bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURAL AND PHYSIOLOGICAL STUDIES ON THE PARASITIC RED ALGA HOLMSELLA
Authors: EVANS L. V. , CALLOW J. A. , CALLOW MAUREEN E.
Published: May 2006

A study has been made of the structural and physiological relationship between the autotrophic red alga, Gracilaria verrucosa, and the parasitic, chloroplast‐free, red alga, Holmsella pachyderma. By means of 14C‐labelling experiments, the major product of photosynthesis in the Gracilaria was found to be the alcohol glycoside, floridoside. Chromatography and autoradiography showed that 14C was transferred to Holmsella and accumulated there as floridoside, mannitol and starch. This transfer probably occurred through endophytic filaments which arise from the base of the parasite and penetrate between the cells of the Gracilaria.
NITROGEN FIXATION BY LICHENS IN SCOTLAND
Authors: HITCH C. J. B. , STEWART W. D. P.
Published: May 2006

Of thirty‐six species of metabolically active lichens taken mainly from Scottish coastal habitats, eight showed a capacity to reduce acetylene to ethylene. These were species of Collema Web., Lichina C. Ag., Peltigera Willd. and Placopsis Nyl. and all contained a blue‐green alga as the primary or secondary phycobiont. Acetylene reduction rates were sometimes high in the field and showed marked diurnal and seasonal variations. Nitrogenase activity was higher in vegetative than in fruiting thalli of Peltigera rufescens, and in P. canina was higher nearer the apices of the thalli than in older parts. Of the environmental factors affecting fixation, desiccation was the most important, temperature was less important and the lichens, while requiring light, could continue to fix nitrogen in the dark for up to 18 hours (Lichina confinis) and 26 hours (Peltigera rufescens). The average percentage nitrogen contents of nitrogen‐fixing lichens (2·20%) was significantly higher than the non‐nitrogen‐fixing lichens (0·83%). The maximum and mean rates of nitrogen fixation by P. rufescens were 38·1 and 4·1 μg N (mg N)‐1 day‐1 respectively. The corresponding values for Lichina confinis were 29·4 and 0·4.
LICHEN PHYSIOLOGY XIII. EFFECTS OF REWETTING DRY LICHENS
Authors: SMITH D. C. , Molesworth SUSAN
Published: May 2006

Two distinct phenomena occur when water is added to air‐dry lichens: (1) an immediate non‐metabolic release of a substantial volume of gas containing 75–80% CO2; and (2) a rapid rise in respiration to rates well above control values. This excess respiration (‘resaturation respiration’) persisted for about 9 hours in Peltigera polydactyla and about 2 in Xanthoria aureola and was, unlike basal respiration, azide‐ and cyanide‐sensitive. When the mannitol content of Peltigera discs had been doubled by feeding glucose before drying, the initial rate of subsequent resaturation respiration was correspondingly much higher. Cycles of wetting and drying caused progressive reductions both in mannitol content and resaturation respiration. In Peltigera, resaturation respiration occurred if the water content of discs had fallen below approximately 40% of maximum. Xanthoria aureola, which grows in drier habitats than Peltigera polydactyla, was much more tolerant of cycles of wetting and drying and showed much less intense resaturation respiration.
POST‐FERTILIZATION DEVELOPMENT IN INDOTRISTICHA RAMOSISSIMA (WIGHT) VAN ROYEN
Authors: MUKKADA ANTONY J. , CHOPRA R. N.
Published: May 2006

In Indotristicha ramosissima (Wight) van Royen there is normal syngamy. However, the polar nucleus is not fertilized so that a primary endosperm nucleus is not formed. Consequently, there is no endosperm in the seed. The post‐fertilization dissolution of the nucellar cells below the embryo sac results in the formation of a pseudo‐embryo sac into which the growing pro‐embryo penetrates. The first division of the zygote is transverse and the development of the embryo conforms to the Solanad type. The embryo possesses a large, coenocytic haustorial cell which disorganizes by the time the embryo is fully differentiated. The integuments and the ovary wall are rich in starch deposits which disappear during maturation. In the mature seed, the outermost layer of the outer integument becomes mucilaginous. The cells of the inner epidermis of the ovary wall become binucleate and occasionally multinucleate.
CALCULATION OF THE PRIMARY TRAJECTORIES OF PLUMED SEEDS IN STEADY WINDS WITH VARIABLE CONVECTION
Authors: BURROWS F. M.
Published: May 2006

The aerial paths described by plumed seeds shed from motionless plants and moving in steady horizontal winds with vertical convection currents are discussed and formulae established for calculating them both roughly and fairly accurately. Most of the formulae are simple and of practical use to botanists. Example calculations show the effect of release height, convection velocity, and the terminal velocity of fall of the seed in still air, and the various trajectory shapes concocted can be used to account for seed behaviour as observed and reported in the literature. It is also shown how, under certain conditions, some approximate calculations can be very much in error.
POLLEN ANALYSIS AND RADIOCARBON DATING OF A PEAT ON SLIEVE GALLION, CO. TYRONE, N. IRELAND
Authors: PILCHER J. R.
Published: May 2006

A radiocarbon dated pollen diagram is presented from 430 m altitude on Slieve Gallion, Co. Tyrone, N. Ireland. Deposits of reedswamp peat overlain by blanket peat cover the period c. 8000 B.C.* to the present. Total tree‐pollen remains mostly below 60% of total pollen throughout the Post‐glacial indicating more open conditions than are found in the lowlands. Lack of herb pollen suggests areas of bare rock on the mountain top before c. 7650 B.C. The early Post‐glacial juniper period is estimated to have lasted 300–400 years. Hazel expands rapidly at c. 7050 B.C. and oak and elm appear at c. 6800 B.C. Elm expands some 800 years before the oak. The arrival of alder is dated to c. 5000 B.C. and its expansion to about 4250 B.C. An elm decline is shown dating from just after 3000 B.C. and a decline of pine pollen at c. 2000 B.C. in common with other sites in this area.
SYSTEMATIC DISTRIBUTION OF RIBITOL IN THE FUNGI
Authors: PFYFFER GABY E. , RAST DORA M.
Published: May 2006

