bluuebunny/crossref_metadata_2025 huggingface dataset:
Crassulacean acid metabolism in the epiphytic ferns Drymoglossum piloselloides and Pyrrosia longifolia: studies on responses to environmental signals
Authors: ONG B. L. , KLUGE M. , FRIEMERT V.
Published: April 2006

Abstract The paper reports the results of the comprehensive study of crassulacean acid metabolism in two epiphytic tropical ferns, Drymoglossum piloselloides and Pyrrosia longifolia. The plants were investigated under different light, temperature and water status. It was found that both species are obligate CAM plants. The diurnal acidity rhythm is due to the fluctuation in malic acid concentration, which accounts for the change in titratable acidity. Besides malic acid, shikimate and oxalate are found to be present, but not contributing to the CAM acid rhythm. The diurnal rhythm of malic acid content results in a corresponding rhythm in leaf water relations. Both ΦΦ and Φtotal, were lowest at the end of the night, i.e. when the level of malic acid was highest.

The effects of temperature on CO2 exchange were inverse to those observed in other CAM plants. In both ferns studied, dark CO2 fixation increased when the night temperature was increased. Increase in day temperature reduced CO2 uptake during phase IV and during the following night. The observed responses of the ferns to temperature changes suggest that the in situ environmental conditions are optimal for their CAM performance. In weak light, the plants showed net CO2 output during the midday deacidification period. Increases in light intensity reduced such CO2 output.

Under drought conditions, the CO2 exchange in the ferns was reduced to zero within 5–6 d, indicating that the ferns studied are more susceptible to water deficiency than other CAM plants. This could be due to a higher cuticular conductance for water.

The results are discussed, in particular, in relation to CAM performance of epiphytes growing in the wet tropics.
Effects of external NaCl on the growth of Atriplex amnicola and the ion relations and carbohydrate status of the leaves
Authors: ASLAM Z. , JESCHKE W. D. , BARRETT‐LENNARD E. G. , SETTER T. L. , WATKIN E. , GREENWAY H.
Published: April 2006

Abstract Atriplex amnicola, was grown in nutrient solution cultures with concentrations of NaCl up to 750 mol m−3. The growth optimum was at 25–50 mol m−3 NaCl and growth was 10–15% of that value at 750 mol m−3 NaCl. Sodium chloride at 200 mol m−3 and higher reduced the rate of leaf extension and increased the time taken for a leaf to reach its maximal length.

Concentrations of Na+, K+ and Mg2+ in leaves of different ages were investigated for plants grown at 25, 200 and 400 mol m−3 NaCl. Although leaves of plants grown at 200 and 400 mol m−3 NaCl had high Na+ concentrations at young developmental stages, much of this Na+ was located in the salt bladders. Leaves excluding bladders had low Na+ concentrations when young, but very high in Na+ when old.

In contrast to Na+, K+ concentrations were similar in bladders and leaves excluding bladders. Concentrations of K+ were higher in the rapidly expanding than in the old leaves. At 400 mol m−3 NaCl, the K+:Na+ ratios of the leaves excluding bladders were 0.4–0.6 and 0.1 for rapidly expanding and oldest leaves, respectively. The Na+ content in moles per leaf, excluding bladders, increased linearly with the age of the leaves; concurrent increases in succulence were closely correlated with the Na + concentration in the leaves excluding the bladders.

Soluble sugars and starch in leaves, stems and buds were determined at dusk and dawn.

There was a pronounced diurnal fluctation in concentrations of carbohydrates. During the night, most plant parts showed large decreases in starch and sugar. Concentrations of carbohydrates in most plant organs were similar for plants grown at 25 and 400 mol m−3 NaCl. One notable exception was buds at dusk, where sugar and starch concentrations were 30–35% less in plants grown at 400 mol m−3 NaCl than in plants grown at 25 mol m−3 NaCl.

The data indicate that the growth of A. amnicola at 400 mol m−3 NaCl is not limited by the availability of photosynthate in the plant as a whole. However, there could have been a growth limitation due to inadequate organic solutes for osmotic regulation.
BEHAVIOUR THERAPY IN CLINICAL CHILD PSYCHIATRY: A PRELIMINARY REPORT
Authors: LEVERE RUTH H.
Published: April 2006

Summary This paper reports on the practice of behaviour therapy with children and families in a clinical setting. The behavioural treatment of 33 cases is discussed. The cases are characterized by the range of problems treated and the variety of behavioural techniques used. Behaviour therapy is shown to be an approach that can be used effectively in a variety of different settings and alongside, or together with treatments based on different theoretical orientations.
DIFFERENCES IN READING ACHIEVEMENT BETWEEN SPINA BIFIDA CHILDREN ATTENDING NORMAL SCHOOLS AND THOSE ATTENDING SPECIAL SCHOOLS
Authors: TEW BRIAN , LAURENCE K. M.
Published: April 2006

