bluuebunny/crossref_metadata_2025 huggingface dataset:
THE POSSIBLE ROLE OF MEMBRANE ELECTROPHORESIS IN THE POLAR TRANSPORT OF IAA AND OTHER SOLUTES IN PLANT TISSUES
Authors: Raven J. A.
Published: May 2006

Summary

Polar transport of IAA in young higher plant shoot tissue requires an asymmetric distribution of membrane‐transport sites in the plasmalemma of the cells. The ‘chemiosmotic’ hypothesis of IAA transport requires that IAA‐ uniporters be largely on the basal side of the cells. It is suggested that the longitudinal gradient of electrical potential difference (PD, base positive to apex) which may result from activation of plasmalemma H+ efflux in the basal cells by transported IAA, may serve to maintain and reinforce this asymmetric distribution of carriers by the process of membrane electrophoresis of the carriers. The origin of this asymmetric distribution (and hence of polar IAA transport) may lie in electrical potential differences in maternal tissue around the developing embryo. Maintenance of polarity through seed dormancy may be related to gradients in cell‐wall fixed charges (and hence of electrical potential difference) along the shoot axis related to the uronate content of cell walls at different stages of cell development. The possibility of testing this hypothesis, and its relevance to other polar transport phenomena in plants, are briefly discussed.
EFFECTS OF BENZYLADENINE AND GIBBERELLIC ACID ON THE RESPONSES OF TOMATO PLANTS TO ANAEROBIC ROOT ENVIRONMENTS AND TO ETHYLENE
Authors: JACKSON M. B. , CAMPBELL D. JOAN
Published: May 2006

Summary

Benzyladenine (BA) and gibberellic acid (GA) were applied together as a foliar spray to young tomato plants growing in pots of well drained soil, waterlogged soil or in nutrient solution supplied with air (aerobic), nitrogen gas (anaerobic), or ethylene (20 or 100 ul 1−1 in air) for up to 6 days.

BA and GA (10 fig ml−1) lessened the inhibitory effects of waterlogging on stem elongation, transpiration and the increase of fresh and dry wt of the shoots. In absolute terms the promotion of shoot growth by BA and GA was greater in plants growing in non‐waterlogged than in waterlogged soil. Root growth was inhibited by BA and GA. The effect of waterlogging in promoting adventitious rooting at the base of the stem was reduced by BA and GA.

Epinastic curvature by petioles was promoted by growing plants in waterlogged soil or anaerobic solution culture in association with an increase in the production of ethylene by the petioles. Applications of BA and of GA inhibited this epinastic growth but they did not lower the rate of ethylene production. However BA and GA diminished the effectiveness of ethylene as a stimulator of epinastic curvature.

The application of ethylene to the roots inhibited the accumulation of dry wt by the root system and decreased slightly the growth promoting effects of BA and GA in the shoots.

The inhibiting effect of waterlogging the root system on stem elongation could be offset if adventitious roots maintained in well aerated conditions were previously induced on the main stem above the primary roots. Epinastic curvature and ethylene production were not decreased by the presence of an adventitious root system. The extent to which applications of BA and GA may reflect the activity of endogenous hormones produced by aerobic roots is discussed.
THE OCCURRENCE OF MULTIPLE FRUITING LATERALS AT SINGLE NODES OF RASPBERRY CANES
Authors: JENNINGS D.L.
Published: May 2006

Summary

Raspberry canes frequently have several buds at a node, but it was found that the ability of more than one to develop into a fruiting lateral was influenced by several genetic and non‐genetic factors. Cane diameter was important: a high diameter favoured the production of multiple laterals at a node but reduced the percentage of lateral‐bearing nodes. Consequently, overall lateral production remained nearly constant over a range of cane diameters. Cultivar Glen Clova and other genotypes with a high incidence of multiple laterals were used as donor parents of multiple lateral production in a breeding programme and were shown to transmit the character through genes acting in an essentially additive way. Genes affecting cane diameter contributed to these genetic differences but genotypes differed in their response to cane diameter variation. Gene L1 reduced the incidence of multiple laterals. Frost injuries checked the primary laterals and induced a very high incidence of multiple laterals; performance in a frost year may not be related to performance in other years.

