bluuebunny/crossref_metadata_2025 huggingface dataset:
A CHECK‐LIST OF MYCORRHIZA IN THE BRITISH FLORA—ADDENDA, ERRATA AND INDEX
Authors: HARLEY J. L. , HARLEY E. L.
Published: April 2006

PREAMBLE

A check‐list of mycorrhiza in the British Flora was published in February 1987 as a supplement to Vol. 105, No. 2 of this journal. As stated in the Editorial Note in Vol. 105, No. 2 itself, it was intended that additions to the list should be published from time to time, and it was for this reason that species for which no information was to hand at the time the compilation was made were included in the list.

In this first list of Addenda, the opportunity has been taken not only to correct mistakes in the original check‐list but also to add an Index to facilitate retrieval of information. This Index, the need for which was suggested to us by Dr E. I. Newman, is of families and genera only: species are in alphabetical order within genera. Nomenclature follows Clapham, A. R., Tutin, T. G. & Warburg, E. F. (1981), Excursion Flora of the British Isles (3rd edition). Cambridge University Press, Cambridge.

The original check‐list and a copy of these addenda etc. may be obtained from the Executive Editor, The New Phytologist, Department of Botany, The University, Sheffield S10 2TN, UK on receipt of a sterling cheque for £6 made payable to The New Phytologist Trust and an adhesive label addressed to the orderer. The cheque covers cost and postage.
INCOMPATIBILITY IN CULTURED EXPLANT‐GRAFTS BETWEEN MEMBERS OF THE SOLANACEAE
Authors: PARKINSON M. , JEFFREE C. E. , YEOMAN M. M.
Published: April 2006

Summary

The development in culture of explant‐grafts between compatible and incompatible combinations of three solanaceous species parallels that of the corresponding whole‐plant grafts in respect of the pattern of vascular development and the functional status of the vascular system. In culture, incompatible explant‐grafts attain greater mechanical strength than corresponding whole‐plant grafts, and consequently this parameter of their development is an unsuitable criterion for judging the compatibility of explant‐grafts. The findings demonstrate that graft compatibility/incompatibility is determined by local factors operating close to the graft union, possibly at a cellular level between the opposing cells of stock and scion. Explant grafting in culture offers an ideal system for experimental analysis of the cellular basis of incompatibility in internode grafting.
AMINOPEPTIDASE FROM THE COTYLEDONS OF VICIA FABA L. VAR. MINOR SEEDS: PARTIAL PURIFICATION AND SOME PROPERTIES
Authors: CITHAREL J. , GARREAU C.
Published: April 2006

Summary

Leucine aminopeptidase from field beans was studied in the cotyledons of dry and germinating seeds. The partially purified enzyme had a molecular weight of about 60000 (determined by gel filtration). Activity was maximal at pH 7.5, with leucine‐p‐nitroanilide or leucine naphthylamide as substrates, and was stimulated by dithiothreitol and mercaptoethanol and inhibited by Cu and Zn ions. During germination, the highest enzyme activity in the cotyledons occurred after 2d.
INOCULUM EFFICIENCY AND PATHOZONE WIDTH FOR TWO HOST‐PARASITE SYSTEMS
Authors: GILLIGAN C. A. , SIMONS S. A.
Published: April 2006

Summary

Experiments involving direct placement of inoculum at various distances from an infection court are used to estimate the probability of infection and/or disease of seminal roots of wheat by Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker and of germinating seeds of radish by Rhizoctonia solani Kühn. Two concepts underlie the relationships under investigation. These are the pathozone, which is characterized by the furthest extent of inoculum from the host from which infection is recorded (z), and infection efficiency, which is characterized by two parameters α and β. The asymptotic infection efficiency, β, is estimated by the proportion of propagules that cause infection when placed in contact with the host; a is a measure of the decline in infection efficiency of propagules of inoculum with increasing distance from the host. Three non‐linear models are used to describe the profile of infection efficiency over distance.

The sensitivity of the method of placement of inoculum in detecting treatment effects is demonstrated first by showing differences in response amongst two isolates of G. graminis and two times of observation. Maximal values of z for G. graminis ranged from 4 to 8 mm, depending upon the type of inoculum of G. graminis and the growth medium used. Values of z for R. solani and germinating radish seeds varied from 12 to 16 mm for propagules comprising fragments of chopped potato soil inoculum sieved to 1 to 2 mm.

The amounts and nutritional basis of inoculum influenced the probability of infection and the parameters α, β and z. Thus, for G. graminis, estimated values for α−1, β and z were greater for inoculum comprising colonized millet grains than for colonized sand particles. When seedlings of radish were exposed to clumps of propagules of R. solani, the parameters β and z increased, while β decreased with increasing clump density. Reduction in propagule size to 0.5 to 1.0 mm reduced the proportion of infected hosts. When clumps of seedlings of radish were challenged with clumps of inoculum of JR. solani, the probability of infection of clumps increased with clump density, but there was no evidence for an effect on the probability of infection of individual seedlings within a clump. The relationship between the estimates of pathozone width and infection efficiency and models for infection of subterranean organs is discussed.
EFFECTS OF A SIMULATED ACID RAIN EPISODE ON PHOTOSYNTHESIS AND RECOVERY IN THE CARIBOU‐FORAGE LICHENS, CLADINA STELLARIS (OPIZ.) BRODO AND CLADINA RANGIFERINA (L.) WIGG.
Authors: SCOTT MARTHA G. , HUTCHINSON THOMAS C.
Published: April 2006