Summary This paper reports the reading scores measured on Neale's Analysis of Reading Ability of a series of 55 spina bifida children, some of whom attended normal schools and the remainder attended special schools and matched controls. A multiple regression equation was used to compare observed scores with the expected scores. The children receiving a normal school education were reading up to the level expected from their intelligence test scores, but the children in special schools had significant differences between observed and expected scores. The discrepancies may be accounted for by more profound physical handicap among the special school children but teachers' expectations may also be important in influencing reading achievement.
CONSIDERATIONS IN THE ASSESSMENT OF BLIND CHILDREN WHO FUNCTION AS SEVERELY OR PROFOUNDLY RETARDED
Authors: ROGOW SALLY M.
Published: April 2006

Summary Unevenness in development of blind children who function as severely or profoundly retarded, particularly in language and communication, needs to be considered as a feature of the child's ability to learn rather than as characteristics of his retardation. Impact of blindness on early development, environment and previous opportunities for learning need to be considered as part of the assessment process as well as of education and treatment.
EVALUATION OF BARRIERS TO EXPRESSION
Authors: GRUNWELL PAMELA
Published: April 2006

For the child or young person diagnosed as having a ‘communication disorder’, his linguistic disabilities almost always result in major social and educational difficulties. We are all aware of the seriousness of these difficulties, and have probably found that they present us with problems almost as daunting as those which face the child. Our primary concern is the management of the person with the disorder. Put in very broad terms, our aim is to remediate, facilitate and habilitate an individual's communicative performance, so that he is enabled both to achieve efficient social interaction and to realize his intellectual potential. However, in order to devise an appropriate management policy that is to change and improve communicative performance, one must have detailed knowledge of the present status of this behaviour and information about relevant related abilities. Evaluation is therefore a very necessary prerequisite to management.
WHAT KIND OF THING IS ‘BEING CLUMSY’?
Authors: TAYLOR DAVID C. , McKINLAY IAN A.
Published: April 2006

Summary The term ‘clumsy’ is used both as a colloquial pejorative and as a specific diagnostic entity. The meaning of the word and the possible means by which a child may come to be regarded as clumsy are discussed. The implications for management are considered.
CHILD HEALTH PROBLEMS AND PROGRAMMES IN TWO UNDERDEVELOPED AREAS OE THE USA
Authors: JR CHRISTIAN M. HANSEN
Published: April 2006

Summary There are areas in the USA where the health problems of children are similar to those of children in some developing countries. Traditional US health programmes have contributed to an improvement in the health status of many of these children but there remains much more to be done.
NEW TECHNIQUES FOR ASSESSING VISION IN INFANTS AND YOUNG CHILDREN
Authors: ATKINSON JANETTE , BRADDICK OLIVER
Published: April 2006

Summary A range of methods has been developed, which can be used both to investigate the course of normal visual development and to assess clinical vision problems in infants. The behavioural ‘preferential looking’ method has been used to test acuity and contrast sensitivity in infants aged between 1–6 months and shows a rapid improvement in acuity (from 6/180 to 6/60) between I and 3 months. We have made monocular assessments and found, in most infants, similar acuity for each eye but somewhat better binocular acuity. A tracking test is under development for measurements in older infants and we have used an operant procedure with 3‐year‐olds which shows adult acuity at this age, These results have been extended to the newborn by measuring the amplitude of visual evoked potentials to patterned stimuli, indicating an acuity of approximately 6/180. The infants' refractive state has been studied by means of ‘photorefraction’. Many infants under 1 year are astigmatic but this has decreased to adult levels of incidence by 2 years. Infants of 6 months and older accurately accommodate over the adult range; younger infants accommodate appropriately for distances closer than 75 cm. Neural development rather than accommodative error appears to be the principal factor in limiting infants' acuity. A development of this technique may provide an effective means of refractive screening in young infants.
APPLIANCES USED TO HELP THE HANDICAPPED UNDER THREES TO FOLLOW THE NORMAL DEVELOPMENTAL SEQUENCE
Authors: BARTON E. MARY , HOLLOBON BARBARA , WOODS GRACE E.
Published: April 2006

Summary An account is given of all the varying types of aids and appliances which were prescribed to the under 3‐year‐old handicapped children of all categories at the Regional Child Assessment Centre, Leeds, UK, between the years 1972–1977. They were required to help the child live as normal a life as possible, and progress along normal developmental lines. Altogether 430 aids were given to 163 children. The names of suppliers and the means of obtaining the aids are detailed at the end of this article.
EPIDEMIOLOGY OF SERIOUS HEAD INJURIES IN CHILDHOOD
Authors: MOYES C. D.
Published: April 2006

Summary
A survey of 87 serious head injuries of children from 3–14 years old revealed road traffic accidents to be the cause of most of the long‐term morbidity and nearly all the mortality. Social background of these children was not significantly different from the general population in respect of class or family size, but there was an excess of children of high birth order and probably from single parent families, suggesting a lack of supervision. The need for a multidisciplinary approach to the rehabilitation of the child with severe head injury is emphasized.
NURSING ASSISTANTS AS CO‐THERAPISTS
Authors: BAILEY ROY D. , CRAZE ANDREW
Published: April 2006

