bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of a potassium‐channel blocker and metabolic and ATPase inhibitors on potassium and malate content of Phaseolus coccineus L. pulvini
Authors: BIAŁCZYK JAN , LECHOWSKI ZBIGNIEW
Published: April 2006

summary

The effect of the K+ channel blocker tetraethylammonium chloride (TEA‐C1), of non‐specific ATPase inhibitors (dicyclohexylcarbodiimide and diethylstilbestrol) and of the uncoupler, carbonyl cyanide‐m‐chloro‐phenyl‐hydrazone (CCCP) on the contents of K+ and malate was investigated in the intact motor system of Phaseolus coccineus pulvini. The results suggest that in these conditions the activity of K+‐channels in motor cells of extensor and flexor parts is limited. Treatment of detached leaves with 20 mol m−3 TEA‐C1 completely blocked K+ and malate movement and also limited the K+ flux between the opposite parts of the pulvinus. In these conditions K+ and malate contents in the two parts of the pulvinus was reduced in both phases of the diurnal cycle as compared with the control (plants treated with potassium iminodiacetate). A similar effect was found when the activity of the proton pump was decreased by H+‐ATPase inhibitors or CCCP. The transport of potassium and the effect of its content on the level of malate in motor cells of Phaseolus coccineus pulvinus were also investigated.
Role of light in the biosynthesis and turnover of photosynthetic fructose‐1, 6‐bisphosphatase in pea (Pisum sativum L.) seedlings
Authors: SAHRAWY M. , CHUECA A. , HERMOSO R. , LÁZARO J. J. , GORGÉ J. LÓPEZ
Published: April 2006

summary

Photosynthetic fructose‐ 1, 6‐bisphosphatase (FBPase) determined immunologically by ELISA undergoes a sharp increase when etiolated pea (Pisum sativum L. cv. Lincoln) seedlings are illuminated for 24 h. The rise of enzyme activity appears slower than that of FBPase protein, which means an earlier synthesis of a precursor or some other immunologically related but inactive form of the enzyme. A second possibility is a delayed synthesis of a factor – i.e. a component of the ferredoxin‐thioredoxin activation system – necessary for the expression of the enzyme activity. With more extended illumination times, the highest FBPase content, as well as maximum activity, was obtained after 4 d of light exposure, the former representing 0.66 % of the total soluble protein. After that time, a decrease of both FBPase protein and enzyme activity was observed, probably as a consequence of a premature senescence promoted by such an extended and continuous light exposure. A maximum FBPase labelling was obtained at 6.5 h after leaf application of a [35S]methionine pulse to etiolated pea seedlings, which were then continuously illuminated. From the pattern of the radioactive decay of FBPase labelling, a half‐life of 14 h was calculated for this photosynthetic enzyme.
Extension growth in a barley mutant with reduced sensitivity to low temperature
Authors: POLLOCK C. J. , TOMOS A. D. , THOMAS A. , SMITH C. J. , LLOYD E. J. , STODDART J. L.
Published: April 2006

summary

The ‘slender’ mutant of barley (Hordeum vulgare) shows high rates of leaf extension and a reduced temperature threshold for extension growth compared with normal seedlings. The turgor pressure of epidermal and mesophyll cells within the extension zone was unaffected by localized cooling. Measurements of linkage patterns in cell wall carbohydrates isolated from the extension zone showed no variation with genotype or growth temperature, suggesting that the gross chemical architecture of the cell walls was similar.

Differences between genotypes were observed when the rheological properties of extending leaves were measured using an extensiometer. Leaves from mutant seedlings showed greater plastic deformation than those from normal seedlings. These differences were absent in mature leaves or in growing leaves killed in boiling methanol prior to measurement. Differences were observed in the patterns of autolytic release of carbohydrates from cell wall extracts, in the incorporation of radioactivity from14CO2into specific components of the extending cell wall and in the amounts of uronic acids released following treatment with pectolytic enzymes. These results are discussed in relation to the hypothesis that the mutation acts by modifying the patterns of turnover of structural components in the extending cell wall, thereby affecting extensibility.
Stamen ontogeny in the temperature‐sensitive ‘stamenless‐2’ mutant of tomato (Lycopersicon esculentum L.)
Authors: POLOWICK P. L. , BOLARIA R. , SAWHNEY V. K.
Published: April 2006

summary

In the temperature‐sensitive ‘stamenless‐2’ (sl‐2/sl‐2) mutant of tomato (Lycopersicon esculentum L.), normal‐looking stamens are produced under low temperatures, but under high temperature conditions carpelloid stamens develop. Under low temperature conditions, the mutant stamens follow a pattern of development comparable to the normal (+/+) stamens in all respects, e.g. initiation, locule formation and hair production. The ontogeny of carpelloid stamens under high temperature conditions diverged from that of the normal and low temperature‐grown mutant stamens at an early stage of development (<0.2 mm), and followed a sequence of development similar to that of the apocarpous gynoecia of other species.
Ozone effects on the fatty acid composition of loblolly pine needles (Pinus taeda L.)
Authors: FANGMEIER A. , KRESS L. W. , LEPPER P. , HECK W. W.
Published: April 2006

