bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ecophysiology of salt excretion in the xero‐halophyte Reaumuria hirtella
Authors: RAMADAN T. 
Published: March 2003

Different aspects of salt excretion from leaves of the xero‐halophyte Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert. The diurnal excretion pattern, which gradually decreased toward midday, showed a negative correlation with the daily transpiration pattern. The relative excretion, which is the ratio between the absolute excretion of Na+ and the change in its internal content, was maximal at sites with low salinity, and decreased when the concentration of NaCl in the root environment increased. By contrast, the absolute excretion increased from 253 to 323 mmol Na+ g−1 f. wt per 12 h with increase in the total soil salinity from 0·24 to 1·23%, respectively. Water stress conditions, caused either by increasing soil salinity or by dryness of the atmosphere, greatly influenced the efficiency of excretion process.Six ions: Na+, K+, Ca2+, Mg2+, Cl− and SO42− constituted 96·8% of the d. wt of the field‐collected secreted salts. Na+ and Cl−, which were the predominating ions in the soil solution of the root environment, were also the predominantly secreted, constituting c. 89% of salts secreted. The proportion of Na+ which was prevented from entry into the roots increased with increasing Na+ concentration in the soil solution. More than 67% of the absorbed NaCl was secreted by leaves during the day. However, the accumulated salts contributed to the osmotic potential (ψs) and improved the plant water status. The osmotic potential of the plant sap at the end of the day or during periods of low excretion rates was shown to be decreased −7·3 to −13·7 bar from that in the morning. The fraction of osmotic potential decreased during the day (Δψs) was positively correlated with the soil salinity. These retained salts are expelled from the leaves by increased efficiency of extraction during the night and early morning, so that the plant begins the day with low internal salt content, and the leaf reservoirs become suitable for a new supply. The rejection mechanism at the plant roots and the secretion mechanism at shoots allow the plant to maintain its internal salt content at an approximately constant level despite the great variation in soil salinity.
Corner's rules revisited: ontogenetic and interspecific patterns in leaf–stem allometry
Authors: BROUAT C. , GIBERNAU M. , AMSELLEM L. , McKEY D. 
Published: March 2003

We studied interspecific and ontogenetic relationships between the size of a leaf and the primary diameter of the internode bearing it. Although these two variables are known to be strongly correlated across species, the form of this relationship has not been studied. In a re‐analysis of published data on interspecific comparisons of 69 temperate tree species, we showed the existence of a strong relationship between twig cross‐sectional area (before secondary growth) and surface area of leaves borne by it, within each of three morphological groups, deciduous angiosperms, evergreen angiosperms, and gymnosperms. Within each of these groups, this relationship is isometric: across species, primary cross‐sectional area of the stem increases proportionally with leaf surface area. When we consider the relationship between the cross‐sectional area of a twig and the surface area of one leaf borne by it, the y‐intercepts for this relation are different for the three groups. However, when total leaf surface area per first‐year shoot is considered, no differences remained between gymnosperms and evergreen angiosperms, but deciduous angiosperms continued to be distinct. This difference between deciduous and evergreen groups could be due to differences in leaf volume (evergreen species have thicker leaves than deciduous) or in traits related to a trade‐off between life span of leaves and their physiological behaviour.We present results of the first quantitative study of the relationship between leaf size and primary diameter of the stem during ontogeny. Both these parameters increase during development of the plant from seedling to adult. For the four tree species examined, the relationship between primary cross‐sectional area of the stem and leaf surface area is also isometric.These results bear on a functional interpretation of the relationship between leaf and stem dimensions, suggesting that vascular supply is directly proportional to the requirements of leaves supported by the stem.
Editorial
Authors: AYRES P. G. 
Published: March 2003