It is concluded that multiple laterals are a yield component of only limited value. Their potential for increasing yield is rarely fully realized because reduction in other yield components tends to be associated with their development except when cane diameters are very large.
HORMONAL REGULATION OF FLOWERING IN A SYMPODIAL ORCHID HYBRID DENDROBIUM LOUISAE
Authors: GOH C. J.
Published: May 2006

Summary

The growth habit, axillary bud differentiation and flowering behaviour in a sympodial orchid hybrid, Dendrobium Louisae cv. ‘Dark’ were studied. Flowering occurred only after termination of vegetative growth in the pseudobulb. Intermediate shoots with both vegetative and reproductive growth were produced when plants were placed in the shade. Decapitation did not stimulate floral initiation. In mature pseudobulbs, Cytokinin (benzyladenine) stimulated flowering. Gibberellic acid enhanced the cytokinin effect but was itself not effective. It is suggested that flowering in this orchid hybrid is regulated by growth substances, both qualitatively and quantitatively.
PROMOTION OF GERMINATION OF STELLARIA MEDIA SEEDS BY LIGHT FROM A GREEN SAFE LAMP
Authors: BASKIN J. M. , BASKIN C. C.
Published: May 2006

Summary

Seeds of Stellaria media (L.) Cyrill. given short exposures to light from a green safe lamp transmitting most of its energy in the 500 to 600 nm region of the spectrum germinated to a high percentage in darkness. The possibility is discussed that the small amount of blue light (400 to 500 nm) or the relatively large amount of yellow‐orange light (550 to 600 nm) transmitted by the safe lamp, rather than green light (500 to 550 nm) per se, may have stimulated germination. However, green light previously has been shown to stimulate seeds to germinate, and great caution should be exercised in treating as dark controls, seeds that have been exposed to light from a green safe lamp.
OXYGEN RELATIONS OF THE ROOT NODULES OF ALNUS RUBRA BONG.
Authors: WHEELER C. T. , GORDON J. C. , CHING TE MAY
Published: May 2006

Summary

The acetylene reducing activity of Alnus rubra nodules is maximal in 15 to 30% oxygen. Within the nodule, the large number and size of many of the intercellular spaces between the uninfected cells in the outer cortex facilitates the diffusion of air through the lenticeb to the infected cells in the mid‐cortex. Access of air to the infected cells, which are arranged in longitudinal bundles separated by one or more lines of starch‐containing uninfected cells and which run at an angle away from the stele towards the nodule apex, is restricted by the reduced number and size of air spaces in this region. The cytoplasm of the infected cells shows high activity of peroxidase and o‐diphenol oxidase, but the lack of correlation between the activity of these enzymes and nitrogenase activity suggests that they are not involved in the control of access of oxygen to the endophyte. It is suggested that one role of nodule peroxidase is the ignification of the infected cells associated with cellular senescence.
RESPONSES OF THREE CROP SPECIES TO VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION ON ZINC‐ DEFICIENT INDIAN SOILS
Authors: SWAMINATHAN K. , VERMA B. C.
Published: May 2006

Summary

Maize, wheat and potato plants were grown on three very zinc‐deficient Indian soils in a pot culture study; the treatments were inoculation of seed with the spores of the vesicular‐arbuscular (VA) mycorrhizal organism, Glomus macrocarpus, dressing with 65ZnSO4 to supply 10 p.p.m. Zn, or both with appropriate controls.

Plants raised from inoculated seed usually exhibited root infection and were observed to assimilate significantly more Zn from the soil, than non‐mycorrhizal plants. For maize grown on Daurala soil, Zn application appeared to stimulate endomycorrhizal efficiency in collecting Zn for the host plant; for other crops and on other soils, fertilizer‐Zn did not improve plant uptake of Zn, and so it was concluded that mycorrhizal infection, by itself, could take care of the total Zn requirement of the higher symbiont.

Yield responses closely followed the pattern of Zn uptake, with the exception that tuber production in the potato was unaffected by any of the treatments on all the soils. The starch contents of the tubers was, however, found to increase commensurately with the level of Zn in leaves.

It is concluded that the observed mycorrhizal effect restricts itself to the more easily available fractions of Zn in deficient soils.

