bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus) and domestic cat (Felis silvestris f. catus)
Authors: Weissengruber G. E. , Forstenpointner G. , Peters G. , Kübber‐Heiss A. , Fitch W. T.
Published: March 2003

Structures of the hyoid apparatus, the pharynx and their topographical positions in the lion, tiger, jaguar, cheetah and domestic cat were described in order to determine morphological differences between species or subfamilies of the Felidae. In the lion, tiger and jaguar (species of the subfamily Pantherinae) the Epihyoideum is an elastic ligament lying between the lateral pharyngeal muscles and the Musculus (M.) thyroglossus rather than a bony element like in the cheetah or the domestic cat. The M. thyroglossus was only present in the species of the Pantherinae studied. In the lion and the jaguar the Thyrohyoideum and the thyroid cartilage are connected by an elastic ligament, whereas in the tiger there is a synovial articulation. In adult individuals of the lion, tiger and jaguar the ventral end of the tympanohyal cartilage is rotated and therefore the ventral end of the attached Stylohyoideum lies caudal to the Tympanohyoideum and the cranial base. In newborn jaguars the Apparatus hyoideus shows a similar topographical position as in adult cheetahs or domestic cats. In adult Pantherinae, the Basihyoideum and the attached larynx occupy a descended position: they are situated near the cranial thoracic aperture, the pharyngeal wall and the soft palate are caudally elongated accordingly. In the Pantherinae examined the caudal end of the soft palate lies dorsal to the glottis. Differences in these morphological features between the subfamilies of the Felidae have an influence on specific structural characters of their vocalizations.
Central control of upper airway resistance regulating respiratory airflow in mammals
Authors: Paton Julian F. R. , Dutschmann Mathias
Published: March 2003

This article reviews recent studies on the importance of glycine receptors for both the spontaneous and the reflex respiratory modulation of the laryngeal abductors and adductors. Our findings show that strychnine blockade of glycine receptors within the brainstem changes the eupneic three‐phase respiratory pattern into two phases. This has major implications for glottal control: (i) the inspiratory glottic abduction and early expiratory adduction were both compromised – a finding mimicked by 5% hypoxia; (ii) closure of the glottis during defensive upper airway reflexes became intermittent and the reflex apnoea reversed to sustained inspiratory discharge. Based on these data, we predict that periods of prolonged hypoxia, such as those that occur during sleep apnoeas, will constrain inspiratory glottic abduction thereby impeding inhalation.
Use of sugars by intraradical hyphae of arbuscular mycorrhizal fungi revealed by radiorespirometry
Authors: SOLAIMANAND MD. ZAKARIA , SAITO MASANORI
Published: March 2003

summary

Evolution of 14CO2 from onion roots and the intraradical hyphae of Gigaspora margarita Becker & Hall was examined by radiorespirometry after addition of 14C‐labelled glucose or sucrose to mycorrhizal or non‐mycorrhizal roots. In mycorrhizas, the respiration rate from glucose was about twice that from sucrose. The respiration rate from glucose in the mycorrhizas was much higher than that in the non‐mycorrhizal roots, but no differences between mycorrhizal and non‐mycorrhizal roots were found in the respiration from sucrose. Intraradical hyphae were isolated from mycorrhizas by enzyme digestion and homogenization followed by Percoll® gradient centrifugation. The 14C‐labelled glucose, fructose or sucrose was added to the isolated hyphae and the subsequent evolution of 14CO2 was measured. The hyphae mainly used glucose as a substrate for respiration. Although sucrose or fructose was utilized to some degree, the respiration rate from glucose was much higher than that from sucrose and fructose. This is the first direct evidence of use of glucose by the intraradical hyphae of arbuscular mycorrhizal fungi in the symbiotic state.
Growth, phosphorus uptake, and water relations of safflower and wheat infected with an arbuscular mycorrhizal fungus
Authors: BRYLA D. R. , DUNIWAY J. M.
Published: March 2003

Safflower (Carthamus tinctorius L. cv. S555) and spring wheat (Triticum aestivum L. cv. Anza) were grown with or without the arbuscular mycorrhizal fungus Glomus etunicatum Becker & Gerd., under environmentally controlled conditions. Soil phosphate concentrations were adjusted before planting to produce mycorrhizal (M) and non‐mycorrhizal (NM) plants that had similar leaf areas and root length densities at the same stage of development before initiating drought stress treatments. Drought did not affect the amount of mycorrhizal infection in safflower or wheat. Interactions between water stress treatments and mycorrhizal infection on plant growth and phosphorus uptake were limited and only occurred in wheat. NM wheat plants had 28% greater shoot d. wt, slightly greater root length densities, and 39% greater P acquisition than M plants when grown under well watered conditions, but under droughted conditions plant size and tissue P contents of M and NM wheat plants were similar. Mycorrhizas did not affect stomatal behaviour during drought stress in either safflower or wheat, i.e., transpiration and stomatal conductance declined independently of infection as soil water was depleted and leaf water potentials declined. Therefore, mycorrhizal infection did not alter the intrinsic hydraulic properties of the plant/soil system. Whilst wheat maintained turgor of recently expanded leaves during severe drought and safflower did not, mycorrhizal infection had no effect on leaf turgor during drought in either plant species.
Responses of ground vegetation to prolonged simulated acid rain in sub‐arctic pine—birch forest
Authors: SHEVTSOVA A. , NEUVONEN S.
Published: March 2003