Membership of our Board of Advisors to the Editors has remained almost static since the Board was founded in 1995, but significant turnover begins this summer. Accordingly, I offer a warm welcome to new members of the Board and thank those who have agreed to extend their membership. I thank especially those leaving the Board for their invaluable support during the first three years of its life. The workplaces and interests of Board members reflect both the international base of the New Phytologist and the wide range of subjects that it regularly publishes. SCI ratings support the belief that the New Phytologist is the world's leading broad‐spectrum botanical journal. Given that breadth of subject matter, it is all the more remarkable that the journal has a high Impact Factor, 2·2.The good health of the New Phytologist, and the charitable Trust that owns it, is further indicated by recent expansion of our activities. For each of the last three years, symposia, to which numerous distinguished international speakers contributed, have been organized in the UK. Proceedings have been published in the journal but they have also been made available for purchase as attractively bound separates, the most recent being Major Biological Issues Resulting from Anthropogenic Disturbance of the Nitrogen Cycle (eds. T. A. Mansfield, L. Sheppard and K. W. T. Goulding). This year, the symposium will be held in Montpellier, France, on the subject The Gap between Isolated Plants and Growing Canopies, while in 1999 it will move to the USA. In response to numerous requests, particularly from university teachers, we are now collecting recent Tansley Reviews around themes and publishing these too as separates. The first collection, Leaf Development and Function, is now available.Like many forward looking journals, the New Phytologist is fully online (at http://www.journals.cup.org): unlike that of many other journals, our online version was launched free of charge to subscribers. This is just one of the many ways in which this independent journal can help botany and botanists. Indeed, monies from the Trust support a range of activities that promote botany (see volume 134, facing p. 197 for details). The journal will be 100 years old in 2002. The Trustees would be especially pleased to receive requests for support for activities that would mark the centenary.As I noted in my previous Editorial, three years ago, Independent and International remain our key words.
Low‐light carbon balance and shade tolerance in the seedlings of woody plants: do winter deciduous and broad‐leaved evergreen species differ?
Authors: WALTERS MICHAEL B. , REICH PETER B. 
Published: March 2003

An appendix is available for this article which was not included in the print edition of the Journal. The appendix may be found at the rear of the full text, PDF version of the article. A popular conceptual model asserts that shade tolerance is characterized by morphological and physiological traits that enhance the net rate of carbon capture in low light. We tested this model by quantitatively reviewing growth, leaf lifespan, CO2 exchange and morphological data from 76 studies on woody seedlings grown under conditions of low light. Data were placed into three tolerance categories (intolerant, intermediate, tolerant), two light categories (less than 4% and 4–12%) and two leaf phenology categories (broad‐leaved evergreen and winter deciduous). For both evergreen and deciduous groups, intolerant species had traits conferring greater growth potential than tolerant species in both light categories. These traits included greater leaf mass ratio, leaf area ratio, specific leaf area and mass‐based photosynthetic rates above light compensation. However, in 0–4% light, growth rates were similar for intolerant and tolerant species, because low light together with higher respiration rates for intolerant species limited the expression of their growth potential differences. Deciduous and evergreen intolerant species were similar in many respects. However, both intermediate and tolerant deciduous species had markedly lower leaf mass ratios and higher root mass ratios than intermediate and tolerant evergreen species. In addition, deciduous species and intolerant evergreens must cope with as much as sixfold higher leaf turnover rates than tolerant evergreen species. Thus, rather than maximizing growth rates in low light, tolerant evergreen species minimize biomass loss through long leaf lifespans and low respiration rates. Tolerant deciduous species also minimize biomass losses by minimizing whole‐plant respiration rates but they accomplish low biomass turnover though low leaf mass ratio and not low leaf turnover rates. Furthermore, unlike most tropical evergreens, tolerant deciduous species can gain large fractions of their total growing season carbon during short periods when the overstory is leafless and then allocate this carbon to storage (as reflected by high root mass ratios) rather than new leaves. In conclusion, we found no support for the low‐light‐enhanced carbon capture model of shade tolerance as viewed strictly from the perspective of physiological growth capacity. This can be explained by the disadvantages to net growth and survival of maintaining a high growth potential at low light, because high growth potential results in greater rates of whole‐plant respiration, tissue turnover, herbivory and mechanical damage and in decreased storage. Thus, shade tolerance can be characterized by traits that maximize survival and net growth, where net growth includes losses to all agents.
Scaling ozone effects from seedlings to forest trees
Authors: Samuelson Lisa , Kelly J. Michael 
Published: March 2003

