bluuebunny/crossref_metadata_2025 huggingface dataset:
NITROGEN FIXATION IN THE ROOT NODULES OF VICIA FABA L. IN RELATION TO THE ASSIMILATION OF CARBON. II. THE DARK FIXATION OF CARBON DIOXIDE
Authors: LAWRIE ANN C. , WHEELER C. T.
Published: May 2006

High activity of phosphoenolypyruvate carboxylase, malate dehydrogenase and malic enzyme has been found in extracts from broad bean nodules. Tracer studies of the metabolism of 14CO2 fixed by detached nodules showed that the amino acid fraction sequestered most radioactivity and that no radioactivity was associated with glucose and fructose, the main free sugars in ethanolic extracts of the nodules. The pattern of labelling supports an important role for glutamate, aspartate and asparagine in the metabolism of the fixed carbon, but relatively little radioactivity was associated with glutamine. Most of the radioactivity in the acidic fraction of the nodules was in malic and itaconic acids. Although the latter was not detected immediately on detachment of the nodules, it was present in amounts equal to malic acid 30 min after detachment.
POLYPHOSPHATE IN EUCALYPT MYCORRHIZAS: A CYTOCHEMICAL DEMONSTRATION
Authors: ASHFORD A. E. , LEE M. LING , CHILVERS G. A.
Published: May 2006

Small, more or less spherical metachromatic granules have been detected within the Hartig net and inner sheath hyphae of Eucalyptus fastigata mycorrhizas, and shown by various cytochemical tests to contain polyphosphates. These granules are believed to be the cytological equivalent of the biochemically characterized phosphate storage pool which other workers have defined on the basis of radiotracer studies.
THE EFFECT OF MYCORRHIZAL INFECTION OF PINUS SYLVESTRIS AND PICE A ABIES BY TWO BOLETUS SPECIES ON THE ACCUMULATION OF PHOSPHORUS
Authors: MEJSTŘÍK V. K.
Published: May 2006

Seedlings of Pinus sylvestris and Picea abies in sterile forestsoil or in a mixture of vermiculite and peat were inoculated with Boletus luteus, B. bovinus, both species, non‐sterile forest soil or non‐sterile soil plus B. bovinus. Following mycorrhizal development, the increase of the dry weight of roots and shoots over controls was highly significant in all combinations. The phosphorus content in mycorrhizal seedlings was higher than in nonmycorrhizal controls but only small differences were noted between different combinations. B. luteus was the better symbiont for uptake of phosphorus by Pinus sylvestris and Boletus bovinus for Picea abies.
LATERAL ROOT ELONGATION IN VICIA FABA L: THE PLANES OF CELL DIVISION IN THE EPIDERMIS, CORTEX AND STELE
Authors: MacLEOD R. D. , McLACHLAN S. M.
Published: May 2006

Planes of cell division have been investigated in the epidermis, cortex and stele, 400–1000 μm behind the cap apex, in lateral roots of Vicia faba, as they lengthened from just emerged to 4 cm. The frequency with which cells divided in any one plane differed in the various root tissues. Also, changes took place in the frequency with which the spindle was oriented in a radial, tangential or longitudinal plane in each tissue basally along these roots and as the laterals elongated. The contributions of cell division and cell expansion to increase in the dimensions of each tissue are discussed.
NITROGEN METABOLISM IN LICHENS
Authors: HITCH C. J. B. , MILLBANK J. W.
Published: May 2006

The blue‐green algal population and heterocyst frequency in Peltigera aphthosa, P. canina and P. polydactyla have been estimated by means of a chromium trioxide maceration technique followed by visual and photographic observation. Populations of the order of 107 cells/sq cm thallus in P. canina and P. polydactyla, and 106/sq cm in P. aphthosa have been found. These figures are some threefold greater than previously reported; the earlier results are explained by unexpectedly high fragility of the algal cells.

A heterocyst frequency of c. 3.5% in P. canina confirms previous estimates obtained by another technique; P. polydactyla is similar but P. aphthosa has a very high heterocyst frequency, c. 22% of the total cells. These findings are reflected in the nitrogenase activity and support the concept that the enzyme is only active in heterocysts.
KINETIC STUDIES ON THE BINDING OF ZINC IONS BY THE LICHEN USNEA FLORIDA (L.) WEB.
Authors: WAINWRIGHT S. J. , BECKETT P. J.
Published: May 2006

It is shown that the binding of zinc by Usnea florida is reversible and follows a classical Langmuir adsorption isotherm. Zinc binding is dependent on pH and this can be explained as competitive inhibition of zinc binding by protons.
POPULATION GROWTH IN CLADONIA STELLARIS (OPIZ.) POUZ. AND VEZDA
Authors: YARRANTON G. A.
Published: May 2006

Populations of Cladonia stellaris in burnt areas of the northern Ontario clay belt were observed photographically from 1968 to 1974. Population growth is logistic with a typical convergent standing crop of 500 g per m2, reached about 30 years after establishment. There is considerable oscillation about the convergent standing crops with time, as well as environmentally determined variations between crops at different sites. Rates of growth are strongly correlated with successional maturity, so that time of establishment may influence the subsequent population size. Final carrying capacity is apparently determined by a complex of factors effective through their influence on light and water availability and by direct physical interference of other species. Ericaceous shrubs and Pleurozium schreberi seem to be the most influential. Cladonia stellaris does not appear until 25 years after fire, but rapidly becomes the most abundant lichen by means of clonal growth. Clones develop by three kinds of budding and subsequently undergo fusion and fission as growth proceeds. Longer range dispersal is by means of small thallus fragments and is evidently highly efficient as newly colonized areas exhibit widespread potential distributions.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE V. THE EFFECTS OF MYCORRHIZAL INFECTION, SOIL TYPE AND PARTIAL SOIL‐STERILIZATION (BY GAMMA‐IRRADIATION) ON GROWTH OF CRANBERRY (VACCINIUM MACROCARPON AIT.)
Authors: STRIBLEY D. P. , READ D. J. , HUNT R.
Published: May 2006

Vaccinium macrocarpon was grown in open pots for 20 weeks on three heathland soils of decreasing fertility. Interactions between the effects of mycorrhizal infection, soil type and partial soil‐sterilization (by γ‐radiation) were studied by the calculation of various growth‐functions from fitted curves.

