A Critical Oxygen Pressure for Root Extension in Rice

Armstrong, W. and Webb, T. 1985. A critical oxygen pressurefor root extension in rice.—J. exp. Bot. 36: 1573–1582. The relationship between oxygen partial pressure and root extensionwas investigated using a method designed to circumvent boundarylayer resistance effects. Roots were made wholly dependent uponoxygen transported longitudinally from the atmosphere throughthe aerenchymatous and intercellular spaces and the internaloxygen pressure in the extension zone was altered when requiredby adjusting the oxygen content of gas mixtures applied to theshoot (whole plants) or basal cut-end of the root (excised roots).Platinum cathodes sleeving the root in the extension zone wereused to monitor root surface oxygen partial pressure continuously,root extension was measured half-hourly by means of travellingmicroscopes. The results confirmed that internal oxygen transport is sufficientto support root extension in rice and that, at least in theshort term, extension is not greatly influenced by oxygen concentrationuntil very low values are reached. A certain degree of variabilitywas noted when using whole plants but this was no longer evidentwith excised roots. The results from the latter suggest a figureof 0.8 kPa for the critical oxygen pressure of root extension,which is much lower than any previously published values. Itis supposed that such a low value is probably not a unique characteristicof rice roots but rather is the result of the measurements havingcircumvented both the boundary layer effects external to theroot and the normal influence of the epidermal and hypodermallayers. Key words: Roots, growth, oxygen, rice     

Alteration of transpiration rate, by changing air vapour pressure deficit, influences leaf extension rate transiently in Miscanthus

A controlled environment chamber for whole plants is described in which vapour pressure deficit (VPD) and temperature can be controlled independently. Plant responses to changes in VPD at constant temperature were measured in terms of leaf extension and plant transpiration rates. Manipulation of VPD independently of temperature was shown to be capable of altering the leaf extension rates of the C4 grass Miscanthus x giganteus grown in hydroponics. The effects of VPD on leaf extension are attributed to changes in transpiration rate and hence leaf water status. It was found that, at a temperature of 20C, the influence of a fixed change in VPD was proportionally less than those observed at temperatures which are close to the threshold for growth (between 6 and 10C). These responses are discussed in relation to our current understanding of the mechanisms of cell growth. The fact that the VPD effects on leaf expansion rates were largely transient suggest that simple models driven by temperature alone are adequate to predict leaf expansion within the temperature range 6-20°C, for this genotype of Miscanthus, in the field.Key words: Leaf growth, Miscanthus x giganteus, temperature, vapour pressure deficit, C4 plants.      

Growth Reductions of Rice at Low Root Temperature: Decreases in Nutrient Uptake and Development of Chlorosis

The physiological mechanisms for growth reductions of rice atlow root temperatures were investigated in detail via time coursesin nutrient status of several cultivars. During short-term exposureto low temperature, i.e. between 0–2.5 d with roots at10°C, leaf extension rates were reduced approximately 80%-95%in all cultivars. In contrast, relative growth rates of shootson a dry weight basis were often even greater for plants withroots at 10°C relative to 30°C. During long-term growthat low root temperatures, i.e. between 2.5–10 d, relativegrowth rates of shoots were reduced, chlorosis developed andcultivar differences were observed which were consistent withfield observations of cold-tolerant and cold-intolerant cultivars. The results indicate that decreases in nutrient concentrationsin plants could not account for growth reductions during short-termexposure to low root temperatures. However, it is possible thatthey are responsible for most of the growth reductions and chlorosislater than 2.5 d. The latter suggestion is not proven unequivocallybut is supported by: (i) similar results when plants were transferredto CaSO⁴ solutions at 30°C in terms of growth, nutrientdecreases with time and chlorosi (ii) N and sometimes P concentrationsfalling below critical levels for rice and (iii) lower nutrientuptakes and concentrations, particularly of N, in a cold-intolerantthan a cold-tolerant cultivar. Key words: Root temperature, growth, rice, nutrient uptake     

Predictive model for the growth of Yersinia enterocolitica under modified atmospheres

A quadratic response surface model is presented to describe the maximum specific growth rate of Yersinia enterocolitica, at refrigeration temperatures, under modified atmospheres. The presence of CO2 affected mainly the lag phase of the organism. The length of the lag phase increased with higher levels of CO2 in the atmosphere, and this effect was more noticeable at low temperatures. The effect of oxygen was similar but less pronounced. The observed growth was slower with higher CO2. Oxygen also decreased the growth rate, but its effect was significant only when its proportion in the atmosphere was greater than about 40%. Model predictions were compared with growth rates obtained in sea food inoculated with Y. enterocolitica and packaged under modified atmospheres. Predictions were also checked to determine whether they were inside the strict interpolation region of the model.     