Summary

The effect of simulated acid rain on net photosynthesis of two common boreal forest lichens, Cladina stellaris and Cladina rangiferina, was investigated. Repeated measurements of net photosynthetic rate (NPR) were conducted on podetial tips over a week‐long period to assess both immediate response to an acid spray treatment (2:1 H2SO4:HNO3; pH range 2.5 to 3.5) and subsequent photosynthetic recovery after the solution of artificial rain had been rinsed out of the cells. A control group, which was treated with pH 5.6 episodes, was used to monitor natural fluctuations in NPR over time in a laboratory environment. Although lowered photosynthetic rates were observed for both species immediately following a low pH treatment, differences between groups were not significant. Three days following treatment, however, significant decreases in photosynthesis of up to 40% of pretreatment values were found for pH 2.5 and 3.0‐sprayed C. stellaris, and a decline in NPR of 25% was recorded for pH 3.0‐treated C. rangiferina. Six days after the simulated rain episode, a 20% recovery of photosynthesis had occurred in pH 2.5‐treated C. stellaris, while pH 3‐0‐sprayed C. rangiferina underwent a 20% stimulation of NPR compared to the pretreatment value. In spite of the demonstrated ability to recover partially following a single low pH event, it is hypothesized that even temporary declines in NPR could restrict growth potential and biomass accumulation of boreal cyptogamic species which have a short growing season and photosynthesize only when moisture is available. Results of the study indicate that C. stellaris is more sensitive to single low pH events than is C. rangiferina.
EFFECTS OF SIMULATED ACID RAIN ON PRODUCTION, MORPHOLOGY AND COMPOSITION OF EPICUTICULAR WAX AND ON CUTICULAR MEMBRANE DEVELOPMENT
Authors: PERCY K. E. , BAKER E. A.
Published: April 2006

Summary

Leaves of Phaseolus vulgaris L., Vicia faba L., Pisum sativum L. and Brassica napus L. were exposed to simulated rain from emergence to full expansion at seven pHs between 5.6 and 2.6, applied at 2 mm h−1 in amounts and at intervals representative of ambient rain in southwestern England. Leaf expansion was unaffected by rain pH greater than 30 in V. faba, and pH 2–6 in the other species. Macroscopic foliar injury was induced at pH 3.4 in non‐wettable leaves of P. sativum and B. napus which had relatively large deposits of crystalline epicuticular wax, and at pH 3.0 in wettable leaves of P. vulgaris and V. faba which had small deposits of amorphous wax. Foliar injury was greatest in species with crystalline wax. Wax production was affected by simulated acid rain in all species and was often accompanied by changes in wax composition. Wax quantity was reduced on leaves of P. vulgaris exposed to rain at pH 4.6, while wax on leaves of P. sativum and B. napus had increased numbers of smaller plates and tubes, respectively, per unit area at pH 4.6. Leaves of B. napus, stripped of crystalline epicuticular wax at about 20% full expansion, regenerated less wax at pH 3.4 than at pH 5.6. The thickness of the cuticular membranes in leaves of P. vulgaris, V faba and P. sativum exposed to simulated acid rain at pH 4.2 decreased by 28 to 35 % compared with those exposed to pH 5.6 rain. Membrane ultrastructure was also altered in leaves of P. vulgaris. Taken together, these changes could have important consequences for leaf wettability, rainfall retention, foliar uptake of chemicals and host‐parasite interactions.
SOME PHYSIOLOGICAL RESPONSES OF THEOBROMA CACAO VAR. CATONGO SEEDLINGS TO AIR HUMIDITY
Authors: GOMES A. R. SENA , KOZLOWSKI T. T. , REICH P. B.
Published: April 2006

Summary

The stomata of three‐month‐old seedlings of Theobroma cacao L. var. Catongo were more open in high relative humidity (RH) (76 to 89%) than in low relative humidity (39 to 62 %). In both regimes, stomata closed gradually during the day, with the rate of closure accelerating in the late afternoon. Transpiration rate (TR) was correspondingly high early in the day and low late in the day. Average leaf diffusive resistance (r1) was 26% lower at the high RH. Nonetheless, TR was generally higher for plants in the low RH, because of the much greater vapour pressure gradient between the leaf and air. Abruptly lowering the RH at noon rapidly increased (r1) and increasing RH decreased r1, In another experiment conducted in constant high or low RH regimes, r1 was lower, the rate of net photosynthesis (Pn) was higher, leaf water potential (Φ) was lower (more negative), and TR was lower in the high RH regime. Water‐use efficiency (WUE) was higher in high than in low RH. The relationships between Pn and r1 were identical at high and low RH. Thus, differences in TR and WUE at high vs low RH were a direct result of variations in vapour pressure deficit (VPD) between the two humidity regimes. Stomatal opening and closing reflected direct effects of humidity on guard cells rather than responses to changes in bulk leaf Φ. In addition, root to leaf hydraulic conductivity apparently was greater at low than at high RH.
EFFECTS OF EXPERIMENTAL DEFOLIATION ON A POPULATION OF PEDUNCULATE OAK (QUERCUS ROBUR L.)
Authors: HILTON G. M. , PACKHAM J. R. , WILLIS A. J.
Published: April 2006

Summary

An experiment simulating defoliation at three levels of severity was conducted on 196 young oaks in a plot at Wolverhampton.

In comparison with control plants, defoliation caused (1) earlier production of growth spurts (which are normal in undefoliated trees) and formation of more lateral branches, which were susceptible to winter frost damage; (2) production of more abundant, smaller leaves; (3) reduced diameters of main stems, from which can be calculated growth rates, varying with both defoliation treatment and growing conditions over the year, and returning to normal values as soon as defoliation ceased; (4) formation throughout the season of xylem of early wood type having a lower proportion of xylem fibres.

