bluuebunny/crossref_metadata_2025 huggingface dataset:
STOMATAL DEVELOPMENT AND SEASONAL CHANGES IN DIFFUSIVE RESISTANCE OF PRIMARY AND REGROWTH FOLIAGE OF RED OAK (QUERCUS RUBRA L.) AND RED MAPLE (ACER RUBRUM L.)
Authors: TURNER N. C. , HEICHEL G. H.
Published: May 2006

From foliar emergence until senescence, the abaxial diffusive resistance of primary foliage, and of regrowth foliage produced after defoliation, was measured at several irradiances with a ventilated diffusion porometer. Concurrent measurements were made of stomatal dimensions and frequency, including scanning electron‐microscopy, and of leaf area. The diffusive resistance of newly emerged primary leaves was about 15 s cm−1 in maple and 20 s cm−1 in oak at all irradiances. The stomata became sensitive to light within 2 weeks of emergence, oak being slightly earlier than maple. Thereafter, the resistance at an irradiance of 0.5 cal cm−2 min−1 fell to a seasonal minimum of 3 s cm−1 in oak and 5–7 s cm−1 somewhat later in maple. With the onset of senescence, and earlier in maple than in oak, the resistance of primary leaves in bright light increased and the stomata became less sensitive to light. As leaf colour changed from green to red or brown, the resistance increased to about 60 to 80 s cm−1 in both oak and maple.

The resistance of regrowth foliage that emerged in July was about 5–7 s cm−1 in maple and 12–15 s cm−1 in oak, thus lower than that in newly emerged primary foliage. Within a week of emergence, 3 weeks sooner than with primary foliage, the resistance at 0.5 cal cm−2 min−1 fell to about 3 s cm−1 in both species. During July and August, the resistance of regrowth foliage of maple was about one‐third that of the primary foliage, but about the same in both regrowth and primary foliage of oak.

At the time of regrowth leaf emergence (July), the mean temperature was 10° C higher than that at primary leaf emergence (May), but in both species the initial rates of leaf expansion were similar. Although the areas of individual primary leaves were about twice those of regrowth leaves, the stomatal frequencies and dimensions were similar. Maximum stomatal length was achieved before the leaves were fully expanded and before the stomata became responsive to light. The development of light sensitivity was apparently independent of leaf expansion and the attainment of final stomatal size, but strongly dependent on environmental regulation of stomatal metabolism.
MEVALONATE‐ACTIVATING ENZYMES IN WHEAT ETIOPLASTS
Authors: COOKE R. J.
Published: May 2006

(2‐14C)‐MVA (mevalonic acid) is metabolized to two major products by sonicated preparations of purified intact etioplasts isolated from wheat leaves. These metabolites have been identified by their RF values and from the products of their hydrolysis as MVAP and MVAPP (mevalonate‐5‐phosphate and mevalonate‐5‐pyrophosphate, respectively). Intact preparations of etioplasts are essentially impermeable to (2‐14C)‐MVA, even after a red light irradiation.
RADIOAUTOGRAPHY OF MYO‐INOSITOL IN CULTURED FRAXINUS CALLUS
Authors: WOLTER KARL E. , MURMANIS LIDIJA
Published: May 2006

Radioautographs by light and electron microscopy of callus cells of green ash (Fraxinus pennsylvanica Marsh.) that had been fed low levels of the growth factor 3H myo‐inositol indicated an almost exclusive incorporation of the label into the cytoplasmic constituents. These results contrast with those from most other studies of incorporation in higher plants. The incorporation here of myo‐inositol suggests that its prime function is the synthesis of cytoplasmic membrane systems of the cell rather than in the polysaccharide component of the primary wall.
EFFECTS OF AQUEOUS SULPHUR DIOXIDE ON CHLOROPHYLL DESTRUCTION IN PINUS CONTORTA
Authors: MALHOTRA S. S.
Published: May 2006

The effects of aqueous SO2 on chlorophyll breakdown in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) were determined under laboratory conditions. Aqueous SO2 concentrations ranging from 100 to 500 ppm resulted in a sharp decrease in total chlorophyll content. Chlorophyll a was more sensitive to SO2 than chlorophyll b. Quantitative determinations of various pigments suggested that's SO2 causes the conversion of chlorophyll a into phaeophytin a (100–500 ppm SO2) and chlorophyll b into chlorophyllide b (10–50 ppm SO2). The suggested conversion of chlorophyll into chlorophyllide induced by SO2 was supported by increased activity of pine needle chlorophyllase at low aqueous SO2 concentrations (10–50 ppm). The breakdown of chlorophyll molecules by SO2 as measured by loss of Mg++ and total chlorophyll was accompanied by a decreased ability of pine needles to photosynthesize H14CO3. The effect of SO2 on pigment breakdown and rate of photosynthesis was due mostly to the specific direct actions of SO2 and was not a function of increased acidity.
SULPHUR DIOXIDE METABOLISM IN SOY‐BEAN, GLYCINE MAX VAR. BILOXI
Authors: GARSED S. G. , READ D. J.
Published: May 2006

First‐trifoliate leaves of four‐leaved soybean plants were exposed to 35SO2 in the light or dark, and the uptake and translocation of radioactivity measured. Nearly four times more 35SO2 was taken up in the light (stomata open) than in the dark (stomata closed) but approximately 50% of the radioactivity was leached from the leaf surface in the dark compared with 5% in the light. A greater proportion of the source‐leaf radioactivity was translocated in the dark but, in absolute terms, the quantity of radioactivity moved was less. Radioactive products were found in all parts of the plant after exposure in both light and dark. The expanding trifoliate leaf contained the greatest concentration of translocated radioactivity in both cases. Light and dark pre‐ and post‐treatments had little effect on uptake of 35SO2 or translocation of the products. 35SO42− was detected in the nutrient solution within 1 h of exposure of leaves to 35SO2.
THE EFFECT OF L‐ARGININE ON THE GROWTH OF HETEROTROPHIC CULTURES OF THE EMERSON STRAIN OF CHLORELLA
Authors: THINH L. V. , GRIFFITHS D. J.
Published: May 2006

