bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of mass flow of water in the stems of herbaceous plants
Authors: BAKER J. M. , VAN BAVEL C. H. M. 
Published: April 2006

Abstract. Heat balance methods of stem flow measurement offer the opportunity to measure directly the mass flow rate of water in plants. We have tested one such approach; the constant power heat balance method of Sakuratani (1981). The results supported his statement of an approximate accuracy of 10% when measuring the transpiration rate of herbaceous plants. The response to sudden changes in stem flow rate is not instantaneous, but investigation of the time constant shows that it decreases as stem flow increases, to the extent that, at flow rates typical of daytime conditions the system is capable of accurately tracking changes in stem flow within 5 min or less.We describe a new gauge design that is relatively rugged, simple to use with an appropriate digital datalogger and suitable for field use over prolonged periods of time. It does not injure or penetrate the stem, is amenable to continuous and direct recording of the mass flow rate of water in the stem and requires no calibration. A further refinement, which should improve both the accuracy and the dynamic response of the system, is proposed.
Changes in sensitivity of Amaranthus retroflexus L seeds to ethylene during preincubation. II. Effects of alternating temperature and burial in soil
Authors: SCHONBECK MARK W. , EGLEY G. H. 
Published: April 2006

Abstract. The effects of diurnally alternating temperatures and of prolonged burial in the soil on germination response of redroot pigweed (Amaranthus retroflexus L.) seeds to ethylene were investigated. Percentage germination in a 12 h/12 h, 23° C/35° C temperature regime roughly equalled that observed at constant 35° C, and greatly exceeded that observed at 30°C. Preincubation for 61 d in alternating temperatures, which were gradually increased to simulate soil warming in spring, caused little germination in the absence of ethylene, but considerably enhanced sensitivity to ethylene. Seeds kept in soil in the same temperature regime failed to show the response to ethylene, and the soil itself removed ethylene from the soil atmosphere.After burial in a field plot either over winter or during the summer, seeds had a very low ethylene response threshold (0.01−0.05 cm3 m−3) and strong response to ethylene (70–95% germination at 51 cm3 m−3 compared to 1–20% without ethylene). Germinability of seeds buried overwinter declined between 10 May (85%) and 24 May (7%), and 90% of those recovered on or after 24 May had a visible rupture in the seed coat. Apparently, germination had begun during burial, but was arrested by unknown causes in an early phase and was followed by seed deterioration.Although the role of ethylene in germination of buried seeds remains uncertain, the greatly enhanced sensitivity to ethylene observed in pigweed seeds after burial deserves further investigation.
Optimization of red light‐induced elongation in Avena coleoptile sections and properties of the phytochrome‐mediated growth response*
Authors: SHINKLE J. R. , BRIGGS W. R. 
Published: April 2006

Abstract Optimal conditions for studying the elongation response to a 1 mmol m−2, 2‐min pulse of red light in subapical coleoptile sections from dark‐grown oat (Avena sativa L. ev. Lodi) seedlings have been determined. A technique for obtaining standard‐length coleoptile sections without exposing either seedlings or sections to any light has been developed, and is described. The optimal conditions found were: sampling time, 12 h after irradiation; buffer conditions, 5 mol m−3 potassium phosphate with 5% (w/v) sucrose (pH 5.9). The optima were determined by obtaining the time course for light‐induced growth under various conditions. The red light‐induced growth response is linear until 12 h after irradiation, when it undergoes an interruption. Optimal incubation conditions were determined by varying the buffer contents systematically and measuring the responses at the optimal lime determined. The results indicate a distinct difference between auxin‐induced and light‐induced growth responses. Even with variations of basal growth rate and several incubation conditions, the red light‐induced elongation appears to be of a constant magnitude, to persist for a constant time period. and to exhibit a constant lag period between irradiation and the onset of response.The use of sections that were produced and handled in complete darkness yielded an unusual response to fusicoccin. A linear, high growth rate in response to I mmol m−3 FC was observed for more than 12 h, both in the irradiated sections and in the dark controls.
Ethanol synthesis and loss from flooded roots of Medicago sativa L. and Lotus corniculatus L.
Authors: BARTA A. L. 
Published: April 2006