With light defoliation, most of these responses were scarcely apparent, but with more severe defoliation, morphological effects dominated. The most noticeable effects of total defoliation were low growth rates and effects on wood anatomy.

The results suggest that substantial natural defoliation could cause failure of regeneration, although in un shaded plots of young trees leaf loss results in retarded growth rather than death.
THE EFFECTS OF PLANT DENSITY AND SNAIL GRAZING ON FEMALE AND MALE SPINACH PLANTS
Authors: MILLER JOY , DOUST JON LOVETT
Published: April 2006

Summary

Male and female plants of the dioecious herb, Spinacia oleracea L. cv. Viking were grown in pots of five, 10 and 20 plants. Pots at each density were also exposed to grazing by the landsnail, Helix aspersa Muller (Helicidae; Gastropoda). Leaf longevity and rates of production for each of 13 leaf cohorts were determined for grazed and ungrazed female and male plants at each density. Dates of initiation of seed set and anthesis were recorded. At harvest, plant height, total dry weight and dry weights of leaves and stem, and of fruits and male reproductive organs were recorded. There were significant differences between females and males in time to anthesis, number of leaves per plant, leaf birth rate and reproductive effort. Females flowered and senesced later than males. Density had a significant effect on total number of leaves, leaf birth rate and leaf longevity. The only significant effect of snail grazing was a reduction in leaf longevity, particularly at the highest density. This corroborates recent suggestions that grazing has more effect on plants already exposed to relatively high levels of other pressures.
GENETIC DIFFERENTIATION IN TEMPERATURE‐ENFORCED SEED DORMANCY AMONG GOLF COURSE POPULATIONS OF POA ANNUA L.
Authors: WU LIN , TILL‐BOTTRAUD IRENE , TORRES ARMANDO
Published: April 2006

Summary

Seed germinability at high temperature (25 °C) was found to differ among golf course populations of Poa annua L. located along a gradient of different intensities of turf irrigation and mowing practices. A seed germination index was calculated to express the effect of temperature on seed germination. The seed germination indices of the less managed populations from the golf roughs were uniformly low and less than 30%, with a mean index of 5%. Conversely, the germination indices of the golf green populations were high. Most seed families of the golf green populations had a germination index higher than 60%. A wide range of seed germination indices was found in seed families of the fairway populations, ranging from 10 to 90% with a mean index of 49%, and with a bimodal distribution. The results of this study indicate that rapid genetic differentiation in temperature‐enforced seed dormancy among populations of Poa annua had taken place at the micro‐ecological level.
REGULATION OF RESERVE CARBOHYDRATE METABOLISM IN MESEMBRYANTHEMUM CRYSTALLINUM EXHIBITING C3 AND CAM PHOTOSYNTHESIS
Authors: KEILLER D. R. , PAUL M. J. , COCKBURN W.
Published: April 2006

Summary

Differences in carbohydrate metabolism between the C3 and CAM forms of Mesembryanthemum crystallinum L. were demonstrated and studied. The CAM form accumulated less starch (defined as boiling water‐insoluble polyglucan) than the C3 form at high irradiances, but at limiting light diverted a greater proportion of photosynthate to starch. Starch accumulation was more sensitive to the effects of exogenous inorganic phosphate in the C3 form than in the CAM form.

Following induction of CAM by salt treatment, the CAM form ceased to accumulate glucose and fructose and commenced accumulating pinitol. Pinitol is not involved directly in CAM but may act as a compatible osmoregulatory solute.

Concentrations of fructose 2,6‐bisphosphate in the C3 and CAM forms were similar, but the cytosolic fructose 1,6‐bisphophatase extracted from the two forms was markedly different in sensitivity to this effector. The two enzymes also differed both in their sensitivity to inorganic phosphate and in their affinity for fructose 1,6‐bisphosphate.

The concentrations of key intermediates of carbohydrate metabolism, fructose and glucose 6‐phosphate and fructose 1,6‐bisphosphate were measured in the C3 and CAM forms. Concentrations of fructose 1,6‐bisphosphate were higher in the CAM form, whereas those of glucose and fructose 6‐phosphate were higher in the C3 form.

The differences observed are discussed in relation to the regulation of storage carbohydrate metabolism in the two forms. A partial explanation is offered for the differences in the characteristics of starch accumulation between the C3 and CAM forms through the influence of the effector fructose 2,6‐bisphosphate on the enzyme fructose 1,6‐bisphosphatase.
SEASONAL AND DIURNAL CHANGES IN ABSCISIC ACID AND WATER RELATIONS OF APRICOT LEAVES (PRUNUS ARMENIACA L.)
Authors: LOVEYS B. R. , ROBINSON S. P. , DOWNTON W. J. S.
Published: April 2006

Summary

Seasonal and diurnal changes in leaf water relations, stomatal behaviour and abscisic acid were studied in apricot (Prunus armeniaca L.) trees growing in Adelaide, Australia. Diurnal changes in stomatal conductance and foliar abscisic acid (ABA) were small and the ABA content of expressed xylem sap was low (0·3 to 0·9 × 10−4 mol m−3). This concentration of ABA was too low to influence stomatal conductance, although diurnal changes and some seasonal changes in leaf ABA could be accounted for by uptake from the xylem. Water potential fell throughout the growing season but high values of turgor were maintained by a corresponding fall in leaf osmotic potential. The fall in leaf osmotic potential was partly accounted for by a decrease in relative water content but measurements of osmotic potential at full turgor showed that there was a net accumulation of solute between December and March. Sorbitol was the solute chiefly responsible for this increase.