Mycorrhizal infection increased whole‐plant dry weight and relative growth‐rate but decreased the root/shoot ratio of plants grown on two of the irradiated soils. These plants contained a greater percentage of nitrogen and had higher specific absorption rates for N than uninfected controls.

The fertility of each soil was increased by partial sterilization. On one irradiated soil, mycorrhizal infection was without effect: all plants grew rapidly and had large specific absorption rates which were associated with a large net mineralization of NH4+‐N.

Changes in the values of growth‐functions with time occurred in most treatments and were especially marked in plants grown on the irradiated soil with marked mineralization of NH4+‐N. The importance of these ontogenetic variations is considered in relation to other experiments on the response of higher plants to mycorrhizal infection.
TYPES OF VERNATION IN THE CYATHIA OF EUPHORBIA MILLI DES MOULINS
Authors: BAHADUR BIR , REDDY N. PRATAP
Published: May 2006

Four types of vernation in the cyathia are described. The cyathium is subtended at the base by two bracts whose vernation may twist to the left or to the right or it may be neutral; two neutral types are possible. Counts made on sixteen different plants from various localities show that left and right‐handed cyathia occur with equal frequency but that neutral cyathia are less common. The different types of cyathia appear to occur at random in the umbels in which they are grouped.
CYTOGENETIC STUDIES IN THE GENUS POTENTILLA L.
Authors: GOSWAMI D. ACHARYA , MATFIELD B.
Published: May 2006

Cytogenetic studies involving eighteen species of Potentilla of the section Gymnocarpae were made to investigate their phylogenetic relationships and to see whether any correlation exists between morphology and crossing relationships.

The chromosome numbers of Potentilla ambigens Greene (2n = 82) and P. montenegrina Pant, (2n = 28) were determined for the first time. New intraspecific chromosome races were observed in three species: P. pennsylvanica L. (2n = 42), P. astrisanguinea Lodd. (2n = 84) and P. grandiflora L. (2n = 42).

Hybrids were obtained from only four of 628 crosses in 111 different combinations (P. nepalensis Hook, ×P. montenegrina Pant., P. astrisanguinea Lodd. ×P. ambigens Greene, P. recta L. × P. cf. hirta L. and P. grandiflora L. ×P. crantzii (Crantz) Beck.). The position of the crossing barrier in the unsuccessful crosses varied. Sometimes the pollen failed to germinate but in other cases well‐developed pollen tubes were observed. No definite correlation was found between the morphological similarity of species and their crossing ability.

Meiotic studies on the hybrids indicated some chromosomal homologies between the genomes of P. recta and P. cf. hirta and between P. grandiflora and P. crantzii, but not between P. nepalensis and P. montenegrina.
POLLEN FLOW IN LYTHRUM JUNCEUM, A TRISTYLOUS SPECIES
Authors: ORNDUFF ROBERT
Published: May 2006

Studies of the pollen loads present on stigmas of flowers of the self‐incompatible tristylous Lythrum junceum in Morocco indicate that the position of the stigma has an important effect on the proportion of pollen from long‐level anthers that is deposited on the stigmas. The greatest amount of large pollen from the longest set of stamens is found on stigmas of long‐styled flowers. Because of the inability to discriminate between small pollen grains from mid‐level anthers and those from short‐level anthers it is not clear how stigma position may influence the distribution of these small pollen grains. In the Moroccan population studied, plants with long‐, mid‐, and short‐styled flowers are present in a 1:1:1 ratio. The chief pollinator during the period of study was the honey bee, Apis mellifera, which preferentially removes large pollen grains from flowers. Longs and Mids produce approximately equal numbers of pollen grains per flower, and Shorts produce c. 77% of the pollen of each of these two forms. Acetolysis of stigmas provides more accurate estimates of stigmatic pollen loads than does microscopic examination of intact stigmas, although the proportional representation of the two size classes of pollen is similar with either method. This study represents the first published analysis of pollen flow in a tristylous species within its native range and suggests that tristyly serves to promote compatible pollinations, thus supporting the classical interpretation of the biological significance of tristyly.
EFFECTS OF CCCP ON PHOTOSYNTHESIS AND ON ACTIVE AND PASSIVE CHLORIDE TRANSPORT AT THE PLASMALEMMA OF HYDRODICTYON AFRICANUM
Authors: RAVEN J. A. , GLIDEWELL S. M.
Published: May 2006

CCCP inhibits photosynthetic CO2 fixation more than photosynthetic O2 evolution in Hydrodictyon africanum, while the photosystem two inhibitor, DCMU, inhibits the two processes equally. These results are consistent with CCCP acting as an uncoupler of photophosphorylation, thereby inhibiting CO2 fixation, and the remaining O2 evolution being associated with the ATP‐independent reduction of some (unknown) electron acceptor. Analysis of tracer chloride fluxes at the plasmalemma into active influx, exchange diffusion and passive uniport components supports previous conclusions, based on the assumption that all the tracer influx was due to active transport, that active chloride influx is relatively ATP‐independent. Some problems inherent in the occurrence of redox‐coupled active transport at the plasmalemma of eukaryotes are discussed, and a scheme which accounts for active chloride transport at the plasmalemma of H. africanum is proposed.
THE UPTAKE OF COPPER AND ITS EFFECT UPON RESPIRATORY PROCESSES OF ROOTS OF COPPER‐TOLERANT AND NON‐Tolerant CLONES OF AGROSTIS STOLONIFERA
Authors: WU L. , THURMAN D. A. , BRADSHAW A. D.
Published: May 2006