The ability of L‐arginine to stimulate autospore production in heterotrophic cultures of the Emerson strain of Chlorella is reversed by chloramphenicol. The antibiotic does not affect the uptake of glucose, neither does it alter significantly the pattern of incorporation of radioactivity from 14C glucose into the major fractions of arginine‐treated cultures. The inhibitory effect of the antibiotic is largely restricted to those aspects of development which specifically respond to arginine. Thus, the stimulation of DNA synthesis by arginine is strongly reversed by chloramphenicol suggesting the involvement of some chloroplast‐centered event. Chloramphenicol does not inhibit the uptake of arginine but affects the subsequent metabolism of the amino acid. It is concluded that addition of arginine may lead to the synthesis in the chloroplast of specific polypeptides necessary for nucleic acid synthesis and cell division.
ULTRASTRUCTURAL STUDIES IN THE BROWN ALGA ECTOCARPUS IN CULTURE: AGEING*
Authors: OLIVEIRA LUIS , BISALPUTRA THANA
Published: May 2006

Ultrastructural changes associated with ageing of the vegetative sporophytic cells of Ecto‐carpus are described. Nuclei, endoplasmic reticulum and dictyosomes become reduced or disappear; mitochondria are also much affected. Of all cell organelles, plastids display the most striking alterations. These include the formation and release into the cytoplasm of electron‐dense material, probably of lipid nature, and the budding off of portions of the plastids. The cytoplasm, congested with a variety of inclusions, shows toward the end of the ageing process the first signs of autolysis (rupture of the tonoplast). Conspicuous wall ingrowths are also formed along the cross and end walls of the cells. Ingrowths that occur at the cross walls do not seem to disrupt plasmodesmatal continuity. The maintenance of symplast continuity is believed to be significant to the progress of the ageing process. The present findings are discussed in relation to available data obtained from other plant studies.
MYCORRHIZAL ENDOGONACEAE IN A NEW ZEALAND FOREST
Authors: JOHNSON P. N.
Published: May 2006

Most vascular plants and some liverworts in a New Zealand coniferous‐dicotyledonous forest harboured typical vesicular‐arbuscular endophytes, Rhizophagus tenuis or mixtures of the two. At least nine sporing fungi were present but non‐sporing races probably predominated. Spores were present in variable densities (2–17 × 103 1−1) in forest soils but their distribution was not obviously related to that of host plants.

In inoculation experiments, fungi had a wide host range and, in terms of growth response, hosts showed no clear preferences for particular endophytes. There was some indication of fungi being specific to soil type.

Many tree seedlings begin growth perched on rocks or logs and Rhizophagus tenuis is a pioneer endophyte there.
THE BREEDING SYSTEM OF PONTEDERIA ROTUNDIFOLIA L., A TRISTYLOUS SPECIES
Authors: BARRETT S. C. H.
Published: May 2006

Populations of Pontederia rotundifolia in the Lower Amazon and Costa Rica are tristylous. A strong pollen trimorphism is associated with differences in stamen and style length in the three floral forms. The results of a controlled pollination programme with thirty individual plants of P. rotundifolia demonstrate that floral trimorphism is accompanied by a physiological self‐incompatibility system typical of many heterostylous plants. Legitimate pollinations are considerably more productive of seed than illegitimate pollinations. Individual plants exhibit differences in the strength of self‐incompatibility, but in general, short‐styled plants possess the strongest self‐incompatibility, long‐styled plants are intermediate and mid‐styled plants have the weakest self‐incompatibility. Large differences in the strength of self‐incompatibility are expressed in self‐pollinations with pollen from the two anther levels of each style form.

Natural populations of P. rotundifolia often contain only a single style form or contain unequal proportions of style forms. Seed set, resulting from moderate self‐compatibility, occurred in a Cosra Rican population that contained only short‐styled plants. Two populations associated with rice cultivation in the Lower Amazon contained equal proportions of the three style forms. The seed set of the three forms within these populations was similar. The floral trimorphism and breeding system of P. rotundifolia are compared with those of the related P. cordata and Eichhornia crassipes.
STUDIES OF MALATE FORMATION IN ‘ISOLATED’ GUARD CELLS
Authors: TRAVIS A. J. , MANSFIELD T. A.
Published: May 2006

After they had been ‘isolated’ by a low pH treatment which destroyed all the other cells of the epidermis, stomatal guard cells retained the capacity to produce malate when presented with fusicoccin as a stimulus to opening. For a given level of stomatal opening, the amount of malate in epidermis with isolated stomata was practically the same as in intact epidermis. It is concluded that malate transport to and from the subsidiary cells is not an essential part of the stomatal mechanism. Changes in CO2 concentration over the range 0–100 ppm affected neither stomatal aperture nor malate levels in epidermis of Commelina communis. This suggests that carboxylation of phosphenolpyruvate plays no major part in the formation of malate in guard cells.
GAS EXCHANGE AND ENZYME ACTIVITY DURING LEAF EXPANSION IN PHASEOLUS VULGARIS L.
Authors: O'TOOLE J. C. , LUDFORD P. M. , OZBUN J. L.
Published: May 2006

Net photosynthesis, transpiration, boundary layer plus stomatal resistance to CO2 diffusion, and CO2 compensation point were monitored in the central leaflet of expanding first trifoliate leaves of Phaseolus vulgaris L. Simultaneously, the activities of three enzymes related to net photosynthesis, photorespiration and dark respiration were measured. Net photosynthesis rate and ribulose 1,5‐diphosphate carboxylase activity increased with leaflet expansion, reaching peaks just prior to full expansion. Concurrently, boundary layer plus stomatal resistance, CO2 compensation point and malate dehydrogenase activity decreased, reaching lowest values at full leaflet expansion.