The ability of apricot leaves to synthesize ABA in response to zero turgor was greatly reduced between November and March, although this ability was partly regained in April. ABA appears to be relatively unimportant in the control of stomatal conductance in apricot.
WATER RELATIONS OF SOME NATIVE AND EXOTIC SHRUBS OF NEW ZEALAND
Authors: KISSEL RUTH M. , BASTOW WILSON J. , BANNISTER PETER , MARK ALAN F.
Published: April 2006

Summary

The water relations of three native and four exotic shrub species occurring in semi‐arid Central Otago, New Zealand were examined. Water potentials at midday were low in the native Kunzea ericoides, while those in the exotic Lupinus arboreus remained high, but there were no other obvious distinctions between the field water potentials of the native and exotic species. An examination of the relation between water potential and water content, however, showed a low potential at full turgor in the native Coprosma propinqua, while the exotic species Rosa rubiginosa and L. arboreus both showed large changes in water potential for relatively small changes in water content after turgor had been lost. The exotics R. rubiginosa and Thymus vulgaris showed a rapid loss of water content in drying conditions; the exotic ‘broom’Cytisus scoparius and the native ‘broom’Carmichaelia compacta showed the lowest rates. It is concluded that there is no overall difference between the mechanism of adaptation of the native and exotic species; the exotic species that invaded are those that were pre‐adapted to the conditions.
THE EFFECT OF LIGHT ON THE RELATIONSHIP BETWEEN APHIS FABAE SCOP. AND ITS HOST PLANT, VICIA FABA L.
Authors: GARSED S. G. , GALLEY D. J. , MUELLER P. W.
Published: April 2006

Summary

Plants of Vicia faba were grown in pots at photosynthetic photon flux densities (PPFD) of 143, 315 or 906 μmol m−1 for 8, 13 or 18 d. The effects of the dry matter loss caused by the feeding of Aphis fabae, or by removal of the cotyledons, were measured. Differences in dry weight between infested and control plants were positively correlated with the dry matter ingested, and increased with PPFD and time. Dry weights of aphid colonies increased non‐linearly, but the honeydew produced per unit weight of aphid linearly, with PPFD. Aphid production/ consumption (P/C) ratios had a significant inverse linear relationship to log PPFD (r= 098). Net assimilation rates (NAR) calculated from the dry weights of the infested plants alone were significantly lower than in controls, but when calculated with the ingested dry matter added to the plant weight were little different from controls. No stimulations of NAR were found. Dry weights of all plant components, leaf area and specific leaf area were reduced by low light, removal of the cotyledons and by infestation. The last increased leaf area ratio (LAR) at the two later harvests but, otherwise, the treatments had only minor effects on the partitioning of dry matter in the plants.
DEVELOPMENT OF SYMPTOMS OF BROWN RUST OF BARLEY IN RELATION TO THE DISTRIBUTION OF FUNGAL MYCELIUM, STARCH ACCUMULATION AND LOCALIZED CHANGES IN THE CONCENTRATION OF CHLOROPHYLL
Authors: SCHOLES J. D. , FARRAR J. F.
Published: April 2006

Summary

The development of symptoms of brown rust (Puccinia hordei Otth.) of barley was examined in relation to the distribution of fungal mycelium within the leaf, the accumulation of chloroplastic starch and localized changes in the concentration of chlorophyll. Symptom development correlated exactly with the growth and distribution of mycelium within the leaf. Starch accumulated in cells associated with or directly surrounded by fungal mycelium, but rarely in cells beyond the leading edge of the colony. A photographic study of the development of a group of brown rust pustules from the flecking stage to the formation of green islands, using incident light and light transmitted through the leaf, suggested that the yellow colour of the flecks was not caused by chlorophyll breakdown, but that the major loss of chlorophyll occurred from regions between fungal pustules. This conclusion was supported by a study of the density of chlorophyll within different regions of the leaf (using the absorption of red light as a measure of chlorophyll density) and by extraction of chlorophyll from different regions of the leaf. These results are discussed in relation to the controversy surrounding the mode of formation of green islands.
FUNGAL COMMUNITIES IN ATTACHED ASH BRANCHES
Authors: BODDY LYNNE , BARDSLEY D. W. , GIBBON O. M.
Published: April 2006

Summary

Attached dead and partly living ash branches of (Fraxinus excelsior) were cut from mature trees and the three‐dimensional structure of their decay communities analyzed. The communities were characterized by three Ascomycotina, seven Basidiomycotina and two Deuteromycotina, which varied in their ecological roles. The Ascomycotina Daldinia concentrica (Bolt: Fr.) Ces. & DeNot. and Hypoxylon rubiginosum Pers.: Fr. were pioneers growing in partly living or recently dead wood but causing only slow decay. D. concentrica is very combative and was apparently often able to persist until the wood was well decayed. Peniophora limitata (Fr.) Cooke was also probably a pioneer but tended to be found mainly in middle or terminal regions, as did Peniophora quercina (Fr.) Cooke on the few occasions that the latter was found. Both P. limitata and P. quercina caused extensive white rot. Exidia thuretiana was found fruiting on the bark but was not isolated from wood and appeared to cause cambial death. An unidentified ascomycete was also found in small superficial regions associated with bark death or wounds. Peniophora lycii (Pers.) Höhn & Litsch and Peniophora violaceolivida were secondary invaders usually found in distal regions which were subject to desiccation. Radulomyces confluens (Fr.) M. P. Christ was found in two branches in similar positions to P. limitata and P. quercina; its role was not completely clear but it was probably acting as a secondary colonizer. Mycoacia uda (Fr.) Donk was isolated once from terminal regions where it was replacing other species. In addition two Deuteromycotina, Phomopsis platanoidis Died, and a sterile unidentified sp., were isolated on a number of occasions, the former apparently resulted in little decay, although the latter was often found in decayed wood.
SURVIVAL AND GROWTH OF MICROCOLONIAL ROCK FUNGI AS AFFECTED BY TEMPERATURE AND HUMIDITY
Authors: PALMER F. E. , EMERY D. R. , STEMMLER J. , STALEY J. T.
Published: April 2006