The effects of prolonged simulated acid rain on percentage cover of ground vegetation, and on growth and reproduction of two dominating dwarf shrubs (Emapetrum nigrumandVaccinium vaitisidaea)were examined in a field experiment in the Finnish Subarctic, in an area with low ambient levels of sulphur and nitrogen deposition. Acid rain treatments included moderate (pH 3.8) and high (pH 2.9) concentrations of either H2SO4, or HNO3, or a mixture of them, and were compared with irrigated (pH 6) and dry control plots.

Long‐term application of acid rain caused significant alteration in the cover and composition of ground vegetation. Effects of acid ram depended on the accompanying anion and on pH. Sub‐plots under different canopy tree species differed in responses indicating that spatial heterogeneity is important in predicting the effect of acidifying pollution on this plant community.

In the bottom layer, acid rain caused significant reduction in cover of the cyanobacterial lichensNephroma arcticumandPeltigeraspp. Decrease in cover of fruticose lichens, mainly composed ofCladinaspp., more likely resulted from additional watering.

In the field layer, acid rain containing moderate concentrations of NO−3caused an increase in cover of graminoid species. There were only slight alterations in growth and cover of the two dominant evergreen dwarf shrubs,EnigrumandV. vitis‐idaea, indicating that these species are tolerant to acid rain of as low as pH 3. Even some positive responses of dwarf shrubs were observed, depending on canopy tree. Application of acid rain of pH 3 to plots under pine trees caused an increase in cover of I,vitis‐idaeaand, when the nitric acid only was applied, a short‐term increase in the number of new shoots ofE. nigrum.

In contrast to vegetative growth, reproduction of the dwarf shrubs was more strongly affected by acid rain, but this also depended on local conditions and anion composition of acid rain. On ‘pine’ plots, rain of pH 3 reduced the number of berries and flower buds on terminal current shoot ofE. nigrum, however, this was partially compensated by an increase in berry production at the ramet level. Simulated acid rain had mainly negative effects on berry production byV. vitis‐idaea.
The use of longitudinal data analysis to study the multi‐seasonal growth responses of Norway and Sitka spruce to summer exposure to ozone: implications for the determination of critical levels
Authors: LUCAS PETER W. , DIGGLE PETER J.
Published: March 2003

summary

A common feature of many pollutant exposure studies is that data from these experiments often consist of either plant biomass or yield, and the response to the pollutant is usually based on a simple comparison of means determined at the end of each growing season. This type of data is now being used to quantify critical levels for different types of vegetation. Such an approach is, however, inappropriate for the relatively short‐term exposure studies with trees since, due to their longevity, it is nor possible to determine a final yield. Instead these studies should be regarded as a type of intervention experiment in which only a small part of the life cycle of the tree is investigated. Moreover, critical levels as they are now defined focus on the cumulative exposure to ozone concentrations over time. Hence, any analysis of the effects of ozone on the growth of trees should similarly focus on the behaviour of growth functions over time and not on a comparison of biomass at the end of a growing season or experiment.

Here we report on the statistical analysis of a longitudinal study, where the term ‘longitudinal’ refers to the analysis of repeated measurements over time, and which was used to investigate relative differences in the growth of Sitka spruce and Norway spruce seedlings during three summers'exposure to ozone over three (Norway) or four (Sitka) growing seasons. Measurements of total seedling height and stem diameter were made at frequent intervals over the period of the experiment and the above‐ground growth of individual trees (as log d2h) analysed for each growing season using a statistical model of the form:m(t) = a + b(t ‐ t0), No statistically significant differences in the growth of Norway spruce were observed after three summers of ozone exposure. The growth of Sitka spruce was, however, reduced by ozone during the third growing season and in the following year, even in the absence of the pollutant.

For the Sitka spruce, the fitted model was used to calculate the time at which a 10% reduction in growth had occurred in the ozone‐exposed trees. In combination with ozone AOT40 indices for the relevant growing seasons, this was then used to determine a critical level of 21.3 ppm‐h for this species. Since the growth of the Norway spruce was unaffected by exposure to ozone it was not possible to calculate a critical level other than to surmise that it is in excess of 30 ppm‐h.
On the response of pigments and antioxidants of Pinus halepensis seedlings to Mediterranean climatic factors and long‐term ozone exposure
Authors: ELVIRA SUSANA , ALONSO ROCÍO , CASTILLO FEDERICO J. , GIMENO BENJAMÍN S.
Published: March 2003

An experiment was carried out in open‐top chambers located in eastern Spain. One‐yr‐old Pinus halepensis Mill. seedlings were exposed during three consecutive summers to the following ozone (O3) treatments: charcoal‐filtered air (CFA), non‐filtered air (NFA) or non‐filtered air plus 40 nl l−1 O3, 9 h d−1, 5 d wk−1 (NFA+40). Seasonal variations in Aleppo pine performance were observed since reductions in chlorophyll and cellular peroxidase levels associated with increases in superoxide dismutase activity, were recorded during the summer. Similarly, a reduction in epoxidation state was found at midday during the summer, derived from an activation of the xanthophyll cycle associated to an increment in radiation and temperature levels.

