nitrogen assimilation in the leaves of H. annuus following petiolar nitrate feeding at two concentrational levels have been investigated by an 15N infiltration technique in the presence of the glutamine synthetase inhibitor, methionine sulphoximine (MSO). In the absence of MSO and over a 30 min time‐course the main diversion of newly reduced nitrate was to glutamine with a secondary enrichment of glutamate. In the presence of MSO intracellular pools of all the amino compounds, with the exception of threonine, became conspicuously depleted, suggesting that conditions of nitrogen stress had been induced. There was an almost complete restriction of the supply of newly reduced 15N to amino acid assimilation with the resultant accumulation of large 15N ammonium pools. Glutamate dehydrogenase activity was unaffected by the MSO treatment.These experimental results indicate the almost exclusive role of the glutamine synthetase‐ glutamate synthase pathway in the assimilation of newly reduced nitrate into amino acid metabolism in the leaves of H. annuus.