bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative study of the metabolic responses during food shortage and subsequent recovery at different temperatures in the adult lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae)
Authors: Renault D. , Hervant F. , Vernon P. 
Published: March 2003

Abstract.Metabolic responses to prolonged food shortage (35 days) and subsequent re‐feeding (14 days) were investigated in adults of an introduced beetle, Alphitobius diaperinus Panzer, as a function of temperature (12, 16, 20 and 24 °C). Various qualitative and quantitative changes that greatly vary according to the temperature experienced occurred in metabolite levels during prolonged starvation. Whereas levels of protein and ATP did not change significantly, triglycerides decreased markedly and glycogen changed little. Metabolite levels were differently affected by temperature, with triglycerides being less rapidly degraded at 20 than at 24 °C and almost completely depleted at 12 and 16 °C; in contrast to higher temperatures, glycerol is accumulated at 12 °C. Physiological adaptation to starvation and low temperatures are highly linked and energy allocation for starvation vs. temperature acclimation must be strictly regulated, both being essential for insect survival. Re‐synthesis rates during recovery are probably highly temperature‐dependent for all metabolites. The proteins retained during starvation and the preferential degradation of lipids allowed a rapid recovery. Above 16 °C, adult A. diaperinus regained locomotory activity rapidly and the triglyceride, glycerol and glycogen reserves were restored. This tropical species may be able to colonize other environments such as natural and/or artificial biotopes where conditions are close to those of its natural habitat.
Root porosity and oxygen movement in waterlogging‐tolerant Trifolium tomentosum and ‐intolerant Trifolium glomeratum
Authors: Gibberd M. R. , Colmer T. D. , Cocks P. S. 
Published: March 2003

ABSTRACT Trifolium tomentosum and T. glomeratum are small (< 0·5 mg) seeded pasture legumes which are considered to be waterlogging tolerant and intolerant, respectively. The root porosity of the two species was compared for plants raised for 10 d in aerated nutrient solution and then transferred to either aerated (0·25 mol O2 m–3) or ‘hypoxic’ (0·031–0·069 mol O2 m–3) solutions for a further 7 and 21 d. After 21 d, T. tomentosum developed a root porosity of 11·2% in ‘hypoxic’ solution, which was significantly higher than the 6·1% developed by T. glomeratum. When grown in aerated solution, T. tomentosum also had a larger constitutive porosity (6·7%) than T. glomeratum (3·9%). Cylindrical root‐sleeving O2 electrodes were used to measure the rates of radial O2 loss (ROL) from roots of the two species when in an O2‐free medium. In general, roots previously grown in ‘hypoxic’ solution had higher rates of ROL than roots grown in aerated solution. Moreover, the rates of ROL along the main root of T. tomentosum were ≈ 5‐fold faster than from equivalent locations along roots of T. glomeratum. Manipulations of the shoot O2 concentration resulted in rapid changes in ROL near the root tip of T. tomentosum plants raised in aerated or ‘hypoxic’ solutions, whereas for T. glomeratum ROL only increased for roots of plants raised in ‘hypoxic’ solution. Thus, the cortical air spaces in roots of both species raised in ‘hypoxic’ solution formed a continuous, low resistance pathway for O2 diffusion from the shoots to the roots. ROL from the lateral roots was also evaluated and it was 3‐fold faster from T. tomentosum than from T. glomeratum. Moreover, ROL from lateral roots of T. tomentosum was 10–20‐fold higher than from a position on the primary root axis the same distance from the root/shoot junction. Relatively, high rates of ROL were also recorded for young (40 mm in length) lateral roots of T. glomeratum which were previously grown in ‘hypoxic’ solution, but the ROL was low for the older lateral roots of this species. The substantial amounts of ROL from the lateral roots may limit O2 supply to the lower parts of the primary root axis, so that the laterals probably become the main functional root system in waterlogged soils.
Carbohydrate partitioning into starch in leaves of Ricinus communis L. grown under elevated CO2 is controlled by sucrose
Authors: Grimmer Claudia , Bachfischer Tanja , Komor Ewald 
Published: March 2003