The first O3‐induced effects were recorded in previous‐year needles (1991) during the first summer exposure as an increase in extracellular and total peroxidase activities and in zeaxanthin levels in the NFA+40 treatment along with a trend to a higher SOD activity in this treatment. A carry‐over effect was detected since a lower winter recovery of chlorophyll levels was found in the NFA+40 seedlings along with a reduction of xanthophyll levels. A reduction in chlorophyll levels was observed in the previous‐year needles (1992) from the NFA+40 treatment at the end of the second fumigation period. Realistic ozone exposures induced alterations in plant antioxidative systems and plant pigments as shown in this paper. These observations together with the reductions in stomatal conductance and net photosynthesis recorded in the same experiment, indicate that Aleppo pine is a species sensitive to ozone.
Cluster root development in Grevillea robusta (Proteaceae). I. Xylem, pericycle, cortex, and epidermis development in a determinate root
Authors: SKENE KEITH R. , RAVEN JOHN A. , SPRENT JANET I.
Published: March 2003

The cluster roots of Grevillea robusta A. Cunn. ex R. Br. are composed of determinate rootlets that stop growing, but remain physiologically active for several months. Their apical organization, both before and after maturation, was studied by light and transmission electron microscopy. Each cell layer forms a dome, with an initial cell at its end. Xylem elements form a complicated triarch array at the base of the rootlet, passing along the rootlet as two files, and then joining at the tip to form a single file, surrounded by six pericycle cells. At the base of the rootlet, shorter xylem cells and thick‐walled support cells are visible. A root cap, present in rootlets grown in vermiculite, was eventually displaced by root hair growth. Rootlets grown in Hoagland's solution lacked root caps and were significantly shorter than those grown in vermiculite. Cell fate was analysed in terms of cell position and is discussed in terms of pattern and development.
Cluster root development in Grevillea robusta (Proteaceae). II. The development of the endodermis in a determinate root and in an indeterminate, lateral root
Authors: SKENE KEITH R. , SUTHERLAND JOAN M. , RAVEN JOHN A. , SPRENT JANET I.
Published: March 2003

Light, fluorescence and electron microscopy were employed to follow the development of the endodermis in cluster roots and lateral roots of Grevillea robusta A. Cunn. ex R. Br. Endodermal cells had three different origins: rootlet endodermis arose from the rootlet meristem; endodermis covering the primordium shortly after initiation came from division of parental endodermis; cells at the junction between parent and rootlet endodermis developed from re‐differentiated rootlet cortical cells. In the cluster root, the Casparian band formed in three ways, and was not initially present opposite the two sets of single xylem elements in the rootlet stele. A new clearing technique was developed that allowed visualization of xylem, suberized endodermis, Casparian band formation and phenolic compounds. In lateral roots, endodermal differentiation was asynchronous, but was related to position relative to protoxylem poles. However, the observed delay began before these poles had differentiated. At the tip of mature rootlets, which are determinate, the endodermis terminates in a ‘dome’ of cells, with the initial cell differentiating as an endodermal cell. Results are discussed in terms of determinate development in roots and the spatial and temporal contexts within which this development takes place.
The daily integral of photosynthesis by Planktothrix rubescens during summer stratification and autumnal mixing in Lake Zürich
Authors: MICHELETTI SILVIA , SCHANZ FERDINAND , WALSBY ANTHONY E.
Published: March 2003

It has been suggested that the populations of planktonic cyanobacteria that occupy the metalimnion of stratified lakes during the summer months may be aestivating between the main periods of growth during entrainment in the epilimnion in spring and summer. We determined the vertical distribution of the biomass and daily integral of photosynthesis of the population of Planktothrix (Oscillatoria) rubescens in Lake Zürich for 136 d from July to November 1995. The population showed an 80‐fold increase during the stratified period but it only doubled over the subsequent period of entrainment. During the first eight days, part of the increase was attributed to recruitment of filaments floating up from greater depths but all of the subsequent production could be accounted for by photoautotrophic growth. On sunny days the biomass‐specific photosynthesis of this population reached some of the highest values over the whole period despite its depth (>13 m). On very cloudy days, however, primary productivity was very low and on 4 days, when the mean depth of the population exceeded 15 m, there was no net production. Over the whole period of the study, the accumulated photosynthetic production exceeded the increase in biomass of the population by a factor of 9·5. Although much of this production occurred during the period of entrainment only a small proportion was translated into growth of the population. It is concluded that the growth that takes place in the period of stratification in the metalimnion is essential to subsequent production.
Aspects of methane flow from sediment through emergent cattail (Typha latifolia) plants
Authors: YAVITT J. B. , KNAPP A. K.
Published: March 2003