Summary

Microcolonial rock fungi occur most typically in conditions of high temperature, sparse water, and low nutrients. This study was designed to assess their growth and survival under various conditions of temperature and relative humidity. In one set of experiments, rocks containing microcolonial fungi (MCF) from Arizona and Oregon deserts were exposed in the laboratory to different temperatures and humidities, and the survival of MCF was tested by transferring them to growth medium. The survival of MCF from Oregon and Arizona rocks was similar: many survived at 70 and 80°C even after 21 d of exposure. Those from the Sonoran Desert in Arizona which were exposed to 100°C were dead after 4 d. Low humidity favoured tolerance to high temperatures. Pure cultures of MCF from these locales in the USA as well as from Australia and Egypt were tested for growth at various temperatures and relative humidities. No isolates were able to grow at water activities below 0–95. Some strains grew at temperatures as low as 4°C, but none grew at 50°C or higher. These results indicate that these MCF are not able to grow during the hot periods encountered on desert rock surfaces regardless of the humidity, but they are able to survive for extended periods under these conditions.
PHOSPHATASE ACTIVITY ASSOCIATED WITH THE ROOTS AND THE RHIZOSPHERE OF PLANTS INFECTED WITH VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: DODD J. C. , BURTON C. C. , BURNS R. G. , JEFFRIES P.
Published: April 2006

Summary

Acid phosphatase activity associated with the root and in the rhizosphere of rape (Brassica napus) L., wheat (Triticum aestivum L.) and onion (Alliutn cepa L.) plants was investigated in the presence or absence of vesicular‐arbuscular mycorrhizal fungi. The plants were inoculated singly with three different species of Glomus, or were left uninfected, and were grown in sand with little available phosphorus. Root and rhizosphere levels of phosphatase activity were higher for plants infected with G. geosporum (Nicol. & Gerd.) Gerd. & Trappe and G. mosseae (Nicol & Gerd.) Gerd. & Trappe compared with control plants. Infection with G. monosporum Gerd. & Trappe did not result in a similar increase in phosphatase activity but significant increases in plant growth nevertheless occurred. Further experiments, using wheat only, showed that increases in phosphatase activity induced by infection by G. geosporum or G. mosseae became apparent between 25 and 51 d after sowing.
SPATIAL VARIATION IN INOCULUM POTENTIAL OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI CAUSED BY FORMATION OF GOPHER MOUNDS
Authors: KOIDE R. T. , MOONEY H. A.
Published: April 2006

Summary

Two sites in California, on serpentine soil bearing annual grassland, were studied. Spatial (horizontal and vertical) variation in inoculum potential of vesicular‐arbuscular mycorrhizal fungi in soils was measured by a bioassay. Unvegetated gopher mounds had significantly lower inoculum potentials than did undisturbed soils. The decreased inoculum potential in gopher mounds is attributed to the reduced amount of inoculum in subsurface soil brought to the surface during formation of mounds. A difference in inoculum potential between two distinct types of vegetation (grass‐or forb‐dominated) was also found.
EFFECTS OF ARTIFICIAL ACID PRECIPITATION ON THE MYCORRHIZAS OF SCOTS PINE SEEDLINGS
Authors: DIGHTON J. , SKEFFINGTON R. A.
Published: April 2006

Summary

Roots were examined from three‐year‐old Scots pine seedlings (Pinus sylvestris L.) growing on a humo‐ferric podzol in monolith soil lysimeters which had received simulated acid rain at pH 3 or non‐acidified rain. This is about 30 times the rate of wet H+ deposition at the site from which the lysimeters were taken. Root biomass was similar between treatments, but acid‐treated root systems showed significantly reduced fine root branching compared to the controls. The reduced branching of acid‐treated root systems was attributed to a significant reduction in the occurrence of two corralloid mycorrhizal morphs. The coralloid mycorrhizas were characterized by profuse extramatrical hyphal development, the growth of which was retarded by soil conditions in the acid‐treated lysimeters. Soil solution measurements showed the major effects of the acid treatment to be increases in concentrations of H+, Ca2+, A1 and SO42−. It seems likely that an increase in Al and reduction of pH had affected the growth of these mycorrhizas. This may have nutritional consequences for trees on acidic soil.
A MINI‐MONOLITH CUTTER FOR ABSOLUTE POLLEN ANALYSIS AND FINE SECTIONING OF PEATS AND SEDIMENTS
Authors: CLOUTMAN E.W.
Published: April 2006