ABSTRACT Ricinus communis plants were grown under normal (350 ppm) and elevated (700 ppm) CO2 atmosphere and the growth and carbohydrate status of leaf 2 (first leaf above the pair of primary leaves) was studied. Elevated carbon dioxide stimulated the growth of leaves 1·7‐fold. The glucose and fructose concentrations exhibited the same diurnal rhythm under both growth conditions. The sucrose concentrations stayed relatively constant and at 700 ppm were one‐third higher than at 350 ppm. The starch content increased steadily during the day and disappeared overnight at 350 ppm CO2, but remained partially in plants at 700 ppm CO2. Consequently at 700 ppm CO2, the leaves accumulated starch continuously over their life time. The rate of starch synthesis was correlated to the activity of ADP‐glucose pyrophosphorylase, which was related to the sucrose concentration in the leaf. It is concluded that sucrose controls the expression of ADP‐glucose pyrophosphorylase, leading to a shift of carbohydrate partitioning into starch when more sucrose is produced than consumed or exported, a situation which is especially pertinent at elevated CO2. These results show that the previously experimentally observed transscriptional regulation of starch synthesis by sucrose occurs in vivo in the daily life of a leaf.
Quantifying the response of photosynthesis to changes in leaf nitrogen content and leaf mass per area in plants grown under atmospheric CO2 enrichment
Authors: Peterson A. G. , Ball J. T. , Luo Y. , Field C. B. , Curtis P. S. , Griffin K. L. , Gunderson C. A. , Norby R. J. , Tissue D. T. , Forstreuter M. , Rey A. , Vogel C. S. , Participants Cmeal 
Published: March 2003

ABSTRACTPrevious modelling exercises and conceptual arguments have predicted that a reduction in biochemical capacity for photosynthesis (Aarea) at elevated CO2 may be compensated by an increase in mesophyll tissue growth if the total amount of photosynthetic machinery per unit leaf area is maintained (i.e. morphological upregulation). The model prediction was based on modelling photosynthesis as a function of leaf N per unit leaf area (Narea), where Narea = Nmass×LMA. Here, Nmass is percentage leaf N and is used to estimate biochemical capacity and LMA is leaf mass per unit leaf area and is an index of leaf morphology. To assess the relative importance of changes in biochemical capacity versus leaf morphology we need to control for multiple correlations that are known, or that are likely to exist between CO2 concentration, Narea, Nmass, LMA and Aarea. Although this is impractical experimentally, we can control for these correlations statistically using systems of linear multiple‐regression equations. We developed a linear model to partition the response of Aarea to elevated CO2 into components representing the independent and interactive effects of changes in indexes of biochemical capacity, leaf morphology and CO2 limitation of photosynthesis. The model was fitted to data from three pine and seven deciduous tree species grown in separate chamber‐based field experiments. Photosynthetic enhancement at elevated CO2 due to morphological upregulation was negligible for most species. The response of Aarea in these species was dominated by the reduction in CO2 limitation occurring at higher CO2 concentration. However, some species displayed a significant reduction in potential photosynthesis at elevated CO2 due to an increase in LMA that was independent of any changes in Narea. This morphologically based inhibition of Aarea combined additively with a reduction in biochemical capacity to significantly offset the direct enhancement of Aarea caused by reduced CO2 limitation in two species. This offset was 100% for Acer rubrum, resulting in no net effect of elevated CO2 on Aarea for this species, and 44% for Betula pendula. This analysis shows that interactions between biochemical and morphological responses to elevated CO2 can have important effects on photosynthesis.
Individuation in Sorghum bicolor: a self‐organized process involved in physiological adaptation to salinity
Authors: Amzallag G. N. 
Published: March 2003