summary

Loblolly pine trees were fumigated with ozone in open‐top chambers and the fatty acid content of the needles was analysed. Fatty‐acid composition depended on needle age. Ozone effects also differed with needle age. In needles treated during the needle elongation period, ozone fumigation decreased the C18:3 and increased the C18:2 and C18:1 content. In needles already elongated before ozone treatment was initiated, fatty acid content decreased. The results suggest different pathways of ozone attack in elongated and elongating needles. No differences in response to ozone were found for fatty acids in needles of four different half sib families.
Antagonistic interactions involving plant pathogens: fitting and analysis of models to non‐monotonic curves for population and disease dynamics
Authors: GILLIGAN C. A.
Published: April 2006

summary

Nonlinear models were fitted to selected data sets, obtained from published papers, in which inoculum of a fungal plant pathogen or microbial antagonist of a pathogen increased and then decreased with time. Conventional models that have been widely used in botanical epidemiology, such as the logistic, monomolecular and Weibull functions, could not be fitted to these non‐monotonic curves. Two models, the over‐damped in which Y=A+B exp (α1t +C exp (α2t), and the critically damped in which Y=A+ (B+Ct) exp (–λt), were fitted: Y is a measure of the pathogen or antagonist, t is time, A is an asymptote, B and C are locational parameters and α1, 2 and λ are rate parameters. These models are standard solutions of a second order differential equation. They have a single cycle, involving a rise and subsequent decline in the population density of the micro‐organism which ultimately tends to an asymptotic equilibrium. The over‐damped model was successful only in fitting large data‐sets and was used to describe the population dynamics of bacterial colonization of live‐ and heat‐killed conidia of Cochliobolus sativus (Ito & Kurib.). Drechs. ex Dastur as well as the population dynamics of Laetisaria arvalis Burdsall in untreated and in pasteurized soil with and without subsequent reinfestation with Pythium ultimum Trow. The critical damping model was used to describe pre‐emergence damping‐off of Rhizoctonia solani Kühn in successive crops of radish, the population dynamics of P. ultimum and low‐temperature Pythium spp. in untreated soil and pasteurized soil with L. arvalis, the population dynamics of Trichoderma viride Pers. ex S. F. Gray in plant growth media and, similarly, of Macrophomina phaseolina (Maub.) Ashby in soil and, lastly, the colonization of organic fragments by P. ultimum with and without antagonism from P. nunn Lifshitz, Stanghellini & Baker. The selected model was first fitted to the empirical progress curve for each treatment. Subsequently one or more common parameters were constrained to fit all treatments while the remaining parameters were fitted separately. None of the treatments affected the rate parameters but treatments did affect the asymptote and locational parameters. The shapes of the models are discussed in relation to initial amounts of inoculum, the initial rate of increase of inoculum and the time to achieve maximum levels of disease or microbial biomass. The over‐damping model is shown to represent the solution of a set of simple linked differential equations for two interacting populations. The derivation of these elementary models is discussed in relation to the study of biological control of plant pathogens.
Cryopreservation of spores of vesicular–arbuscular mycorrhizal fungi*
Authors: DOUDS DAVID D. , SCHENCK N. C.
Published: April 2006

summary

Storage of spores of vesicular‐arbuscular (VA) mycorrhizal fungi in soil at 5 °C is a common way of preserving these fungi. This method was satisfactory for Glomus intraradix Schenck & Smith but not for Gigaspora margarita Becker & Hall, Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe, and Acaulospora longula Spain & Schenck. Preservation of spores at −60 to −70 °C was examined. Cryoprotectants such as DMSO, glycerol, mannitol, and sucrose were ineffective using the freeze‐damage sensitive species G. margarita. Incubation for 47 h in 0.75 to 1.0 M trehalose conferred a measure of freeze damage protection to the spores such that germination rates of previously frozen spores of G. margarita were one tenth to one sixth of controls. The best method of cryoprotection and cryopreservation was found to be slow drying of pot culture soil and freezing the spores in situ. This procedure was satisfactory for the five genera of VA mycorrhizal fungi evaluated.
Effects of liming on ectomycorrhizal fungi infecting Pinus sylvestris L.
Authors: ERLAND SUSANNE , SÖDERSTRÖM BENGT , ANDERSSON SOLBRITT
Published: April 2006

summary

Growth rates of ectomycorrhizal fungi were measured in pure culture at pH 3–8 on MMN‐agar and sterilized peat, with and without nutrients added. Mycorrhizas were synthesized with Pinus sylvestris L. seedlings and the growth rate of the external mycelium was measured in peat at pH 3.8 and 7.3. The fungi were three isolates of Piloderma croceum Erikss. & Hjorts., two isolates of an unidentified (pink) mycorrhizal type and one isolate of another unidentified (white long) mycorrhizal type, all isolated from P. sylvestris roots.

All three fungi showed much higher (2–5 times) growth rates when grown as symbionts than when grown in pure culture. The P. croceum isolates also grew as symbionts at pH 7.3, where no growth occurred in pure culture. These findings emphasize the danger of generalizing from data obtained in pure culture studies to explain what may happen when fungi grow in symbiosis with host plants.