Summary
The present study was conducted in a small 20‐bed hospital for severely subnormal children. Ten children who had evidenced a history of problem behaviour were the subjects of behaviour modification programmes aimed at reducing the frequency of problem behaviour. The main aim of the study was to establish if nursing assistants can become effective co‐therapists. Two questions were investigated: (1) Can nursing assistants after 12 months' training have a sound knowledge of the principles of behaviour modification and (2) Can these nursing assistants effectively employ behaviour modification techniques which result in reductions of problem behaviour episodes? It is argued that although nursing assistants may have had an inadequate and erroneous knowledge of the principles of behaviour modification, they were able to employ behavioural techniques which affected reductions in the problem behaviours recorded. Clinical difficulties related to applied research of this kind are raised in discussion.
HOME TEACHING IN THE NORTH‐WEST: A PILOT SURVEY
Authors: PETRIE IAN , TAYLOR PATSY
Published: April 2006

Summary
The home teaching services in three counties and two metropolitan districts in the north‐west were surveyed. A questionnaire was used to gather information relating to the number of children and range and types of problems referred, organization and staffing, and changes and developments in the services. Wide differences were found among the individual education authorities in these various aspects of home tuition. Although home teaching demands high professional skills it does not offer an attractive career structure and is very largely staffed by part‐time women teachers.
Some conditions affecting manipulative play with objects in severely mentally handicapped children
Authors: THOMAS G. V. , PHEMISTER M. R. , RICHARDSON A. M.
Published: April 2006

Summary
Four experiments investigated contact and manipulative activity with play materials in severely handicapped children functioning at the I‐2‐year‐old stage of normal development. Experiment 1 found that many mentally handicapped children were as quick to contact and manipulate a novel object as were comparable normal children and that auditory (or visual) feedback seemed to be effective in sustaining attentive activity with an object. A small minority of the handicapped children, however, were very slow to contact either familiar conventional toys or a novel object. Experiments 2 and 3 found that adding stimulus features such as lights, sounds or bright colours to an object had no consistent effect on the latencies of these ‘slow responders’ to contact the object. Experiment 4 found that the amount and kinds of manipulative play of mentally handicapped children with a range of conventional toys could be similar to that of comparable normal children. The mentally handicapped children differed from the normal children only in that they interacted less with an attendant adult and displayed less frequent representational use of toys in pretend play. The play of both normal and handicapped children was relatively unaffected by whether only a few (four) or many (15) toys were provided.
Schools in the welfare network*
Authors: WELTON JOHN
Published: April 2006

Summary
This paper examines the place of schools within the welfare network for children and young people, and notes potentially disfunctional elements of the social division of welfare. The stratification between welfare professions and the relationship between normal and crisis care is discussed. Three levels of school based welfare systems are identified, working alongside school attached and community based professions, each with its own characteristics. Trends are identified which reflect the development of more effective multi‐professional cooperative care.
Developing coping styles and social support networks: an intervention outcome study with mothers of handicapped children
Authors: KIRKHAM MAURA A. , SCHILLING ROBERT F. , NORELIUS KRISTINE , SCHINKE STEVEN PAUL
Published: April 2006

Summary
This paper describes an intervention programme, evaluation procedures, and results from a study of skills training for reducing stress with parents of handicapped children. Four mothers of developmentally disabled children participated in an 8‐week training programme designed to teach parents ways to enhance their coping skills, increase their social support networks, and collectively make changes in their environment. Post‐test data indicate that the programme shows promise for teaching coping and social support enhancement skills to parents.
Nocturnal enuresis and the use of desmopressin: is it helpful?
Authors: Bath R , Morton R , Uing A , Williams C
Published: April 2006

We assessed the outcome of the use of an enuretic alarm and desmopressin according to conventional guidelines and investigated the reasons for resistance to desmopressin. Children were given a 4 month course using an enuretic alarm if they had not previously used one; 12 out of 21 were dry (57%) after 4 months and one relapsed 1 month later. Those who had previously failed with an alarm or were considered poorly motivated to use it, were given a 4 month course of intranasal desmopressin. Of these 26 children, 10 (38%) were dry at the end of 4 months but only two (7%) remained dry after this was withdrawn. After the initial treatment with alarm or desmopressin, 27 children were still enuretic and attending the clinic. They were shown how to use the alarm and eight also used the dry bed training technique: 15 had become dry after a further 6 months. Of the 12 children who made no response to intranasal desmopressin, nine were given this medication under supervision in hospital; seven of these children still wet the bed despite producing small amounts of concentrated urine overnight. They also had small measured diurnal bladder capacities. We conclude that if a 4 month course with an enuretic alarm is unsuccessful, rather than using desmopressin, the alarm should be continued with relearning and consideration given to additional use of the dry bed training technique. The major factor causing nocturnal enuresis in children is likely to be a small nocturnal bladder capacity.
TH2‐polarized immunological memory to inhalant allergens in atopies is established during infaney and early childhood
Authors: YABUHARA A. , MACAUBAS C. , PRESCOTT S. L. , VENAILLE T. J. , HOLT B. J. , HABRE W. , SLY P. D. , HOLT P. G.
Published: April 2006

Background
There is increasing evidence that the T‐cell reactivity to environmental allergens underlying expression of allergic disease in adulthood, develops initially during childhood. However, there is little information available on the kinetics of these early responses, or on the patterns of cytokine production during this period.