SummaryBiospheric ozone has become a widely distributed air pollutant, and a growing body of research indicates that ozone impacts forest health and productivity. Ozone effects are mediated by the ozone concentration present in the external environment and the movement of ozone into the leaf via the stoma. The cumulative dose received by the plant is, in the simplest terms, a function of ambient ozone concentration and stomatal conductance to water vapor. This relationship is important in understanding ozone flux into the leaf and subsequent ozone response in plants. Here, current progress in understanding ozone uptake in juvenile and mature trees is examined. Through an analysis of two long‐term case studies, the significant uncertainty in assessing ozone effects on forests is pinpointed to be the scaling of ozone sensitivity from controlled seedling studies to large forest trees. A rigorous statistical and monitoring approach, which includes ozone uptake as a cause variable, may provide the missing information on processes that are known to be important to risk assessment of ozone impacts on forest trees.ContentsSummary21I.Introduction221.Background222.Characterization of ozone exposure223.The need for scaling23II.Scaling from seedling to tree, evidence from aQuercus rubracase study241.Study background242.Facilities and measurements243.Ozone exposure dynamics244.Above‐ground processes255.Below‐ground processes266.A process modelling exercise277.Conclusions28III.Scaling from chamber to forest, evidence from a field case study291.Study background292.Field sites and measurements303.Ozone exposure dynamics304.Stomatal conductance and ozone uptake in forest trees305.Conclusions32IV.Evidence from a scaling exercise33V.Concluding remarks36Acknowledgements37References37
Trehalose induces resistance to powdery mildew in wheat
Authors: Reignault PH. , Cogan A. , Muchembled J. , Lounes‐Hadj Sahraoui A. , Durand R. , Sancholle M. 
Published: March 2003

Summary• Reduction in the degree of powdery mildew infection of wheat leaves is observed after treatments with trehalose, a nonreducing disaccharide commonly found in a wide variety of organisms, including fungi.• Wheat (Triticum aestivum) cv. Sideral plants grown in phytotrons were inoculated withBlumeria graminisf.sp.tritici. In addition to degree of infection, the effect of trehalose solution was further investigated using light and fluorescence microscopy and enzyme assays.• Infection in wheat leaves was reduced by 50 and 95% with trehalose solution (15 g l−1) following a single spraying and three sprayings, respectively; in a detached leaf assay, trehalose was effective at concentrations as low as 0.01 g l−1. Trehalose did not inhibit conidial germination and differentiation of appressoria (in vitroor on the leaf epidermis), but enhanced papilla deposition in epidermal cells. Trehalose also enhanced phenylalanine ammonia‐lyase (PAL) and peroxidase (PO) activities; both markers of plant defence responses. However, the level of three cinnamyl alcohol dehydrogenase (CAD) activities (conyferyl,p‐coumaryl and sinapyl alcohol dehydrogenase) was unchanged.• Trehalose treatment of wheat confers resistance toB. graminisinfection by activating plant defence responses (e.g. papilla deposition, PAL and PO activities).
Linking wood density with tree growth and environment: a theoretical analysis based on the motion of water
Authors: Roderick Michael L. , Berry Sandra L. 
Published: March 2003

Summary• An hydraulic model of a tree stem is presented to help understand how the carbon storage in ecosystems varies with changing environmental conditions.• The model is based on the assumption that a tree stem is a collection of parallel pipes and was used to (qualitatively) predict how the mass concentration of dry matter ([D]) would vary with water temperature (via changes in viscosity), nitrogen supply and atmospheric CO2.• There was qualitative agreement between model predictions and observed gross trends. The model predicted that the flow rate would be relatively insensitive to variations in [D] in angiosperm stems; this was consistent with observations. It is concluded that other factors need to be considered to explain variations in [D] in angiosperm wood. The flow rate of water through gynmosperm stems was predicted to be very sensitive to variations in [D] and the model explained why [D]; decreases with decreases in water temperature, decreases with increases in nitrogen supply and increases with elevated CO2.• The model captured some of the important underlying relations linking water transport with wood density and environment and qualitative testing of the model is recommended.
Short photoperiods induce fructan accumulation and tuberous root development in Dahlia seedlings
Authors: Legnani Garry , Miller William B. 
Published: March 2003

Summary

• The effect is reported here of photoperiod on fructan accumulation in the tuberous roots of Dahlia sp. cv. Sunny Rose seedlings.