Generally, growth rates in pure culture were higher and the pH tolerance levels were wider on agar than on peat. The exceptions were one P. croceum isolate, which had the fastest pure culture growth rate on peat with MMN, and the pink isolates, which grew at higher pH on peat than on agar. There were no significant differences between growth on peat with and without MMN.
Genetic variation in ectomycorrhiza formation byPisolithus arhizusonPinus pinasterandPinus banksiana
Authors: LAMHAMEDI MOHAMMED S. , FORTIN J. ANDRÉ , KOPE HARRY H. , KROPP BRADLEY R.
Published: April 2006

summary

The ability of 28 monokaryons and 78 reconstituted dikaryons ofPisolithus arhizus(Scop, pers Pers.) Rauchert [Syn.:Pisolithus tinctorius(Pers.) Coker & Couch] to form ectomycorrhizas onPinus pinaster(Ait.) Sol. andPinus banksiana(Lamb.) was studied using the growth pouch method. The ability to form mycorrhiza and promote growth ofP. pinasterdiffered both between and within monkaryons and dikaryons. Some monokaryons and dikaryons failed to form ectomycorrhizas. Monokaryons formed fewer ectomycorrhizas onP. pinasterthan dikaryons. The heterokaryotic state was necessary for the full expression of ectomycorrhiza‐forming ability. Growth ofP. pinasterwas more strongly correlated with ectomycorrhiza formation by dikaryons than by monokaryons.
The interaction of sodium and calcium chlorides and light on growth, potassium nutrition, and proline accumulation in callus cultures of Medicago sativa L.
Authors: SHAH S. H. , WAINWRIGHT S. J. , MERRETT M. J.
Published: April 2006

Callus cultures, established from cultivars of Medicago sativa L., Dupuits and Spredor2, were used to investigate salt‐induced changes in metabolism. With increase in NaCl concentration there was a progressive reduction in growth rate but this effect was ameliorated by increase in the Ca2+ concentration. The concentration of Na+ in the callus increased in response to NaCl in the medium but not proportionally, while the K+ concentration was lowest in calli grown at the highest NaCl concentration. High Ca2+ partially reversed the salt‐induced decrease in K+, so overall, the effect of Ca2+ was to decrease the Na+/K+ ratio. Proline concentration in the callus increased in response to NaCl. With callus cultures grown in the absence of supplemental NaCl there was no correlation between growth and proline concentration, whereas at the highest NaCl concentration used (150 mol m−3) there was a strong positive correlation between growth and proline concentration of individual calli. Increased Ca2+increased the proline concentration in callus of both cultivars, and at the highest salt concentration resulted in higher proline concentration and increased growth. It is suggested that proline accumulation is important for cell growth only when a certain level of salt‐stress is attained, and this level will depend on the presence or absence of other protectant mechanisms in the tissue.
Seasonal variations in mineral concentrations in the trunk xylem sap of beech (Fagus sylvatica L.) in a 42‐year‐old beech forest stand
Authors: GLAVAC V. , KOENIES H. , EBBEN U.
Published: April 2006

In a 42‐yr‐old beech forest stand, growing on acid brown earth, five trees were felled every 2 wk. From their lowest trunk segments, each 100 cm in length, tracheal sap was collected by water displacement. The investigation was performed from mid‐October 1988 to mid‐October 1989, comprising a total of 130 sample trees. Xylem sap concentrations of calcium, magnesium, potassium, and manganese of 26 sampling series were analysed by atomic absorption spectrophotometry, and the pH values of fresh sap samples were determined. The seasonal variation in xylem sap concentrations of Ca, Mg and Mn in the lowest trunk sections showed a strong increase in the second half of March and in April, a decrease in May, after the leaves had expanded, a low level in summer, and a new increase in late autumn and winter. Potassium showed a different pattern with maximal xylem sap concentrations in autumn. Additionally, at four sampling dates (mid‐March, beginning of May, mid‐August and mid‐November), four trees, one at each date were cut into sections for the determination of the mineral concentrations in the xylem sap along the stem.
The growth and development of Vicia faba L. in filtered and unfiltered open‐top chambers
Authors: SANDERS G. E. , TURNBULL N. D. , CLARK A. G. , COLLS J. J.
Published: April 2006

The response of Vicia faba cv. Ticol to ambient levels of air pollutants was investigated using open‐top chambers (OTCs) ventilated with ambient air (NF treatments) and charcoal‐filtered air (CF treatments). The OTCs were placed over a conventionally drilled crop shortly after emergence in April 1988, and remained in place until after the crop was harvested in September 1988. The daily mean pollutant concentrations were 15, 7, 6 and 9 nl 1−1 for O3, SO2, NO and NO2 respectively inside NF OTCs, and 6, 3, 8 and 5 nl I−1 respectively for CF OTCs. These pollutant levels were accompanied by changes in both the vegetative and the reproductive development of V. faba. The upper leaves of plants growing in CF air expanded to larger areas than corresponding leaves on NF plants, and the canopy of CF plants intercepted more radiation than that of NF plants. At flowering, CF plants had 11 % more flowers than NF plants. This difference was maintained during early pod development and was caused by greater retention of pods on the upper racemes of CF plants. As the pods dried however, more pods were abscised from CF plants than from NF plants, and by harvest the number of pods per plant was comparable for the two treatments. Thus the observed differences in growth and development were transient and did not result in differences in final yield.
Effects of simulated acid rain on epicuticular wax production, morphology, chemical composition and on cuticular membrane thickness in two clones of Sitka spruce [Picea sitchensis (Bong.) Carr.]
Authors: PERCY K. E. , BAKER E. A.
Published: April 2006