Objective
The purpose of this study was twofold: to obtain further information on the reported differences between responses to food versus inhalant allergens during early childhood, and to ascertain the age‐range over which T‐cell responses to inhalant allergens become polarized towards the TH2 cytokine profile, in potentially atopic children.

Methods
In vitro cytokine responses to house dust mite (HDM) and egg (OVA) were assessed by semiquantitative RT‐PCR in panels of 2‐ and 5‐year‐old children and adults; lymphoproliferative responses to OVA were subjected to epitope analysis.

Results
At age 2 years IL‐4/IL‐5 responses to HDM grouped with positive atopic family history, and by age 5 years cytokine responses correlated strongly with individual SPT reactivity to HDM. In contrast, OVA responses were restricted to weak and transient IL‐5 signals in the 2‐year‐old family history positive group. Lymphoproliferation assays performed in parallel indicate a log‐scale greater postnatal expansion of T‐cell reactivity to the inhalant allergen; preliminary epitope analysis of OVA responses indicate that the number of OVA epitopes recognised decrease during early childhood.

Conclusions
Inhalant allergen‐specific in vitro cytokine production associated with positive skin‐prick test (SPT) reactions, one of the hallmarks of adult atopy, manifests in children at or before 5 years of age; additionally, cytokine responses in SPT negative 5 year‐olds are restricted to IFNγ, as per normal adults. In contrast, T‐cell responses to a typical food allergen appear to be deleted during early childhood.
Expression of interleukin (IL)‐4 and IL‐5 proteins in asthma induced by toluene diisocyanate (TDI)
Authors: MAESTRELLI P. , OCCARI P. , TURATO G. , PAPIRIS S. A. , DI STEEANO A. , MAPP C. E. , MILANI G. F. , EABBRI L. M. , SAETTA M.
Published: April 2006

Background
TDI‐induced asthma exhibits clinical, functional and morphological similarities with allergen‐induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDL In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T‐cell clones derived from bronchial mucosa of subjects with TDI‐induced asthma produced IL‐5 and interferon‐gamma, but not IL‐4, upon in vitro stimulation.

Objectives
To investigate in vivo the role of IL‐4 and IL‐5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies.

Methods
We obtained bronchial biopsies from six subjects with TDI asthrha 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1–4 weeks after the last exposure to TDI (chronic group), and in six non‐asthmatic controls. The number of eosinophils, mast cells, T‐lymphocytes, and IL‐4 and IL‐5 protein positive cells was determined by immunohistochemistry in the area 100 μn beneath the epithelial basement membrane.

Results
The characteristic increase of submucosal eosinophils, but not of mast cells and T‐lymphocytes, was observed in the subjects with TDI‐induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI‐induced asthma, cell immunoreactivity for IL‐5 was increased when compared with normal controls. There was no difference in the expression of IL‐5 protein between challenged and chronic asthmatics. In contrast, the expression of IL‐4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI.

Conclusions
We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL‐4 and IL‐5, whereas chronic TDI asthma was associated with increased expression of IL‐5, but not of IL‐4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL‐5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH2‐like cytokines in TDI‐induced asthma may not always be co‐ordinately regulated in vivo.
Substance P is generated in vivo following nasal challenge of allergic individuals with bradykinin
Authors: BAUMGARTEN C. R. , O'CONNOR A. , DOKIC D. , SCHULTZ K. D. , KUNKEL G.
Published: April 2006

Background
Bradykinin, a potent inflammatory mediator, is released during allergic and non‐allergic rhinitis and asthma in man. Nasal bradykinin challenge induces a dose‐dependent plasma leakage into the nasal cavity and relevant symptoms of rhinitis.

Objective
We now report on substance P generation during nasal bradykinin challenge in vivo.

Methods
The effect ot locally applied bradykinin on substance P generation was studied in nine individuals, allergic to grass pollen and six non‐allergic controls. In the allergies TAME‐esterase activity, histamine and substance P concentrations were measured in nasal lavages and correlated to the clinical symptoms.

Results
Substance P concentrations in nasal lavages increased in a dose‐dependent fashion during nasal bradykinin challenge in both groups. In the allergic group Substance P‐increases correlated with the production of TAME‐esterase activity (r= 0.9. P < 0.05) whereas these allergic individuals did not produce any histamine increases. The generation of substance P and the increase of TAME‐esterase activity was associated with the onset of clinical symptoms. Correlation of oedema and hypersecretion to substance P were signiticant by linear regression analysis (r = 0.88, P < 0.005 and r= 0.89. P < 0.02, respectively). Bradykinin induced irritations like burning and itching were shortterm and rare. Serial dilutions of nasal washes produced Substance P‐RIA displacement curves that paralleled the standard curve and recovery of standard substance P that was added to nasal washes was 76 ± 4% (mean ± sem), n= 8.