Shortly after peak photosynthetic activity was reached all trends reversed, as the physiological activity of the first trifoliate leaf of this determinate type bean plant changed to that characterized by a senescing leaf.
A FAST‐READING VISCOUS FLOW LEAF POROMETER
Authors: SHIMSHI D.
Published: May 2006

A field porometer is described for measuring the permeability of amphistomatous leaves. The apparatus is a light (2.8 kg) portable version of Gregory and Pearse's porometer, which enables the operator to read the permeability immediately after clamping the leaf, thus obviating changes of stomatal aperture during measurements. The apparatus has two sensitivity ranges; details on its construction and calibration are presented.
THE DEVELOPMENT OF OEDOCEPHALUM‐TYPE CONIDIA IN THE FUNGI CUNNINGHAMELLA ECHINULATA AND FOMES ANNOSUS
Authors: COOK BERYL E.
Published: May 2006

Oedocephalum‐type conidiophores of the zygomycete Cunninghamella echinulata, and the basidiomycete Fomes annosus, studied by light and electron microscopy, developed in similar ways: vesicles were present in the cytoplasm of all regions of growth and development, initiation and growth of the conidium stalks and conidia were synchronous and conidia were delimited by occlusion of the stalk by a thickened wall layer. However, in Cunninghamella, conidia were produced holoblastically while, in Fomes, they were formed enteroblastically.
GLUTAMINE SYNTHETASE AND NITROGENASE ACTIVITY IN THE BLUE‐GREEN ALGA ANABAENA CYLINDRICA
Authors: ROWELL P. , ENTICOTT S. , STEWART W. D. P.
Published: May 2006

On adding NH4+ to nitrogen‐fixing cultures of Anabaena cylindrica, the glutamine pool of the intact filament increases within seconds. Nitrogenase activity and then glutamine synthetase activity decline. There are no changes in the activities of glutamate‐aspartate aminotrans‐ferase, or in the pools of alanine, glycine and aspartate during this period. Nitrogenase activity is usually inversely related to the size of the glutamine pool and shows little correlation with glutamine synthetase activity per se. There is no evidence of adenylylation or dead‐enylylation of glutamine synthetase (snake venom phosphodiesterase has no effect on activity, there is no serological homogeneity with the Escherichia coli enzyme which shows a covalent modification; the ratio of biosynthetic: transferase activity does not change markedly on the addition of NH4+ and the kinetics of decrease in glutamine synthetase activity are not consistent with adenylylation of the enzyme).

Feed‐back inhibition occurs, with alanine and glycine being particularly effective inhibitors and with some inhibition occurring with AMP, carbamoyl phosphate and aspartate. Histidine, lysine, ornithine, citrulline and arginine were non‐inhibitory at the concentrations used. There is no evidence of inhibition of glutamine synthetase by glutamine. The addition of azaserine inhibits glutamine uptake by intact filaments and reduces the subsequent conversion of glutamine to glutamate within the filament by 77%. Such results are consistent with the operation of the glutamine synthetase‐glutamate synthase pathway in Anabaena cylindrica.
DENSITY LABELLING DURING MICROBODY DEVELOPMENT IN COTYLEDONS
Authors: BROWN RICHARD H. , MERRETT MICHAEL J.
Published: May 2006

During the development of pumpkin (Cucurbita pepo) cotyledons peroxisomal development was dissociated completely from glyoxysomal decline by keeping seedlings in darkness for up to 20 days; glycollate oxidase activity resulting from illumination then occurred after complete decay of isocitrate lyase. During cotyledon development a peak of phosphoryl‐choline glyceride transferase activity preceded maximal development of glyoxysomes while a second peak of activity occurred after illumination but before maximal development of peroxisomes. When dark‐grown cotyledons were illuminated on transfer to 2H2O and micro‐bodies isolated by gradient centrifugation, peroxisomes were separated from glyoxysomes because of their greater equilibrium density. The observed density shift for peroxisomes suggests that they arise by de novo synthesis rather than by modification of glyoxysomes.
CONTROL OF POLYPHENOL OXIDASE (O‐DIPHENOLASE) IN DE‐EMBRYONATED BARLEY AND WHEAT GRAINS
Authors: JENNINGS P. H. , DUFFUS C. M.
Published: May 2006

Different control mechanisms were shown to exist which affected the level of o‐diphenolase (o‐Diphenol: Oxygen oxidoreductase, E.C.I. 10.3.1) activity in extracts of two barley cultivars and one wheat cultivar. Both the increase in o‐diphenolase activity which occurs in Kleiber wheat during half‐grain incubation and the activity promoted by gibberellic acid (GA3) were dependent on protein synthesis and could be inhibited by cycloheximide and abscisic acid respectively. Incubation with GA3 lowered o‐diphenolase activity in the barley, Nakta, which was not due to GA3 promoted protease activity. The role of protein synthesis and protease activity in controlling the levels of detectable o‐diphenolase activity is discussed. GA3 caused a direct, stimulatory effect on o‐diphenolase activity extracted from both Kleiber and Nakta when the hormone was added to the assay mixture.
SHIFTS IN PHOTOSYNTHETIC CARBON LABELLING PATTERN BY ETIOLATED RICE (ORYZA SATIVA L.) SEEDLINGS DURING GREENING
Authors: RAGHAVENDRA A. S. , DAS V. S. R.
Published: May 2006

The carbon assimilation pattern in light by dark‐grown rice (Oryza sativa) seedlings was studied during greening. After exposure of etiolated seedlings to light their capacity to synthesize the C4‐acids, malate and aspartate, increased for 12 h. The labelling of 3‐phospho‐glycerate, sugar phosphates, sucrose and insolubles, did not increase until after 12 h. Thereafter a continuous steep increase in synthesis of Calvin cycle intermediates, but not of C4‐acids, recurred. The levels of carboxylating enzymes (phosphoenolpyruvate and ribulose diphosphate carboxylases) in the seedlings correlated positively with the appearance of label in C4 acids and in Calvin cycle compounds. We suggest that a β‐carboxylation mechanism was activated immediately on illumination but was persistent for only 12 h. After an 8‐h lag period following illumination, the Calvin cycle began to operate and continued during further growth of seedlings in light.
UPPER CRITICAL LEVELS OF TOXIC ELEMENTS IN PLANTS
Authors: BECKETT H. T. , DAVIS R. D.
Published: May 2006

This study examined the effect of Cu, Ni, Zn or Cd in the leaves and shoots of young barley on their yield of dry matter.