Abstract Field flooding of established alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) for up to 12 d resulted in a significant increase in alcohol dehydrogenase activity (ADH) and an increase in the Km of ADH in both species. Root concentration of ethanol increased throughout the flooding regime in alfalfa roots. No ethanol was detected in any trefoil root samples. Alfalfa plants which had shoots removed 5 d prior to flooding accumulated significantly higher levels of root ethanol and showed flooding injury sooner, indicating a significant effect of shoots on development of flooding injury.Alfalfa and trefoil plants grown in the greenhouse were flooded and ethanol in the transpiration effluent was trapped and measured. Alfalfa transpired measurable quantities of ethanol which peaked just prior to development of shoot injury symptoms. No ethanol was detected in the transpiration effluent from trefoil shoots. Flooded roots of both alfalfa and trefoil excreted ethanol but alfalfa roots synthesized more total ethanol and retained a larger proportion in the roots than did trefoil.While the ethanol accumulation response in alfalfa and trefoil are consistent with the ethanol ‘self‐poisoning’ hypothesis of flooding injury, the very small quantities of ethanol found in these roots still raises questions as to its absolute effect in the plant.
Characterization of a proton pump from pea stem microsomes
Authors: VIANELLO A. , MACRÍ F. 
Published: April 2006

Abstract The present work deals with the characterization of an ATP‐dependent proton translocation monitored by the ΔpH probe acridine orange.The ATP‐dependent proton translocation has an optimum activity at pH 6.5 and is substrate specific for ATP. It is stimulated by Cl−, HCO3− and Br−, but is insensitive to several monovalent cations. Divalent cations (Mg2+ or Mn2+) are required for proton translocation, while in the presence of Ca2+ no uptake is observed. NO3−, NO2− and citrate strongly inhibit proton uptake. On the contrary, F−, SO42−, malate, pyruvate, succinate, oxalate and acetate have no inhibitory effect. Proton uptake is stimulated by valinomycin and unaffected by molybdate. Two thiols, dithioerythritol and dithiothreitol, are able partially to prevent the FCCP‐abolished proton uptake or partially restore the ATP‐dependent proton translocation in FCCP‐collapsed vesicles.It is suggested that pea stem microsomes possess an electrogenic ATPase, acting as a proton pump, which, on the basis of its characteristics, can be tentatively associated with membranes of tonoplast origin.
Contrasting types of photoperiodic response in the control of dormancy
Authors: VINCE‐PRUE DAPHNE 
Published: April 2006

Abstract The effect of night‐break or day‐extension treatments with red (R) and/or far‐red (FR) light were examined in the control of dormancy and extension growth in Weigela florida and Picea abies.Dormancy in Weigela (as assessed by the continued production of new leaves) was completely prevented by a 30 min night‐break treatment with R: the effect of R was prevented by a subsequent exposure to 30 min FR. A day‐extension treatment for 8.25 h with R or with R+FR also completely prevented dormancy, irrespective of whether it was given before or after a short day (SD) in sunlight. There was no significant difference between any dayextension treatment, nor between day‐extension treatments and a night‐break with R.Dormancy in Picea (as assessed by the maintenance of shoot growth) was also delayed by a night‐break with R but less effectively than the most effective day‐extension. A day‐extension treatment for 9 h with R light was more effective when it preceded than when it followed a SD in sunlight. The addition of FR in the second but not in the first 9 h of a 17 h photoperiod increased its effectiveness.It is concluded that the mechanisms of the control of dormancy must differ in the two species.A day‐extension for 16 h with light from tungstenfilament lamps increased stem elongation in Weigela when compared with an R night‐break. This resulted from an increase in internode length and there was no significant difference between the two treatments in their effect on leaf production.
Tropic responses of hypocotyls from normal tomato plants and the gravitropic mutant Lazy‐1
Authors: ROBERTS JEREMY A. 
Published: April 2006