Sticklings (rooted cuttings) of two Sitka spruce [Picea sitchensis (Bong.) Carr.] clones were exposed to simulated rain of 4 pH values (5.6, 4.2, 3.4, 2.6). Rain was applied at 2 mm h−1 for 1 h, three times weekly, for 11 wk starting 1 wk prior to bud break. A range of physicochemical cuticular characteristics were investigated on current‐year needles following 2, 6, and 11 wk of exposure. Cuticular effects were initiated well above the threshold for visible injury (pH 2.6). The magnitude and direction of cuticular response differed significantly between clones. Amount of epicuticular wax recovered was not affected by the pH of the simulated rain. Wax structure was greatly modified at pH ≤ 3.4 on needles from one clone. Changes in wax structure were accompanied by changes in chemical composition, formation of amorphous deposits with increasing rain acidity coinciding with decreases in nonacosane‐diols and increases in estolides. Cuticular membrane thickness was increased significantly (P > 0.001) in one clone and decreased in the other due to simulated rain pH. Such alterations to physico‐chemical cuticular characteristics would be expected to have consequential effects on needle surface properties such as needle wettability and retention of acidic rain.
The endophytic fungal community in leaves of a coastal redwood population diversity and spatial patterns
Authors: ESPINOSA‐GARCIA F. J. , LANGENHEIM J. H.
Published: April 2006

Leaf endophytic fungi were isolated from 1 to 12‐yr‐old leaves of mature trees and basal sprouts of coastal redwood [Sequoia sempervirens (D. Don ex Lamb.) Endl.] in a redwood forest in Central California. Almost all samples yielded at least one species. The two most frequent species were Pleuroplaconema sp. and Cryptosporiopsis abietina Petrak. Among isolated taxa are endophytic generalists, species previously known as pathogens and a possible specialist. Species composition in leaves of progressing age in single branches revealed a patchy pattern of leaf colonization without an obvious sequence of succession. Changes in diversity and equitability in the endophytic community with leaf age are linked with differential distribution of some species in young versus old leaves and the increase in species richness in 4‐ and 5‐yr‐old leaves. The endophytic communities from leaves of trees and sprouts were generally similar, but with important differences in species richness and in distribution of Pleuroplaconema sp. and Pestalotiopsis funerea (Desm.) Stey. Principal component analysis based on endophytic frequency also indicated closeness of trees and sprouts as groups, but clearly separated each tree from its sprout. Differential susceptibility between trees and sprouts to endophytic infection is suggested on the basis of their endophytic communities.
Induction of protoplast formation in the ectomycorrhizal fungus Paxillus involutus by the root rot pathogen Fusarium oxysporum
Authors: FARQUHAR M. L. , PETERSON R. L.
Published: April 2006

Co‐culture of the pathogenic fungus Fusarium oxysporum f. sp. pini Schlecht. emend Snyd. & Hans, with the ectomycorrhizal fungus Paxillus involutus Fr. on potato dextrose agar caused no visible morphological changes in the fungi. Co‐culture on modified Melin Norkrans medium in petri plates yielded, however, protoplast formation at or near tips of P. involutus hyphae. No changes were visible in F. oxysporum as a result of co‐culture and the two fungi grew in close association with each other without inhibition. Staining with Calcofluor White M2R New and fluorescein diacetate displayed that, at this stage in development, a wall surrounding the protoplast was absent but a plasma membrane sheathed by an extracellular mucilage was present. Protoplasts lacking definite form adhered closely to adjoining hyphae while those with the characteristic spherical form were easily dislodged from hyphae. Average size of spherical protoplasts was 17–20 μm. Breaks were present in the hyphal wall in regions adjacent to protoplast formation and these may have been pathways for cytoplasmic leakage. Transmission electron microscopy revealed these breaks more clearly, and provided additional evidence of a plasma membrane around protoplast cytoplasm. Protoplasts contained few organelles except vesicles, larger electron dense bodies and occasional nuclei. Hyphae forming protoplasts often lacked cytoplasmic integrity although those not forming protoplasts appeared healthy.
Infectivity of pine and eucalypt isolates of Pisolithus tinctorius (Pers.) Coker & Couch on roots of Eucalyptus urophylla S. T. Blake in vitro
Authors: LEI J. , LAPEYRIE F. , MALAJCZUK N. , DEXHEIMER J.
Published: April 2006

An ultrastructural comparison of early stages of mycorrhiza formation on Eucalyptus urophylla was carried out using two isolates of P. tinctorius, one cultured from a sporocarp collected under pine and the other cultured from a sporocarp collected under eucalypt. Major differences at the fungus–root interface were observed 2 and 4 d following inoculation. Eucalypt root cells in contact with the isolate from pine developed a thickened cell wall, whereas the isolate from eucalypt was associated with an accumulation of extracellular fibrils. The fibrils stained positively for carbohydrates and protein. They were absent with the isolate from pine. Four days after inoculation with the isolate from eucalypt, acid phosphatase activity was detected along the fungal plasmalemma at the interface with host cells. This enzyme activity was not detected with the isolate from pine. Vacuolar acid phosphatase activity was detected in both fungal isolates when in contact with Eucalyptus roots. It is suggested that host recognition of ectomycorrhizal symbionts can be manifested within hours of inoculation with the fungal partner.
Proteinase activity in mycorrhizal fungi
Authors: LEAKE J. R. , READ D. J.
Published: April 2006

The ericoid mycorrhizal endophyte, Hymenoscyphus ericae (Read) Korf & Kernan, was grown in liquid media containing either ammonium, the amino acid alanine, peptide (di‐, tri‐, tetra‐ or hexa‐alanine), or bovine serum albumin (BSA) as sole nitrogen (N) source. The effects of the various N sources upon production of extracellular acid proteinase, its specific activity and growth of the fungus were determined.