As expected, the yield of dry matter, or the uptake of heavy metals from a given solution, varies considerably with growing conditions. However, the minimum concentrations of these elements in the plant tissue that was necessary before the yield of dry matter was reduced by their toxic effects (‘upper critical level’) proved to be independent of growing conditions varied enough for the control plants to have required 14–31 days to reach the five‐leaf stage, and for the weights of the control plants to have ranged from 76 to 214 mg.

This being so it is suggested that if young barley plants were used to monitor accumulations of heavy metals in the soil environment, the quantity would provide a good measure of the hazard of any accumulation relative to the onset of toxicity, where To and Tc are standard values for the background (unpolluted) and the upper critical level of the element in plant tissue, and Tits level in a test crop. This reduces to [m. Log10T/n] and if T is measured in ppm of dry matter, m and n are approximately,

image

A graph of Relative Hazard against tissue concentration is presented.
STUDIES ON INSECT‐FREE GROWTH, DEVELOPMENT AND NITRATE‐ASSIMILATING ENZYMES OF DROSERA ALICIAE HAMET*
Authors: SMALL G. C. , ONRAËT ANGELA , GRIERSON D. S. , REYNOLDS GAYNOR
Published: May 2006

The carnivorous plant, Drosera aliciae, cultivated insect‐free from seed showed better growth with nitrogen as NH4Cl and NH4NO3 than with NaNO3. Highest yields of NaNO3‐treated plants were obtained at pH 4.0 and 4.5 whereas with NH4Cl and NH4NO3 yields increased with increasing pH. Plants grown on a nitrogen‐free medium but fed cheese were little affected by pH. Plants flowered and produced viable seeds in all treatments. The enzymes, nitrate reductase, nitrite reductase, a peroxidase capable of reducing nitrate, gluta‐mate dehydrogenase, glutamate synthase and glutamine synthetase were demonstrated in cell‐free extracts of roots and leaves. Enzyme levels in ammonium, cheese and nitrate‐fed plants were compared.
POTASSIUM EFFLUX BY LICHEN THALLI FOLLOWING EXPOSURE TO AQUEOUS SULPHUR DIOXIDE*
Authors: PUCKETT K. J. , TOMASSINI F. D. , NIEBOERJ E. , RICHARDSON D. H. S.
Published: May 2006

Potassium efflux is a useful experimental quantity for assessing damage to lichens exposed to SO2. This SO2‐induced K+ efflux is biphasic in response to increasing concentrations of aqueous SO2. The first phase can be extrapolated to identify the SO2 concentration at which no K+ release occurred above the control values. This threshold concentration was used to determine the relative sensitivities of various lichen species. Good agreement was observed between the total K+ lost and the reduction in the total photosynthetic 14C‐fixation rates. The magnitude of the SO2‐induced K+ efflux indicated that release occurred from intra‐cellular sources. The kinetics of the release process and the effects of SO2 on membrane integrity are discussed.
A MODEL FOR THE RELATIONSHIP BETWEEN GASEOUS AND AQUEOUS CONCENTRATIONS OF SULPHUR DIOXIDE IN LICHEN EXPOSURE STUDIES*
Authors: NIEBOER E. , TOMASSINI F. D. , PUCKETT K. J. , RICHARDSON D. H. S.
Published: May 2006

The linear relationship, ppm SO2 (wt/wt, aqueous) = 10.3 , is evaluated experimentally for the gaseous concentration range 0–5 ppm and is confirmed theoretically. It is suggested that this physicochemical equilibrium expression is applicable to lichen exposure studies because lichens are poikilohydrous plants.
NUMERICAL TAXONOMIC STUDIES ON SPECIES IN ALLIUM SUBGENUS RHIZIRIDEUM
Authors: EL‐GADI A. , ELKINGTON T. T.
Published: May 2006

Numerical taxonomic studies have been carried out on fifteen operational taxonomic units (O.T.U.'s) belonging to Allium subgenus Rhizirideum. The data comprise measurements and observations of forty‐nine morphological and cytological characters and thirty‐eight chemical characters which are volatiles detected by gas liquid chromatography of direct vapour samples and mainly identified as sulphides. The CLASP program has been used to analyse the data. Classifications derived from hierarchical cluster analyses and principal co‐ordinates analyses are presented as dendrograms and vector plots respectively, the latter with the minimum spanning trees added. Classifications produced by analysis of the morphological and cytological characters and chemical characters are compared both with one another and with those produced by analysis of all characters.