We measured the flow of methane in Typha latifolia L. (cattail)‐dominated wetlands from microbial production in anoxic sediment into, through, and out of emergent T. latifolia shoots (i.e. plant transport). The purpose was to identify key environmental and plant factors that might affect rates of methane efflux from wetlands to the Earth's atmosphere. Methane accumulated in leafy T. latifolia shoots overnight, reaching concentrations up to 10000 μl l−1 (vs. atmospheric concentrations <4 μl l−1), suggesting that lower stomatal conductance at night limits methane efflux from the plant into ambient air. Daytime light and (or) lower atmospheric humidity that induce convective gas flow through the plant coincided with (a) an increase in the rate of methane efflux from T. latifolia leaves to ambient air (from <0·1 to >2·0 μmol m−2 (leaf) s−1) and (b) a decrease in shoot methane concentration to <70 μl l−1. Very short fluctuation in stomatal conductance during the day did not affect the methane efflux rate unless, possibly, the rate of photosynthesis decreased. A strong relationship between the maximum daily rate of methane efflux and shoot methane concentration (measured before the onset of convective gas flow) suggests T. latifolia plants behave like a capacitor (filling with methane at night, emitting the stored methane during the day). Experimentally cutting leaves (to prevent pressurization) reduced plant capacitance for methane.
Dark septate endophytes: a review of facultative biotrophic root‐colonizing fungi
Authors: JUMPPONEN ARI , TRAPPE JAMES M.
Published: March 2003

Dark septate root endophytes (DSE) are conidial or sterile fungi (Deuteromycotina, Fungi Imperfecti) likely to be ascomycetous and colonizing plant roots. They have been reported for nearly 600 plant species representing about 320 genera and 100 families. DSE fungi occur from the tropics to arctic and alpine habitats and comprise a heterogeneous group that functionally and ecologically overlaps with soil fungi, saprotrophic rhizoplane‐inhabiting fungi, obligately and facultatively pathogenic fungi and mycorrhizal fungi. Numerous species of undescribed sterile and anamorphic taxa may also await discovery. Although DSE are abundant in washed root and soil samples from various habitats, and are easily isolated from surface‐sterilized roots of ecto‐, ectendo‐, endo‐ and non‐mycorrhizal host species, their ecological functions are little understood. Studies of DSE thus far have yielded inconsistent results and only poorly illustrate the role of DSE in their natural habitats. These inconsistencies are largely due to the uncertain taxonomic affinities of the strains of DSE used. In addition, because different strains of a single anamorph taxon seem to vary greatly in function, no clear generalizations on their ecological role have been drawn. This paper reviews the current literature on DSE and the ecology and discusses the need for and direction of future research.
Involvement of reactive oxygen species in the response of resistant (hypersensitive) or susceptible cowpeas to the cowpea rust fungus
Authors: HEATH MICHELE C.
Published: March 2003

A previous study had indicated that scavengers of reactive oxygen species (ROS) delayed cell death (the hypersensitive response (HR)) triggered in epidermal cells of intact, resistant, cowpea (Vigna unguiculata (L.) Walp) leaves by the monokaryotic stage of the cowpea rust fungus (Uromyces vignae Barclay race 1). This HR had been monitored by cell autofluorescence, which occurs after protoplast collapse. In the present study, when cytoplasmic disorganization was used to monitor cell death more directly, ROS‐scavengers, superoxide dismutase, catalase, horseradish peroxidase, and desferal‐Mn(IV) had no effect on HR development. Cytological staining for superoxide or hydrogen peroxide generation also did not reveal the presence of ROS before or during the early stages of the HR, but did, as in the previous study, suggest a role in the autofluorescence and browning of invaded cells that occur following protoplast collapse. Staining of plant mitochondria with nitroblue tetrazolium, possibly attributable to increased dehydrogenase activity but not superoxide generation, occurred transiently around invasion hyphae (monokaryotic stage of the fungus) or haustoria (dikaryotic stage) of the fungus as they entered a cell in the susceptible or resistant cultivar. Around invasion hyphae in epidermal cells in resistant plants, this staining diminished as cytoplasmic streaming stopped, and gradually disappeared as cell death progressed. These data are consistent with other evidence that rust fungi initially negate non‐specific defensive responses in both resistant and susceptible cells as part of the establishment of biotrophy. They also suggest that the HR in the cowpea–cowpea rust fungus pathosystem is not triggered by an oxidative burst.
Quantification of vessel embolisms by direct observation: a comparison of two methods
Authors: PATE J. S. , CANNY M. J.
Published: March 2003