While extracellular acid proteinase was induced in the presence of each N source, enzyme production was considerably enhanced in the culture grown with BSA. Total enzyme activity in the culture solutions declined in the order BSA ≫ ammonium > peptides and alanine. Enzyme activity per mg dry weight of mycelium was greatest in the presence of BSA.

Similar yields of fungal mycelium and rates of growth were observed regardless of N source.

The results are discussed in relation to quantitative aspects of the N status of heathland soils.
Size classes of root diameter and mycorrhizal fungal colonization in two temperate grassland communities
Authors: REINHARDT D. R. , MILLER R. M.
Published: April 2006

This study addresses the hypothesis that the amount of fibrous roots (i.e., roots > 1.0 mm diameter) colonized by vesicular‐arbuscular mycorrhizal (VAM) fungi in grasslands is dependent upon root morphology. Two grassland communities with contrasting root system morphologies, a restored tallgrass prairie and an ungrazed pasture, were studied over a growing season. Although there was no difference in fibrous root biomass between the two communities, fibrous roots accounted for 99 % of the total root biomass in the pasture; but only 70 % of the total root biomass in the prairie. The length of fibrous roots was greater (P < 0.0001) in the pasture than in the prairie. Correspondingly, the mean diameter of roots in the pasture was 018 mm, but that in the prairie averaged 0.23 mm. Although the total length of fibrous roots colonized by mycorrhizal fungi did not differ between the two communities (P > 0.34), when the colonized lengths of roots within each of three size classes were compared, significant differences between the two communities were found. The ratio of the fraction of the root length colonized within a given diameter size class to the fraction of the total length of root with cortex occurring within that size class was used to compare the degree of association between roots and mycorrhizal colonization among the three diameter size classes. Changes in this ratio, termed the colonization index (CI), indicate that as the diameter size class of roots in a community increases, a greater proportion of the cortical root length within that size class is colonized by mycorrhizal fungi. Furthermore, despite community differences in the cortical and colonized root lengths within each diameter size class, the CI value for each root size class did not differ between communities. These findings suggest that in grasslands the degree of colonization by mycorrhizal fungi is more dependent upon the diameter size class distribution of the fibrous root systems than upon the species composition of the community.
Cell differentiation and mycorrhizal infection in Dactylorhiza majalis (Rchb. f.) Hunt & Summerh. (Orchidaceae) during germination in vitro
Authors: RASMUSSEN HANNE N.
Published: April 2006

Seeds of Dactylorhiza majalis (Rchb. f.) Hunt & Summerhayes were sown in vitro with a compatible fungus. A mycorrhiza was established after infection through the rhizoids of the germinating seedling. Infection through the suspensor did occur, but these hyphae did not form pelotons, and embryo cells in contact with the hyphae were filled with a tannin‐like substance.

Germination, and establishment of mycorrhiza, took about 14 days in vitro. From day 9 the protein reserves were hydrolysed, the protein vacuoles coalesced and starch accumulated in plastids. Certain epidermal cells developed nuclei about eight times original volume and produced rhizoids which emerged from day 11. After infection the hyphae formed pelotons in central cells with enlarged nuclei (16–64 times original volume). The intracellular hyphae developed close contacts with the hypertrophied host nuclei. Collapsed pelotons could be observed in cells from day 12, one day after infection. Meristematic activity in the uninfected chalazal end of the seedling began on day 12. On day 28 the first vascular tissue started to develop and on day 35 the beginning of a leafy shoot could be detected.
Variation in within‐morph incompatibility inhibition sites in heteromorphic Primula L.
Authors: WEDDERBURN FRANCES , RICHARDS A. J.
Published: April 2006

The inhibition sites for within‐morph incompatibility are reported for 52 species of Primula. Pollen tube inhibition usually occurs at more than one site; when only one site is involved, this is at the stigma surface. Inhibition sites usually vary between pins and thrums within a species, and inhibition characteristics vary widely between species, although related species are frequently similar. There is a close relationship between illegitimate seed set and failure of illegitimate tube inhibition.

Total within‐morph incompatibility is only observed in two species, but for almost all species some compatibility is found in both morphs. Inhibition at the stigma surface results in more efficient incompatibility than inhibition within the stigma and style, although multiple‐site inhibition is the most efficient. Within‐thrum inhibition tends to occur more frequently at the stigma surface than does within‐pin inhibition.