Conclusion
Bradykinin induces in vivo a dose‐dependent plasma leakage into the nasal cavity without affecting mast cells, but stimulates nerve endings resulting in the release of the neuropeptide substance P.
The physiology of seed hydration and dehydration, and the relation between water stress and the control of germination: a review
Authors: HEGARTY T.W.
Published: April 2006

Abstract Current interest in seed hydration treatments for the improvement of level, rate and uniformity of germination or field emergence has revealed how little is known of the physiology of germination control under water stress. This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration. Inhibition of germination, though not of seed activation, at certain levels of water stress is likened to various forms of dormancy, and the mechanism governing the initiation of cell elongation is suggested as the possible key to control over germination. Several lines of evidence on cell membrane integrity and action, and their responses to external factors, point to the role that the membrane may play in cell elongation (and hence germination) control, and membrane integrity may also be associated with the transition between seed deterioration at one hydration level and seed activation and repair at slightly higher hydration levels. Seed activation without germination is also considered in an ecological context.
Membrane potentials and salt distribution in epidermal bladders and photosynthetic tissue of Mesembryanthemum crystallinum L.
Authors: LÜTTGE U. , FISCHER E. , STEUDLE E.
Published: April 2006

Abstract Membrane potentials (pd's) of epidermal bladder cells and green leaf cells of Mesembryanthemum crystallinum L. are rather low (between −10 and −40 mV). During growth on 400 mM NaCl membrane potentials decrease further. As shown previously, plants grown on 400 mM NaCl show the diurnal changes of malate levels typical for plants having crassulacean acid metabolism. Therefore, in this study membrane potentials were measured at different times of the day, but no diurnal variations of pd were correlated with diurnal oscillations of malate levels. Resting potentials are similar in bladder cells and in green leaf cells and are similar in continuous light and darkness. Both bladder and leaf cells display light‐triggered photosynthesis‐dependent oscillations of the membrane potential although the bladder cells do not appear to be photosynthetically very active. This suggests electrical coupling between the bladder cells and the underlying green cells. Over a larger distance (2 mm) in the leaves, however, there is no direct evidence for electrical coupling. Cl−, Na+, and K+ concentrations are similar in bladder cells and in the photosynthetically active tissue of leaves and stems. Bladder cells appear to contain high concentrations of free oxalate. The present findings corroborate earlier conclusions that the epidermal bladder cells of M. crystallinum function as peripheral water reservoirs providing protection from short term water stress.
Auxin—controlled root growth and ethylene production
Authors: DUBUCQ M. , HOFINGER M. , GASPAR T.
Published: April 2006

Abstract Growth and ethylene production by lentil root tips treated with varying concentrations of indolylacetic and indolylacrylic acids were measured. Stimulation of growth by low concentrations of auxin was accompanied by a reduced ethylene production; growth inhibition by high levels of auxin induced a diminished ethylene evolution. Application of a rhizobitoxine analogue increased growth and reduced ethylene evolution. Simultaneous application of auxin and rhizobitoxine analog reduced ethylene evolution even though growth was inhibited. This indicated the non‐dependency of auxin‐controlled root growth upon ethylene production.
Differences in thermal properties of NAD malate dehydrogenase in genotypes of Lathyrus japonicus Willd (Leguminosae) from maritime and continental sites
Authors: SIMON JEAN‐PIERRE
Published: April 2006

Abstract The response of the kinetic properties of NAD malate dehydrogenase (MDH) was compared for two clones of Lathy rus japonicus Willd. collected in two contrasting climatic sites in Eastern North America. MDH from the cold adapted maritime genotype (Hudson Bay, Québec) had lower thermostability, reduced apparent (Ea) and free (ΔG†) energy of activation and lower specific activity when compared to MDH of plants from the warm summer continental site (Lake Michigan). Electrophoretic analyses show little differentiation in the isozyme profiles of the two genotypes. Thermostability differences were primarily associated with the mitochondrial isozymes which, however, were not differentiated electrophoretically Substrate binding ability of MDH, as measured by apparent Km, was more sensitive to high assay temperature in the cold adapted maritime genotype.
Adaptation and acclimation of higher plants at the enzyme level: Speed of acclimation for apparent energy of activation of NAD malate dehydrogenase in Lathyrus Japonicus Willd. (Leguminosae)
Authors: SIMON JEAN‐PIERRE
Published: April 2006

Abstract The speed of acclimatory changes in apparent energy of activation (Ea) of NAD malate dehydrogenase was analysed in four clones of Lathyms japonicus Willd. collected over a 16° latitudinal gradient in eastern North America. Plants were grown initially for six months at either 7° night/15° day or 22° night/30° days. Following reciprocal switches in these two contrasting thermo‐periods, energy of activation was relatively stable for 12 h, then oscillated until 48 h, and stabilized in about 72 h. The results suggest that the acclimation response in Ea is not due to near‐instantaneous conformational changes in isozymes, but is directed primarily by temperature‐mediated structural and/or functional modifications during de novo synthesis of the forms of the enzymes.
Properties of phosphoenol pyruvate carboxylase inSedumspecies in relation to Crassulacean Acid Metabolism (CAM)
Authors: KNOPF O. , KLUGE M.
Published: April 2006