Mortality rate and longevity of food-restricted exercising male rats: a reevaluation

Holloszy, John O. Mortality rate and longevity offood-restricted exercising male rats: a reevaluation.J. Appl. Physiol. 82(2): 399-403, 1997.Food restriction increases the maximal longevity of rats. Malerats do not increase their food intake to compensate for the increasein energy expenditure in response to exercise. However, a decrease inthe availability of energy for growth and cell proliferation thatinduces an increase in maximal longevity in sedentary rats only resultsin an improvement in average survival, with no extension of maximallife span, when caused by exercise. In a previous study (J. O. Holloszyand K. B. Schechtman. J. Appl. Physiol. 70: 1529-1535, 1991), totest the possibility that exercise prevents the extension of life spanby food restriction, wheel running and food restriction were combined.The food-restricted runners showed the same increase in maximal lifespan as food-restricted sedentary rats but had an increased mortalityrate during the first one-half of their mortality curve. The purpose ofthe present study was to determine the pathological cause of thisincreased early mortality. However, in contrast to our previousresults, the food-restricted wheel-running rats in this study showed no increase in early mortality, and their survival curves were virtually identical to those of sedentary animals that were food restricted so asto keep their body weights the same as those of the runners. Thus it ispossible that the rats in the previous study had a health problem thathad no effect on longevity except when both food restriction andexercise were superimposed on it. Possibly of interest in this regard,the rats in this study did considerably more voluntary running thanthose in the previous study. It is concluded that1) moderate caloric restrictioncombined with exercise does not normally increase the early mortalityrate in male rats, 2) exercise doesnot interfere with the extension of maximal life span by foodrestriction, and 3) the beneficialeffects of food restriction and exercise on survival are not additiveor synergistic.

     

beta-adrenergic receptor/cAMP-mediated signaling and apoptosis of S49 lymphoma cells

-Adrenergic receptor (AR) activationand/or increases in cAMP regulate growth and proliferation of a varietyof cells and, in some cells, promote cell death. In the current studieswe addressed the mechanism of this growth reduction by examiningAR-mediated effects in the murine T-lymphoma cell line S49.Wild-type S49 cells, derived from immature thymocytes(CD4⁺/CD8⁺) undergo growth arrest andsubsequent death when treated with agents that increase cAMP levels(e.g., AR agonists, 8-bromo-cAMP, cholera toxin, forskolin).Morphological and biochemical criteria indicate that this cell death isa result of apoptosis. In cyc and kin S49cells, which lack G_s and functional protein kinase A(PKA), respectively, AR activation of G_s and cAMPaction via PKA are critical steps in this apoptotic pathway. S49 cellsthat overexpress Bcl-2 are resistant to cAMP-induced apoptosis. Weconclude that AR activation induces apoptosis in immature Tlymphocytes via G_s and PKA, while overexpression ofBcl-2 prevents cell death. AR/cAMP/PKA-mediated apoptosis mayprovide a means to control proliferation of immature T cells in vivo.