Abstract Etiolated hypocotyls from normal tomato plants show a negative gravitropic response within 20 min of stimulation. In contrast, etiolated hypocotyls from the gravitropic mutant Lazy‐l do not reorientate after gravistimulation. Etiolated hypocotyls from both types of plant are positively phototropic, however, Lazy‐l seedlings achieve a greater final angle of bending following phototropic stimulation compared to normal plants.Anatomical studies reveal that etiolated hypocotyls from normal plants contain sedimenting amyloplasts located within the endodermal cells. Such sedimenting amyloplasts are absent in Lazy‐l tissue. It is hypothesized that the hypocotyl of Lazy‐l is agravitropic since it is unable to perceive a gravistimulus.
The partitioning of nitrate assimilation between root and shoot of higher plants
Authors: ANDREWS M. 
Published: April 2006

Abstract The partitioning of nitrate assimilation between root and shoot of higher plant species is indicated by the relative proportions of total plant nitrate reductase activity (NRA) in the two plant parts and the relative concentrations of nitrate and reduced N in the xylem sap. These have been collated here from the literature and temperate and tropical species compared.Both the distribution of NRA and xylem sap nitrate: reduced N indicate that the following four generalizations can be made.

Temperate, perennial species growing in low external nitrate concentrations (about 1 mol m−3) carry out most of their nitrate assimilation in the root. As external nitrate concentration increases (in the range found in agricultural soils, 1–20 mol m−3), shoot nitrate assimilation becomes increasingly important.
Temperate, annual legume species growing in low external nitrate concentrations carry out most of their nitrate assimilation in the root. Shoot nitrate assimilation increases in importance as external nitrate concentration is increased.
Temperate, annual non‐legume species vary greatly in their partitioning of nitrate assimilation between root and shoot when growing in low external nitrate concentrations. Regardless of the proportion carried out in the root at low external nitrate concentrations, nitrate assimilation in the shoot becomes increasingly important as external nitrate concentration is increased.
Tropical and subtropical species, annual and perennial, carry out a substantial proportion of their nitrate assimilation in the shoot when growing in low external nitrate concentrations. The partitioning of nitrate assimilation between root and shoot remains constant as external nitrate concentration increases.

It is proposed that a greater proportion of nitrate assimilation occurs in the shoot when an increase in the rate of nitrate uptake does not induce an increase in NR level in the root. Thus, a greater proportion of the nitrate taken up remains unassimilated and is passed into the xylem. A constant partitioning of nitrate assimilation between root and shoot is achieved by balancing NR levels in the root with rates of nitrate uptake.The advantages and disadvantages of assimilating nitrate in either the root or shoot are discussed in relation to temperate and tropical habitats.
The effect of root temperature on the uptake of nitrogen and the relative size of the root system in Lolium perenne. I. Solutions containing both NH+4 and NO3−
Authors: CLARKSON D. T. , HOPPER M. J. , JONES L. H. P. 
Published: April 2006

Abstract Lolium perenne L. cv. S23 was grown in flowing culture solution, pH 5, in which the concentrations of NH4+, NO3− and K+ were frequently monitored and adjusted to set values. In a pre‐experimental period, plants were acclimatized to a regime in which roots were treated at 5°C with shoots at 25°C. The root temperature was then changed to one of the following, 3, 7, 9, 11, 13, 17 or 25°C, while air temperature remained at 25°C.When root temperature was increased from 5X, the relative growth rate of roots increased immediately while that of shoots changed much less for a period of approximately 9 d (phase 1). Thus, the root: shoot ratio increased, but eventually approached a new, temperature‐dependent, steady value (phase 2). The fresh: freeze‐dried weight ratio (i.e. water content) in shoots (and roots) increased during the first phase of morphological adjustment (phase 1).In both growth phases and at all temperatures, plants absorbed more NH4+ than NO4+, the tendency being extreme at temperatures below 9° where more than 85% of the N absorbed was NH4+. Plants at different root temperatures, growing at markedly different rates, had very similar concentrations of total N in their tissues (cells) on a fresh weight basis, despite the fact that they derived their N with differing preference for NH4+. Specific absorption rates for NH4+, NOx−, K+ and H2PO4− showed very marked dependence on root temperature in phase 1, but ceased to show this dependence once a steady state root: shoot ratio had been established in phase 2.The results indicate the importance of relative root size in determining ion fluxes at the root surface. At higher temperatures where the root system was relatively large, ‘demand’ per unit root was low, whereas at low temperatures roots were small relative to shoots and ‘demand’ was high enough to offset the inhibitory effects of low temperature on transport processes.
Effects of NaCl on ion relations and carbohydrate status of roots and on osmotic regulation of roots and shoots ofAtriplex amnicola
Authors: JESCHKE W. D. , ASLAM Z. , GREENWAY H. 
Published: April 2006