When freshly cut segments of naturally decorticated steles of horizontal roots of the Australian grass tree (Xanthorrhea preissii) are subjected to gentle suction, bubbles of gas sometimes appear, as well as liquid, in capillaries attached to the aspirated ends of the steles. We tested the hypothesis that this gas comes from vessels embolized in the intact xylem stream, and that the gas volume extruded is therefore an effective measure of the extent of this embolism. To do this, twin samples were taken from individual roots of X. preissii in the field, one was fast‐frozen intact for subsequent estimation of vessel embolisms in the cryo‐scanning electron microscope (CSEM), the other 15‐cm segment rapidly assessed for volume of gas aspirated into a standard micropipette tube. The two measures mutually confirmed one another by showing a strong positive correlation between numbers of embolized vessels and extracted gas volume. Similar gas volumes were obtained from replicate root segments excised directly from a root when the ends of the segment were frozen before excision, and aspiration conducted after subsequent thawing of the ends under water. The pattern of changes in embolisms during unstressed conditions in early summer, shown by both CSEM and aspiration, indicated almost no embolisms before dawn, followed by a rapid rise to a peak in mid morning, than a progressive loss of embolisms in late afternoon. It was also shown that the amount of embolism did not change with time after excision of the roots up to at least 30 min. A comparison of changes in leaf transpiration with gas volumes in steles during a 24‐h cycle at peak transpiration stress in mid summer showed rapid rates of transpiration in early morning and late afternoon, with an intervening period of low water loss during the rest of the day. Numbers of embolisms rose to an early morning peak, followed by apparent repair of these before noon. There was a second spate of embolisms in late afternoon, followed by complete refilling of all xylem with liquid by an hour or so after dusk. All vessels then remained fully recharged until the following dawn. We believe that aspiration is a direct and reliable technique, which offers a simple, inexpensive means of assessing the relative extent of embolism of vessels in xylem, and a means to test earlier findings by the other direct method of the CSEM. In a broad context, the technique should provide new opportunities for evaluating water relations of the xylem of whole plants.
Effects of various organic compounds on growth and phosphorus uptake of an arbuscular mycorrhizal fungus
Authors: RAVNSKOV SABINE , LARSEN JOHN , OLSSON PÅL AXEL , JAKOBSEN IVER
Published: March 2003

The influence of three organic compounds and bakers' dry yeast on growth of external mycelium and phosphorus uptake of the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith (BEG 87) was examined. Two experiments were carried out in compartmentalized growth systems with root‐free sand or soil compartments. The sand and soil in the root‐free compartments were left untreated or uniformly mixed with one of the following substrates (0.5 mg g−1 soil): bakers' dry yeast, bovine serum albumin, starch or cellulose. Effects of the organic substrates on biomass and hyphal length density of the arbuscular mycorrhizal fungus were examined by using specific fatty acid signatures in combination with direct microscopy. Micro‐organisms other than the arbuscular mycorrhizal fungus were measured by fatty acid signatures, and radioactive 33P labelling of the root‐free soil was used to determine arbuscular mycorrhizal hyphal phosphorus uptake. In general, hyphal growth of G. intraradices was enhanced by yeast and bovine serum albumin, whereas the carbon sources, starch and cellulose, depressed fungal growth. By analysing the fatty acid 16∶1ω5 from phospholipids (indicating mycelium) and neutral lipids (indicating storage structures) it was shown that increased fungal growth due to yeast was mainly in vegetative hyphae and less in storage structures. Arbuscular mycorrhizal hyphal phosphorus uptake was decreased by cellulose, but unaffected by the other substrates compared with the control. This means that both growth and phosphorus transport by the arbuscular mycorrhizal fungus were decreased under cellulose treatment. However, the composition of the microbial community varied under different substrate conditions indicating a possible interactive component with arbuscular mycorrhizal hyphal growth and phosphorus uptake.
Effects of exogenous application and stem infusion of ascorbate on soybean (Glycine max) root nodules
Authors: BASHOR CALEB J. , DALTON DAVID A.
Published: March 2003

Numerous biochemical and physiological studies have demonstrated the importance of ascorbate (ASC) as a reducing agent and antioxidant in higher plant metabolism. Of special note is the capacity of ASC to eliminate damaging activated oxygen species (AOS) including O2−· and H2O2. N2‐fixing legume nodules are especially vulnerable to oxidative damage because they contain large amounts of leghaemoglobin which produces AOS through spontaneous autoxidation; thus, ASC and other components of the ascorbate–reduced glutathione (ASC–GSH) pathway are critical antioxidants in nodules. In order to establish a meaningful correlation between concentrations of ASC and capacity for N2 fixation in legume root nodules, soybean (Glycine max) plants were treated with excess ASC via exogenous irrigation or continuous intravascular infusion through needles inserted directly into plant stems. Treatment with ASC led to striking increases in nitrogenase activity (acetylene reduction), nodule leghaemoglobin content, and activity of ASC peroxidase, a key antioxidant enzyme. The concentration of lipid peroxides, which are indicators of oxidative damage and onset of senescence, was decreased in ASC‐treated nodules. These results support the conclusion that ASC is critical for N2 fixation and that elevated ASC allows nodules to maintain a greater capacity to fix N2 over longer periods.
Role of ethylene and auxin in regenerative differentiation and orientation of tracheids in Pinus pinea seedlings
Authors: KALEV NATALIE , ALONI RONI
Published: March 2003