ABSTRACTIn Sorghum bicolor, salt‐adaptation was defined as the capacity of plants to grow at 300 m
M NaCl (a lethal concentration) following a 3‐week pre‐treatment with 150 m
M NaCl (a sublethal concentration). Large populations induced for salt‐adaptation were analysed. Two modes of osmotic regulation (Na‐includer and Na‐excluder) were differentiated during induction of salt‐adaptation, in spite of the genetic and environmental homogeneity. This variability was not related to any incapacity of the Na‐includers to control accumulation of Na+ ions in the shoot, because most of the pre‐treated plants displayed a similar capacity of growth and control of Na+ uptake after transfer to 300 m
M NaCl. This unsuspected complexity of initially homogeneous populations points on the inadequacy of physiological studies focused on the ‘average individual’. Further analyses showed that variability was not directly related to micro‐environmental variations. It is concluded that a process of individuation is caused by a third source of variability, which is the expression of a self‐organizing process normally occurring during the transition phases in development. In constraining environments, this phenomenon of individuation includes adaptive modifications.
Trans‐root potential, xylem pressure, and root cortical membrane potential of ‘low‐salt’ maize plants as influenced by nitrate and ammonium
Authors: Wegner L. H. , Sattelmacher B. , Läuchli A. , Zimmermann U. 
Published: March 2003

ABSTRACTUpon addition of nitrate and ammonium, respectively, to the bath of intact ‘low salt’ maize plants, the cortical membrane potential and the trans‐root potential changed in a similar and synchronous way as revealed by applying conventional microelectrode techniques and the xylem pressure‐potential probe ( Wegner & Zimmermann 1998). Upon addition of nitrate, a hyperpolarization response was observed which was frequently preceded by a short depolarization phase. In contrast, addition of ammonium resulted in an overall depolarization response both of the cortical membrane potential and the trans‐root potential. The nitrate‐induced hyperpolarization response and the depolarization following the addition of ammonium were concentration‐dependent.The data suggest that a tight electrical coupling exists between the cellular and tissue level in the root of the intact plant and that the resistance of the cellular (symplastic) space is much less than the resistance of the apoplast.
The effects of UV‐B radiation on epidermal anatomy in loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.)
Authors: Laakso K. , Sullivan J. H. , Huttunen S. 
Published: March 2003

ABSTRACTThe effects of enhanced UV‐B radiation on the needle anatomy of loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.) were studied in the field under supplemental UV‐B radiation supplied by a modulated irradiation system. The supplemental UV‐B levels were designed to simulate either a 16 or 25% loss of stratospheric ozone over College Park, Maryland. Enhanced UV‐B radiation caused different responses in these two species. The needles of loblolly pine had larger amounts of tannin in the lumen of epidermal cells and more wall‐bound phenolics in the outer epidermal walls of UV‐B‐treated needles, whereas the most pronounced effect on Scots pine needles was increased cutinization. In both species, the outer epidermal cell walls thickened and the needle cross‐sectional and mesophyll areas decreased (statistically significantly only in Scots pine). This suggests that more carbon may have been allocated to the protection mechanisms at the expense of photosynthetic area. The difference in response between these species suggests that the response to UV‐B radiation is not mediated by a single mechanism and that no generalization with regard to the effects of UV‐B on conifers can be made.
Process‐based modelling of isoprene emission by oak leaves
Authors: Zimmer W. , Brüggemann N. , Emeis S. , Giersch C. , Lehning A. , Steinbrecher R. , Schnitzler J‐P. 
Published: March 2003

ABSTRACTThe emission rate of the volatile reactive compound isoprene, emitted predominantly by trees, must be known before the level of photo‐oxidants produced during summer smog can be predicted reliably. The emission is dependent on plant species and local conditions, and these dependencies must be quantified to be included in any empirical algorithm for the calculation of isoprene production. Experimental measurements of isoprene emission rates are expensive, however, and existing data are scarce and fragmentary. To overcome these difficulties, it is promising to develop a numerical model capable of precisely calculating the isoprene emission by trees for diverse ecosystems, even under changing environmental conditions. A basic process‐based biochemical isoprene emission model (BIM) has therefore been developed, which describes the enzymatic reactions in leaf chloroplasts leading to the formation of isoprene under varying environmental conditions (e.g. light intensity, temperature). Concentrations of the precursors of isoprene formation, 3‐phosphoglyceric acid and glyceraldehyde 3‐phosphate, are provided by a published light fleck photosynthesis model. Specific leaf and enzyme parameters were determined for the pedunculate oak (Quercus robur L.), so that the BIM is capable of calculating oak‐specific isoprene emission rates as influenced by the leaf temperature and light intensity. High correlation was observed between isoprene emission rates calculated by the BIM and the diurnal isoprene emission rates of leaves measured under controlled environmental conditions. The BIM was even capable of describing changes in isoprene emission caused by midday depression of net photosynthesis.
Stomatal responsiveness to leaf water status in common bean (Phaseolus vulgaris L.) is a function of time of day
Authors: Mencuccini M. , Mambelli S. , Comstock J. 
Published: March 2003