The polyol fractions of the fruit bodies of 12 basidiomycetes and the vegetative mycelia of more than 30 species representing all major classes of fungi were isolated, tested by gas chromatography for the presence of ribitol and found to be free of this compound – with the exception of Mortierella rammaniana, Actinomucor elegans, Mucor miehei and Zygorhynckus moelleri. Using preparative paper chromatography, ribitol was isolated from M. miehei in a yield of about 0·3 % of the mycelial dry wt and its identity confirmed by IR spectroscopy and determination of melting point. The present survey, together with the reported occurrence of ribitol in only two other species, Puccinia graminis f.sp. tritici and Candida polymorpha, shows this polyol to be a rare fungal component that appears to be distributed randomly within the Eumycetes. Clustering of ribitol within the Mucorales can, however, not be overlooked.
THE HOST‐PARASITE RELATIONSHIP BETWEEN ZIZANIA CADUCIFLORA TURCZ. AND USTILAGO ESCULENTA P. HENN. II. USTILAGO ESCULENTA IN CULTURE
Authors: CHAN YUK‐SIM , THROWER L. B.
Published: May 2006

With the exception of dikaryotization, the complete life‐cycle of Ustilago esculenta occurred on potato dextrose agar in culture. In liquid synthetic media, the maximum dry wt of sporidia was reached in 7 days at 27°C compared with 20 days for mycelium. The sporidia were hetero‐trophic for thiamine but not for biotin; the mycelium required neither vitamin. Mannitol supported the best growth of sporidia but only poor growth of mycelium; both stages grew well on fructose, glucose and sucrose. At suitable dilutions, an aqueous extract from culms of the host plant supported growth of sporidia and mycelium that was similar, or superior, to that on synthetic media. The implications of these results for the host‐parasite combination are discussed.
THE HOST‐PARASITE RELATIONSHIP BETWEEN ZIZANIA CADUCIFLORA TURCZ. AND USTILAGO ESCULENT A P. HENN. III. CARBOHYDRATE METABOLISM OF U. ESCULENTA AND THE HOST‐PARASITE COMBINATION
Authors: CHAN YUK‐SIM , THROWER L. B.
Published: May 2006

Sporogenous hyphae and teliospores of Ustilago esculenta, collected from swollen culms of Zizania caduciflora, contained mannitol as the principal carbohydrate, together with erythritol and trehalose in trace amounts. In vitro experiments with labelled sugars showed that both sporidia and mycelium of U. esculenta incorporated fructose and glucose to a similar degree, yielding mannitol as the principal endogenous carbohydrate, erythritol and five amino acids including alanine and arginine. Sucrose was the main translocated sugar in the leaf but the principal sugars in the culms were fructose and glucose. Fructans of high mol. wt were not abundant in the culms but low mol. wt fructans (including fructose) may be important in the metabolism of the culms; the content of such fructans was highest in the non‐sporulating culms. A scheme is proposed for the metabolism of carbohydrates in the formation of gau sun.
THE DEVELOPMENTAL HISTORY OF SCRAGH BOG, CO. WESTMEATH AND THE VEGETATIONAL HISTORY OF ITS HINTERLAND
Authors: O'CONNELL M.
Published: May 2006

Stratigraphical, macrofossil and pollen analytical studies on the sediments of Scragh Bog, a small fen in central Ireland, are described.

The Flandrian pollen diagram is divided into local pollen assemblage zones which in turn are related to the zones of Mitchell (1956). The Ulmus‐Quercus‐Alnus assemblage zone of the Atlantic period is proposed as a regional assemblage for base‐rich areas in Ireland as distinct from the Alnus‐Quercus‐Pinus regional assemblage of Jessen (1949). The changes associated with the Elm decline are considered in detail.

The subfossil records, which are not abundant, include Acrocladium giganteum and Sphagnum contortum from the Late‐glacial and Antitrichia curtipendula and Isothecium myosuroides, both probably from zone VIIIa.

The depositional processes in the basin and the vegetational history of the hinterland are reconstructed. The nature of Landnam and the possibility of in situ survival of the present‐day fen communities are discussed.
EFFECTS OF PHENYLACETIC ACID ON ABAXIAL AND ADAXIAL STOMATAL MOVEMENTS AND ITS INTERACTION WITH ABSCISIC ACID
Authors: PEMADASA M. A.
Published: May 2006

The effects of varying concentrations of phenylacetic acid (PAA), alone and in combination with abscisic acid (ABA), on abaxial and adaxial stomatal movements were examined on isolated epidermis of Commelina communis. Increasing PAA concentration progressively suppressed abaxial opening, while up to 5 mol m−3 PAA produced remarkably wide adaxial apertures but higher concentrations caused closure; the stomatal K.+ changed accordingly. PAA, like the K+ ionophore benzo‐18‐crown‐6, showed strong antagonistic interactions with ABA. The results are interpreted by postulating that PAA, like benzo‐18‐crown‐6, increases the membrane permeability to K+. The normal abaxial permeability allows a net K+ gain required for opening, but the PAA‐induced increase in permeability causes a net K+ loss leading to closure, because the efflux down a concentration gradient outweighs the influx coupled with proton extrusion. In contrast, the normal K+ content is much less in adaxial than in abaxial guard cells, clear evidence of an inherent restriction to K+ fluxes; this is attributed to restricted membrane permeability to K+, which PAA is postulated to alleviate progressively with increasing concentration. Thus, an increase in permeability up to a critical limit favours a net K+ gain and promotes opening, but any further increase leads to a net K+ loss and causes closure, as in abaxial guard cells. This interpretation is substantiated by both the progressive reduction of PAA‐induced closure with increasing KC1 in the medium and the close similarity of the effects of PAA and benzo‐18‐crown‐6, alone and in antagonism with ABA, on abaxial and adaxial stomata.
ABSCISIC ACID EFFECTS ON SPORE GERMINATION AND PROTONEMAL GROWTH IN THE FERN,MOHRIA CAFFRORUM
Authors: CHIA SHIH‐GEE E. , RAGHAVAN V.
Published: May 2006