A low auxin concentration (0.1% naphthalene acetic acid) induced tracheids with longitudinal polarity parallel to the hypocotyl axis in young Pinus pinea seedlings. Application of 0.1% ethrel laterally and 0.1% naphthalene acetic acid apically disturbed axial tracheid polarity and promoted the differentiation of tracheids with a lateral orientation. Ethrel by itself, with no auxin background, did not affect tracheid differentiation. Apical application of 1% gibberellic acid with the low auxin, reversed the polarity disorder induced by ethrel. Disturbance of axial tracheid polarity was observed under a high auxin concentration (0.5% naphthalene acetic acid) which was similar to the combined effect of ethrel and auxin. The high auxin concentration increased tracheid number significantly. This effect was curtailed following treatment with inhibitors of ethylene formation (Co2+; 1‐aminoethoxy‐
vinylglycine) and action (Ag2+). The role of ethylene in controlling the differentiation of radial tracheids, which characterize the vascular rays of pines, is discussed.
Leaf structure and chemical composition as affected by elevated CO2: genotypic responses of two perennial grasses
Authors: ROUMET CATHERINE , LAURENT GÉRARD , ROY JACQUES
Published: March 2003

Genotypic variability was studied in two Mediterranean grass species, Bromus erectus and Dactylis glomerata, with regard to the response to CO2 of leaf total non‐structural carbohydrate concentration ([TNC]lf), specific leaf area (SLA), and leaf carbon and nitrogen concentrations ([C]lf and [N]lf, respectively). Fourteen genotypes of each species were grown together on intact soil monoliths at ambient and elevated CO2 concentrations (350 and 700 μmol mol−1, respectively). In both species, the most consistent effect of elevated CO2 was an increase in [TNC]lf and a decrease in leaf nitrogen concentration when expressed either as total dry mass [Nm]lf, structural dry mass [Nmst]lf or leaf area [Na]lf. The SLA decreased only in D. glomerata, due to an accumulation of total non‐structural carbohydrates and to an increase in leaf density. No genotypic variability was found for any variable in B. erectus, suggesting that genotypes responded in a similar way to elevated CO2. In D. glomerata, a genotypic variability was found only for [Cst], [Nm]lf, [Nmst]lf and [Na]lf. Since [Nm]lf is related to plant growth and is a strong determinant of plant–herbivore interactions, our results suggest evolutionary consequences of elevated CO2 through competitive interactions or herbivory.
Climatic determinants of budburst seasonality in four temperate‐zone tree species
Authors: CHUINE ISABELLE , COUR PIERRE
Published: March 2003

Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the effect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant effect on the timing of budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82–100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly affect budburst and therefore may not need to be considered in phenological models for predicting budburst.
Identification and expression analysis of two fungal cDNAs regulated by ectomycorrhiza and fruit body formation
Authors: NEHLS U. , MIKOLAJEWSKI S. , ECKE M. , HAMPP R.
Published: March 2003

Ectomycorrhiza formation is a complex developmental process that is still not well understood. To study this process, we identified genetic markers for mycorrhiza development by differential screening of a cDNA library obtained from fully developed Picea abies–Amanita muscaria mycorrhizas. Twenty‐three cDNA clones were identified that showed significantly altered gene expression during the ectomycorrhizal interaction. A detailed analysis was performed for two fungal cDNA clones, SC13 and SC25, exhibiting the most pronounced differences. SC13 encodes a protein of 184 amino acid residues that shows no homology with any sequence in databases. It was highly expressed in non‐mycorrhizal hyphae, whereas its expression was decreased at least 50‐fold in mycorrhizas and fruit bodies. SC25 encodes a protein of 198 residues that shows weak sequence homology with extensin‐like plant proteins. The expression of this gene was weak in non‐mycorrhizal hyphae but approx. 30‐fold higher in mycorrhizas and fruit bodies. Because the expression of both developmentally regulated fungal genes was identical for mycorrhizas and fruit bodies, a common regulation mechanism for both developmental processes is proposed.
Effects of fungivory by two specialist ciid beetles (Octotemnus glabriculus and Cis boleti) on the reproductive fitness of their host fungus, Coriolus versicolor
Authors: GUEVARA ROGER , RAYNER ALAN D. M. , REYNOLDS STUART E.
Published: March 2003

On the basis of the evidence that insect fungivory has the potential to affect fungal reproductive fitness, we investigated the effects of two specialist ciid beetles (Octotemnus glabriculus and Cis boleti) on the reproductive potential of their host fungus, Coriolus versicolor. We found, from field data, a negative correlation between the number of individuals of O. glabriculus inhabiting C. versicolor fruit bodies and the percentage of the fungal spore‐producing surface (hymenium) that was functional. By contrast, the number of C. boleti inhabiting C. versicolor fruit bodies did not correlate with the percentage of functional hymenium. Experimentally, O. glabriculus and C. boleti reduced the reproductive potential of C. versicolor by 58% and 30%, respectively, whereas the combined trophic activity of both beetles caused a reduction of 64%. This latter effect was not significantly different from that caused by O. glabriculus alone. These findings disagree with previous assertions that insect fungivory on fruit bodies has only neutral effects on fungal fitness. We conclude that in the short‐term, fungivory by ciids significantly decreases the area of functional hymenium of C. versicolor and is likely to reduce fungal reproductive fitness. Within this perspective the evolution of certain fungal characteristics (i.e. chemical composition, consistency and phenology) can be interpreted as being driven by fungivory.
Arbuscular mycorrhizal colonization of semi‐aquatic grasses along a wide hydrologic gradient
Authors: MILLER SUSAN P.
Published: March 2003