AbstractAtriplex amnicolawas grown at 25, 200 or 400 mol m3NaCl. Root tissues at different stages of development were investigated for concentrations of K+, Na+and Mg2+, and in some cases for Cl−. Sugar and starch concentrations were measured for plants grown at 25 or 400 mol m3NaCl.In the ‘slightly vaeuolated’ root tips, Na+was only 40 mol m−3at an external concentration of 400 mol m−3NaCl. The concentrations of K+were not affected substantially by external NaCl between 25 mol m−3and 400 mol m−3. The ‘highly vacuolated’ root tissues had substantially higher concentrations of K+, Na+and Cl−in plants grown at 200 and 400 mol m3NaCl than in plants grown at 25 mol m−3NaCl. Concentrations of Cr and of the sum of the cations in recently expanded tissue were similar to those in the bulk of the roots, consisting mainly of old cells. However, the K+: Na+decreased with age; at 400 mol m−3external NaCl with a K+: Na+of 0.012, the K+: Na+in recently expanded 12 mm root tips was as high as 1.6, compared with 0.7 for the bulk of the roots.These ion data were used to estimate cytoplasmic and vacuolar concentrations of K+and Na+. Such calculations indicated that between 25 mol m3and 400 mol m−3external NaCl the concentration of the sum of (Na++K+) in the cytoplasm was maintained at about 180–200 mol m−3(cell water basis). In contrast, the (Na++ K+) concentration in the vacuole was 170 mol m−3for plants grown at 25 mol m−3NaCl and 420 mol 400 mol m−3NaCl.The expanding root (issues exhibited greatly decreased soluble sugars and starch between dusk and dawn. Ai both times, sugar and starch concentrations in these tissues were 2.5–4.0 times greater in plants grown at 400 mol m−3NaCl compared with plants grown at 25 mol m−3NaCl. In contrast, carbohydrate concentrations in expanded root tissues were very similar at 25 and 400 mol m−3and showed little diurnal fluctuation.This paper considers the causes for the slower growth ofA. amnicolaat 400 than at 25 mol m”3NaCl, using the data for the roots described here, and those for the shoots presented in the preceding paper (Aslamet al., 1986). There is no support for possible adverse effects by high internal ion concentrations. Instead, there may be deficiencies in supply of organic solutes for osmotic regulation; during part of the night a limited supply of such solutes may well restrict the rate of expansion of cells in plants growing at 400 mol m−3NaCl. There is insufficient evidence to decide whether this limitation in the expanding tissues is particularly prominent for the roots or for the shoots.
Accumulation and subcellular distribution of cations in relation to the growth of potassium‐deficient barley
Authors: LEIGH R. A. , CHATER M. , STOREY R. , JOHNSTON A. E. 
Published: April 2006

Abstract Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg−1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg−1 than in soils with about 90 mg kg−1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m−3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations.When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots.X‐ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m−3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m−3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed.
Nitrate and reduced‐N concentrations in the xylem sap of Stellaria media, Xanthium strumarium and six legume species
Authors: ANDREWS M. 
Published: April 2006