The uptake of copper by non‐tolerant and tolerant clones of Agrostis stolonifera has been studied. In both clones the roots accumulated more copper than the leaves and the roots of the tolerant clone accumulated more copper than the non–tolerant one. When supplied at concentrations above 10 μM in culture solutions copper moved up into the leaves of the non‐tolerant clone more readily than the tolerant one. Uptake of oxygen by roots was only affected when they were pretreated with copper, the non‐tolerant ones being more sensitive to inhibition than tolerant ones. Over the concentration range tested copper had no effect upon l‐malate‐dehydrogenase (MDH) activity in root extracts of either clone. Extracts prepared from non–tolerant roots pretreated with copper were found to contain less MDH activity than those prepared from tolerant ones. It is suggested that this was due to an inhibition of protein synthesis in the roots of the non‐tolerant clone, which did not occur in the tolerant one.
NITROGEN METABOLISM IN LICHENS
Authors: HITCH C. J. B. , MILLBANK J. W.
Published: May 2006

The N2(C2H2) fixing activity was surveyed in lichens of diverse structure and habitat, all containing a blue‐green phycobiont; twenty‐six species from fourteen genera are reported for the first time to fix nitrogen. Rates of N2(C2H2) fixation showed great variability between different lichen samples.

The proportion of heterocysts, as the assumed site of N2 fixation, was estimated in all the above lichens together with fourteen additional species. In lichens with one phycobiont, heterocysts form about 4% of the total algal cell population; in those with two phycobionts the blue‐green member is found in special structures and has a very high proportion of heterocysts, typically 20–30%; the N2(C2H2) activity appears to reflect this. The high proportion may be associated with the proximity of the green phycobiont.
EXPERIMENTAL ECOLOGICAL GENETICS IN PLANTAGO
Authors: WU LIN , ANTONOVICS JANIS
Published: May 2006

Induction of roots and shoots from leaves of Plantago lanceolata L. using IAA is a very effective technique which could be extended to large scale cloning for vegetative propagation and assay procedures in genecological studies on this and other species. In P. lanceolata, there were no differences between populations from contrasting habitats with regard to proportion of leaves producing roots and shoots. There was a high correlation between zinc tolerance measured on rooted leaves and on equivalent rooted tillers.
THE EVOLUTION OF MORPHOLOGICAL NOVELTY EXEMPLIFIED IN THE GROWTH PATTERNS OF SOME GESNERIACEAE
Authors: JONG KWITON , BURTT B. L.
Published: May 2006

The growth pattern of certain South African species ofStreptocarpussub‐genusStreptocarpushas been investigated, using in particular the speciesS. fanniniae.It is shown that the vegetative plant body consists of repetitive units, the first being formed by the accrescent cotyledon. These units are here called phyllomorphs: each has a stalk (the petiolode) showing a mixture of axis‐like and petiole‐like features, and a lamina. The development of the phyllomorph is largely controlled by a triad of meristems situated near junction of petiolode and lamina. The basal meristem provides new growth at the base of the lamina; the petiolode‐meristem contributes to the growth of the midrib as the lamina enlarges and to elongation of the petiolode; the groove‐meristem initiates the growth of new phyllomorphs and of the inflorescences.

Recognition of the phyllomorph as a repetitive structural unit permits satisfactory description and comparison of anomalous growth patterns of various species ofStreptocarpusand of certain other genera of Old World Gesneriaceae. Its evolution and diversification is briefly discussed.
THE HILL VEGETATION OF NORTH HOY, ORKNEY
Authors: PRENTICE H. C. , PRENTICE I. C.
Published: May 2006

North Hoy is an area containing a remarkable diversity of vegetation in a small area. A phytosociological account of the hill vegetation of North Hoy is presented, making use of an ordination method to clarify the inter‐relationships of the moorland vegetation types, as well as traditional methods. It has proved very interesting to compare the vegetation with the account of Scottish Highland vegetation by McVean and Ratcliffe (1962). Birks' (1973) account of the vegetation of Skye has also been drawn on, particularly as a source for a system of classes, orders and alliances applicable to Scottish vegetation. The environmental background (climate, topography, geology, patterned ground phenomena, animal populations and past and present land‐use) is summarized.

Several important general features of the vegetation of North Hoy deserve emphasis, especially from a conservation point of view.

Many good examples of noda characteristic of strongly basic soils, especially mires and grasslands, are found. Some of these have a rather restricted distribution in Scotland.

Small areas of woodland, including one very species‐rich wood, are found in sheltered ravines. These are well‐developed and regenerating, and represent the northernmost occurrence of woodland in Britain.

Many species and many types of vegetation occur at unusually low altitudes (as is also observed in northernmost Sutherland, Caithness and Shetland). Particularly interesting are certain montane dwarf heaths, which are associated with well‐developed patterned ground features.

The area contains both occurrences of ‘Atlantic’ bryophytes and well–developed stands of lichen heath and lichen‐rich bog, which have a strongly ‘continental’ distribution in Scotland. This apparent paradox is discussed but not resolved.

The low level of sheep‐grazing and absence of burning in recent years have led to some unusual vegetation features.