• Growth parameters were measured of shoots and roots on glasshouse‐grown dahlia seedlings subjected to either short day (SD) or long day (LD; 4 h night photoperiod interruption) light regimes. The carbohydrate concentrations of tuberous roots was analysed by high performance anion exchange chromatography.

• Total plant dry weight was unaffected by photoperiod. The LD treatment inhibited tuberous root development but increased shoot dry weight. Tuberous root tissue of SD seedlings showed a 156% increase in total fructan (inulin) concentration compared with LD tuberous root tissue, which had higher reducing sugar concentrations than SD tuberous roots. A wide range of oligomers increased during the SD treatment.

• Sucrose appears to be the regulating factor in fructan metabolism in dahlia. Photoperiod is a valuable tool for studying fuctan metabolism in vivo, as it provides a nondestructive means of regulating sucrose partitioning.
Free‐air CO2 enrichment (FACE) of a poplar plantation: the POPFACE fumigation system
Authors: Miglietta Franco , Peressotti Alessandro , Vaccari Francesco Primo , Zaldei Alessandro , DeAngelis Paolo , Scarascia‐Mugnozza Giuseppe 
Published: March 2003

Summary

A new design of free‐air CO2 enrichment (FACE) is presented that has been used to expose a poplar plantation to elevated atmospheric CO2 concentrations in other‐wise unaltered conditions, in the open.
This system releases pure CO2 at high velocity, through a large number of small gas jets, causing rapid mixing between CO2 and air. The theoretical and practical aspects of this design are described, with emphasis on the fluid mechanics of air–CO2 mixing in sonic jets. Field performance data, including spectral analysis of short‐term fluctuations in CO2 concentrations as well as temporal and spatial CO2 control, are reported for the European project POPFACE facility.
Temporal and spatial performances of the operational POPFACE systems were adequate with average long‐term CO2 mole fractions on target. Averages over 1 min measured in the centre of the rings were within ±20% and ±10% of the target concentration for > 91% and > 75% of the time, respectively.
The data presented provide convincing evidence that a pure‐CO2 FACE system can achieve reliable control, in terms of the quality of the CO2 control, with significant simplification of construction and reduced capital cost.
Stomatal density and needle anatomy of Scots pine (Pinus sylvestris) are affected by elevated CO2
Authors: Lin Jinxing , Jach M. E. , Ceulemans R. 
Published: March 2003

Summary

Morphological and anatomical characteristics of needles from different whorl levels were examined on Scots pines (Pinus sylvestris), grown for 4 yr under either ambient or elevated (ambient + 400 µmol mol−1) CO2 concentrations in open‐top chambers.
Needle characteristics were studied using light microscopy, scanning electron microscopy and laser scanning confocal microscopy.
Under the elevated CO2 treatment stomatal density was reduced on both adaxial and abaxial needle surfaces although the number of rows of stomata did not change significantly. Needle cross‐sectional area increased by 10%; this was largely the result of an increase in needle thickness and, to a lesser extent, needle width. The increase in needle thickness was due to a large increase in mesophyll tissue. The relative area (i.e. proportion of the total area) of epidermis plus hypodermis, of resin canal, of xylem and of central cylinder decreased, whereas the relative area of needle phloem significantly increased.
The results suggest that a prolonged exposure to elevated CO2 has an effect on needle structure, anatomical and stomatal characteristics of Scots pine needles.
The CDPK superfamily of protein kinases
Authors: Harmon Alice C. , Gribskov Michael , Gubrium Erika , Harper Jeffrey F. 
Published: March 2003