AbstractParameters of Crassulacean Acid Metabolism (carbon isotope composition [δ13C values], diurnal acid cycles) were studied together with properties of phosphoenolpyruvate carboxylases (PEP‐C) in eight species of the genusSedum. The δ13C values indicate a considerable variability of CAM capacity among the species investigated. The spectra of organic acids were similar in all species. Malate, citrate, and isocitrate were the main components of the acid fraction. Quinic acid occurred only during the light period. Molecular weights of PEP‐C were in the range of 160,000 and showed no correlation to CAM as indicated by the δ13C values. However, there were differences in the kinetic data of PEP‐C.Sedumspecies with less negative δ13C (i.e. with high CAM capacity) have PEP‐C with higher Vmax, higher Km (PEP) and higher sensitivity for malate inhibition.
Studies on auxin protectors XIV. Chlorogenic acid, a low molecular weight auxin protector in sunflower
Authors: STONIER T. , MACGLADRIE K. , SHAW G.
Published: April 2006

Abstract Acetone extracts of sunflower leaves yielded two low molecular weight compounds with significant auxin protector activity. By means of chromatography, UV spectra, and acid hydrolysis it was possible to ascertain that most of the protector activity was associated with chlorogenic acid. Some protector activity was also associated with a derivative of chlorogenic acid, tentatively identified as isochlorogenic acid. A possible role for chlorogenic acid is proposed.
The effect of stratification on the endogenous levels of gibberellins and cytokinins in seeds of douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) and sugar pine (Pinus lambertiana Dougl.)
Authors: TAYLOR J. S. , WAREING P. F.
Published: April 2006

Abstract Seeds of Douglas‐fir and sugar pine which had been exposed to various periods of moist chilling (stratification) were extracted and bioassayed for gibberellin and cytokinin activity. In Douglas‐fir a peak of gibberellin activity increased progressively during stratification and was seven times higher after 7 weeks, but declined subsequently. No change in the level of cytokinin activity was observed during stratification. However, a slight increase (1.7‐fold) occurred in stratified seeds placed at 22°C for 3 days.

In sugar pine a high level of gibberellin activity, approximately 20‐fold higher than in unstratified controls, was present in extracts of seeds which had been stratified for 8 weeks. After 10 weeks of stratification cytokinin levels had increased approximately 200‐fold. Four cytokinin‐like substances were detected in seeds. Three of the substances are similar in their chromatographic properties to zeatin glucoside, zeatin riboside and zeatin, respectively. Both gibberellin and cytokinin activity declined rapidly after reaching maximum levels.

In seeds with the coats removed, germination was rapid and complete in the absence of stratification. Prior to radicle emergence in coatless seeds cytokinin activity increased to a maximum (approximately a 1‐7‐fold increase) within 24 h. Significant levels of gibberellin‐like substances were present after 8 h. Gibberellin activity could not be detected in coatless seeds which were imbibed in AMO‐1618, and germination was inhibited significantly.
The effect of light on the endogenous levels of cytokinins and gibberellins in seeds of sitka spruce (Picea sitchensis Carriere)
Authors: TAYLOR J. S. , WAREING P. F.
Published: April 2006

Abstract Maximum germination of Sitka spruce seed was obtained at 22°C under continuous fluorescent light or following a single 10 min exposure to red light (RL) given after 48 h of dark imbibition. The levels of endogenous cytokinins and gibberellins were examined in seeds which were exposed to different light regimes. Cytokinin levels in Sitka spruce seeds increased approximately 1.7–fold during exposure to continuous white light, during dark stratification, or within 1 h or a 30 min exposure to RL. A single peak of activity could be eluted from the LH−20 Sephadex column which appeared in the same volume as authentic zeatin riboside. Gibber‐ellin activity in Sitka spruce seeds increased rapidly during exposure to 30 min of RL and then declined during subsequent dark incubation. Similarly, under continuous white light, gibberellin activity was at least twice as high as in the dark. Two gibberellm‐like substances were found in Sitka spruce seeds which appeared to be similar to GA7 and GA9 on the basis of their chromato‐graphic properties. The zone of gibberellin activity directly associated with photo‐excitation of Sitka spruce seeds contains conjugate gibberellins, possibly glucosyl esters, which when hydrolysed with β‐glucosidase form two products which are similar to the free gibberellins which were detected. The light response in Sitka spruce seed is compared to a similar response in Scots pine (Pinus sylvestris L.) seeds.
Consequences of insufficient equations in models of the Münch hypothesis of phloem transport
Authors: MAGNUSON C. E. , GOESCHL J. D. , SHARPE P. J. H. , DEMICHELE D. W.
Published: April 2006

Abstract The suggestion of concentration dependent unloading as a necessary assumption for a closed‐form mathematical expression of the Münch hypothesis of phloem transport (Goeschl et at., 1976) has been recently questioned (Ferrier & Christy, 1977). Also questioned was whether previous models, known to have one less equation than dependent variables, have produced erroneous or misleading results. A review of Münch's original concepts and recent comments by several researchers indicate that an equation describing the exit of solutes from sieve tubes is essential for consistency with the Münch hypothesis. Evidence is presented to show that previous mathematical predictions and interpretations regarding ‘runaway velocities’ have resulted in part from mathematical inconsistencies and characteristics of the numerical solution procedures. Likewise, a proposal that different steady‐state velocities and concentrations of transport at a given loading rate might be determined by ‘previous history’ of the system can be explained on the basis of implied relationships hidden in models with insufficient equations. Finally it is concluded that concentration dependent unloading in models of the Münch hypothesis will not detract, but rather will contribute to their usefulness in experimental testing and other research regarding phloem transport.
Interaction of polyamines and light on biochemical processes involved in leaf senescence
Authors: KAUR‐SAWHNEY RAVINDAR , GALSTON ARTHUR W.
Published: April 2006