Phytosociological tables are presented in an appendix. A second appendix lists the lichens collected, as identified by P. W. James, with a short note on the occurrence of each.
POLLEN DIAGRAMS FROM THE SHETLAND AND FAROE ISLANDS
Authors: JÓHANSEN JÓHANNES
Published: May 2006

Two pollen diagrams are presented, one from Murraster, Shetland Mainland, and one from Hoydalar, Streymoy, Faroe Islands. Both localities are former lakes, now filled up, and in both places the sedimentation started about 10,000 years ago. In the Faroese diagram herbs are dominant throughout, while it can be seen that Juniperus and Salix have been of considerable significance and Betula nana has had a wide distribution in early Flandrian time. In the Shetland diagram large–leaved Betula and Corylus are also present, even though herbs were also dominant.
WIND‐BORNE SEED AND FRUIT MOVEMENT
Authors: BURROWS F. M.
Published: May 2006

Seeds and fruits of widely differing sizes and shapes and which employ different flight styles in wind‐borne movement during dispersal are discussed qualitatively in general aerodynamic terms, and grouped according to aerodynamic rather than botanical features. Most of these groups are considered separately, though not in any great detail, and the salient features of the differing motions belonging to each are described. The response of species, in particular to variations in vertical wind velocities, is mentioned as an important factor affecting‐deposition and dispersal range, and how because of this response some forced deposition may be possible with the introduction of suitably shaped obstacles to wind flow.
CARBOHYDRATE METABOLISM AND DIFFERENTIATION IN SEEDLING ROOTS
Authors: FOWLER MICHAEL W.
Published: May 2006

Information relating to the changing activities of the Embden—Meyerhof—Parnas pathway, the pentose phosphate pathway and tricarboxylic acid cycle during the differentiation of roots is reviewed. Attention is particularly drawn to the operation in roots of a short series of reactions involving the enzymes phosphoenol pyruvate carboxylase, malate dehydrogenase and malic enzyme. The possible role of this pathway in the provision of NADPH for reductive biosynthesis is discussed.

Sucrose is the major carbon source for carbohydrate metabolism in the root. Present information regarding its mode of entry into the root cells is sparse and confused. An attempt is made to pinpoint particular anomalies in the available data and to discuss some of the drawbacks associated with present approaches.

Interactions between the different pathways of carbohydrate oxidation are extremely complex. Some attempts to define these have been made, with specific reference to the roles played in metabolism by the individual pathways. The presence of the pentose phosphate pathway dehydrogenases, the malic enzyme and isocitrate dehydrogenase in roots raises the question of the origin of NADPH for biosynthesis. There is some evidence to suggest a degree of association between specific reaction systems, based on ‘supply’ and ‘demand’ for NADPH.

Very little information is available on the regulation of carbohydrate metabolism in roots. Some possible approaches to gaining more data on this important topic are outlined.
BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)
Authors: BAKER N. R. , HARDWICK K. , JONES P.
Published: May 2006

A quantitative study of the changes in chloroplast ultrastructure and carotenoids was made during cocoa flush leaf development. Plastid length, breadth, number of grana per plastid, index of lamellae per plastid and the number of lamellae per granum all increased with chlorophyll content. The number of chloroplasts per cell remained constant at three throughout leaf development. Lutein, neoxanthin, violaxanthin, α‐carotene and †‐carotene were the only carotenoids found in measureable amounts in cocoa leaves, and they all developed in parallel with chlorophyll. The phase of maximum chloroplast development in cocoa does not occur until after the termination of leaf expansion.
POLYPHOSPHATE GRANULES IN THREE DIFFERENT KINDS OF TREE MYCORRHIZA
Authors: LING‐LEE M. , CHILVERS G. A. , ASHFORD A. E.
Published: May 2006

Using cytochemical techniques, granules containing polyphosphate have been detected in Hartig net and sheath hyphae of Pinus ectomycorrhizas; in sheath, intercellular and intracellular hyphae of Arbutus ectendomycorrhizas; and in hyphae and vesicles of Liquidambar endo‐mycorrhizas.
PHOSPHATE UPTAKE ZONES OF MYCORRHIZAL AND NON‐MYCORRHIZAL ONIONS
Authors: RHODES L. H. , GERDEMANN J. W.
Published: May 2006

Mycorrhizal and non‐mycorrhizal onion seedlings were grown in individual soil chambers in which roots were confined to one side of a barrier. External hyphae of Glomus fasciculatus arising from mycorrhizal roots grew into an adjacent volume of soil. 32P was injected into soil at 1‐cm intervals up to a distance of 8 cm from the confined roots. Relatively high levels of radioactivity were subsequently detected in root segments of mycorrhizal plants at all distances from tracer injection. High levels of radioactivity were detected also in leaf segments of mycorrhizal plants. Radioactivity of root or leaf segments of non‐mycorrhizal plants did not exceed background level at any distance from tracer injection. 32P did not move more than 7.5 mm from the point of injection as indicated by gross autoradiography. Absorption of phosphate and its trans‐location to the host by hyphae of G. fasciculatus can extend the phosphate uptake zone of mycorrhizal onions to at least 7 cm from the root surface.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: POWELL CONWAY LL.
Published: May 2006

Onions were preinfected with seven Endogone spore types and red clover with five spore types and then grown in P deficient, 32P labelled soils. P uptake was much greater in most mycorrhizal plants than in controls. Specific activities of absorbed P were almost identical in all mycorrhizal and control plants.
TRANSLOCATION OF PHOSPHATE IN MOULD MYCELIA
Authors: EZE J. M. O.
Published: May 2006