The effects of abscisic acid (ABA) and its interaction with gibberellic acid (GA), indoleacetic acid (IAA) and kinetin on the germination of spores and growth of protonemata of the fern,Mohria caffrorumSw. were studied. ABA did not affect the initial divisions of the spore protoplast leading to the formation of rhizoid and protonema, but inhibited the subsequent elongation of the latter. The apparent reversal of ABA‐induced inhibition of protonemal elongation by GA appears to be due to an overall growth promotion by GA, rather than due to its interaction with ABA. On the other hand, both IAA and kinetin, which by themselves did not promote protonemal growth, reversed to some extent the inhibitory effect of ABA on the growth of the protonema.
THE INOCULATION OF WHITE CLOVER WITH MYCORRHIZAL FUNGI IN UNSTERILE HILL SOILS
Authors: RANGELEY A. , DAFT M. J. , NEWBOULD P.
Published: May 2006

The response of two cultivars of white clover (Aberystwyth S184 and New Zealand Grasslands Huia), grown under laboratory and field conditions, to inoculation with two endophytes (Glomus mosseae L1 and Glomus etunicatus) was investigated in two hill soils with various amounts of added phosphate.

In the experiment with the deep peat soil in the laboratory, inoculation with either endophyte increased infection from 2% to up to 70%, the increase being less the higher the amount of added P. Shoot growth of white clover was significantly increased (P≤ 0.05) by inoculation at the 0 and 20 kg P ha−1 level and decreased at the highest level of added P (200 kg P ha−1). Both endophytes produced similar effects. With the brown earth soil, total infection of roots with indigenous endophytes ranged from 30 to 50 % and this was significantly (P≤ 0.05) increased by inoculation only at 40 kg P ha−1. However, the introduced coarse endophytes had replaced between a quarter and a half of the predominantly fine indigenous endophyte at each level of added P. This change of endophyte was without significant effect on dry wt of shoots and roots although there was a general trend for inoculation, and with Glomus etunicatus more than with Glomus mosseae LI, to increase shoot and root dry wt. Inoculation also tended to increase the P content of shoots and roots but this was statistically significant only at 40 kg P ha−1.

In the field experiment with the deep peat soil, inoculation with Giomus mosseae L1 doubled the amount of infected root from 18 to 42% but there was no effect on shoot growth or the concentration of P. With the brown earth soil, although the amount of infection was not increased, the introduced coarse endophytes had become established in the roots but no effect on shoot growth was observed in the year of sowing. However, in the first harvest year, in the presence of 40 kg P ha−1, clover inoculated with Glomus etunicatus produced double the amount of dry shoot per hectare produced by uninoculated plants and 75% greater than that produced with Glomus mosseae L1.

These observations encourage the view that inoculation with mycorrhizal fungi of white clover for improved hill pastures might have a practical role if the responses could be made more predictable. It is concluded that further work is justified to understand the ecology of mycorrhizal fungi in hill pastures and how the symbiosis functions, to select suitable endophytes and to develop methods of inoculation appropriate for use in routine field practice.
COMPETITIVE RELATIONSHIPS BETWEEN ATRAZINE RESISTANT AND SUSCEPTIBLE POPULATIONS OF AMARANTHUS RETROFLEXUS AND A. POWELLII FROM SOUTHERN ONTARIO
Authors: WEAVER S.E. , WARWICK S. I.
Published: May 2006

The relative competitive abilities of atrazine resistant and susceptible populations of Amaranthus retroflexus and Amaranthus powellii were compared in a greenhouse experiment using a de Wit replacement series. Both inter and intraspecific differences in competitive ability were apparent when the populations were grown in two‐way combinations of varying proportions but constant overall density. Within both species, the susceptible population had a greater competitive ability with respect to biomass and seed production than the resistant population. The susceptible population of Amaranthus powellii was more competitive than either the susceptible or resistant populations of Amaranthus retroflexus. The resistant population of Amaranthus powellii was more competitive than the resistant population of Amaranthus retroflexus but appeared to have a competitive ability equal to that of the susceptible population of Amaranthus retroflexus.
ANATOMICAL VARIATION IN FIRST LEAVES OF NINE TRITUCUM GENOTYPES, AND ITS RELATIONSHIP TO PHOTOSYNTHETIC CAPACITY
Authors: JELLINGS ANITA J. , LEECH RACHEL M.
Published: May 2006

Summary

The variation in over 20 leaf characters including morphological, anatomical and cellular features have been examined in nine Triticum genotypes at three levels of ploidy. The characters included transectional leaf area, leaf width, distance between vascular bundles, volume occupied by each cell type, cell size and number, and chloroplast size and number. Analysis of these characters showed that the major components of the variation were related to the ploidy level and the genotype of the species and cultivars examined. The measured characters most strongly influenced by ploidy level were cell size, chloroplast number and leaf thickness. Genetic variation accounted for the variation in all other measured characters. The interaction of genetic variation with the major effects attributable to ploidy level creates a characteristic anatomical ‘fingerprint’ for each genotype.