SummaryThe CDPK superfamily consists of six types of protein kinases, which differ in the regulatory domains they contain. CDPKs (calcium‐dependent protein kinases or calmodulin‐like domain protein kinases) are activated by the binding of calcium to their calmodulin‐like regulatory domains. The carboxyl terminal domains of CRKs (CDPK‐related kinases) have sequence similarity to the regulatory domains of CDPKs, but do not bind calcium. PPCKs (PEP carboxylase kinases) contain only a catalytic domain. PRKs (PPCK‐related kinases) have a carboxyl‐terminal domain that has no similarity to that of any other member of the superfamily. CCaMKs (calcium and calmodulin regulated kinases) bind both calcium ions and the calcium/calmodulin complex, whereas CaMKs (calmodulin‐dependent protein kinases) bind the calcium/calmodulin complex, but not calcium. Phylogenetic trees constructed from amino acid sequences of catalytic or regulatory domains show that CDPKs and CRKs are closely related and might share a common ancestor. Plant CCaMKs and CaMK form a group more closely related to protozoan, than to plant, CDPKs. Intron analysis of the 42 CDPK, CRK, PPCK, and PRK genes from Arabidopsis supports the structure of the gene trees, the possibility that PPCKs/PRKs belong to the CDPK superfamily, and suggests that several introns have been added during evolution of the family.
Arsenic uptake and metabolism in arsenic resistant and nonresistant plant species
Authors: Meharg Andrew A. , Hartley‐Whitaker Jeanette 
Published: March 2003

SummaryElevation of arsenic levels in soils causes considerable concern with respect to plant uptake and subsequent entry into wildlife and human food chains. Arsenic speciation in the environment is complex, existing in both inorganic and organic forms, with interconversion between species regulated by biotic and abiotic processes. To understand and manage the risks posed by soil arsenic it is essential to know how arsenic is taken up by the roots and metabolized within plants. Some plant species exhibit phenotypic variation in response to arsenic species, which helps us to understand the toxicity of arsenic and the way in which plants have evolved arsenic resistances. This knowledge, for example, could be used produce plant cultivars that are more arsenic resistant or that have reduced arsenic uptake. This review synthesizes current knowledge on arsenic uptake, metabolism and toxicity for arsenic resistant and nonresistant plants, including the recently discovered phenomenon of arsenic hyperaccumulation in certain fern species. The reasons why plants accumulate and metabolize arsenic are considered in an evolutionary context.

Contents

Summary
29

I.
Introduction
30

II.
Toxicity of arsenic species to plants
33

III.
Arsenic resistance in plants
35

1. Arsenic resistance mechanisms
35

2. Arsenate resistence polymorphism
36

3. Mycorrhizal fungi and arsenic resistance
36

IV.
Complexation of arsenic
37

V.
Arsenic metabolism
37

VI.
Arsenic hyperaccumulation
39

VII.
Evolutionary context
40

VIII.
Conclusions
40

References
40
Is differential phytochelatin production related to decreased arsenate influx in arsenate tolerant Holcus lanatus?
Authors: Hartley‐Whitaker J. , Woods C. , Meharg A. A. 
Published: March 2003

Summary

Phytochelatins (PCs) are required for arsenic (As) detoxification in nontolerant plants. In addition, a role for PCs in arsenate tolerance has recently been proven, with tolerant plants able to accumulate significantly higher concentrations of As–PC complexes at equivalent levels of stress than nontolerant plants.
The relationship between arsenate influx and PC production in tolerant and nontolerant Holcus lanatus plants was determined in this study, along with an investigation of the effect of inhibition of PC synthesis by buthionine sulfoximine (BSO) on arsenate tolerance.
A strong correlation between PC production and arsenate influx was demonstrated in arsenate‐tolerant plants. In addition, inhibition of PC synthesis by BSO in tolerant plants increased arsenate sensitivity to that of the nontolerant clone. This dramatic reduction in tolerance proves that PC production is an essential component of the arsenate tolerance mechanism in H. lanatus .
This study proposes that while there is a single major gene for arsenate tolerance, hypostatic modifiers are also in operation, affecting the expression of the tolerance character.