The main groups distinguished in the analyses are (a) A. cepa, A. cepa cv. Shallot, A. galanthum and A. fistulosum; (b) O.T.U.'s belonging to A. schoenoprasum; (c) A. senescens, A. senescens var. glaucum, A. montanum and A. albidum; (d) A. tuberosum and A. ramosum (e) A. farreri. These groups correspond with biosystematic groupings suggested by hybridization studies. They are also compared with existing sectional classifications of the genus.
DIURNAL VARIATIONS IN ENDOGENOUS ETHYLENE LEVELS IN PLANTS
Authors: KAPUYA J. A. , HALL M. A.
Published: May 2006

Diurnal variations in endogenous ethylene levels occur in Vicia faba, Kalanchoe daigremontana and Caltha polypetala under both long and short days, higher levels being present under the former. The significance of these variations and the factors involved in their causation are discussed.
EFFECTS OF SOME GROWTH REGULATORS ON TILLER BUD ELONGATION IN CEREALS
Authors: JOHNSTON G. F. S. , JEFFCOAT B.
Published: May 2006

The effects of foliar and root applied 6‐benzylamino‐9‐(tetrahydropyran‐2‐yl)‐9H‐purine (PBA), 6‐benzylamino‐purine (BAP), indole‐3‐acetic acid (IAA) or gibberellic acid (GA3) on tiller bud growth were examined in cereal seedlings. Generally IAA and GA3 inhibited tiller bud growth whilst the synthetic cytokinins both markedly promoted growth. Some observations on stem and root growth were also recorded. The results are discussed with respect to the diversion of both assimilates and cytokinins and appear to favour the view that tiller bud development is controlled by a competition for assimilates with the roots and main shoot.
CARBOHYDRATE METABOLISM IN AGARICUS BISPORUS (LANGE) IMBACH.: METABOLISM OF [14C] LABELLED SUGARS BY SPOROPHORES AND MYCELIUM
Authors: HAMMOND J. B. W. , NICHOLS R.
Published: May 2006

When growing sporophores and vegetative mycelium of Agahcus bisporus had been supplied with [14C] labelled hexoses for varying periods of time, the major compounds labelled in both forms were mannitol, trehalose, glutamate, alanine and an unidentified substance. Mannitol was strongly labelled after application of [14C] fructose but only weakly when [14C] glucose was supplied.

The relative rates of oxidation by sporophores of labelled mannitol, trehalose, glucose and fructose were assessed by measuring 14CO2 production. Glucose and trehalose were the most rapidly oxidized substrates.

Glucosephosphatase isomerase (E.C. 5.3.1.9) was extracted from sporophores and assayed. The conversion of glucose‐6‐phosphate to fructose‐6‐phosphate by the enzyme was competitively inhibited in vitro by 6‐phosphogluconate.

The control of mannitol synthesis and the functions of mannitol and trehalose are discussed.
THE INFLUENCE OF STAGE OF HOST DEVELOPMENT ON VESICULAR‐ARBUSCULAR MYCORRHIZAE AND ENDOGONACEOUS SPORE POPULATION IN FIELD‐GROWN VEGETABLE CROPS I. SUMMER‐GROWN CROPS
Authors: SAIF S. R.
Published: May 2006

The pattern of mycorrhizal infection of roots of several fully grown vegetable crops showed three phases, a lag phase, a phase of rapid development and a constant phase. Twenty‐one days after sowing or transplanting, 0–24% of the roots were infected, but the proportion then increased rapidly to a more or less constant value of 55–92%. With musk melon (Cucurbita moschata L.), tomato (Lycopersicon esculentum Miller, Goed) and bringel (Solarium melongena L.), no constant phase was observed within the sampling period. During the first 4–8 weeks of crop growth, the Endogonaceous spore population of the soil decreased, but then increased to final harvest time. Three main types of endophytes were identified, two being members of Endogonaceae and one with very narrow, brown septate hyphae. The relationship between the different phases of mycorrhizal development, spore number in the soil and physiological changes in the host is discussed.
A CYTOLOGICAL ANALYSIS OF THE NOSTOC‐BRYOPHYTE RELATIONSHIP
Authors: DUCKETT J. G. , PRASAD A. K. S. K. , DAVIES D. A. , WALKER S.
Published: May 2006

A comparative light and electron microscope study has been made of the Nostoc colonies within the thalli of Blasia pusilla and the three British species of Anthoceros, and also of the Nostoc isolated from each bryophyte. From their morphology in culture two taxa of Nostoc have been identified; N. sphaericum from Anthoceros punctatus, A. husnotii and A. laevis, and N. calcicola from other gatherings of Anthoceros laevis and Blasia. These findings support the notion that the algal‐bryophyte associations are none specific.

Within bryophyte thalli, the Nostoc trichomes are closely packed and specific features cannot be recognized. Mucilaginous sheaths are much less extensive and there is no evidence that the alga thrive in mucilage produced by the adjacent bryophyte cells. Heterocyst frequencies as high as 50% in the bryophytic Nostoc spp. strikingly recall the Azolla, Gunnera and cycad‐blue‐green algal symbioses. Akinetes, readily produced in culture were only seen in the Nostoc from dormant Anthoceros. The absence of phycobilisomes and high heterocyst frequencies in the bryophytic Nostoc spp. corroborates physiological data that the algae receive organic carbon from their hosts which enable them to fix nitrogen heterotrophically.

The Nostoc colonies in both Blasia and Anthoceros are extensively penetrated by multi‐cellular bryophytic filaments. Whereas in Anthoceros these comprise highly vacuolate, thin‐walled cells, which sometimes contain intracellular Nostoc trichomes, in Blasia the filaments are thick‐walled and often develop labyrinthine wall ingrowths. This transfer cell morphology may be interpreted as an adaptation facilitating interchange of metabolites between Blasia and Nostoc. Its absence in Anthoceros perhaps indicates a far less harmonious relationship or may be related to the higher nutrient status of the habitats where the Anthoceros spp. were collected.
PHYSIOLOGICAL STUDIES ON THE RELATIONSHIP BETWEEN ASCOPHYLLUM NODOSUM AND POLYSIPHONIA LANOSA
Authors: TURNER C. H. C. , EVANS L. V.
Published: May 2006