Four main classes of inhibition characteristics are noted. Some sections show inhibition site complexity in pins, but in others it has developed in thrums. Species with complex within‐morph inhibition in both pins and thrums occur in several unrelated taxonomic groupings.
The name of the pea: a quantitative history of legume classification
Authors: CRONK Q. C. B.
Published: April 2006

During the period from 1753 to 1964, the balance between splitting and lumping (the median genus size) has remained unchanged in five classifications of the Leguminosae (Linnaeus, Persoon, Bentham, Taubert and Hutchinson), which span the period at approximately 50‐year intervals. This is in contrast with the situation in the Gramineae where increased splitting in recent classifications has resulted in smaller median genus size. However, generic sizes in the Leguminosae do not cluster around the median but are uneven: the frequency distribution of genus size in all the classifications is very skew, with many monotypic genera and some exceptionally large genera. This parameter, equality, changes considerably over time with a trend to more inequality of generic size. This is interpreted as a psychohistorical artefact of the classification process with newly discovered species tending to accrete to existing genera which act as‘nuclei’for‘chaining’. The few species which are too anomalous to fit into the large and diverse genera may be placed in monotypic genera, thus producing a pattern of many very small genera and few very big genera. The one exception to this trend is the classification of Bentham which is considerably more even than expected.

The three subfamilies of the Leguminosae show similar overall trends to the family as a whole but exhibit consistent differences between each other in median genus size and equality of genus size. The Caesalpinoideae has even genus sizes and a low median genus size whereas the Mimosoideae shows the opposite, effects too marked to be explained entirely as psychohistorical artefact. These differences may be explained partly as artefact and partly in terms of differing evolutionary history if (1) the Caesalpinoideae is an ancient group primarily of relict species which have undergone little recent speciation, (2) the Mimosoideae are an ancient group which has undergone a massive bloom of recent speciation and (3) the Papilionoideae are a comparatively recently evolved group.
The palynological record of the King's Pool, Stafford, England
Authors: BARTLEY D. D. , MORGAN A. V.
Published: April 2006

The King's Pool is an elongated depression in which up to 21 m of organic sediments have been found. Details of the sediments and the macro fossils are given. The pollen diagram is presented in both percentage and concentration forms, and these show considerable differences especially for the Late Devensian period. The sequence begins at about 13 000 years BP though the pollen diagram begins near the end of the Windermere interstadial. It appears that there are a number of hiatuses in the sequence, the most important spanning most of the Atlantic period (Godwin pollen zone Vila). Forest clearance is evident from early in the Neolithic period with further clearance in the Bronze Age (shown most clearly in the concentration diagram) but with the greatest clearance at the beginning of the Iron Age. This latter clearance is accompanied by increased productivity of the lake, indicated by organic remains, including abundant blue‐green algae, suggesting eutrophication. Arable agriculture including cultivation of cereals and Cannabis seems to have increased near the end of the Roman period.
Fungal decomposition of attached angiosperm twigs I. Decay community development in ash, beech and oak
Authors: GRIFFITH G. S. , BODDY LYNNE
Published: April 2006

Initial stages in the development of fungal decay communities were followed in attached ash (Fraxinus excelsior L.) twigs which had been stressed by girdling and defoliation, and in cut lengths from living twigs of ash, oak (Quercus robur L.) and beech (Fagus sylvatica L.) incubated under controlled drying regimes in the laboratory.

Community development in artificially stressed ash twigs was similar to that predicted from previous direct observations. There was direct evidence that most primary colonizers in ash, including Phomopsis platanoidis Died, and Fusarium lateritium Nees., were present as endophytes in the bark of healthy twigs and subsequently colonized wood from this inoculum source. By contrast, secondary invaders were non‐endophytic fungi, including Peniophora lycii (Pers.) v. Hohn & Litsch and Libertella fraxinea Oganova. Secondary invaders began to colonize twigs after about 11 months; this was associated with a detectable reduction in moisture content.

In healthy ash twigs there was evidence of superficial colonization of woody tissues, lying close to the bark, by endophytes which were not commonly isolated from dead ash twigs, including Aureobasidium pullulans (De Bary) Arnaud and Phoma macrostoma Mont. Superficial colonization was seasonal, reaching a maximum during the winter.

A range of endophytes was isolated from healthy oak and beech bark, including Phomopsis spp., Cryptosporiopsis spp., Daldinia sp. and Xylaria spp. Some, but not all, of these endophytes were also isolated from the wood of dead attached oak and beech twigs, and some were able to colonize dying twig lengths under laboratory conditions. Whilst, Daldinia sp. and Xylaria spp. developed in dying twigs of all three tree species in the laboratory, neither were found in decaying twigs in the field. This may reflect different rates of drying in the laboratory and field.
Nitrogen metabolism in the ectomycorrhizal fungus Laccaria bicolor (R. Mre.) Orton
Authors: AHMAD IFTIKHAR , CARLETON TERRY J. , MALLOCH DAVID W. , HELLEBUST JOHAN A.
Published: April 2006

Blended colonies of the ectomycorrhizal fungus, Laccaria bicolor (R. Mre.) Orton, grew axenically as a suspension of fine hyphae in a defined buffered medium with glucose (doubling time 1–2 d) but not acetate as the carbon source, and either ammonium or nitrate as nitrogen sources. A number of amino acids were found to be excellent nitrogen sources for this basidiomycete, but were less effective as sources of carbon. During post‐exponential growth in medium containing inorganic nitrogen, the fungal symbiont released amino acids.