ABSTRACTStomatal response to leaf water status was experimentally manipulated by pressurizing the soil and roots of potted common bean plants enclosed in a custom‐built root pressure chamber. Gas exchange was monitored using a whole‐plant cuvette and plant water status using in situ leaf psychrometry. Bean plants re‐opened their stomata upon pressurization, but the extent of re‐opening was strongly dependent on the time of day when the soil was pressurized, with maximum re‐opening in the morning hours and limited re‐opening in the afternoon. Neither leaf nor xylem abscisic acid concentrations could explain the reduced response to pressurization in the afternoon. The significance of this phenomenon is discussed in the context of circadian rhythms and of other recent findings on the ‘apparent feed‐forward response’ of the stomata of some species to vapour pressure deficit.
Modelling of reserve carbohydrate dynamics, regrowth and nodulation in a N2‐fixing tree managed by periodic prunings
Authors: Berninger F. , Nikinmaa E. , Sievänen R. , Nygren P. 
Published: March 2003

ABSTRACTWe used a modified transport resistance approach to model legume tree growth, nodulation and dynamics of reserve carbohydrates after pruning. The model distributes growth between roots and shoots applying the transport resistance approach. Within shoots, growth is divided into leaves, branches and stems applying the pipe model theory. The model also accounts for the metabolic differences of principal N sources, nitrate, ammonium and atmospheric dinitrogen, in a mechanistic way. We compared the simulation results with measured biomass dynamics of Gliricidia sepium (Jacq.) Walp. (Papilionaceae: Robinieae) under humid and subhumid tropical conditions. Comparison showed that the biomass production predicted by the model is close to measured values. Total N2 fixation is also similar to measured values. Qualitatively the model increases the proportion of N2 fixation if roots acquire less mineral N. In the present study, the general form of the model is discussed and compared with similar models. The results encourage the use of this approach for studying biomass dynamics of legume trees under the scheme of periodic prunings. Also, it shows that process‐based models have potential in the simulation of trees disturbed by prunings, herbivory or similar factors.
Extracellular complexation of Cd in the Hartig net and cytosolic Zn sequestration in the fungal mantle of Picea abies – Hebeloma crustuliniforme ectomycorrhizas
Authors: Frey B. , Zierold K. , Brunner I. 
Published: March 2003

ABSTRACTCompartmentation of heavy metals on or within mycorrhizal fungi may serve as a protective function for the roots of forest trees growing in soils containing elevated concentrations of metals such as Cd and Zn. In this paper we present the first quantitative measurements by X‐ray microanalysis of heavy metals in high‐pressure frozen and cryosectioned ectomycorrhizal fungal hyphae. We used this technique to analyse the main sites of Cd and Zn in fungal cells of mantle and Hartig net hyphae and in cortical root cells of symbiotic Picea abies – Hebeloma crustuliniforme associations to gain new insights into the mechanisms of detoxification of these two metals in Norway spruce seedlings. The mycorrhizal seedlings were exposed in growth pouches to either 1 mM Cd or 2 mM Zn for 5 weeks. The microanalytical data revealed that two distinct Cd‐ and Zn‐binding mechanisms are involved in cellular compartmentation of Cd and Zn in the mycobiont. Whereas extracellular complexation of Cd occurred predominantly in the Hartig net hyphae, both extracellular complexation and cytosolic sequestration of Zn occurred in the fungal tissue. The vacuoles were presumed not to be a significant pool for Cd and Zn storage. Cadmium was almost exclusively localized in the cell walls of the Hartig net (up to 161 mmol kg−1 DW) compared with significantly lower concentrations in the cell walls of mantle hyphae (22 mmol kg−1 DW) and in the cell walls of cortical cells (15 mmol kg−1 DW). This suggests that the apoplast of the Hartig net is a primary accumulation site for Cd. Zinc accumulated mainly in the cell walls of the mantle hyphae (111 mmol kg−1 DW), the Hartig net hyphae (130 mmol kg−1 DW) and the cortical cells (152 mmol kg−1 DW). In addition, Zn occurred in high concentrations in the cytoplasm of the fungal mantle hyphae (up to 164 mmol kg−1 DW) suggesting that both the cell walls and the cytoplasm of fungal tissue are the main accumulation sites for Zn in P. abies resulting in decreased Zn transfer from the fungus to the root.
Modelling assimilation and intercellular CO2 from measured conductance: a synthesis of approaches
Authors: Katul G. G. , Ellsworth D. S. , Lai C.‐T. 
Published: March 2003