Translocation of 14C labelled products of photoassimilation within Ascophyllum nodosum tissue with or without epiphytic Polysiphonia lanosa was found not to occur. Aerial P. lanosa contains several water‐soluble sugars but only sodium mannoglycerate was radioactive following a 1h pulse in (14C) bicarbonate. Evidence is presented to show the presence of this compound in the rhizoids of P. lanosa and to demonstrate that its metabolism here differs from that in aerial parts of the plant. The ability of aerial parts of P. lanosa to utilize exogenously supplied (14C) glucose has been demonstrated.
THE RESPONSE OF LICHEN GROWTH TO ADDITIONS OF DISTILLED WATER, RAINWATER AND WATER FROM A ROCK SURFACE
Authors: ARMSTRONG R. A.
Published: May 2006

Three lichen species were wetted in the field with distilled water, rainwater or water which had run off a rock surface, during July 1974 to February 1975. The radial growth rate of Parmelia glabratula spp. fuliginosa was not influenced by the wetting treatments. The radial growth rate of P. conspersa with the distilled water treatment was greater than the control, rainwater and runoff treatments. The radial growth rate of Physcia orbicularis was lower with rainwater and runoff treatments than the control and distilled water treatment. These results may be explained by the effect of wetting on the carbon balance of the lichens and by the influence of water chemistry.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A.
Published: May 2006

The rate of natural acclimation of net photosynthetic temperature optima in Peltigera canina var. praetextata has been examined intensively over a short time period. It has also been induced experimentally under controlled conditions in the laboratory: during an unusual pattern of weather conditions in early spring, the temperature optimum for net photosynthesis changed from approximately 5°C to 25°C and back down to 5°C. Concurrently maximum ambient field temperatures changed from 0°C up to 29°C and back down to 6°C over a 2 week period. Replicates of P. polydactyla collected in the field after being cold acclimated in April, showed an identical and immediate response when stored moist for 24 h at 25°C. In October experimental material with a net photosynthetic temperature optimum of 15°C showed a similarly rapid response when stored moist for 24 h at 5°C. However, temperature acclimation in Peltigera also appears to have a strong seasonal component, and low temperature acclimation cannot be induced experimentally during mid‐summer. Similarly high temperature acclimation cannot be induced in mid‐winter. The results are discussed in relation to temperature acclimation and winter hardening in higher plants, and it is suggested that the process of acclimation is particularly important to lichens enabling them to survive successfully in otherwise harsh environmental conditions.
PHYSIOLOGICAL–ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A. , MACFARLANE J. D. , TYSIACZNY M. J.
Published: May 2006

The rapid decline of nitrogenase activity in Peltigera polydactyla and P. canina var. praetextata in the dark, to approximately 50% of its normal level in the light, is shown to be very temperature dependent and is not evident at temperatures of 15°C or less. An exogenous supply of 6% glucose, however, fails to eliminate the decline of activity. Nitrogenase activity in the dark is also completely dependent on aerobic conditions with zero rates being recorded after 1 min in the dark under a helium/acetylene atmosphere. Evidence is presented which shows the actual level of decline of nitrogenase activity in the dark has a seasonal component.

The results are discussed in relation to oxidative phosphorylation and the availability of carbohydrates throughout the seasons. The ability of P. polydactyla and P. canina var. praetextata to maintain high levels of nitrogenase activity in the dark at temperatures of 15°C or less suggests that a large proportion of the nitrogen fixed by lichens with a blue‐green phycobiont in temperate and low arctic regions, is at night.
CYTOTYPE DIVERSITY IN A POPULATION OF BETULA ALBA L.
Authors: BROWN IAN R. , AL‐DAWOODY D. M.
Published: May 2006

A cytological survey of two populations of Betula in Northeast Scotland revealed the existence of 2n= 28, 2n= 56, 2n= 42 cytotypes. In addition, putative mixoploids with mean somatic counts between 2n= 45 and 2n= 52 were found. The 2n= 42 and mixoploid trees are similar in morphology to the 2n= 56 trees and cannot be distinguished in the field. Seed from uncontrolled pollination of the 2n= 42 cytotypes produced seedlings with somatic counts ranging from 2n= 35 to 2n= 56 with 50% of seedlings being 2n= 42.
EFFECTS OF STEROIDAL ESTROGENS AND GIBBERELLIC ACID ON STEM ELONGATION IN TALL AND DWARF CULTIVARS OF PISUM SATIVUM
Authors: JONES THERESA K. , RODDICK† JAMES G.
Published: May 2006

The effects of exogenous estrone, estradiol‐17β and gibberellic acid (GA3) on stem elongation in tall (Alaska) and dwarf (Meteor) cultivars of Pisum sativum grown under red light and under natural illumination have been studied. Test compounds were formulated in a number of ways and applied by a variety of methods. GA3 elicited a characteristic response in almost all experiments, with elongation in the dwarf cultivar being stimulated to a greater extent (relative to the control) than in the tall cultivar, but no effects of steroidal estrogens were observed on any occasion. Nor was there evidence of any interaction between exogenous GA3 and estrone. The lack of effect of estrone did not appear explicable on the basis of seedling age and the claim that red light treatment is a prerequisite for estrone action was not substantiated. Two other dwarf pea cultivars viz. Feltham First and Little Marvel also responded to GA3, but not to estrone. The disparity between the lack of estrone effect on stem elongation reported here and the positive effect reported elsewhere in the literature is discussed.
FURTHER LOCALIZATION OF AUXIN TRANSPORT THROUGH INTERNODE SEGMENTS
Authors: WANGERMANN ELISABETH
Published: May 2006

In Vicia faba, phloem fibres are shown not to take part in the active polar transport of auxin which takes place exclusively through the vascular bundles of young internode segments. Though transport of auxin through parenchyma/fibre strips does not seem to be active, it is slightly polarized in favour of the basipetal direction.
TEMPERATURE REQUIREMENTS FOR GERMINATION OF DRY‐STORED, COLD‐STORED AND BURIED SEEDS OF SOLANUM DULCAMARA L.
Authors: ROBERTS H. A. , LOCKETT PATRICIA M.
Published: May 2006