L. bicolor has the enzymatic potential to assimilate ammonium by the activities of glutamine synthetase, NADH‐glutamate dehydrogenase and NADPH‐glutamate dehydrogenase. It also contains highly active aspartate and alanine aminotransferases. The activities of glutamine synthetase, NADPH‐glutamate dehydrogenase and aspartate aminotransferase were greater in the presence of nitrate than in the presence of ammonium and declined as the culture aged, suggesting a biosynthetic role for these enzymes. In contrast, the activities of NADH‐glutamate dehydrogenase and alanine aminotransferase increased during post‐exponential growth, and also in cultures growing on amino acids as a carbon source, suggesting a catabolic role for these enzymes.
Root growth of Fagus sylvatica: impact of air quality and drought at a site in southern Britain
Authors: TAYLOR GAIL , DAVIES W. J.
Published: April 2006

Transplants of beech, Fagus sylvatica, L. were planted in 1 m plastic tubes containing a mixture of peat and grit and sunk into the ground inside open‐top chambers at a site in southern Britain. Chambers were ventilated with either charcoal‐filtered or unfiltered air and water was withheld from half of the trees within each chamber. The influence of air quality on the growth and development of roots and interactions between air quality and drought were investigated. During May and June 1988 the growth of fine (diameter < 1.5 mm) and large roots (diameter > 1.5 m) was not significantly altered by air quality. A destructive harvest conducted in July revealed that trees exposed to ambient pollution had significantly longer roots (P < 0.05) compared with trees grown in filtered air, despite slightly less root dry weight (not statistically significant). Specific root length (SRL, root length per unit root dry weight) was also significantly larger (P < 0.05) for trees grown in the unfiltered chambers and exposed to pollution, suggesting a root system which was not only longer but also consisted of thinner roots, compared with the roots of trees grown in clean air. The effects of pollution were more pronounced for roots in the lower half of the 1 m profile.

During August 1988, water was withheld from half of the trees within each chamber. Well‐watered trees exposed to unfiltered air had significantly less root dry weight (P < 0.05) compared with well‐watered trees grown in filtered air, although root length and SRL were both greater for trees grown in unfiltered air compared with those grown in filtered air. Again the effects were more pronounced lower in the root profile. Withholding water resulted in less root length being produced irrespective of air quality treatment, suggesting that trees exposed to pollution would not necessarily be more susceptible to drought‐stress. Root length was also measured non‐destructively in 1989 and again trees grown in unfiltered air had longer fine and large roots, compared with those grown in filtered air.

These results illustrate the importance of measuring root length to complement estimates of dry weight, which may not be the best indicator of root function. The production of longer, thinner roots may be an important mechanism to compensate for reduced carbon allocation to, and dry matter accumulation by roots of trees exposed to pollution.
Influence of pH and plant nutrient status on ion fluxes between tomato plants and simulated acid mists
Authors: FOSTER JEFFREY R.
Published: April 2006

Diffusion along concentration gradients, ion exchange, active uptake, and physical damage are possible mechanisms causing fluxes of ions between plant tissues and acidified moisture on plant surfaces. The temporal patterns of ion fluxes during individual wetting events should vary in a predictable manner in relation to moisture pH, plant nutritional status, and the operational mechanism. Tomatoes (Lycopersicon esculentum Mill.) were grown hydroponically at relative nutrient addition rates (Ra) of 7, 12, and 15% per day. At similar growth stages, the plants were exposed to HCl‐acidified mists of pH 2–5, 4–0, or 5–6 for 4 h, or left unmisted as controls. Whole‐plant throughfall was analysed for pH and ion concentrations after 15, 30, 60, 120, and 240 min. Surface chemical contamination was minimized by pre‐rinsing with deionized water. Except for H+ during the first 15–30 min, all ions showed efflux for the duration of the mistings. Effluxes were low (< 150μequiv m−2 h−1), time‐invariant, and unrelated to Ra at mist pH of 4.0 and 5.6. At pH 2.5, effluxes of K+, Mg2+, NO3−, and PO43− increased over time, while Ca2+ efflux increased during the first hour, then remained constant. Maximum efflux (105 to 730 μequiv m−2 h−1) mostly occurred at pH 2.5 and Ra= 17 % d−1, increasing in the order NH4+= SO42− < NO3− < PO43− < Ca2+= Mg2+ < K+ < H+. These results suggested that although ion diffusion and ion exchange contributed to observed effluxes, an additional mechanism, temporally accumulating physical damage to cuticles and cell membranes below a threshold pH between 4˙0 and 2˙5, was involved. Foliar concentrations of K, Ca, and Mg did not differ significantly among treatments, but ion effluxes into pH 2–5 mists removed 1–13 % of the whole‐plant element contents, with the largest removal for Ca.
Salinity effects on the stomatal behaviour of grapevine
Authors: DOWNTON W. J. S. , LOVEYS B. R. , GRANT W. J. R.
Published: April 2006

An investigation of the time‐course of inhibition of photosynthesis in salt‐stressed grapevine (Vitis vinifera L.) leaves revealed two types of stomatal behaviour. Up to tissue concentrations of 165 mM chloride the inhibition was due to a uniform decrease in stomatal conductance, as indicated from autoradiograms of 14CO2 fixation and no change in the relationship of assimilation to calculated intercellular partial pressure of CO2 (A‐C1) compared with control plants. The occurrence of non‐stomatal inhibition of photosynthesis at higher levels of leaf chloride, suggested by a decline in the slope of the calculated (A‐C1) relationship, was associated with non‐uniform 14CO2uptake over the leaf surface similar to that previously observed for ABA‐treated and water‐stressed grapevine leaves where non‐stomatal inhibition of photosynthesis was shown to be an artifact arising from non‐uniform stomatal behaviour. These observations also provide an explanation for the stimulation of photorespiration during salt stress.
The influence of N metabolism and organic acid synthesis on the natural abundance of isotopes of carbon in plants
Authors: RAVEN JOHN A. , FARQUHAR GRAHAM D.
Published: April 2006