Colonies of Phycomyces blakesleeanus, Rhizopus nigricons, Mucor mucedo and M. hiemalis were grown so that the colony was in contact with two different blocks of media; one block of medium was labelled with 32P‐phosphate. When the total phosphate concentration in both blocks was the same, no lateral translocation of 32P occurred, but when the phosphate concentrations in the two blocks differed, 32P was translocated in the direction of the phosphate concentration gradient.
TRANSPORT OF INDOLEACETIC ACID IN PLANT CELLS IN RELATION TO pH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT
Authors: RAVEN J. A.
Published: May 2006

The distribution of IAA between the vacuole and the bathing solution in Hydrodictyon africanum is consistent with passive entry of undissociated IAA and passive efflux of both undissociated IAA and of IAA, with PIAA (permeability coefficient)* about io−3 cm s−1 and PIAA‐ about io‐6 cms −1. The involvement of IAA− in the efflux results from the inside‐negative P.D. between the medium and the vacuole. The cytoplasm is at a higher pH than either the vacuole or the bathing solution used in most experiments; this is maintained by active H+ efflux at the plasmalemma, and active influx at the tonoplast. In this situation the efflux of IAA− is further promoted by the increased concentration of IAA− in the relatively alkaline cytoplasm. Thus the apparent active efflux of IAA from these cells can be explained in terms of passive driving forces of concentration and electrical potential acting on IAA and IAA−, with the distribution of these two species dictated ultimately by PIAA, PIAA‐ the pH of the various compartments and the electrical potential difference between them. If PIAA/PIAA‐ were larger at the apical than at the basal end of coleoptile cells, such an effect could explain polar IAA transport, with metabolic energy being used only to maintain the relative permeabilities to the two species, the pH gradient and the electrical gradient.
MORPHOGENESIS OF AERIAL SCLEROTIA OF COPRINUS LAGOPUS
Authors: WATERS H. , MOORE D. , BUTLER R. D.
Published: May 2006

Aerial sclerotia originated from intercalary cells of aerial hyphae. Initially only a single cell was involved. Repeated branching from the initiation point formed the sclerotium initial which was a more or less spherical mass of undifferentiated, radially arranged cells. Accumulation of glycogen in cells towards the centre of the initial marked the commencement of maturation. Cells of the central (medullary) region went through a differentiation process which involved first a heavy accumulation of glycogen; the glycogen was then mobilized, its reduction in concentration being exactly correlated with the formation of a thick, hyaline, secondary wall. As the medulla developed, differentiation of localized areas of cells just within the margin of the initial occurred to form the protective rind layer. Wall thickening in rind cells was not preceded or accompanied by glycogen accumulation. Strains which failed to produce sclerotia behaved as stable variants, sclerotium non‐production segregating as a single gene. Four such genes were recognized and some linkage information obtained.
THE OCCURRENCE OF A PERIPHERAL RETICULUM IN PLASTIDS OF THE GYMNOSPERM, WELWITSCHIA MIRABILIS
Authors: WHATLEY JEAN M.
Published: May 2006

In cells bordering the vascular bundles of the cotyledons of Welwitschia mirabilis there are starch‐containing chloroplasts which possess a type of peripheral reticulum.
AN ALBINO MUTANT IN PLANTAGO INSULARIS REQUIRING THIAMINE PYROPHOSPHATE—ROLE OF TPP IN PIGMENT AND PROTEIN SYNTHESIS
Authors: MICHAEL SANDRA D. , SPURR ARTHUR R.
Published: May 2006

Seedlings of Plantago insularis were grown in darkness for 5 days and then exposed to white light for 24 h. At the beginning of the light period some plants were treated with thiamine pyrophosphate (TPP). Light exposure caused a marked development of both chlorophyll a and b in the normal (al+/al+) plant, but only a slight formation of chlorophyll in the mutant (al/al) TPP plus light induced the formation of chlorophyll a and b in the mutant to near normal levels. Light alone increased the level of carotenoids in the normal type, but not in the mutant; but TPP plus light increased the carotenoids in the mutant to near normal. Albinism in Plantago is due, in part, to a deficiency in TPP and a consequent deficiency in chlorophyll and carotenoid pigments.

Acid‐soluble nitrogen was distinctly lower in the albino mutant than in normal plants, but increased in the mutant after treatment with TPP and exposure to light. Exposure of dark‐grown normal seedlings to light alone caused a marked increase in acid‐insoluble nitrogen. Recovery in the mutant appeared to be at the expense of the soluble nitrogen fraction, and is attributed to the synthesis of chloroplast proteins. The light‐yellow mutant grown in the dark became bleached on exposure to light, yet a moderate increase in nitrogen occurred during exposure, indicating that some protein synthesis is independent of chlorophyll and carotenoid development in the plastids. A pathway initially involving TPP appears to be affected by light in the formation of chloroplast proteins.
ANALYSIS OF COMPOSITION OF RESPIRATORY GASES IN WOODY STEMS BY MASS SPECTROMETRY
Authors: CARRODUS B. B. , TRIFFETT A. C. K.
Published: May 2006

A method of analysis of small volumes of gases from bulky plant organs, using mass spectro‐metry, is described. Results obtained from woody stems of Acacia mearnsii indicate that the most actively metabolizing tissues exist in an environment whose gaseous component is almost exclusively carbon dioxide. This observation is consistent with previous observations on the effect of carbon dioxide on the formation of compounds characteristic of heartwood in A. mearnsii.
THE CESSATION OF MITOSIS AT THE MARGINS OF A ROOT MERISTEM
Authors: CLOWES F. A. L.
Published: May 2006