Freshly collected seeds of Solarium dulcamara L. germinated almost completely at daily alternating temperatures of 10/25°, 10/30° and 20/30°C but only 20% at constant 30°C, less than 10% at 25°C and not at all at 10°, 15° or 20°C. The only change in 12 months of dry storage was a decrease in capacity for germination at 25° and 30°C. Almost complete germination at these temperatures and also at 20°C was obtained by moistening with 300 ppm of a mixture of gibberellins A4 and A7 instead of water. When stored moist at 4°C for 1 month, germination at 25° and 30°C increased to 80% and there was a progressive increase in germination at lower temperatures during the first 3 months, alternating temperatures gave more than 90% germination. Similar changes occurred during winter in seeds buried 5 cm deep outdoors, and by mid‐April all the seeds had germinated in situ.
SEED PROTEIN HOMOLOGY AND ELUCIDATION OF SPECIES RELATIONSHIPS IN PHASEOLUS AND VIGNA SPECIES
Authors: SAHAI SUMAN , RANA R. S.
Published: May 2006

Electrophoresis of seed proteins from Phaseolus and Vigna species was carried out on poly‐acrylamide gels with cationic and anionic systems. The species were grouped into seven clusters. On the basis of matrices of similarity index, keeping sixty as the minimum intra‐cluster similarity coefficient, a three‐dimensional model was constructed to represent the relationships amongst the clusters. Five Asiatic species including Phaseolus aureus, P. mungo, P. sublobatus, P. angularis and P. calcaratus formed a cluster which was separate from a cluster of American species. The Vigna species forming a third cluster showed greater affinity with the Asiatic Phaseolus species than with the American ones. P. aconitifolius, a form cultivated in India, and two American species, P. lunatus and P. lathyroides, were distinct between themselves and also from other species.
PRELIMINARY STUDIES ON SAPFLOW IN COCOS NUCIFERA L.
Authors: MILBURN JOHN A. , ZIMMERMANN MARTIN H.
Published: May 2006

Techniques are described which enable the transport of phloem sap in the coconut to be studied with greater precision than previously. Factors governing the flow of sap include manipulation and damage to the tissue, which tend to reduce the flow, whilst the use of sharp knives to slice the phloem enhances exudation. A possible role for manipulation is proposed, but it does not seem essential for the induction of exudation. Phloem sap pressures have been measured directly up to about 7.6 bar, agreeing with those that might be expected from measurements of the osmotic pressure of the phloem sap and the water potential of the xylem sap.

Very high rates of specific mass transfer (SMT) have been measured for phloem and sieve tubes, supporting earlier estimates on Arenga, and tentative measurements have been made of the hydraulic conductivity of Cocos sieve tubes. In general, the observations support the view that mass flow through the phloem may be driven osmotically, but the remarkable facility with which the solute content of the sieve tubes can be altered, will make proof difficult.

Implications of the work in relation to the transmission of phloem‐borne pathogens are discussed.
SULPHUR DIOXIDE METABOLISM IN SOY‐BEAN, GLY CINE MAX VAR. BILOXI.
Authors: GARSED S. G. , READ D. J.
Published: May 2006

First‐trifoliate leaves of soybeans Glycine max (L.) Merr. were exposed to 35SO2 in the light or dark, and the chemical distribution of the radioactivity in the source leaves and in the remainder of the plant was determined after 1.5 and 24 h. Only 34SO4 was found in leach‐ates in the light but substantial quantities of 35SO32‐ were present in the dark. Radioactivity was present in all fractions of the source leaves examined (insoluble, centrifuge pellet, soluble protein, chloroform‐soluble and water‐soluble). The main water‐soluble compounds labelled were sulphate > gluthathione > cysteine. Small quantities of sulphite were also recovered in the dark but not in the light. The ratio of soluble: insoluble radioactivity in the sink tissues was influenced more by leaf age than by light treatment. Sulphate, glutathione and cysteine were labelled in the petioles of the source leaves and 35SO4 was found in the nutrient solution after 1.5 h in both treatments. It is concluded that light is not necessary for the reduction of internal 35SO2 products. The results are discussed in relation to current knowledge of 35SO2 metabolism.
EFFECT OF HETEROGENEOUS OAT POPULATIONS ON THE EPIPHYTOTIC DEVELOPMENT OF VICTORIA BLIGHT*
Authors: AYANRU D. K. G. , BROWNING J. A.
Published: May 2006

Yield and yield components of glasshouse‐ and field‐grown mixtures (blends) of near isogenic, highly resistant (HR) and highly susceptible (HS) oat lines increased significantly more than increases attributable to increasing proportions of HR plants in the blends. Disease index (DI) and lodging index (LI) of field stands were highly positively correlated (r= 0.95), while both DI and LI also had high negative correlations with grain yield (r= ‐0.87, and ‐0.95, respectively). The percentage of diseased seedlings in greenhouse mixtures decreased significantly more than decreases due to decreasing proportions of HS plants. Glasshouse stands of HS seedlings developed significantly fewer roots than developed by HR seedlings, or by 1:1 mixture (plant/plant) of the two lines. Soil samples from the rhizosphere of field blends with 20%+ HR plants had significantly fewer Helminthosporium victoriae spores than those from samples with lower proportions. In both field and glasshouse experiments, alfalfa had no significant interaction with disease incidence or yield. The buffering of HS plants against Victoria blight incidence by HR plants in mixtures is suggested.
ATP AND NITROGENASE ACTIVITY IN NITROGEN‐FIXING HETEROCYSTOUS BLUE‐GREEN ALGAE
Authors: BOTTOMLEY P. J. , STEWART W. D. P.
Published: May 2006