     

Water Stress and Leaf Growth of Field Beans (Vicia faba L.) in the Field: Leaf Number and Total Leaf Area

The leaf area growth of field beans grown under covers in thefield was measured non-destructively on plants subjected tothree different degrees of soil water stress by means of dryingcycles of different lengths in 1974 and 1975. After a periodof 46 days the total leaf area of the well-watered plants wasabout double that of the non-watered ones. The total leaf areaat the final-sampling and the mean plant water potential duringthe observation period were linearly related with highly significantcorrelation coefficients (0·96 in 1974 and 0·86in 1975). The differences between treatments in total leaf areawere mainly produced by the mechanisms determining leaf sizerather than those associated with leaf production and maintenance,namely leaf production, unfolding and death. In neither yearwas leaf production or unfolding sensitive to water stress beforeflowering. Plant water potential () exerted a cumulative longterm effect on these two mechanisms. The threshold values of for reducing the rates of leaf production and unfolding weremore negative in the drier year (1975). Leaf death was affectedby drought earlier than leaf production and unfolding. Vicia faba, field bean, water stress, leaf area     

Physiological responses to stoichiometric constraints: nutrient limitation and compensatory feeding in a freshwater snail

Nitrogen (N) and phosphorus (P) are considered to be essential nutrients that control secondary production in various ecosystems; insufficient availability of N and P can limit herbivore growth. Here, data are presented from field samplings and from a laboratory experiment on the potential of primary producers low in P, N, or P and N to constrain growth of the freshwater gastropod Radix ovata . The filamentous green alga Ulothrix fimbriata was cultured under different nutrient regimes, resulting in algae with different C:N:P ratios. The pure algae were fed in high and low quantities to juvenile R. ovata . Low availability of N and especially P in the algae strongly constrained the biomass accrual of the herbivore. In accordance with theoretical predictions, these food quality differences were highly dependent on the food quantity. The snails' growth rate was significantly related to their body C:P ratio, thereby supporting the growth rate hypothesis. R. ovata displayed a pronounced compensatory feeding response to low-nutrient food that could partly dampen but not fully compensate the food quality effects on snail growth. Increased feeding of gastropods at low P and/or N availability leads to depletion of periphyton biomass; hence compensatory feeding would shift the benthic herbivore community from a P or N limitation to a C limitation and thus have whole-ecosystem effects.     

Diverse scaling relationships of tree height and diameter in five tree species

Background: Allometric scaling relationships are important in ecology and forestry. The metabolic scaling theory (MST) predicts a universal invariant scaling relationship for tree growth, relating height and diameter to each other.

Aims: Data on five tree species (Pinus taeda L., Pinus virginiana Mill., Liquidambar styraciflua L., Liriodendron tulipifera L., and Pinus palustris Mill.) were used to test the predictions from MST on the scaling of height–diameter and also diameter growth.

Methods: Data on tree height and diameter for five tree species from both natural forests and plantations were collected to study two types of scaling relationships: tree height–diameter and stem diameter growth. A reduced major axis of regression analysis model type II was used to determine scaling exponents from each species under different environmental conditions.

Results: No universal invariant scaling exponent was found in height–diameter and diameter growth for the five species. The scaling varied across natural forests, plantations and scales (e.g., time and number of measured trees). However, in some situations the scaling exponents failed to show significant difference with the predicted values (e.g., 2/3 or 1).

Conclusions: Diverse scaling exponents were observed for the five tree species with the scaling relationships varying with environmental settings.     

Growth Regulation of Galium mollugo L. Cell Suspensions by a-Naphthalene Acetic Acid

Fidgeon, C. and Wilson, G. 1987. Growth regulation of Galiummollugo L. cell suspensions by -naphthalene acetic acid.—J.exp. Bot. 38: 1491–1500. Galium mollugo cell suspension cultures were found to requirethe plant growth regulator -naphthalene acetic acid (-NAA) forcontinued growth and cell division. This requirement could notbe substituted in either batch or semi-continuous culture byindole-3-acetic acid (IAA) or 2,4-dichlorophenoxy acetic acid(2,4-D) at any concentration tested. However, ß-naphthaleneacetic acid (ß-NAA) and indole-3-butyric acid (IBA)were found to support growth when supplied at a concentrationtwo orders of magnitude greater than the normal media level(0–5 mg dm³). The growth of Galium cells was found to be influenced not onlyby the -NAA initially supplied in the medium but also by theexposure to -NAA in previous growth cycles. Preculture of cellsfor 3 d in an -NAA containing medium, followed by cell washingand re-inoculation into -NAA free medium, supported a quantitativegrowth response similar to that obtained after 14 d in the control-NAA containing medium. Even short-term exposures between 0·5and 6·0 h stimulated a detectable growth response 14d later. These observations raise questions relating to theuptake and perception of exogenously supplied growth regulatorsby cultured cells. The delayed kinetics of this form of response is of significancein culture regimes in which cells are transferred from one mediumto another, differing in their growth regulator composition,in order to induce morphogenesis     