Summary

The construction and operation of a mini‐monolith cutter is presented. The apparatus will allow the extraction of accurate volumes of peats and sediments for absolute pollen techniques, or cut thin sections for fine resolution analysis. The design ensures a minimum amount of compression or contamination. The overall error of the machine is 4·6%.
Structural and ultrastructural disorders in cadmium‐treated bush bean plants (Phaseolus vulgaris L.)
Authors: BARCELÓ J. , VÁZQUEZ M. D. , POSCHENRIEDER Ch.
Published: April 2006

summary

The effect of a growth reducing cadmium concentration (5 μg ml−1) on the structure and ultrastructure of leaves, stomata and plastids of bush bean plants (Phaseolus vulgaris L. cv. Contender) grown on perlite was studied using light, transmission electron and scanning electron microscopy. The structural and ultrastructural alterations observed were not directly related to the average Cd content of the whole organs. In roots, where the highest Cd concentration was found, plastid ultrastructure was hardly affected, while in the upper parts of the plant the chloroplasts showed severe alterations. Disruption of chlorophyll synthesis and plastid ultrastructure was greater in young trifoliate leaves than in primary leaves. The effects of Cd toxicity on the structure and ultrastructure and their physiological implications are discussed in relation to Cd uptake.
Iron‐deficiency specifically limits nodule development in peanut inoculated with Bradyrhizobium sp.
Authors: O'HARA G. W. , DILWORTH M. J. , BOONKERD N. , PARKPIAN P.
Published: April 2006

summary

Severely iron‐deficient peanuts (Arachis hypogaaea L.) grown on calcareous soils in central Thailand failed to nodulate until given foliar iron applications. Glasshouse experiments were conducted on two cultivars (Tainan 9 and Robut 33–1) to identify which stage of the nodule symbiosis was most sensitive to iron‐deficiency.

Iron‐deficiency did not limit growth of soil or rhizosphere populations of peanut liradyrhizobium. Similar numbers of root nodule initials formed in the roots of both control and iron‐sprayed plants, showing that iron‐deficiency did not directly affect root infection and nodule initiation. Plants sprayed with iron produced greater numbers of excisable nodules and carried a greater nodule mass than untreated plants. Five days after iron application, nodules on sprayed plants of CV. Tainan 9 contained 200–fold higher bacteroid numbers per unit weight and 14–fold higher concentrations of leghaemoglobain. The onset of nitrogenase activity was also delayed by iron deficiency in both cultivars. Tainan 9 appeared more sensitive to iron‐deficiency than Robut 33‐1 in terms of nodule mass produced, but both cultivars showed the same effect of iron‐deficiency on nitrogenase activity per plant.

It is concluded that the failure of the infecting rhizobia to obtain adequate amounts of iron from the plant results in arrested nodule development and a failure of nitrogen fixation.
Growth and phosphorus inflows of Trifolium repens L. with a range of indigenous vesicular‐arbuscular mycorrhizal infection levels under field conditions
Authors: McGonigle T. P. , Fitter A. H.
Published: April 2006

summary

Since vesicular‐arbuscular mycorrhizas (VAM) are believed to play a fundamental role in phosphorus (P) uptake for many plant species, an experiment was performed to test the hypothesis that rates of P uptake per unit root length (P inflow) should be proportional to the extent of infection. Plants of Trifolium repens L. were grown in pots containing different proportions of sterile and non‐sterile soil in radially arranged rooting compartments and transplanted with a consequent range of mycorrhizal infection into the field at a hay meadow of moderate P fertility. Even though plant growth in the field was exponential, plants with greater proportions of their root systems infected did not have higher P inflows or dry matter production. For much of the experiment P inflows were below the levels at which it would be necessary to invoke mycorrhizally assisted uptake. It is suggested that for Trifolium repens, even while the plant is growing actively in the field, VAM do not always function mutualistically.
Effects of sulphur dioxide and acid rain alone or in combination on growth and yield of broad bean plants
Authors: ADAROS G. , WEIGEL H. J. , JÄUGER H.‐J.
Published: April 2006

summary

Potted plants of Vicia faba L. cv. ‘Con Amore', grown either in soil or quartz gravel were exposed in eight open‐top chambers to two levels of SO2 (charcoal‐filtered air and charcoal‐filtered air enriched with SO2) and two artificial rain treatments (pH 5.6 and pH 3.0/4.0), alone or in combination. SO2 was dosed continuously (55–90 μg m−3 for 56 days) and rain solutions were applied on three days each week for 8–9 min each day resulting in 4.45 mm rainfall per week and a total H+ deposition of 0.15 kg ha−1 and a total water deposition of 37 mm. Variables measured at different stages of plant development included fresh and dry weight of whole plants, leaves, stalks, fruits and roots; number of leaves, stalks, blossoms, pods and seeds; leaf area; plant height; sulphur content. While the sulphur content of the leaves of all plants significantly increased due to the SO2 fumigation, the effect on the growth of young plants depended on the root medium; plants grown in soil were mainly influenced in a positive manner (increase of fresh and dry weight; number of leaves, blossoms and pods), whereas plants grown in quartz gravel were negatively affected. At maturity these tendencies were only observed in marketable products like seeds (plants grown in soil) or pods (plants grown in quartz gravel). The acid‐rain treatment resulted in a decrease of total fresh and dry weight and fruit production of plants grown in soil, while, particularly at the beginning of the rain treatments, dry weight of whole plants and leaves as well as the number of leaves of plants grown in quartz gravel decreased. Some interactions between the two pollutants, which were mostly negative in nature, were also observed.
Phenols and bud dormancy I. Variations in total phenols and phenylalanine ammonia lyase activity in dormant buds of Fagus sylvatica L.
Authors: CODIGNOLA ARNALDO , MAFFEI MASSIMO , FIESCHI MAURIZIO
Published: April 2006

summary

Quantitative analyses of the total phenols (glucosides and aglycones and phenylalanine ammonia lyase (PAL) activity were determined separately in bud scales and the leaf primordia of dormant buds (apical, subapical and basal) of Fagus sylvatica L, until bud burst.