Abstract The rapid senescence of detached oat leaves in darkness is first manifested by a sharp rise in RNase activity (about 50% within 1 h), then by a rise in protease activity (indicated by an increase in non‐protein α‐amino nitrogen within 6 h) and ultimately by chlorophyll degradation (beginning after 18 h). These degradative changes are delayed or prevented by low concentrations (1–10 mM) of the naturally‐occurring polyamines cadaverine, putrescine, spermidine and spermine. The tetraamine spermine is generally more active than the triamine spermidine, which is in turn more active than the diamines putrescine and cadaverine. All the polyamines are more active than kinetin or cycloheximide. As little as 10 min of exposure to 1 mM spermine, especially at the beginning of the dark period, produces a marked retardation of chlorophyll degradation over a 48 h period, and 60 min of exposure saturates the effect.

In the light, all polyamines promote, rather than retard, the disappearance of chlorophyll but, as in the dark, they inhibit the rise in RNase and non‐protein α‐amino nitrogen. The photobleaching of chlorophyll in the presence of polyamines is proportional to the duration of exposure to high irradiance (16.5 Wm−2) fluorescent light. Such light is more effective toward the end of the 48 h post‐excision test period than at the beginning.

Calcium ion (1–10 mM) supplied together with the polyamines diminishes their action in dark and light, indicating probable involvement of an initial ionic attachment mechanism.

The loss of chlorophyll from the leaves of four species of dicotyledonous plants (pea, bean, rape, tobacco) in the darkness is similarly retarded by 1–10 mM polyamines. In rape, the most rapidly senescing species, 1 mM spermine almost completely arrests chlorophyll degradation over a 96 h period. It is suggested that polyamine metabolism in plants may be related to normal physiological control mechanisms as in microorganisms and animals, and that polyamines could find use as anti‐senescence agents for plants.
Why does DNA‐dependent RNA polymerase I from higher plants possess a more complex subunit structure than the enzyme from Escherichia colil? A hypothesis
Authors: GROSSMANN KLAUS
Published: April 2006

Abstract. During the emergence of the eukaryotic line and the three classes of DNA‐dependent RNA polymerases with their specific transcriptional tasks, the subunit structure of these enzymes became more complex when compared with the prokaryotic enzyme. It is proposed, especially for the RNA polymerase I from higher plants, that the increase in the complexity of subunit structure during evolution was associated with an increase in the degree of co‐operativity of substrate binding sites. This multiplicity of substrate binding sites could be useful for fitting and proper base‐pairing between the incoming substrate molecules and the DNA template.
Calmodulin and calmodulin‐mediated processes in plants
Authors: DIETER PETER
Published: April 2006

Abstract. The Ca2+ ‐binding protein calmodulin is found in all plants investigated so far. The comparison of the biochemical and functional properties reveals that it is structurally conserved and functionally preserved throughout the plant and animal kingdom. Among the plant enzymes so far known to be dependent on the Ca2+ ‐calmodulin complex are NAD kinase(s), Ca2+ ‐transport ATPase, quinate: NAD+ oxidoreductase, soluble and membrane bound protein kinases, and H+ ‐transport ATPase. Calmodulin may play also an important role in the regulation of other cellular reactions, such as hormone‐mediated processes, secretion of enzymes, and contractile mechanisms. On the basis of the NAD kinase and its regulation by light and Ca2+ ‐calmodulin, it is suggested that changes in the cellular, free Ca2+ concentration following stimulation may alter the metabolism of a plant cell. According to this suggestion free Ca2+ may act as a second messenger in plants much as it does in animal cells.
Calcium as an environmental variable
Authors: RORISON I. H. , ROBINSON DAVID
Published: April 2006

Abstract. The chemical state of calcium in the soil and the effects, both direct and indirect, which this can have on the growth and distribution of plants are considered. Recent advances in knowledge refer mainy to interactions (between nitrogen source, aluminium and pH, for example) for which there is now experimental evidence and which themselves are influenced by calcium. The impact of physical variables is less marked than first thought although seasonal effects of waterlogging and drought can be critical. It is emphasized that the terms ‘calcicole’ and ‘calcifuge’ are generally acceptable in classifying plants according to the degree of calcareousness of the soils in which they occur but only if the wider implications are appreciated.
Calcium as a plant nutrient
Authors: KIRKBY E. A. , PILBEAM D. J.
Published: April 2006