The value of artificial inoculation with VA‐mycorrhizae under field conditions to upgrade nutrient‐deficient soils is discussed in the light of the above findings.
MID‐FLANDRIAN CHANGES IN VEGETATION ON MAINLAND ORKNEY
Authors: KEATINGE T. H. , DICKSON J. H.
Published: May 2006

Summary

The presence of birch‐hazel scrub with a rich ground flora of tall herbs and ferns in the mid‐Flandrian on Mainland, Orkney, suggested by Moar (1969), is supported, but no evidence was obtained for Pinus, Quercus, Alnus or other major forest trees as indigenous species. Evidence from lake muds and intertidal peat in the region of the Bay of Skaill suggests an increase in onshore wind speeds with the formation of the Bay of Skail and the beginning of sand‐blow c. 5000 B.P. The birch‐hazel scrub declined at this time and the remaining tall herb and fern vegetation was replaced by pasture within c. 200 years under the influence of neolithic man and his grazing animals. At c. 3400 B.P. a combination of increased oceanicity of climate and high grazing pressure appear to have led to the initiation of blanket peat formation on the hills. A contribution to the interpretation of 14C dates derived from marly sediments is included.
SOME UNUSUAL CHARACTERISTICS OF NITRATE REDUCTION IN ERYTHRINA SENEGALENSIS DC.
Authors: STEWART G. R. , OREBAMJO T. O.
Published: May 2006

Summary

The characteristics of nitrate reduction exhibited by the tropical leguminous tree Erythrina senegalensis differ in several respects from those of other higher plants. Nitrate reduction in this species can best be characterized as being a high activity‐low affinity system. High levels of nitrate reductase can be demonstrated using in vivo (50 to 278 μmol h−1 g fresh wt−1) or in vitro (360 μmol h−1 g fresh wt−1) assay procedures. The enzyme extracted from leaf tissue can utilize both NADH and NADPH as electron donors. The enzyme has a low affinity for nitrate, Kspp194 8 to 10 mM. The NADH and NADPH activities co‐chromatograph using several chromatographic procedures, suggesting a single molecular form of nitrate reductase is present.
COMPARISON OF THE ONION PLANT (ALLIUM CEPA) AND ONION TISSUE CULTURE
Authors: SELBY C. , GALPIN I. J. , COLLIN H. A.
Published: May 2006

Summary

The system for flavour production in the onion consists of the enzyme alliinase and the flavour precursors, the S‐alkyl‐L‐cysteine sulphoxides. Flavour production in the onion and in the callus were compared by looking at each part of the system in turn. Measurement of the specificity and Km values of the alliinase from onion bulb and callus showed the enzymes to be identical. The total amino acid level was lower in the callus tissue than onion bulb tissue and the composition was altered. However, this change in amino acid metabolism did not appear to affect the synthesis of the flavour precursors since addition of the important amino acids L‐cysteine and L‐valine to the medium did not lead to the production of an onion smell from the callus upon crushing. The most noticeable difference was in the composition of the flavour precursors. In the callus S‐methyl‐l‐cysteine sulphoxide was present at a low concentration while the major precursor of onion flavour S‐trans‐prop‐1‐enyl‐l‐cysteine sulphoxide, was absent altogether. It was suggested that the biosynthetic pathway for S‐trans‐prop‐1 ‐enyl‐l‐cysteine sulphoxide was not functioning in the callus.
SOME EFFECTS OF DAZOMET ON 0‐DIPHENOLOXIDASE ACTIVITY IN HOMOGENATES OF SOLANUM TUBEROSUM
Authors: VAUGHAN D. , ORD B. G.
Published: May 2006

Summary

Dazomet, a commercially available soil fumigant, inhibited 0‐diphenoloxidase activity in homogenates of potato tubers. This inhibition was prevented in the presence of sufficient quantities of Cu2+. Dazomet affected the V(max) of the enzyme reaction, but had no effect on the affinity of the enzyme for its substrate. Similar results were obtained using the Cu2+ chelating agent sodium diethyldithiocarbamate.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A. , MORRIS T. , TYSIACZNY M. J. , MacFARLANE J. D.
Published: May 2006

Summary

The occurrence of dark CO2 fixation in Peltigera cardna var. praetextata and Parmelia caperata is reported, with rates of 15 to 27 % and 10 to 12 % respectively of the equivalent light photo‐synthetic rate. The pattern of incorporation into oxaloacetate, malate, citrate, alanine and aspartate points to fixation via PEP and provides both anaplerotic replenishment of TCA cycle intermediates as well as active amino acid and protein synthesis in the dark.