The observation that photosynthetic capacity is negatively correlated with the ratio of mesophyll cell size to nuclear genome size, and with no other character, is discussed.
THE DEVELOPMENT OF ENDOMYCORRHIZAL ROOT SYSTEMS V. THE DETAILED PATTERN OF DEVELOPMENT OF INFECTION AND THE CONTROL OF INFECTION LEVEL BY HOST IN YOUNG LEEK PLANTS
Authors: BUWALDA J. G. , STRIBLEY D. P. , TINKER P. B.
Published: May 2006

Summary

Leek plants (Allium porrum L.) were grown on partly sterilized soil, in tall pots so that roots grew downwards unimpeded, with inoculum of the vesicular‐arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe placed either under the seedling or dispersed uniformly throughout the soil. The age of each individual root, and the distribution of infection in single roots were both determined in each of a series of sequential harvests.

The development of the root systems was unaffected by placement of inoculum. Formation of adventitious roots continued up to 42 d, when branching commenced. The rate of initiation of roots was approximately exponential but more accurately fitted a logistic function. The increase with time in total length of root for the root system (Lt) was approximately exponential but the length of the single roots (Ltr) increased linearly.

The total length of infection in whole root systems (Lir) also increased exponentially with time, but the rate of extension for the sum of the individual lengths of infected root (infection ‘segments’) in single roots (Ltr) was linear, with an apparent delay of approx. 5 d before infection could be observed.

The rate of increase in Lir was very similar for placed (0.53 cm d1) and dispersed (0.58 cm d1) inocula, even though the number of infection segments per root differed widely. This suggests that the host controls the rate of growth of the fungus. On this basis, and assuming each root encountered a new propagule every 4 d, it was possible to predict the lengths and numbers of infection segments in single roots.

The percentage infection in whole root systems and single roots, plotted against time, showed a delay, then a sharp rise to a final constant value. This pattern of development can be explained for single roots by simple arithmetical rules. Using these simple rules, and assuming that the rate of production of adventitious roots fitted either a logistic or exponential equation, it was possible to model the development of infection up to 42 d for a whole root system either algebraically or by numerical simulation.
PHOTOSYNTHETIC CAPACITY CHANGES IN PELTIGERA
Authors: BROWN D. , KERSHAW K. A.
Published: May 2006

Summary

The seasonal net photosynthetic response matrix to moisture, temperature and light has been examined in two populations of Peltigera rufescens (Weis) Mudd, geographically widely separated and representative of arctic and temperate climates, respectively. The arctic population shows a seasonally constant net photosynthetic rate whereas the temperate population exhibits a marked summer increase of photosynthetic capacity under high temperatures and levels of illumination. This change in capacity is shown by use of photosynthetic‐illumination curves to be due to temperature acclimation, presumably involving a seasonal enzymatic change in the Calvin cycle. Experimental induction of the summer or winter response can be achieved by storage of air‐dry thalli under an appropriate combination of ambient temperature and day length. The data are discussed both in relation to the ecology of the two contrasting populations and to seasonal changes in the photosynthetic capacity of other lichen species.
A HYPOTHESIS RELATING CRITICAL POTASSIUM CONCENTRATIONS FOR GROWTH TO THE DISTRIBUTION AND FUNCTIONS OF THIS ION IN THE PLANT CELL
Authors: LEIGH R. A. , WYN JONES R. G.
Published: May 2006

Summary

The growth and metabolism of plants in response to different concentrations of tissue K is discussed in relation to current knowledge about the distribution and functions of this ion in plant cells. In the cytoplasm, K has an important role in providing the correct ionic environment for metabolic processes. The ionic requirements of protein synthesis seem to be particularly important in determining the composition of the cytoplasm. Potassium is not replaceable in its cytoplasmic functions and the plant probably needs to maintain the cytoplasmic concentration of K in the range of 100 to 200 mM. Potassium salts in the vacuole are involved in the generation of turgor but when unavailable they can be replaced by other solutes. Salts of other cations such as Na and Mg are often a readily available alternative to K but in their absence organic solutes must be accumulated.

With these observations as a basis, a model is proposed in which, as the concentration of K in the tissue declines, the concentration in the cytoplasm is initially maintained constant, while that in the vacuole decreases. In order to maintain turgor, alternative solutes are accumulated in the vacuole as replacements for K. It is assumed that K in the vacuole can only drop to a certain minimum level and, once this is reached, any further decline of tissue K must be at the expense of that in the cytoplasm. This leads to a decrease in the rate of metabolic processes that depend on K and so to a decline in growth. The hypothesis explains the observed relationships between growth and concentrations of K in tissues, and their modification by Na and other cations.
WHY DOES PINGUICULA VULGARIS L. TRAP INSECTS?
Authors: KARLSSON P. S. , CARLSSON B.
Published: May 2006

Summary

Growth and nutrient content were studied when various nutrients were fed to the carnivorous plant Pinguicula vulgaris L. through its leaves. Agar blocks containing different combinations of three nutrient solutions [N, P and micronutrients (M), i.e. all other essential nutrients] simulating insects were supplied in a factorially designed experiment. Plants not exposed to any treatment, and plants supplied with insects, were used as controls. Only P had a significant effect on plant biomass. The root/leaf ratio increased as a result of N treatment and decreased as a result of the NPM interaction. The NPM interaction also markedly affected the N and P content of the plants. No treatment had any significant effect on the concentration or total content of micronutrients in tissues.