Effect of laterality discrimination on joint position sense and cervical range of motion in patients with chronic neck pain: a randomized single-blind clinical trial

Purpose: The main objective of the present study was to evaluate the effects of laterality discrimination training on neck joint position sense and cervical range of motion (ROM) in patients with chronic non-specific neck pain (NSCNP).

Materials and methods: Forty-eight patients with NSCNP were randomly assigned to the neck group (NG) that observed neck images or the foot group (FG) that observed foot images. Response time, response accuracy, cervical ROM, and joint position error (JPE) were the main variables. The secondary outcome measures included psychosocial variables.

Results: Differences between groups in the cervical ROM for flexion (p?=?.043) were obtained, being NG group the one which obtained greater values. NG showed an improvement in right rotation (p?=?.018) and a decrease in flexion was found in the FG (p?=?.039). In JPE, differences between groups were obtained in the left rotation (p?=?.021) and significant changes were found in the NG for flexion, extension, and left rotation movements (p?<?.05). Moderate associations were found between left and right accuracy regarding to post-intervention flexion and right rotation (r?=?0.46, r?=?0.41; p?<?.05) in NG.

Conclusion: Improvements in cervical range of motion and joint position sense are obtained after the performance of the laterality discrimination task of images of the neck but not the feet. Visualization of images of the painful region presents moderate correlations with the accuracy and response time in the movements of flexion and right rotation.     

Validating predictive models of food spoilage organisms

The accuracy and bias of a predictive model for the maximum specific growth rate of Pseudomonas spp. were studied by means of percentage discrepancy and bias indicators. These were calculated for observations obtained both in laboratory media and in food. When independent pseudomonad data generated in broth were compared with model predictions, the error was smaller than in the case of food. The extent to which the food structure and composition of the microflora contribute to the overall error of the model was quantified.     

Relative Uptake Rates of Inorganic Nutrients by NO3- and NH4+ Grown Ricinus communis and by two Plantago Species

Allen, S., Thomas, G. E. and Raven, J. A. 1986. Relative uptakerates of inorganic nutrients by and grown Ricinus communis and by two Plantago species.—J. exp. Bot. 37: 419–428. The relative rates of uptake and assimilation of C, N, P, S,Cl^–, K⁺ , Na⁺ Ca²⁺ and Mg²⁺ by and grown Ricinus conimunisand by NH₄NO₃- grown Plantago lanceolata and P. major were calculatedfrom data presented elsewhere. Results showed that for grown Ricinus the short term relativeuptake rates, for each nutrient X did not change significantly over the steady-state periodof exponential growth. The average gave , the mean relative uptake rate during exponential growth, for each nutrient. The amountof each nutrient taken up from a nutrient solution over a periodof time could, therefore, be calculated. For and -grown R. communis,the relative uptake rate of each nutrient was a constant fractionof the relative rate of carbon assimilation. It is suggestedthat this is typical of plants of cauline habit. For both Plantago spp., the relative rates of nitrogen uptakeand assimilation fell significantly during the exponential growthphase It is suggested that this could be a characteristic ofthe growth habit of the rosette plant. Key words: Relative uptake rates, Ricinus, Plantago, ammonium, nitrate, cauline, rosette     

Post-mortem interval estimative through determination of catalase and Δ-aminolevulinate dehydratase activities in hepatic,renal, skeletal muscle and cerebral tissues of Swiss mice

Purpose: Determining the post-mortem interval (PMI) is one of the challenging tasks in forensic science due to the lack of quick and inexpensive methods. Our objective is to develop innovative and alternative means for PMI evaluation.

Methods: The relationship between PMI and enzymatic modifications in mice tissues was described. After being sacrificed, Swiss mice were randomly divided into groups according to the time elapsed since death. The activities of catalase (CAT) and δ-aminolevulinate dehydratase (δ-ALA-D) were determined in hepatic, renal, skeletal muscle and cerebral tissues.