The relationship between ATP and nitrogenase activity has been investigated using the obligate photoautotroph Anabaena cylindrica and Anabaenopsis circularis strain 6720, a photoautotroph which can also use exogenously supplied carbon. In the light photophosphorylation supports maximum observed rates of nitrogenase activity (0.60 and 1.2 μmoles C2H4 mg chl a−1 min−1 under aerobic and microaerobic conditions respectively). The ATP pools sustained under both conditions are similar at 160–200 μmoles mg chl a−1. Oxidative phosphorylation and substrate level phosphorylation are unimportant in supporting nitrogenase activity in the light. Cyclic photophosphorylation can supply all the necessary ATP provided fixed carbon compounds from photosynthetic CO2 fixation (Anabaena) or supplied exogenously (0.2%, w/v, fructose) (Anabaenopsis) are available. When the algae are placed in the dark nitrogenase activity declines. In Anabaenopsis, after an initial rapid drop, nitrogenase activity can be sustained in the presence of exogenous carbohydrate in the dark at up to 70% of the light rate under air, but not under anaerobic conditions. This decreased nitrogenase activity in the dark is not due to a lack of nitrogenase synthesis or of penetration of fixed carbon into the cells, but appears to be due to an inherent inability of dark metabolism to generate sufficient ATP and/or reductant for maximum nitrogenase activity. The ATP pool can be sustained at maximum levels when photophosphorylation, cyclic photophosphorylation, and oxidative phosphorylation operate individually, and to a lesser extent when substrate‐level phosphorylation operates. No consistent correlations were found between the ATP pool and nitrogenase activity, except under dark anaerobic conditions where there was a positive correlation. The data suggest either that the ATP pool which supports nitrogenase activity is distinct from that which supplies ATP for general filament metabolism, and/or that the supply of ATP is not the most critical short‐term factor in controlling nitrogenase activity in Anabaena and Anabaenopsis.
THE OXYGEN TENSION WITHIN LICHEN THALLI
Authors: MILLBANK J.W.
Published: May 2006

A technique is described for estimating the internal pO2 of moisture saturated lichen thalli under conditions of known light intensity and temperature. The method is polarographic, using unprotected microelectrodes, with brief experimental periods.

In lichens with the phycobiont forming a zone of the thallus (Peltigera canina, P. poly‐dactyla and P. aphthosa) the pO2 in the algal zone is normally slightly hypoaerobic rising to aerobic in bright sunny conditions, and becoming substantially hypoaerobic (pO2= 1–1.5 × 104 Pa) in darkness. The pO2 within external cephalodia of lichens which have them is more affected by light. P. aphthosa and Placopsis gelida were examined and showed large and abrupt responses to changes in light intensity, the pO2 ranging from 3 × 104 Pa to 104 Pa in Peltigera aphthosa; 2.1 × 104 Pa to 104 Pa in Placopsis gelida. The nitrogenase activity shown by these lichens is probably due to the high proportion of heterocysts, conferring some immunity to high pO2 conditions.
MITOSIS AND CELL PROLIFERATION IN LEMON FRUIT EXPLANTS INCUBATED ON ATTENUATED NUTRIENT SOLUTIONS
Authors: KORDAN H. A.
Published: May 2006

Excised juice vesicle stalks from mature lemon fruits manifest mitotic activity and cell proliferation when incubated on attenuated nutrient solutions consisting maximally of two mineral salts and sucrose or minimally of sucrose alone. Neither cell proliferation nor mitotic activity become manifest in vesicle stalks incubated on glass‐distilled water alone or on mineral salts without sucrose. The findings presented here demonstrate that mitosis and cell proliferation can be activated in this tissue system on nutrient media far simpler in composition than any of those usually employed for higher plant cell or tissue cultures. Evidence is also presented here which suggests that cell wall deformation in the form of wall growth is required for the manifestation of mitotic activity in this tissue system.
A DIRECT TEST OF THE ABILITY OF VESICULAR‐ARBUSCULAR MYCORRHIZA TO HELP PLANTS TAKE UP FIXED SOIL PHOSPHATE
Authors: BARROW N.J. , MALAJCZUK N. , SHAW T.C.
Published: May 2006

When phosphate is added to soil, it slowly becomes more firmly bound and less available to plants. This change is accelerated by high soil temperatures. The present results show that this effect extends to at least 80°C. Incubation of soil and phosphate at high temperatures was therefore used to provide treatments with firmly bound phosphate equivalent to that achieved after a much longer period of contact in the field. Responses to freshly added and to firmly held phosphate were then compared in the presence and in the absence of vesicular‐arbuscular (VA) mycorrhiza to test whether VA mycorrhiza improved the plant's access to firmly held phosphate.

Incubation of soil and phosphate for 12 days at 70°C reduced the availability of the phosphate to about one fifth of that of freshly added phosphate. Inoculation with VA endophytes more than doubled availability of the phosphate to both Trifolium subterraneum and Allium cepa but the improvement was no bigger for firmly held phosphate than for freshly added phosphate.
VESICULAR‐ARBUSCULAR INFECTION AND SOIL PHOSPHORUS UTILIZATION IN LUPINUS SPP.
Authors: TRINICK M. J.
Published: May 2006

Lupinus angustifolius, L. cosentinii and L. luteus were weakly infected (<10% of root length) with vesicular‐arbuscular endophytes and hence VA mycorrhizas were not considered of any value in their phosphorus uptake on the nutritionally poor sandy soils of Western Australia. Vesicles were present in approximately 30% of field plants and less often in the glasshouse. Arbuscules were observed on only one specimen of L. cosentinii in a restricted section of one lateral root. Infection was reduced further when soil moisture was high and by small additions of phosphorus to the soil. Under certain conditions, VA mycorrhizal infection in L. cosentinii was stimulated by the growth of red clover. ‘Proteoid’ ‐like rootlets were observed on lupins and these had specialized root‐soil surface properties that may be responsible for improved phosphorus uptake.