ABSTRACTA spectrum of models that estimate assimilation rate A from intercellular carbon dioxide concentration (Ci) and measured stomatal conductance to CO2 (gc) were investigated using leaf‐level gas exchange measurements. The gas exchange measurements were performed in a uniform loblolly pine stand (Pinus taeda L.) using the Free Air CO2 Enrichment (FACE) facility under ambient and elevated atmospheric CO2 for 3 years. These measurements were also used to test a newly proposed framework that combines basic properties of the A–Ci curve with a Fickian diffusion transport model to predict the relationship between Ci/Ca and gc, where Ca is atmospheric carbon dioxide concentration. The widely used Ball–Berry model and five other models as well as the biochemical model proposed by Farquhar et al. (1980) were also reformulated to express variations in Ci/Ca as a function of their corresponding driving mechanisms. To assess the predictive capabilities of these approaches, their respective parameters were estimated from independent measurements of long‐term stable carbon isotope determinations (δ13C), meteorological variables, and ensemble A–Ci curves. All eight approaches reproduced the measured A reasonably well, in an ensemble sense, from measured water vapour conductance and modeled Ci/Ca. However, the scatter in the instantaneous A estimates was sufficiently large for both ambient and elevated Ca to suggest that other transient processes were not explicitly resolved by all eight parameterizations. An important finding from our analysis is that added physiological complexity in modeling Ci/Ca (when gc is known) need not always translate to increased accuracy in predicting A. Finally, the broader utility of these approaches to estimate assimilation and net ecosystem exchange is discussed in relation to elevated atmospheric CO2.
Diurnal changes in the photochemical efficiency of the symbiotic dinoflagellates (Dinophyceae) of corals: photoprotection, photoinactivation and the relationship to coral bleaching
Authors: Jones R. J. , Hoegh‐Guldberg O. 
Published: March 2003

ABSTRACTThe photochemical efficiency of symbiotic dinoflagellates within the tissues of two reef‐building corals in response to normal and excess irradiance at water temperatures < 30 °C were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence techniques. Dark‐adapted Fv/Fm showed clear diurnal changes, decreasing to a low at solar noon and increasing in the afternoon. However, Fv/Fm also drifted downwards at night or in prolonged darkness, and increased rapidly during the early morning twilight. This parameter also increased when the oxygen concentration of the water holding the corals was increased. Such changes have not been described previously, and most probably reflect state transitions associated with PQ pool reduction via chlororespiration. These unusual characteristics may be a feature of an endosymbiotic environment, reflective of the well‐documented night‐time tissue hypoxia that occurs in corals. Fv/Fm decreased to 0·25 in response to full sunlight in shade‐acclimated (shade) colonies of Stylophora pistillata, which is considerably lower than in light‐acclimated (sun) colonies. In sun colonies, the reversible decrease in Fv/Fm was caused by a lowering of Fm and Fo suggesting photoprotection and no lasting damage. The decrease in Fv/Fm, however, was caused by a decrease in Fm and an increase in Fo in shade colonies suggesting photoinactivation and long‐term cumulative photoinhibition. Shade colonies rapidly lost their symbiotic algae (bleached) during exposure to full sunlight. This study is consistent with the hypothesis that excess light leads to chronic damage of symbiotic dinoflagellates and their eventual removal from reef‐building corals. It is significant that this can occur with high light conditions alone.