In all the leaf primordia, the phenol and glucoside contents did not change substantially from November to March. From dormancy break to bud burst, phenols and glucosides accumulated in the subapical and basal buds. PAL activity, after a drop at the inception of dormancy, followed a trend similar to that of the total phenol content during dormancy. After dormancy break, the PAL activity of the apical bud was higher than that of the subapical and basal buds. During this period several differences were observed between PAL activity and phenolic content along the branch. No aglyeortes were detected during dormancy (except small quantities in the subapical buds). However, small amounts were detected in all three bud types after dormancy break.

On the other hand, in the bud scales during the winter total phenols per bud, glucosides and PAL activity values (except in the apical buds) show a slight decrease. After dormancy break, PAL activity disappeared and aglycone levels increased slightly. At the same time it was not possible to determine any clear net variation in the levels of phenols and glucosides.

It seems, therefore, that the inception and maintenance of dormancy in F. sylvatica buds buds cannot be correlated to the total phenolic pool and PAL activity in leaf primordia, while some kind of correlation seems to occur in the case of bud scales.
Pollen wall development in Olea europaea L.
Authors: FERNÁNDEZ M. C. , RODRÍGUEZ‐GARCÍA M. I.
Published: April 2006

summary

The ontogeny of the olive pollen grain (Olea europaea L.) wall is related to the structural changes which take place during the various stages of pollen grain development. The tetrad stage sees the deposition of the primexine, with probacules forming by deposition of material adjacent to the plasmalemma. Endexine development commences subsequently. The bacules and foot‐layer are formed mainly from dense material found within the special callose wall. By the young free microspore stage the definitive structure of the exine has been determined. Throughout development microchannel‐like structures are present in both bacules and the foot‐layer. An electron‐lucent zone appears between the plasmalemma and the endexine. This is the future site of intine deposition which occurs during the vacuolated microspore stage before postmeiotic mitosis. A fibrillar layer lines the arcade spaces of the exine. Between this stratum and the exine lies a thin layer of polysaccharides probably representing the remains of the primexine or glycocalyx. In the mature pollen grain the exine arcades contain numerous lipid drops (or pollenkitt), originating from the degenerating tapetum.
Dinoflagellates, their cysts and Quaternary stratigraphy
Authors: HARLAND REX
Published: April 2006

summary

Dinoflagellates are described, with particular emphasis on their feeding strategies and role within the phytoplankton. The potential ecological value of the fossilizable hypnozygotic cyst in reconstructing the climate throughout the Quaternary marine record is noted. Dinoflagellate cysts can be used to detect changing climates in marine Quaternary sediment sequences as pollen is used for continental Strata. The unique capacity of dinoflagellate cysts in effecting correlations from the deep ocean to the inner shelf is of potential importance.
Acquisition of nitrogen by the shoots of land plants: its occurrence and implications for acid‐base regulation
Authors: RAVEN J. A.
Published: April 2006

summary

The typical N source for terrestial vascular plants is the soil in which they are rooted. N exchange between the aerial shoot and its environment, as gaseous, dissolved or particulate N, can involve either net loss or net gain of N by the plant. Net gain of N by the plant shoot at the expense of its aerial environment can be significant, under natural or agricultural conditions, for all three forms of aerial N (NH3,N2,NO3), Gaseous N gain can be substantial, as NH3, for plants growing on soils receiving large inputs of animal excreta and faeces. Soluble N uptake by shoots is the major N source for ‘atmospheric’ epiphytes. Particulate N supply to shoots is a major N source for carnivorous plants. Experimentally, several plants which normally grow with N supply mainly via their roots can be grown with a predominant, or sole, supply via their shoots.

Plant growth with CO2, as C source, SO42−as S source and H2PO4, as P source generates excess OH (∼ 0.78 OH−/N assimilated) in the synthesis of core metabolites when the N source is NO3−supplied to roots or shoots. All other N sources (except dicarboxylic amino‐acids) yield excess H+during synthesis of core metabolites. NH4+(in solution) supplied to roots or shoots yields some 1.22 H+/N assimilated, while NH3, N2or NO2supplied to shoots as gases, dissolved urea supplied to shoots or roots, and animal protein supplied to shoots of carnivorous plants, yields some 0.22 H+/N assimilated.

These biochemically caused acid‐base perturbations may be exacerbated (NO2) or partially or, occasionally, completely offset (NH3) by effects related to solution and dissociation of the gas in growing shoots.

Assimilation of the shoot‐acquired N in the shoots leads to somewhat different constraints on acid‐base homoiostasis relative to those found with assimilation of root‐acquired N. The shoot cannot generally excrete excess H+or OH−to its environment (as is so for root‐assimilation of N), nor can it dispose of H+biochemically without co‐operation of root metabolism and root–shoot and root‐rhizosphere transport processes. Excess OH−from shoot‐acquired and shoot‐assimilated NO3−can, by contrast, be disposed of biochemically after the fashion of root‐acquired, shoot‐assimilated NO3−. Tentative conclusions as to the disposal of excess H+generated in shoot acquisition and assimilation of N‐sources other than NO3−and NO2−are different for rhizophytes and for haptophytes. Rhizophytes probably carry out a net synthesis of organic acid in the roots, with subsequent cation‐H+exchange at the root plasmalemma, transport of cation salt of the organic acid to the shoot in the xylem, and metabolism of the organic acid anion in the shoot to yield OH−. Haptophytes probably have an excess of liquid water supply over their needs for growth and transpiration due to the very low N concentration in this water; they thus have the potential for H+(as strong acid) excretion to the excess surface water which is lost, at least in part, as liquid water.
Dry matter, phosphorus and nitrogen partitioning in three Eucalyptus species grown under a nutrient deficit
Authors: MULLIGAN D. R. , SANDS R.
Published: April 2006