It is concluded that P is the most important nutrient gained by P. vulgaris through carnivory. The interactive effect of a complete nutrient solution is also important for nutrient relations.
DIURNAL CHANGES IN WATER RELATIONS AND ABSCISIC ACID IN FIELD‐GROWNVITIS VINIFERACULTIVARS
Authors: LOVEYS B. R. , DÜRING H.
Published: May 2006

Summary

Diurnal changes in endogenous abscisic acid (ABA) in the leaves, together with stomatal conductance and water relations, were studied in grape vines (Vitis viniferaL. cvs Riesling and Silvaner) growing in the field in Adelaide, South Australia.

There was an increase in ABA content of the leaves which commenced in the morning and reached a peak of approximately twice the pre‐dawn level at midday. Wilted excised leaves from the same vines accumulated ABA at a higher rate. The increase in attached leaves was sometimes unrelated to low leaf turgor. Import via the xylem may account for this increase during the early part of the day. Leaf conductance in Riesling was high in the early morning but fell as leaf ABA rose, and it is suggested that midday stomatal closure was due to ABA accumulation. Stomatal behaviour later in the day was more readily accounted for by environmental variables such as temperature and atmospheric vapour pressure deficit than by changes in ABA.

Abscisic acid did not consistently accumulate in attached leaves in response to zero turgor, even if this condition was maintained for the greater part of the day. It is suggested that loading into the phloem and transport out of the leaf may be important in controlling stress‐induced accumulation of ABA.
ENERGETIC CONSIDERATIONS OF ION TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK
Authors: RITCHIE RAYMOND J.
Published: May 2006

Summary

Thermodynamic analyses have already shown that K+and Cl−are taken up actively byEnteromorpha intestinalis(L.) Link cells and Na+is actively excluded in seawater and in low‐salinity media (25 mM Cl−). The proton motive force (pmf) has been estimated across the plasmalemma ofEnteromorpha intestinalis. The pmf is about zero in plants in seawater but in low‐salinity medium there is apparently a proton extrusion pump at the plasmalemma producing a pmf of about − 6 kj mol−1. Secondary active transport cannot be responsible for the active uptake of K+and Cl−or the active efflux of Na+by plants in seawater. It is thermodynamically possible (but unlikely) that K+is taken up by plants in low‐salinity medium by an electrogenic K+/H+coport mechanism but secondary active transport of Na+or Cl−is not thermodynamically possible. The Hodgkin‐Katz equation shows that the membrane potential ofEnteromorphain seawater is consistent with a diffusion potential but in low‐salinity medium (ACBSW, 25.5 mM Cl−) the observed membrane potential is more negative than the calculated diffusion potential in both the light and dark and an electrogenic proton extrusion pump appears to be likely in those plants.

Various estimates of the power requirements of active transport of K+in, Cl−inand Na+outhave been made and compared to the power available from respiration and photosynthesis. Na+is very far from electrochemical equilibrium but the power consumption of Na+transport is less than 0.2 mW m−2because the Na+fluxes are very low. Even though both K+and Cl−are close to electrochemical equilibrium, the active transport of these ions accounts for most of the power consumed in ion transport. The power requirements of active K+and Cl−transport are approximately equal.

In plants in seawater and low‐salinity medium photosynthesis provides about 400 mW m−2and respiration about 70 mW m−2of power which is available for the metabolism of the plant. In plants in seawater, the power dissipation necessary to maintain the observed K+, Cl−and Na+gradients is about 5 to 19 mW m−2or about 7 to 20% of the total respiratory power available in the dark. The power requirement of ion transport at low‐salinity is about 10 to 20 mW m−2and so would consume about 15 to 30% of the total power available in the dark. In the light the power requirement of ion transport is less than 5% of the total metabolic power available in both seawater and low‐salinity. The power requirements of active K+and Cl−transport are both large and it is not clear why the plant expends so much power on the active transport of Cl−. The metabolic power requirements of the active transport of K+and Cl−may account for the K+sensitivity ofEnteromorphain culture and in the field.
SOME RESPONSES OF LADINO CLOVER (TRIFOLIUM REPENS L. CV. REGAL) TO LOW CONCENTRATIONS OF SULPHUR DIOXIDE
Authors: MURRAY FRANK
Published: May 2006

Summary

Ladino clover (Trifolium repens L. cv. Regal) was exposed to mean SO2 concentrations of 215, 78 or 2.8 μg m−3* in open top fumigation hambers for up to 175 d. Exposure to 215 μg m−3 for 28 d significantly increased leaf area and number of leaves per plant, and exposure to 78 μg m−3 significantly reduced the shoot: root ratio, and increased the leaf area ratio, compared with control plants exposed to 2.8 μg m−3. Exposure to 215 or 78 μg m−3 had no significant effect on shoot or root weight, and all other effects had decreased beyond the level of statistically significant differences between treatment and control after 63 d of fumigation.

Exposure to SO2 for 175 d had no effect on leaf protein concentration but exposure to 215 or 78 μg m−3 significantly reduced the concentrations of L‐ascorbic acid and starch in leaves, and increased the sulphur concentrations in the shoot. The specific energy of leaves was not significantly changed by 78 μg m−3 but was significantly increased by exposure to 215 μg m−3 of SO2 for 28 d and significantly decreased by the same concentration after 175 d. Exposure to SO2 for 175 d had no significant effect on the specific energy of shoots. The SO2‐induced reduction in ascorbic acid concentration may suggest a mechanism for reduced freezing resistance in plants exposed to SO2.
PHYSIOLOGICAL PROCESSES IN SOYBEAN INHIBITED BY GASEOUS POLLUTANTS BUT NOT BY ACID RAIN
Authors: NORBY R. J. , RICHTER D. D. , LUXMOORE R. J.
Published: May 2006