The effect of soil flooding on arbuscular‐mycorrhizal (AM) fungal colonization of wetland plants was investigated using Panicum hemitomon and Leersia hexandra, two semi‐aquatic grasses (Graminaceae) that grow along a wide hydrologic gradient in Carolina bay wetlands of the southeastern US coastal plain. Three related investigations were conducted along the dry‐to‐wet gradient in these wetlands; a field survey of AM fungal root colonization in eight wetlands, monthly monitoring of colonization patterns in P. hemitomon over a growing season, and an inoculum potential bioassay of soils collected along the gradient. The field survey showed that AM fungal colonization was strongly negatively correlated with water depth, but colonization was present in most root samples. The monthly assessment indicated that AM fungal colonization was lowest in plots that were consistently wet but rose as some plots underwent seasonal drying. The inoculum potential assay of dry, intermediate, and wet soils performed under both dry and saturated conditions showed that soils that were wet for >1 yr had the same ability to form mycorrhizas in bait plants as those that had remained dry. These findings suggested that the lower degree of colonization in wet areas observed in the field survey was because of the presence of surface water rather than low numbers of mycorrhizal propagules in the soil. Overall, the results of these investigations show that flooding is partially but not totally inhibitory to AM fungal colonization of wetland grasses.
Phosphorus concentrations in the leaves of defoliated white clover affect abscisic acid formation and transpiration in drying soil
Authors: SINGH DHANANJAY K. , SALE PETER W. G. , PALLAGHY CHARLES K. , MCKENZIE BLAIR M.
Published: March 2003

Increased leaf phosphorus (P) concentration improved the water‐use efficiency (WUE) and drought tolerance of regularly defoliated white clover plants by decreasing the rate of daily transpiration per unit leaf area in dry soil. Night transpiration was around 17% of the total daily transpiration. The improved control of transpiration in the high‐P plants was associated with an increased individual leaf area and WUE that apparently resulted from net photosynthetic assimilation rate being reduced less than the reductions in the transpiration (27% vs 58%). On the other hand, greater transpiration from low‐P plants was associated with poor stomatal control of transpirational loss of water, less ABA in the leaves when exposed to dry soil, and thicker and smaller leaf size compared with high‐P leaves. The leaf P concentration was positively related with leaf ABA, and negatively with transpiration rates, under dry conditions (P < 0.001). However, leaf ABA was not closely related to the transpiration rate, suggesting that leaf P concentration has a greater influence than ABA on the transpiration rates.
Use of stable isotopes to quantify nitrogen, potassium and magnesium dynamics in young Scots pine (Pinus sylvestris)
Authors: PROE M. F. , MIDWOOD A. J. , CRAIG J.
Published: March 2003

Two‐yr‐old Scots pine (Pinus sylvestris) seedlings were grown in sand culture for 1 yr with a generous supply of
a balanced nutrient solution. Trees were repotted into clean sand in February 1998 and given either a reduced or
adequate nutrient supply containing enriched 15N, 41K and 26Mg to label nutrient uptake during spring 1998.
Trees doubled their biomass during the experiment. Whole‐tree net photosynthesis was reduced by 43% after 95
d in trees that received the lower nutrient supply (P < 0.001), although differences in biomass between the two
treatments were less pronounced. Remobilization contributed 83, 82 and 52% of the N, K and Mg, respectively,
used to support growth of new tissues in trees that received reduced nutrient supply. Those receiving the higher
nutrient supply still obtained 44–59% of nutrients used for spring growth of new tissues from remobilization.
Current nutrient supply had no significant effect on the amount of N or Mg remobilized to new tissues but K
remobilization was less in trees that received the lower nutrient supply (P = 0.025). The importance of remobilization in young trees and problems associated with quantifying internal cycling of nutrients are discussed.
A new dawn – the ecological genetics of mycorrhizal fungi
Authors: TAYLOR D. LEE
Published: March 2003

Many human activities, such as ore mining and smeltering, sewage sludge treatment and fossil fuel consumption, result in toxic soil concentrations of ‘heavy metals’ (Al, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ti, Zn and others) (Gadd, 1993). There are also natural soils, such as serpentine, with levels of heavy metals that inhibit or preclude the growth of many plants and soil micro‐organisms. However, certain plants and microorganisms do grow in these metalliferous sites. Understanding the physiology, ecology and evolution of tolerance to elevated soil metal concentrations is important in an applied setting, and is also of interest in theoretical biology. Applied importance relates to the improvement of forest health in areas subject to increasing pollution, rehabilitation of severely polluted sites by phytostabilization of metals, and metal removal using hyperaccumulating plants (Krämer, 2000; Ernst, 2000). Areas of theoretical interest include the evolution of local adaptation (Sork et al., 1993) and how it is shaped by the combined influences of natural selection, gene flow and genetic architecture, as well as metal influences on various species interactions (Pollard, 2000). A paper appears on pages 367–379 in this issue by Jan Colpaert and coworkers which adroitly combines the disparate fields of physiology, genetics and ecology to answer several outstanding questions concerning heavy metal tolerance in mycorrhizal fungi.