summary

Seedlings of Eucalyptus grandis Hill ex Maiden, E. gummefera (Sol. ex Gaertner) Hochr. and two provenances of E. pilularis Smith [Coffs Harbour (CH) and Myall Lakes (ML)] were grown for 21 weeks in sand culture under nutrient‐limiting conditions. Over this period the seedlots originating in the more phosphorus‐deficient sites, E. gummifera and E. pilularis (ML), produced a larger mass and extracted 2–5 times more phosphorus (but 60–70% less nitrogen) from the sand than did the representatives from fertile habitats, E. grandis and E. pilularis (CH). Large seed reserves of phosphorus were a contributing factor to the success of E. gummifera and in both species adapted to low phosphorus, the early establishment of a larger root system conferred an advantage.

E. grandis and E. pilularis (CH) had lower tissue phosphorus concentrations (approx. 160 μg g−1) and hence by definition would be considered more efficient utilizers of phosphorus. However, this ‘efficiency’ was the result of an internal partitioning strategy that permitted growth to proceed unchecked and phosphorus dilution to continue. Under the severe limitations to phosphorus supply of this experiment, the more effective strategy was that adopted by E. pilularis (ML) and E. gummifera. These species developed a storage or buffer strategy which would allow longer‐term survival by ensuring critically low phosphorus concentrations were not reached. The difficulties of the less tolerant E. grandis and E. pilularis (CH) were compounded by a disproportionate amount of nitrogen uptake which created an ion imbalance in the tissues.
Characterization of sucrose: sucrose fructosyltransferase from crested wheatgrass*
Authors: CHATTERTON N. J. , HARRISON P. A. , THORNLEY W. R. , BENNETT J. H.
Published: April 2006

summary

Biosynthesis of the trisaccharide precursor of fructan occurs through the action of sucrose: sucrose fructosyltransferase (SST). This study defines the optimal conditions for in vitro SST and invertase activities from a crested wheatgrass hybrid developed from a cross between Agropyron cristatum (L.) Gaertn. ×A. desertorum (Fisch. ex Link) Schult. Enzyme extracts were prepared from field‐grown plants. The optimum pH for SST and invertase activities were 5.0 and 4.5, respectively. The effective Km for SST (100 mol m−3) is much larger than invertase (15 mol m−3). Sodium pyrophosphate differentially reduced invertase activity without affecting SST activity. Conversely, CaCl2 and CsCl reduced SST activity without altering invertase activity. Optimal in vitro reaction temperatures for SST and invertase were 30 and 50°C, respectively. SST activity was 30% of maximum at temperatures as cool as 5°C. In contrast, invertase activity was only 10% of maximum at 15 °C. The responses of SST and invertase to changes in pH, temperature, and additives provide additional evidence that the two activities are the result of two distinct enzymes. It is hypothesized that cool‐season grasses such as crested wheatgrass have the ability to fix carbon photosynthetically at lower temperatures than starch‐accumulating species because of their capacity to synthesize fructans.
Blue light effects on the growth ofLolium multiflorumLam. leaves under natural radiation
Authors: CASAL J. J. , ALVAREZ M. A.
Published: April 2006

summary

Plants ofLolium multiflorumLam. were grown under natural radiation supplemented with blue light during the photoperiod. The blue light treatment reduced final length of the leaf sheath but did not modify lamina length compared with control non‐irradiated plants. Leaf sheath length was linearly and inversely related to the log‐fluence rate of supplementary blue light. The rate of leaf elongation was unaffected until the target leaf reached 35–70% of its final length. Red light had no effect at fluence rates that were inhibitory in the case of blue light and promoted leaf growth at high fluence rates. Plants grown under natural canopies also responded to supplementary blue light. Fully de‐etiolatedL. multiflorumplants respond to different fluence rates of blue light within a range found in natural canopies. The possible photoreceptor and ecological implications are discussed.
Bicarbonate utilization by the marine diatomPhaeodactylum tricornutumBohlin
Authors: DIXON G. K. , MERRETT M. J.
Published: April 2006

summary

The measurement of inorganic carbon dependent photosynthetic oxygen evolution in air‐grown cells ofPhaeodactylum tricornulumBohlin has shown that sodium ions increased the affinity of the cells for bicarbonate. Lithium ions (50 mmol 1−1) inhibited bicarbonate‐dependent photosynthetic oxygen evolution but this inhibition was overcome at saturating bicarbonate concentrations. Bicarbonate‐dependent photosynthetic oxygen evolution was also inhibited by lithium ions in cells ofPhaeodactylumgrown in high CO2, (5 % v/v). Acetazolamide and ethoxyzolamide were potent inhibitors of carbonic anhydrase in cell extracts. At pH 8.0 the K0.5(the concentration of inorganic carbon required for 50% or the maximal rate of photosynthetic oxygen evolution) was increased from 53 to 542 μmol I−1in the presence of ethoxyzolamide whereas in the presence of acetazolamide the K0.5.(CO2) increased to 130 μmol 1−1. In the presence of ethoxyzolamide the internal dissolved inorganic carbon (DIC) concentration was increased but this increase was prevented in the presence of lithium ions when bicarbonate transport into the cell is inhibited. These results are in agreement with bicarbonate transport across the plasmalemma and intracellular carbonic anhydrase increasing the steady‐state flux of CO2from inside the plasmalemma to ribulose‐1,5‐bisphosphate carboxylase‐oxygenase by facilitating the interconversion of HCO−3and CO2.