Summary

The responses of several physiological processes and indices were studied in soybean plants [Glycine max (L.) Merr. cv. ‘Davis’] exposed to combinations of polluted air (0.1 μl l−1 SO2+ 0.05 μl l−1 O3) and simulated acid rain (pH 3.4, 4.2 and 5.0). Plants exposed to the gaseous air pollutants had lower foliar concentrations of mineral nutrients and chlorophyll. Leaf abscission was increased and photosynthesis, nitrogen fixation, and vegetative growth were inhibited by SO2+ O3. There was no evidence of adverse effects from acid rain on the physiology of this cultivar, regardless of the gaseous pollutant treatment. In the absence of fundamental physiological dysfunctions, acid rain is unlikely to reduce yield; hence, this study with ‘Davis’ soybeans supports the conclusion of those field studies that have indicated no adverse effects of acid rain on soybeans.
DICHOTOMOUS BRANCHING IN LATERAL ROOTS OF PINE: TYPES OF FORKING IN LONG AND SHORT SECONDARY ROOTS OF PINUS RADIATA D. DON.
Authors: WILSON E. R. L. , FIELD R. J.
Published: May 2006

Summary

Three classes of non‐mycorrhizal forking secondary roots on young seedlings of Pinus radiata D. Don grown in solution are described and illustrated. Roots are distinguished on the basis of their pattern and degree of forking and the extent of elongation before and after forking. Both long and short roots exhibited forking in the absence of mycorrhizal development.
THE SPREAD OF GLOMUS FASCICULATUM THROUGH ROOTS OF TRIFOLIUM SUBTERRANEUM AND LOLIUM RIGIDUM
Authors: SCHELTEMA M. A. , ABBOTT L. K. , ROBSON A. D. , DE'ATH G.
Published: May 2006

Summary

The lateral spread in a steamed lateritic podsol of Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe from localized inoculum was examined in two pasture species: Trifolium subterraneum L. (subterranean clover) and Lolium rigidum Gaud. (Wimmera ryegrass). Mycorrhizal infection was estimated 21, 28, 38 and 59 d after sowing at points 2, 4, 6, 8, 10, 14, 20 and 26 cm from the inoculum.

The proportion of root length infected by G. fasciculatum at increasing distances from the inoculum could be best described by a Gompertz curve in both plant species at all harvests. Thus the curve had an upper plateau of the maximum percentage infection close to the inoculum, an exponential decline in the spread of G. fasciculatum and a lower plateau of infection. It is suggested that the pattern of spread of G. fasciculatum through roots of subterranean clover and ryegrass is related to changes in the amount of inoculum with distance from the point of inoculation, as well as over time.

The rate of spread of the infection front was not constant. Thus it may not be appropriate to calculate mean rates of spread of mycorrhizal fungi over long time periods.
HOMOSERINE SYNTHESIS IN DARK‐GROWN AND LIGHT‐GROWN SEEDLINGS OF PISUM SATIVUM
Authors: MELCHER INGA M.
Published: May 2006

Summary

The synthesis of homoserine has been studied in pea seedlings (Pisum sativum L. cv. Rondo) supplied with l‐[U‐14C]amino acids. The results demonstrate that both labelled aspartate and glutamate produce similarly large quantities of labelled homoserine. It is suggested that, in addition to asparagine and glutamine, homoserine also has an important function as a transport metabolite.
POLYAMINES IN THE ROOTS OF TURNIP INFECTED WITH PLASMODIOPHORA BRASSICAE WOR.
Authors: WALTERS D. R. , SHUTTLETON M. A.
Published: May 2006

Summary

The concentrations of three amines (putrescine, spermidine and spermine) are much increased in ‘clubbed’ regions of roots of turnip infected by Plasmodiophora brassicae, whilst the concentrations, particularly that of putrescine, decreased in regions of infected roots not exhibiting symptoms of clubroot development. The possible involvement of these polyamines in the formation of ‘clubs’ on infected roots is discussed.
EXPERIMENTAL ECOLOGY OF DRYAS OCTOPETALA ECOTYPES: RELATIVE RESPONSE TO COMPETITORS
Authors: McGRAW JAMES B.
Published: May 2006

Summary

A competition experiment was performed to determine the relative competitive abilities of fellfield and snowbed ecotypes of Dryas octopetala L. under conditions of high nutrients, high light, and high water availability. Pots were designed to allow the effects of root competition and shoot competition to be assessed separately. The large‐leaved snowbed ecotype responded positively to shoot competition, producing larger leaves and higher biomass than in control pots (no competition). Root competition resulted in a decrease in leaf size and an increase in root: shoot ratio, but no significant effect on shoot number or biomass accumulation. In contrast, the fellfield ecotype responded to shoot competition with an increase in root:shoot ratio, with no effect on biomass or shoot numbers. However, root competition caused a reduction in plant growth. Under growth chamber conditions of high resource availability, the snowbed ecotype is the superior competitor, probably due to ecotypic differences in both root and shoot characteristics.
A CONTRAST BETWEEN OOMYCETES AND OTHER TAXA OF MYCELIAL FUNGI IN REGARD TO METACHROMATIC GRANULE FORMATION
Authors: CHILVERS G. A. , LAPEYRIE F. F. , DOUGLASS P. A.
Published: May 2006

Summary

Forty‐nine cultures of mycelial fungi, representing five different taxonomic classes and diverse ecological groupings, were screened for the presence of metachromatic granules by staining hyphae with toluidine blue. Regardless of the ecological roles of the fungi, granules were detected in all representatives of the following classes: Zygomycetes, Ascomycetes, Deuteromycetes and Basidiomycetes. When selected mycelia were starved of phosphorus during growth, they lacked granules. However, these same mycelia would subsequently form granules readily if they were incubated for several hours in a phosphate‐containing solution, which supports the belief that these met achromatic granules represent a store of polyphosphate.