Abstract At an applied nitrate concentration of 1 mol m−3, the proportion of xylem sap nitrogen as nitrate was < 15% for Cajanus cajan, Lupinus albus and Trifolium repens, 33% for Pisum sativum and within the range 57–62% for Glycine max, Phaseolus vulgar is, Stellaria media and Xanthium strumarium. At an applied nitrate concentration of 10 mol m∼3 the value had increased to 66% for T. repens while at 20 mol m−3 nitrate values had increased to 46, 51 and 49% for C. cajan, L. albus and Pisum sativum, respectively, and 89% and 85% for 5. media and X. strumarium, respectively. Glycine max and Phaseolus vulgaris differed from the other species in that the proportion of their xylem sap nitrogen as nitrate remained constant (∼ 60%) as applied nitrate concentration increased from 1 to 20 mol m−3.The proportion of total plant nitrate reductase activity in the shoot of C. cajan, S. media and X. strumarium increased as applied nitrate concentration increased from 1 to 20 mol m−3. Values at the lower and upper concentrations were, respectively, 26 and 72% for C. cajan. 48 and 80% for X. strumarium and 68 and 87% for S. media. The partitioning of nitrate assimilation between root and shoot in these species is discussed.
The development of allergy in high‐risk children
Authors: BURR M. L. , MERRETT T. G. , DUNSTAN F. D. J. , MAGUIRE M. J. 
Published: April 2006

SummaryBackground
It is uncertain as to what extent the development of allergic disease in childhood is predictable during early infancy. A number of environmental factors have been suspected of increasing the risk of acquiring allergy, but the evidence is conflicting.Objective
To observe the development of atopy and allergic disease in a cohort of high‐risk children so as to determine the importance of certain environmental factors and to study the relationship between early and later manifestations.Methods
A cohort of infants, all at high risk of allergy, was followed up from birth to the age of 7 years. In half, selected at random, cow's milk protein was avoided for 4 months. Skin‐prick tests were performed and serum IgE measured in infancy and at 7 years, when an AlaTOP test was also performed.Results
Skin sensitivity to egg in the first year of life was strongly associated with eczema, asthma, mite sensitivity and serum IgE at the age of 7 years, when mother's atopic history was associated with AlaTOP status, father's atopic history with skin sensitivity, and male sex with both. Maternal smoking during pregnancy was associated positively with IgE at 3 months and negatively with skin sensitivity at 7 years. The development of allergy was unrelated to infant feeding method or number of older siblings.Conclusion
Allergic disease in childhood is to a large degree determined before birth or during infancy.
Interleukin‐4, interferon‐gamma and interleukin‐5 in peripheral blood of children with moderate atopic asthma
Authors: HOEKSTRA M. O. , HOEKSTRA Y. , DE REUS D. , RUTGERS B. , GERRITSE J. , KAUFFMAN H. F. 
Published: April 2006

SummaryBackground
In asthmatic inflammation, TH2 cells play an important role. TH2 cells specifically secrete cytokines like IL‐4 and IL‐5. IL‐4 stimulates IgE production and IL‐5 is involved in hemopoiesis, chemotaxis, priming and activation of eosinophils. IFNγ, produced by TH1 cells, has an inhibitory action on IgE production.Objectives
To investigate the TH1/TH2‐cell pattern in the cytokine production of peripheral blood of asthmatic children. We determined IL‐4, IFNγ and IL‐5 in serum and in supematants of unstimulated and stimulated (24 h with Concanavaline A) cultures of peripheral blood mononuclear cells (PBMCs) in 22 children with moderate asthma (mean age 9.3 years) and in 17 healthy controls (mean age 10.3 years). All children visited the outpatient department (OPD) where history taking, physical examination and blood sampling took place. Children younger than 8 years of age performed symptom and peak flow registration during 1 week after the visit to the OPD.Results
The number of eosinophils were significantly higher in children with asthma, compared with healthy controls. The concentration of IFNγ in supematants of cultures of stimulated PBMCs was significantly lower and the ratio of IL‐4/IFNγ was significantly higher in children with asthma compared with healthy controls. The FEV1 was directly and IgE was inversely related to the concentration of IFNγ in supematants of cultures of stimulated PBMCs.Conclusion
IFNγ may play an important role in the pathophysiology of childhood atopic asthma.