Mycorrhizal fungi, which interact mutualistically with the majority of plant species, are well known for improving the P status of their hosts (Smith & Read, 1997). Some mycorrhizal fungi are also able to mobilize N and P from organic substrates and to provide plants with improved micronutrient and water acquisition, pathogen resistance, and a variety of other benefits (Smith & Read, 1997). One of these additional benefits is the amelioration of toxicity in metalliferous soils.
Tansley Review No. 115
Authors: BLACK V. J. , BLACK C. R. , ROBERTS J. A. , STEWART C. A.
Published: March 2003

Sexual reproductive development is a crucial stage in the life cycle of higher plants as any impairment of the processes involved might have significant implications for the productivity of crop plants and the survival of native species. There is considerable evidence that exposure to ozone, even at current ambient levels in many industrialized countries, reduces grain and fruit yields and adversely affects yield quality. It is also well established that sensitivity to ozone may differ not only between species, but also between cultivars and populations of individual species, and that the impact of exposure is highly dependent on ozone concentration and the duration and timing of exposure. However, few studies have attempted to distinguish between the direct effects of air pollutants on reproductive development, and indirect effects mediated by injury to the vegetative organs and associated changes in the supply of assimilates and other essential resources to support reproductive growth, or the levels of endogenous growth regulators. This review considers the impact of ozone on the reproductive biology of agricultural and native species, and examines its direct effects on specific reproductive processes. The extent to which compensatory responses redress the adverse effects of exposure is also explored, with particular reference to recent studies of Brassica napus (oilseed rape), Brassica campestris (Wisconsin Fast Plants), Plantago
major (greater plantain) and Triticum aestivum (wheat).

contents

Summary
421

I.
introduction
421

II.
effects of ozone on reproduction
423

III.
influence of reproductive habit and implications for field‐grown plants
438

IV.
conclusions and future research
441

Acknowledgements
442

References
442
Ancestry of plant MADS‐box genes revealed by bryophyte (Physcomitrella patens) homologues
Authors: KROGAN N. T. , ASHTON N. W.
Published: March 2003

Three MADS‐box cDNA clones and two corresponding genomic sequences (gDNAs) have been isolated from the bryophyte Physcomitrella patens and sequenced. Our findings indicate that the genes may be expressed in a tissue‐
or age‐specific manner, and that expression of one of them is regulated by an alternative splicing mechanism.
Conceptual translation of the clones reveals that the encoded MADS‐domain proteins have the typical plant‐domain pattern (MIKC). Additionally, there is a high degree of conservation of intron number and positions
between angiosperm MADS‐box genes and the moss loci. These observations confirm the homology of moss and
higher plant MADS‐box genes. We conclude that the MIKC pattern evolved in MADS‐box genes after the
separation of the plant lineage from that of fungi and animals, and that it must have been present in the common
ancestor of mosses, ferns and seed plants. Therefore it evolved at least 400 million yr ago. Phylogenetic analysis
of a large subset of the sequenced plant MADS‐box genes, incorporating those from P. patens, indicates that the bryophyte genes are not orthologues of spermatophyte genes belonging to any of the well recognized higher plant gene subfamilies. This conclusion accords well with reports that the known fern MADS‐box genes also comprise subfamilies distinct from those of higher plants. Therefore we tentatively propose that the gene duplication and diversification events that created the MADS‐box gene subfamilies, discernible in extant angiosperm and other spermatophyte groups, occurred after separation of the moss and fern lineages from the lineage which produced the higher plants.
Component growth efficiencies of mycorrhizal and nonmycorrhizal plants
Authors: KOIDE R. T. , GOFF M. D. , DICKIE I. A.
Published: March 2003

Two mycotrophic species (Lactuca sativa and Abutilon theophrasti) and one nonmycotrophic species (Beta
vulgaris) were grown in a P‐deficient soil, and the effects of mycorrhizal inoculation on three variables that
determine growth rate were assessed for each. The phosphorus‐use efficiency (PUE, dW/dP) is the ratio of d. wt
increase to P content increase. Plant P is the amount of P (the limiting resource) controlled by the plant, which
can be allocated to various purposes. The phosphorus efficiency index (PEI, dP/Pdt) is the efficiency with which
plant P is used to acquire P from the soil. Inoculated and control plants of a given species initially contained the
same amount of P because all plants were grown from seed. Mycorrhizal colonization significantly increased the
PEI of Lactuca and Abutilon (by 23 and 32%, respectively). As expected, mycorrhizal inoculation did not
significantly increase the PEI of Beta. As a result, mycorrhizal inoculation significantly increased the P content
of Lactuca and Abutilon, but not Beta. Mycorrhizal colonization decreased the PUE of lettuce, but did not
significantly affect that of Abutilon or Beta. Mycorrhizal inoculation therefore slightly increased the growth rate
of Lactuca, greatly increased the growth rate of Abutilon, and ultimately had no significant effect on the growth
rate of Beta.