The mean rates of mitosis for all cycling cells and the cell‐doubling times have been measured independently by pulse‐labelling and by blocking the cell cycle and then used to measure the fraction of cycling cells along the meristem of primary roots of Zea mays. The attenuation of mitotic activity that occurs towards the proximal and distal margins of the meristem is due solely to a reduction in growth fraction and not at all to a change in the rate of cycling. This is contrasted with the situation in the quiescent centre of the meristem where the low rate of cell formation results from both a reduction in growth fraction and prolongation of cell cycles. DNA synthesis outside a normal mitotic cycle begins to occur in regions containing cycling cells on both sides of the quiescent centre.
HYBRIDS BETWEEN LOLIUM PERENNE AND FESTUCA PRATENSIS
Authors: GYMER P. T. , WHITTINGTON W. J.
Published: May 2006

Meiosis and fertility have been studied in natural and artificial hybrids between Lolium perenne and Festuca pratensis. In diploids, meiosis was normal except for a few desynaptic hybrids, but pollen fertility was very low, probably because of genie or chromosomal unbalance. In triploids the extent of homoeologous pairing varied, as did fertility.

Several categories of synthetic hybrids were compared with their natural equivalents, and it is considered most likely that all the natural hybrids studied were F1 plants, although there were some discrepancies. Those that were triploid were probably produced by unreduced pollen grains.
SOME ASPECTS OF POLLINATION ECOLOGY OF ARMERIA MARITIMA (MILL.) WILLD. IN BRITAIN
Authors: EISIKOWITCH DAN , WOODELL STANLEY R. J.
Published: May 2006

Pollen and stigmata of Armeria maritima are very tolerant of sea water, maritime plants showing greater tolerance than those from an inland serpentine site. After pollination, sea water impairs pollen germination only briefly, whereas distilled water adversely affects pollen tube production. The tolerance of pollen to sea water is associated with the relative humidity of the air in a way not fully understood. Bumblebee behaviour in an area of saltmarsh, dune and shingle appears to be affected by the bending of inflorescence stalks and consequent deposition of bees on wet ground. The bees’ behaviour results in restriction of gene flow between adjacent populations in different habitats.
POLLEN ANALYTICAL EVIDENCE FOR PREHISTORIC FOREST CLEARANCE IN THE UPLAND AREA WEST OF RISHWORTH. W. YORKSHIRE
Authors: BARTLEY DAVID D.
Published: May 2006

A pollen diagram from blanket peat at about 410 m on Rishworth Moor in the Yorkshire Pennines is discussed with particular reference to forest clearance. The evidence suggests that there was relatively little clearance in the Neolithic and Bronze Age but considerable activity accompanied by pastoral and some arable agriculture occurred in the Iron Age. This intensive agriculture seems to have ended early in the Roman period, when there was a recovery of the woodlands. The sequence is dated by four radiocarbon assays and its significance is discussed in relation to the archaeological and historical data available.
STIMULATION OF PHOTOSYNTHETIC STARCH FORMATION BY SEQUESTRATION OF CYTOPLASMIC ORTHOPHOSPHATE
Authors: SHEU‐HWA CHEN‐SHE , LEWIS D. H. , WALKER D. A.
Published: May 2006

Photosynthetic starch formation in leaf discs of spinach beet and related species can be increased more than ten fold by the presence of exogenous mannose at 10−2 M. In these species, carbon from mannose is not incorporated into starch to a significant extent and the stimulation is believed to be an indirect effect resulting from the sequestration of cytoplasmic ortho‐phosphate as mannose phosphate. In species such as tobacco, there is substantial incorporation of carbon from mannose into starch and into soluble compounds other than mannose‐6‐phos‐phate.
THE ROLE OF THE COTYLEDONS IN FOUR ACER SPECIES AND IN FAGUS SYLVATICA DURING EARLY SEEDLING DEVELOPMENT
Authors: AMPOFO S. T. , MOORE K. G. , LOVELL P. H.
Published: May 2006

Studies on seedlings of Acer negundo, A. platanoides, A. pseudoplatanus, A. pseudoplatanus‐atropurpureum and Fagus sylvatica showed that the smaller seeded Acers had a shorter lag period before the onset of rapid growth than the larger seeded Fagus. Relative growth rates and net assimilation rates were high during the early stages of seedling growth when cotyledons constituted the major proportion of the photosynthetic surface area indicating the importance of cotyledon photosynthetic activity. Acer negundo which had the lowest seed weight and the smallest initial cotyledon area of the four Acer species had the most rapid dry weight increase. It also had stomata on both upper and lower surfaces of the cotyledons in contrast to A. platanoides and A. pseudoplatanus which had stomata only on the lower surface. Although this difference in stomatal distribution could be an important factor in the higher photosynthetic rate and more substantial dry weight increases in A. negundo, it is suggested that the latter is due mainly to the more rapid rate of leaf production.
COTYLEDON PHOTOSYNTHESIS DURING SEEDLING DEVELOPMENT IN ACER
Authors: AMPOFO S. T. , MOORE K. G. , LOVELL P. H.
Published: May 2006

The major storage function of cotyledons of Acer negundo, A. platanoides and A. pseudoplatanus is completed shortly after seedling emergence. Cotyledon photosynthates are essential for the maintenance of leaf production and seedling dry weight increase during the first week after emergence. However, cotyledon photosynthesis is not essential for seedling survival. Initially, much of the photosynthate exported from the cotyledons moves into the developing first leaf pair. This is most marked in A. platanoides and A. pseudoplatanus. Later, as the requirement for cotyledon photosynthate declines, less is exported from the cotyledon, mostly to the hypo‐cotyl and roots. In A. negundo successive pairs of leaves are produced before the preceding pair have fully expanded and the cotyledons supply photosynthates to the latter in contrast to A. platanoides and A. negundo in which they are presumably supplied by the first leaf pair.