Results: CAT activity increased in kidney and brain 6?h after death and this increase remained for up to 24?h in the brain and 48?h in the kidney. δ-ALA-D had its activity decreased in the liver and kidneys in 6?h. In the skeletal muscle, δ-ALA-D activity was reduced only 48?h after death. Conversely, an increase on δ-ALA-D activity was observed in the brain at 6?h, followed by its decrease at 24 and 48?h.

Conclusion: With the association of this set of results, it is possible to provide an estimate of PMI. Additionally, these results can be used as an auxiliary parameter associated with other methods to estimate PMI.     

A model for short-term control of the bacterioplankton by substrate and grazing

Substrate supply and grazing are the factors with the greatest potential for short-term control of planktonic bacterial density and productivity. A model was developed based on Monod kinetics, where growth rates are limited by food supply in a saturation type equation. In the model, substrate, bacteria, heterotrophic flagellates and zooplankton are state variables linked by trophic transfer and expressed as carbon. The steady state assumption allows calculation of equations indicating the following: (l) bacterial density is determined primarily by the ratio of substrate input to grazing rate; (2) bacterial production is balanced by a combination of losses due to maintenance, death and grazing, and occurs at a rate determined by the rate of substrate input and the growth yield; (3) ambient substrate concentration is directly related to grazing rate. Sensitivity analysis of the model on a computer demonstrates some differences between grazer-controlled and substrate-controlled bacterial systems, and predictions of the model are listed for possible validation in natural systems. The model is potentially useful in evaluating the ‘link vs. sink’ question, as it provides a framework for investigating energy flow through the microbial food web as a function of controlling factors.     

Plant Growth in Polyethylene Glycol Solutions in Relation to the Osmotic Potential of the Root Medium and the Leaf Water Balance

The changes in leaf extension, plant dryweight, leaf area, netassimilation rate (E), relative growth-rate (R_W), and relativeleaf growth-rate (R_L), have been studied for four species grownfor 2 weeks in solutions of polyethylene glycol 4000 of controlledosmotic potentials. All aspects of growth were decreased bydecreasing the osmotic potential (_sol) of the root medium andthe leaf water potential (), and ceased when _/ was greater than— 10 bars in bean, cotton, maize. These plants were moresusceptible than ryegrass to water stress. Growth of bean stoppedat equal to about —6 bars, but even at —10 barsryegrass was capable of some growth. Slight decrease in fromthe values in the control plants decreased growth during thefirst week but partial recovery was apparent during the secondweek's growth in solution culture, when leaf extension, E, R_Land R_W increased in plants subjected to stress. Examinationof the water balance, water potential, osmotic potential andturgor of the leaf in relation to relative water content suggeststhat recovery was related to increased turgor and that the abilityof the plants to grow at reduced values of the osmotic potentialof the root medium and of the leaf water potential depend onthe maintenance of turgor.     

DomHR: Accurately Identifying Domain Boundaries in Proteins Using a Hinge Region Strategy

Motivation

The precise prediction of protein domains, which are the structural, functional and evolutionary units of proteins, has been a research focus in recent years. Although many methods have been presented for predicting protein domains and boundaries, the accuracy of predictions could be improved.

Results

In this study we present a novel approach, DomHR, which is an accurate predictor of protein domain boundaries based on a creative hinge region strategy. A hinge region was defined as a segment of amino acids that covers part of a domain region and a boundary region. We developed a strategy to construct profiles of domain-hinge-boundary (DHB) features generated by sequence-domain/hinge/boundary alignment against a database of known domain structures. The DHB features had three elements: normalized domain, hinge, and boundary probabilities. The DHB features were used as input to identify domain boundaries in a sequence. DomHR used a nonredundant dataset as the training set, the DHB and predicted shape string as features, and a conditional random field as the classification algorithm. In predicted hinge regions, a residue was determined to be a domain or a boundary according to a decision threshold. After decision thresholds were optimized, DomHR was evaluated by cross-validation, large-scale prediction, independent test and CASP (Critical Assessment of Techniques for Protein Structure Prediction) tests. All results confirmed that DomHR outperformed other well-established, publicly available domain boundary predictors for prediction accuracy.