This paper relates the13C/12C ratio of C3plant material relative to that of source CO2to the N source for growth, the organic N content of the plant, and the extent of organic acid synthesis. The13C/12C ratio is quantified as Δ, defined as (δ13C substrate –δ13C product)/(1+δ13C product), where δ13C values of substrate or product (i.e. the samples) are defined as [13C/12C]sample]/[(13C/12C)standard]−1. The computation is performed by relating differences in plant composition as a function of N nutrition and acid synthesis to the fraction of plant C which is acquired via Rubisco and via other carboxylases. The fractional contribution of the different carboxylases to C gain is then related, using the known isotopic fractionations exhibited by these carboxylases, in a model to predict the final Δ of the plant (relative to atmospheric CO2). Application of this approach to a ‘typical’ C3land plant yields predictions of the decrease of Δ relative to a hypothetical case in which all C is fixed via Rubisco. The predicted decreases range from 0–24 %, for NH4+assimilation (which always occurs in the roots) to 2–80%, for NO3−assimilation in shoots with the organic acid salt which results from acid‐base balance, plus any additional organic acid salts plus free acids for a plant with a basal C:N molar ratio in organic material of 15. Intermediate values are predicted for symbiotic growth with N2, or where NO3−assimilation in root or shoot is accompanied by some acid‐base regulation via OH‐ loss to the root medium.

Comparison with published data on the difference in Δ ofRicinus communiscultured with NH4+or NO3−shows that the measured influence of nitrogen source is in the right direction (NO3−grown plants with a smaller Δ, i.e. a larger deviation from the value predicted for the absence of non‐Rubisco carboxylations) to be explained by the observed difference in composition and hence fractional C contribution by the various carboxylases. However, the effect of N source on Δ is greater than that predicted by the model, i.e. a 2.1 % decrease as opposed to a 0.10 % decrease. It is likely that the major cause of the difference in δ13C of the plants grown on the two N sources is a change in the ratio of transport and biochemical conductances of leaf photosynthesis. Such a change is quantitatively consistent with the lower water use efficiency of NH4+‐grown plants.

The predicted, and observed, changes in Δ as a function of N source are of the same magnitude as those found for C3terrestrial species grown at different temperatures or photon flux densities, or in environments yielding different water use efficiencies by changing root water supply relative to shoot evaporation potential. Variations in N source should be added to the factors which might alter δ of plants growing in the field.
Characteristics of pollen production in a population of New Zealand snow‐tussock grass (Chionochloa pallens Zotov)
Authors: MCKONE MARK J.
Published: April 2006

Intraspecific variation in pollen production and pollen size were studied within a population of Chionochloa pallens, an alpine snow‐tussock grass of New Zealand. I sampled plants from two sites at the altitudinal extremes (1620 and 1070 m) of the distribution of C. pallens on Mt. Hutt, South Island. There was a highly skewed distribution of pollen production among plants; the largest 10% of plants produced over a third of the pollen. In contrast to some other species, pollen production in C. pallens can be accurately estimated by simple measures such as tussock area and number of flowering shoots. Other components of yield (number of spikelets per shoot, number of florets per spikelet, and average anther length) varied significantly among individuals, but these characteristics had a small impact on total pollen yield. There was continuous variation in pollen size among individuals; between the plants with the largest and the smallest pollen grains, there was a 21 % difference in pollen diameter and a 76% difference in pollen volume. Interplant differences in pollen size have been found in a number of plants, although the biological significance of this variation is unknown. There were few differences in pollen characteristics between sites. Plants at the low‐altitude site had slightly greater pollen yield because total plant size was greater.
The significance of changes in the red/far‐red ratio, associated with either neighbour plants or twilight, for tillering in Lolium multiflorum Lam.
Authors: CASAL J. J. , SANCHEZ R.A. , GIBSON DIANA
Published: April 2006

Lolium multiflorum Lam. plants were used to investigate whether phytochrome‐mediated tillering responses, anticipatory to competition: (a), are potentially disturbed by the twilight drop in the red to far‐red ratio (R:FR) of sunlight (caused by atmospheric factors), and (b), occur in densely‐sown (> 280 plants m−2) grass canopies, where competition is quickly established.

Isolated plants grown under sunlight received natural low R: FR during twilight, but supplementary R provided simultaneously did not increase tillering. When a wide range of R: FR was provided at the end of natural or fluorescent light photoperiods, tillering was reduced only by very low R: FR (lower than natural twilight R: FR). Leaf sheath length followed a similar pattern of response.

Single plants were grown in pots placed at various densities. High densities reduced the R:FR at plant bases and the number of tillers per plant before changes in dry weight and leaf number were found.

Both very low R:FR provided at the end of the photoperiod, and increasing plant densities, caused more erectophile shoots.

In densely‐sown canopies of Lolium multiflorum both R:FR signals caused by neighbours, and tillering responses occur well before strong competition is established. Tillering is not obviously affected by the twilight drop in R: FR.