Substantial losses of radioactivity occur from the seedlings after 14CO2 application to cotyledons of A. pseudoplatanus, mainly during the first 48 h; this coincides with the maximum rate of radiocarbon export from the cotyledon. It is suggested that these losses are due to respiration and that they probably take place from the whole seedling, not merely from the treated organ.
TRANSLOCATION OF LABELLED ASSIMILATE IN MORPHOLOGICALLY CONTRASTING COTTON PLANTS
Authors: BHATT J. G.
Published: May 2006

In normal cotton plants and in a variety with short fruiting branches, labelled assimilate was translocated to fruiting bodies on upper and lower sympodia when the sympodial leaf on the first node of the fourth sympodium was treated with I4C sucrose. Main stem leaves similarly treated, exported the assimilate to fruiting bodies only on the lower sympodia in the long‐branch variety whereas in the short‐branch variety, the assimilate also reached the upper sympodia. This higher efficiency of the main stem leaf in short‐branch cotton may be related to a reduction in the translocation path because of the particular spatial arrangement of its leaves and fruits.
ADVENTITIOUS ROOT INITIATION AND GROWTH IN RELATION TO OXYGEN SUPPLY IN GERMINATING RICE SEEDLINGS
Authors: KORDAN H. A.
Published: May 2006

Adventitious root initiation and root growth occur in rice seedlings germinating under favourable environmental oxygen concentrations whereas rice seedlings germinating at low oxygen concentrations or under anaerobiosis form adventitious root primordia but show no visible adventitious root growth. Transferring the seedlings from unfavourable to favourable oxygen environments results in root growth. Thus the phenomena of adventitious root primordia initiation and of root growth differ profoundly with respect to their oxygen requirements.
THE ULTRASTRUCTURE OF COLLEMA TENAX, WITH PARTICULAR REFERENCE TO MICRO‐TUBULE‐LAKE INCLUSIONS AND VESICLE PRODUCTION
Authors: BOUSFIELD JOAN , PEAT ALANT
Published: May 2006

An ultrastructural study of the vegetative thallus of Collema tenax (SW). Ach, showed that although haustorial connections were absent, the mycobiont did occasionally penetrate the algal sheath material. Concentric bodies and mesosome‐like structures were characteristically found in the mycobiont.

Normal and senescent blue‐green algal cells were found alongside unusual vesiculating cells. Vesicles from these latter cells are apparently produced by reverse pinocytosis of plastoglobuli. These vesicles were occasionally found in close juxtaposition to the fungal hyphae, after dissolution of the algal sheath, and the hypothesis is advanced that they may be implicated in lipid transfer.‘Microtubule‐like’structures were observed in the algal cells and their relationship to similar structures in free living Nostoc, other blue‐green algae, bacteria, algal and higher plant chloroplasts and to typical microtubules is discussed.

The ultrastructure of fresh and rehydrated material was compared. There was no apparent difference in the ultrastructure of material which had been dried for 3 months and rehydrated and that of material which had been freshly fixed.
GROWTH OF LATERAL ROOT PRIMORDIA IN VICIA FABA L.
Authors: MacLEOD R. D.
Published: May 2006

Over the 136 h period between the initiation of a lateral root primordium and its subsequent emergence as a secondary root, cell number, length and volume of the primordium tended to increase in a linear manner, each increase being closely correlated with the others. The corresponding rates of increase, however, when calculated for different stages of primordium development, fluctuated greatly. Thus, the rate of cell proliferation was high 10 h following anlage initiation, but was subsequently very low. The rates of increase in meristem volume and length were also high at an early stage of primordium development (28–45 h), but decreased to reach minimal values between 62 and 78 h before increasing again.

These changes in rate are discussed with respect to the development of a cavity in the adjacent cortical tissues of the primary root. Such cavities, which are initiated as a result of mechanical pressure, begin to form when the primordium has attained a cell number of about 1490 and reach a maximum size when the primordium contains about 10,800 cells.
VARIATION WITHIN COMMON GROUNDSEL, SENECIO VULGARIS L.
Authors: ABBOTT RICHARD J.
Published: May 2006

Variation within and between four populations of the highly plastic and ephemeral plant Senecio vulgaris L. has been evaluated for several quantitative characters in three environments and at four stages of development. The populations were from soils of high and low nutrient levels and in habitats of different degrees of exposure. There are significant differences between the means and phenotypic variances of populations for most characters but the degree of difference tends to change both in level and direction between environments and throughout development. However, there are some consistent differences and these seem closely related to the differences between habitats. Of special interest was the variation within populations where it emerged that samples of the populations from sites that were highly heterogeneous for exposure showed much more heritable variation for height and several other characters which might influence the expression of stature than samples from apparently homogeneous sites. It is suggested that though S. vulgaris is capable of showing a wide measure of phenotypic plasticity which could be of adaptive significance in the field, many differences between and within populations may in part be attributed to gene differences that are likely to have resulted from the action of natural selection.
ACTIVE INFLUX OF HEXOSE IN HYDRODICTYON AFRICANUM
Authors: RAVEN J. A.
Published: May 2006

The glucose analogue, 3‐O‐methyl glucose, is actively transported inwards at the plasmalemma of Hydrodictyon africanum. It is likely that a similar mechanism is operative for glucose influx, although demonstration of its active transport is complicated by an apparent coupling of the rates of glucose entry and metabolism. Active OMG Transport, and the influx and metabolism of glucose, need ATP. This ATP can be supplied, in order of increasing rates of the two processes, by fermentation, cyclic photophosphorylation, oxidative phosphorylation and by photo‐phosphorylation plus oxidative phosphorylation.
NUCLEOTIDE EFFECTS ON THE OXIDATION OF MALATE AND OXALOACETATE BY ARUM MITOCHONDRIA
Authors: WEDDING RANDOLPH T. , McCREADY CHRISTOPHER C. , HARLEY JOHN L.
Published: May 2006