Availability

The DomHR is available at http://cal.tongji.edu.cn/domain/.     

Food from dumps increases the reproductive value of last laid eggs in the White Stork Ciconia ciconia

Capsule Accessing extra food from waste dumps increases egg volume and hatching mass in White Storks.

Aim To test how White Storks vary their investment in egg size, especially in last laid eggs, in relation to food availability, and to improve our understanding of the importance of extra feeding on intra-clutch variation.

Methods The study was carried out in three White Stork breeding colonies in northern Algeria. Breeding performance was recorded in 70 nests over three years. White Stork colonies situated close to chicken farms were considered to be part of a ‘pseudo experiment’ where parents had access to extra food. Egg volume, laying order, hatching order and hatching weight were recorded.

Results Egg volume and hatching mass in White Storks was significantly greater when they had access to extra food. The reproductive value of last laid eggs (fourth and fifth) doubled when females had access to extra food.

Conclusion Laying smaller last eggs within a clutch provides a mechanism to facilitate early brood reduction in the White Stork, and so should be advantageous when food is scarce. On the contrary, when females had access to extra food, last laid eggs were as big as first eggs which suggests egg size variation is adaptable to local conditions.     

Water Potential and Mechanical Properties of the Cell Wall of Hypocotyls of Dark-Grown Squash (Cucurbita maxima Duch.) under Water-Stress Conditions

Hypocotyl growth of seedlings of dark-grown squash (Cucurbitamaxima Duch.) was greatly reduced by the addition of 60mM polyethyleneglycol (PEG) to hydroponic solution (water stress). Apoplastic solution (A) and cell sap (C) were separately collectedfrom the hypocotyl segments by a centrifugation method. Theosmotic potentials of A (_A) and C (_c), and (=_c–_A) ofstressed hypocotyls were always lower than those of unstressedhypocotyls. Suction force was measured by immersing the segments into solutionsof different concentrations of mannitol. Suction force was significantlycorrelated with _C (r= –0.99). The mechanical properties of the cell wall of hypocotyl segmentswere measured by stressrelaxation technique. Minimum stressrelaxation time (T_o), relaxation rate (R) and residual stressof unstressed hypocotyls were low during the growth period andincreased when the growth ceased. T_o and R of stressed hypocotylsdecreased one day after the stress treatment, but the residualstress was not decreased by the water stress throughout theexperiment. These results suggest that the suppressed growth of dark-grownsquash hypocotyls under water stress was due neither to thereduction of the osmotic potential difference between innerand outer space of the cell, nor to the decrease in suctionforce, but was partly due to the unchanged mechanical propertiesof the cell wall, as represented by one stress-relaxation parameter,residual stress. (Received February 5, 1988; Accepted September 8, 1988)     

Rainfall,but not temperature,negatively affects the growth of Blue Tit Cyanistes caeruleus nestlings

Capsule: Growth trajectories of Blue Tit Cyanistes caeruleus nestlings differed between sexes and were negatively affected by rain but not by temperature during the linear growth phase (LGP).

Aims: To model the growth trajectories of Blue Tit nestlings and to identify the main ecological factors affecting them.

Methods: Sixty-five nestling Blue Tits from a population in northern Italy were weighed at regular intervals and sexed using molecular genetic techniques. The LGP period was identified and analysed to test for the influence of age, sex, hatching date, brood size, temperature and rainfall on individual daily growth rates during the LGP.

Results: Growth curves showed no pre-fledging mass loss. Body mass differed between the sexes, with males being 5% heavier than females at the pre-fledging stage. Daily growth rates during the LGP were higher for males and on non-rainy days, while they were not affected by other factors.

Conclusion: The higher daily growth rate observed in males during the LGP may determine the extent of sexual size dimorphism at the pre-fledging stage. Susceptibility of growth trajectories to environmental conditions was limited to rainfall and was similar in the two sexes. This contrasts with findings from previous studies, which found sex-biased environmental sensitivity of Blue Tit nestlings.