No met achromatic granules could be detected in any of the fungi from the class Tomcats, which provides further evidence of the unique nature of this particular group of fungi. If their inability to form met achromatic granules is indicative of a limited capacity to store phosphorus, it could explain why no reliable examples have been discovered of Oomycete fungi forming symbiotic mycorrhizal associations with higher plants.
INFLUENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZA ON GROWTH, WATER RELATIONS, AND LEAF ORIENTATION IN LEUCAENA LEUCOCEPHALA (LAM.) DE WIT*
Authors: HUANG RUEY‐SHYANG , SMITH WILLIAM K. , YOST RUSSELL S.
Published: May 2006

Summary

Plant growth characteristics, nutrient absorption and water relations were compared for plants of Leucaena leucocephala (Larn.) de Wir that were non‐mycorthizal and those that were infected with the vesicular‐arbuscular (VA) mycorrhizal fungus Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe. Mycorrhizal plants had substantially greater shoot and root dry weight, leaf area and root length than non‐mycorrhizal plants, and alsos greater P, K, and Ca uptake. Leaf area was over five times greater and leaf conductance to water vapour diffusion was nearly twice as great for mycorrhizal plants, yet the difference between xylem pressure potential and soil water potential were considerably less in mycorrhizal plants than in non‐mycorhizal plants. Stomatal responses to the humidity deficits of the air during the day were nearly twice as great in mycorrhizal plants. Leaflet folding and orientation responses to avoide direct sunlight during the day were also much greater in non‐mycorrhizal plants. Lower leaf conductances and increased leaf folding leading to less absorption of sunlight may contribute significantly to the reduction in growth rate observed in non‐mycorrhizal plants.
ECTOMYCORRHIZA FORMATION BY GLOMUS TUBIFORME
Authors: WARCUP J. H.
Published: May 2006

Summary

Glomus tubiforme Tandy, a white sporocarpic species with chlamydospores about 20 to 45 × 18 to 38 μm and fine hyphae ± 2 μm wide, forms ectomycorrhizas in association with a range of plants including Eucalyptus, Pinus and Quercus. The mycorrhizas have a thin sheath, one to a few cells thick, and a Hartig net. Glomus tubiforme has also been grown in agar culture on simple weak media.
RHIZANTHELLA GARDNERI (ORCHIDACEAE), ITS RHIZOCTONIA ENDOPHYTE AND CLOSE ASSOCIATION WITH MELALEUCA UNCINATA (MYRTACEAE) IN WESTERN AUSTRALIA
Authors: WARCUP J. H.
Published: May 2006

Summary

Rhizanthella gardneri R. S. Rogers, a rare subterranean achlorophyllous orchid which grows in Western Australia near plants of the Myrtaceous shrub Meialeuca uncinata R. Br. ex Alton f., is associated with an undescribed species of Rhizoctonia which forms hyphal coils within cortical cells of the orchid rhizome. The Rhizoctonia also forms ectomycorrhizas with sheath and Hartig net on Meialeuca uncinata and other ectomycorrhizal plants including Eucalyptus.

Seeds of R. gardneri may germinate without the Rhizoctonia but their growth soon ceases unless the protocorm is invaded by the fungus through the protocorm hairs. Two plants of R. gardneri raised from seed in association with Rhizoctonia ectomycorrhizas on M. uncinata have flowered after 15 months.

The Rhizanthella endophyte stimulated germination of seed of R. gardneri but not seed of two chlorophyllous terrestrial orchids, Prasophyllum regium R. Rogers and Microtis unifolia (Forster f.) Reichb. f. However, germination of these two orchids was stimulated by five of six other Rhizoctonias, including Tkanatephorus cucumeris (Frank) Donk and two species of Tulasnella, also isolated from soil and litter from two Rhizanthella sites.
IS ABSCISIC ACID A UNIVERSALLY ACTIVE CALCIUM AGONIST?
Authors: HUDDART H. , SMITH R. J. , LANGTON P. D. , HETHERINGTON A. M. , MANSFIELD T. A.
Published: May 2006

Recent studies of the control of stomatal aperture by abscisic acid (ABA) have suggested that its cellular action depends on the availability of calcium ions, which appear to function as secondary messengers. Stimulus‐response coupling may, therefore, be similar to that found in many animal tissues.

We report here preliminary evidence that ABA has a profound effect on some mammalian tissues and on a cyanobacterium. Studies on smooth muscles from the vas deferens and bladder of rat showed that 10−6 M ABA enhanced field stimulation responses by about 25 %. This effect was inhibited by the calcium‐channel blocker, nifedipine. In K+‐depolarized bladder smooth muscle in which the fast calcium channels were voltage‐inactivated, 10−6 M ABA augmented contracture tension, and enhanced the slow tonic phase of the response which is known to be dependent on the activity of slow calcium channels. Comparative studies using ABA and the synthetic calcium agonist BAY K 8644 suggested that there are close parallels in the mode of action of the two compounds. Heal smooth muscle was remarkably sensitive to ABA, showing enhancement of K+ contracture tension by up to 400% at only 10−9 to 10−8 M ABA.

In cultures of Nostoc 6720, low concentrations of ABA (about 10 −7 M) caused a substantial increase in the heterocyst/vegetative cell ratio. Addition of ABA further enhanced the increase in heterocyst content caused by increases in the concentration of Ca2+ in the medium. These observations provide further support for the proposal that ABA functions as a calcium agonist, a concept consistent with similarities between the action of ABA and the calcium ionophore A23187. In cultures of Nostoc 6720, high (> 10−5 M) concentrations of ABA had an inhibitory effect, and some evidence of a similar dose‐response relationship was found in mammalian tissues.