Malate oxidation by mitochondria prepared from stage γArum spadices is inhibited by ADP. When oxaloacetate is also present, the effect of ADP is to increase the rate of oxygen uptake to one well in excess of the rate with malate alone. Arum mitochondria cannot oxidize oxaloacetate alone, but when increments of ADP or other nucleotides are added with oxaloacetate, oxygen uptake begins and continues for an extended period at a constant rate. The rate is proportional to the amount of nucleotide added. The stimulation of oxaloacetate oxidation by nucleotides increases in the order AMP < ADP < ATP, and Mg2+, but not PO2−3, is required for the stimulatory effect of the nucleotide. These responses to nucleotides are thought to be occasioned by the role of these substances as effectors of an enzyme or enzymes concerned with the metabolism of malate and oxaloacetate rather than involving the phosphorylative capacity of the mitochondria because the results are independent of the presence or absence of uncoupling substances.
EFFECTS OF SULPHUR DIOXIDE ON BIOCHEMICAL ACTIVITY AND ULTRASTRURAL ORGANIZATION OF PINE NEEDLED CHOROPLASTS
Authors: MALHOTRA S. S.
Published: May 2006

The effects of aqueous SO2 on the ultrastructural organization of pine (Pinus contorta Dougl. var. latifolia Engelm.) chloroplasts and on their photosynthetic activity were determined under laboratory conditions. At aqueous concentrations of 100 and 500 ppm, SO2 caused swelling of thylakoid discs and disintegrated other intrachloroplast membranes, resulting in the formation of small vesicles (in older, matured tissues). Chloroplast structural injury was more pronounced in old tissues than in younger and more metabolically active tissues. The biochemical observations (Hill reaction activity) made on chloroplasts isolated from SO2‐treated pine needle segments are in good agreement with the cytological observations.
THE INFLUENCE OF LEAVES ON COTYLEDON PHOTOSYNTHESIS AND EXPORT DURING SEEDING DEVELOPMENT IN ACER
Authors: AMPOFO S. T. , MOORE K. G. , LOVELL P. H.
Published: May 2006

The photosynthetic contributions of the cotyledons and of leaf pair one to seedling growth of Acer and the interactions between them were studied using 14CO2. During early development the cotyledons of A. negundo, A. platanoides and A. pseudoplatanus exported photosynthates to the hypocotyl, roots and young expanding leaves. When the first pair of leaves began to export photosynthate, export from the cotyledons declined in A. negundo and A. pseudoplatanus and was directed increasingly to the roots and hypocotyl. As further leaf pairs were produced, the movement of photosynthates from the first leaf pair became increasingly basipctal (as occurred at an earlier stage for the cotyledons).

The decline in total fixation in, and percentage export from, cotyledons of A. negundo and A. pseudoplatanus was shown to be due to the increase in other sources of photosynthesis (leaves) and a consequent reduction in the demand for cotyledon photosynthetic products. Removal of the expanded leaves resulted in an increase in cotyledon fixation and export and also a rapid, marked change in the direction of export. Thus, the cotyledons maintained a high potential for photosynthesis although this was realized later in seedling development only if other sources of photosynthetic products were removed.

A. platanoides differed from the other two species in that there was an increase in export from both cotyledons and leaf pair one about 30 days after seedling emergence, coinciding with the production of leaf pairs two and three. Presumably these constituted a major sink which created a greater demand for photosynthetic products, thereby increasing fixation and export rates of the photosynthetic organs present.
ESTIMATION OF CAFFEINE, THEOPHYLLINE AND THEOBROMINE IN PLANT MATERIAL
Authors: JALAL M. A. F. , COLLIN H. A.
Published: May 2006

A method for the combined estimation of caffeine, theophylline and theobromine in plant material is presented. The method involved a chloroform‐ammonia extraction, separation of the bases in the chloroform extract by thin layer or paper chromatography and finally estimation of the eluted bases by spectrophotometry. Good recoveries of all three compounds were recorded. The method was used to estimate the level of these compounds in tea, coffee beans and cocoa cotyledons.
FACTORS AFFECTING POTASSIUM UPTAKE AND LOSS BY BEECH MYCORRHIZA
Authors: EDMONDS A. S. , WILSON J. M. , HARLEY J. L.
Published: May 2006

Maximum potassium uptake is achieved by beech mycorrhizas from concentrations of chloride of about 0.2 mM. Addition of NaCl up to 0.5 mM does not significantly reduce K+ uptake from 0.1 mM chloride solutions, although the KCl significantly reduces Na+ uptake. Potassium is rapidly lost from mycorrhizal tissues at temperatures above 20° C, but only after some delay from tissues at lower temperatures. Addition of calcium ions (up to 1.0 mM CaCl2) does not significantly affect potassium uptake or loss. CaCl2 added to RbCl solutions slightly reduces Rb+ uptake. Losses of K+ from mycorrhizal tissues at temperatures above 20°C may be prevented by the application of glucose or fructose. Neither the process of carbohydrate uptake nor the increased internal concentration of carbohydrate itself is responsible for the reduction in potassium loss. It seems probably that factors bringing about the retention of potassium are generated in carbohydrate metabolism. The potassium loss engendered by high osmotic pressure of the external solution seems to be a separate phenomenon from that which occurs at high temperatures.