Abstract. Calcium occurs as a relatively large, divalent ion which readily enters the apoplast and is bound in exchangeable form in cell walls and on the exterior surface of the plasmalemma. It occurs in only very low concentrations in the cytoplasm and chloroplasts and appears to have a limited role as an enzymatic cofactor. The soil solution usually provides an adequate supply of Ca to plants. The well known physiological disorders resulting from localized Ca deficiencies within the plant are thus attributable to poor Ca distribution rather than restriction in uptake. Calcium is moved largely in the xylem and only to a very limited extent in the phloem. The phloem/xylem ratio of the solute input can be particularly critical in organs which are naturally low in Ca, such as fruits and young leaves. Factors which influence the distribution of Ca such as humidity, root pressure, phytohormone activity, can also affect the occurrence of these disorders.
Calcium transport between tissues and its distribution in the plant
Authors: CLARKSON DAVID T.
Published: April 2006

Abstract. The low cytosol concentration of free Ca2+ makes the symplast of roots an ineffective pathway for the supply of the calcium needed for healthy growth in the aerial parts of plants. Ca2+ moves rapidly across the cortical apoplast by diffusion and mass flow but is probably diverted across the plasmamembranes of endodermal cells by Casparian bands. A proposal is made to account for the movement of calcium across the endodermis and it is estimated that Ca‐fluxes are likely to be appreciably greater than in the regulation of cell Ca level by cortical cells.

Ca transport in the xylem occurs by mass flow of free Ca2+, and some organically complexed Ca, and by chromatographic movement along Ca‐exchange sites in the xylem walls. Delivery of Ca to transpiring leaves and to weakly transpiring meristematic zones is discussed in relation to the two modes of Ca movement in the xylem. Competition between sinks is intensified when [Ca2+] in xylem is low and transpiration is great.

Tropic growth responses involve pumping of vacuolar calcium into the apoplast followed by its migration along gradients of electrical potential which develop in the apoplast after geo‐stimulation. An attempt is made to estimate plasmalemma efflux during this process.

Redistribution from mature tissues to meristems in the pholem is likely to be small, if it occurs at all, since sieve tubes cannot have more than micro‐molar concentrations of free‐Ca2+ in them.
Calcium in plant senescence and fruit ripening
Authors: FERGUSON I. B.
Published: April 2006

Abstract. Calcium has long been associated with regulation of the ripening process of fruit and post‐harvest storage life. Specifically, maintenance of relatively high calcium concentrations in fruit tissue results in a slower rate of ripening, as seen in lower respiration rates, reduced ethylene production, and slower softening of fruit flesh. There are also some specific fruit disorders such as bitter pit, which can be prevented if sufficient calcium is present. Senescence of other plant tissues such as leaves and flowers has also been shown to be retarded by the application of calcium.

Work leading to the above information is reviewed and discussed in the context of what is currently known of cellular regulation of calcium in plants. The major sites for the action of calcium in senescence and ripening are suggested to be in membrane structure and function, and in cell wall structure. Although high external concentrations of calcium are an advantage in reducing the rate of senescence or ripening, it is emphasized that normal cell function requires the maintenance of low concentrations of free calcium in the cell cytosol. It is suggested that one possible feature of senescence is a breakdown in such cellular regulation.
Effects of weak acids on proline accumulation in barley leaves: a comparison between abscisic acid and isobutyric acid
Authors: PESCI P. , BEFFAGNA N.
Published: April 2006

Abstract. When isobutyric acid (IBA) or abscisic acid (ABA) are supplied to leaf sections a similar rapid and marked decrease in the intracellular pH is observed. This acidification is accompanied by an increase in proline level which is about the same for both 3 mol m−3 IBA and 1 mol m−3 ABA treatments.

Fusicoccin (FC), known to act at the proton pump level, almost completely suppresses the ABA‐induced acidification of the cell sap, whereas it only partially counteracts the acidifying effect of IBA, in particular during short periods of treatment. This effect of FC is paralleled by a similar inhibition of the induced proline accumulation: in fact, FC completely suppresses the ABA‐induced increase in proline during short treatment periods, whereas it is only effective in inhibiting the IBA‐induced proline accumulation after long treatment periods.

These data seem to suggest that the ABA‐ and IBA‐induced changes in proline level might be mediated by changes in the intracellular pH.
Germination and seedling growth of cotton: salinity‐calcium interactions
Authors: KENT L. M. , LÄUCHLI A.
Published: April 2006

Abstract. The effects of NaCl salinity on germination and early seedling growth of cotton were studied. Germination was both delayed and reduced by 200 mol m−3 NaCl in the presence of a complete nutrient medium. Seedlings, 7–9 d old, were greatly reduced in fresh weight by salinity. The addition of supplemental Ca2+ (10 mol m−3 as SO42− or Cl−) to the medium did not improve germination but, to a large degree, offset the reduction in root growth caused by NaCl. Roots growing in the high salt medium without supplemental Ca2+ appeared infected by microbes. The cation specificity of the beneficial Ca2+ effect on growth was ascertained by testing additions of MgSO4 or KCl to the NaCl treatments. The contents of K4 and Ca2+ were reduced in both roots and shoots by the NaCl treatments. Supplemental Ca2+ partially offset this effect for K4 in the roots and for Ca2+ in both roots and shoots. Sodium contents were not affected by the supplemental Ca2+. It is concluded that the beneficial effect of high Ca2+ concentrations on root growth of cotton seedlings in a saline environment may be due to maintenance of K/Na‐selectivity and adequate Ca status in the root.