Preliminary studies using 45Ca2+ suggested that ABA stimulates the influx of calcium into both vasa deferentia and Nostoc 6720. It is concluded that ABA may function as a calcium agonist when applied to a wide range of prokaryotic and eukaryotic cells. A recent observation that it is present in the brain of some mammals suggests that this ‘plant hormone’ may be of much wider biological significance than hitherto recognized. The similar responses of plant, animal and cyanobacterial cells to ABA might indicate the presence of cellular mechanisms which have been genetically conserved through many stages of evolution.
LONG DAY CONTROL OF FLOWERING IN POA NEMORALIS IN CONTROLLED AND NATURAL ENVIRONMENTS
Authors: HEIDE OLA M.
Published: May 2006

Flower initiation and development in a local population of Poa nemoralis L. were studied in controlled and natural environments at As, Norway, 59° 40′ N. At temperatures ranging from 6 to 21 °C flowering occurred in long days (LD) only. At 12 h photoperiod the plants remained vegetative for at least 145 d. The critical photoperiod for floral initiation was about 14 h at IS and 21°C, slightly longer at 9 °C. A minimum of two LD cycles was required for floral induction at 15 °C when flower development took place in 12 h photoperiod, while more than four LD cycles were required for flower development in 8 h photoperiod. Viviparous proliferation of inflorescences resulted from marginal LD induction and subsequent flower development in short days (SD). The observed critical photoperiods agreed well with the time of floral initiation in the field, the critical photoperiod being reached as soon as growth is initiated in the spring. It is concluded that P. nemoralis is an obligatory long day plant with no SD or low temperature vernalization requirement.
THE ACTIVITY AND CHARACTERIZATION OF ACID PHOSPHATASES IN ENDOMYCORRHIZAL FUNGI OF THE ERICACEAE
Authors: Straker C. J. , Mitchell D. T.
Published: May 2006

Endomycorrhizal fungi were isolated from the root systems of Vaccinium macrocarpon Aiton, Rhododendron ponticum L., Calluna vulgaris (L.) Hull (Ericaceae) and also from a South African erica, Erica hispidula L. They were grown on a liquid medium containing inositol hexakisphosphate, fractionated into cytoplasmic, extracellular and wall‐ and membrane‐bound fractions and assayed for acid phosphatase. Extracellular phosphatase was demonstrated in all cultures but its activity was highest in the endophyte of E. hispidula. The wall‐ and membrane‐bound acid phosphatase was the dominant fraction in the European endophytes. The extracellular acid phosphatase of high P‐fed (3.23 mM P) mycelia of the endophytes of E. hispidula had the greatest activity (76% of total activity), whereas in low P‐fed (0.1 mM P) mycelia both wall and extracellular fractions contributed almost equally to form 80% of total activity. All the fractions contained an acid phosphatase of 173858 MW with a broad pH optimum of 2.0 to 6.0 but a smaller enzyme of 68028 MW with a pH optimum of 6.5 also occurred in the wall fraction from low P‐fed mycelia. All the enzymes were inhibited by fluoride, molybdenum, arsenate, cyanide, mercury and phosphate but stimulated by EDTA, citrate and the ferric ion at low concentrations. A wide substrate specificity was demonstrated with maximum affinity for inorganic pyrophosphate, high affinities for α and β‐naphthyl phosphate, phenyl phosphate and a‐glycerophosphate and a low affinity for phytic acid. The low molecular weight enzyme was the only one which hydrolysed organic anhydrides (ATP, ADP and AMP).
MICROPROPAGATION OF CHESTNUT AND CONDITIONS OF MYCORRHIZAL SYNTHESES IN VITRO
Authors: STRULLU D. G. , GRELLIER B. , MARCINIAK D. , LETOUZÉ R.
Published: May 2006

Summary

Chestnut (Castanea sativa Mill.) was cloned in vitro. Mycorrhizal syntheses were obtained between cloned plants and Paxillus involutus (Batsch.) Fr. In the case studied, MNM nutrient solution did not favour the development of the host plants. The composition of an original nutrient solution was determined for the mycorrhizal infection of chestnut in vitro. The mycorrhizas obtained were studied by scanning electron microscopy.
VESICULAR–ARBUSCULAR MYCORRHIZA IN NATURAL VEGETATION SYSTEMS
Authors: FRANCIS R. , FINLAY R. D. , READ D. J.
Published: May 2006

Summary

The role of inter‐plant hyphal bridges formed by vesicular‐arbuscular (VA) mycorrhizal mycelia was investigated using double pots in which donor plants were grown in the mycorrhizal (M) or non‐mycorrhizal (NM) condition with root systems split so that they could be supplied with nutrients in the donor pot. Plantago lanceolata L. and Festuca ovina L. were grown in intra‐and inter‐specific combination as donors and receivers. The normally non‐mycorrhizal species Arabis hirsuta L. was included as an additional potential receiver. Nutrient solution or distilled water was applied to the donor pot and the patterns of growth responses, and of nitrogen and phosphorus accumulation were compared in receiver plants with and without mycelial interconnections.

Yields of M receivers were significantly higher than those of NM plants in all combinations of plants at the second or third harvest, except in the case of the intra‐specific combination of Plantago. A. hirsuta showed no response to nutrient application. Mycorrhizal infection of receivers in the distilled water treatment produced a relatively small response indicating that improved exploitation of sand in the receiver pots was not the cause of growth stimulation in M receivers.

Yield increases were associated with higher total N contents of the mycorrhizal receiver plants in three of the species combinations and of P content in all combinations, by the third harvest the gain in P concentration being relatively greater than that of N.

The results confirm that VA infection can provide channels for direct inter‐plant nutrient transfer and that transfer is sufficient to sustain significant enhancement of both growth and nutrient composition of receivers, in some cases within six weeks of commencement of the treatment. The probable physiological and ecological significance of these observations is discussed.