The environmental control of the rate of dark CO2 fixation by temperature, moisture and season is factorially examined and the potential role of dark CO2 fixation in the ecology of a lichen is briefly discussed.
ULTRASTRUCTURAL ASPECTS OF THE SYMBIOSIS BETWEEN ALGAL CHLOROPLASTS AND ELYSIA VIRIDIS
Authors: Hawes C. R.
Published: May 2006

Summary

The ultrastructure of chloroplasts in the frond of Codium fragile and in symbiotic association with the digestive cells of Elysia viridis is described. In the hepatopancreas the chloroplasts are always bounded by a host membrane and contaminant algal cytoplasm may be attached to the chloroplast envelope. The possibility that‘butterfly’shaped chloroplasts and chloroplasts with membranous baffles represent different forms of chloroplast division is discussed. The presence of non‐Codium chloroplasts in the digestive cells of E. viridis is reported.
Studies ON THE MECHANISM OF ACTION OF THE ANTIFUNGAL COMPOUND FALCARINDIOL
Authors: Garrod B. , Lea E. J. A. , Lewis B. G.
Published: May 2006

Summary

The mode of action of the polyacetylenic antifungal compound falcarindiol was explored. Chlamydospores of Mycocentrospora acerina removed falcarindiol from test solutions. Falcarindiol at 28 μg ml−1 burst bimolecular lipid membranes formed from lecithin or lecithin‐cholesterol and caused haemolysis in erythrocytes. At a concentration of 100 μg ml‐1 falcarindiol caused rapid electrolyte loss from both chlamydospores of M. acerina and discs of Doucus carota. Hyphal tips of M. acerina burst, and the internal structure of chlamydospores of M. acerina was altered by concentrations of 75 μg ml‐1 falcarindiol. The hypothesis is advanced that falcarindiol acts on the plasma membrane or affects some process needed for membrane function.
THE PERIHAUSTORIAL MEMBRANE IN HOP CELLS INFECTED BY PSEUDOPERONOSPORA HUMULI
Authors: Pares R. D. , Greenwood A. D.
Published: May 2006

Summary

The part of the host plasmalemma invaginated around the haustorium of Pseudoperonospora humuli was examined after staining with (a) Uranyl acetate followed by lead citrate and (b) a mixture of phosphotungstic acid and chromic acid. It was also examined by using a tilting and rotating goniometer stage.

After staining with uranyl acetate and lead citrate the membrane could only be detected on about 45 % of the periphery of the haustorium transected in a section and only the outer dark component of the triplet unit membrane structure could be detected. The use of phosphotungstic acid‐chromic acid enabled the whole of the triplet membrane structure to be seen but did not enable the membrane to be detected over a greater percentage of the haustorium periphery than with the first procedure.

The use of the goniometer stage resulted in the membrane being seen around 95 % of the periphery of the haustorium.
THE GERMINATION OF SOME WOODLAND HERBACEOUS SPECIES UNDER LABORATORY CONDITIONS: A MULTIFACTORIAL STUDY
Authors: SLADE ELIZABETH A. , CAUSTON D.R.
Published: May 2006

Summary

The effects of five potentially dormancy‐breaking treatments – potassium nitrate, scarification, ethylene, light, and scarification ‐ were tested on 13 species from deciduous woodland, in a complete factorial experiment. The seeds were about 6‐months‐old and were germinated at 18°. None of the treatments induced germination in Mercurialis perennis or Sanicula europaea. Milium effusum and Silene dioica germinated well over a very wide range of conditions. Stratification promoted the germination of Endymion non‐scriptus, Galium aparine and Veronica hederifolia; while scarification mostly had a depressive effect, except in the cases of E. non‐scriptus and Geranium robertianum where some promotion of germination was discovered. Circaea lutetiam and Veronica montana appeared to have highly specific germination requirements: the former species required nitrate, ethylene, and light in combination; while the latter required nitrate, light and stratification in combination for germination. Geum urbanum germinated well if treated with nitrate alone, while Veronica chamaedrys required light only, and Stachys sylvatica gave good germination with stratification alone. There were also several significant first‐ and second‐order interactions. Where possible, the results are discussed in relation to previous work and to the ecology of the species.
THE BIOLOGY OF AMBROSIA TRIFIDA L. IV. DEMOGRAPHY OF PLANTS AND LEAVES
Authors: ABUL‐FATIH H. A. , BAZZAZ F.A.
Published: May 2006

Summary

In low‐density populations of Ambrosia trifida plants grown in monoculture in the field all individuals survived to maturity. The plants had high rates of leaf birth and death. However, under high densities there was death of whole plants and a decline in leaf birth ‐ and death‐rates. Furthermore, under high densities leaves lived longer than did leaves under low density. Thus, regulation of populations in response to density occurs at two levels: whole plants and individual leaves.
MODERN POLLEN SAMPLES FROM WEST GREENLAND AND THE INTERPRETATION OF POLLEN DATA FROM THE BRITISH LATE‐GLACIAL (LATE DEVENSIAN)
Authors: PENNINGTON WINIFRED , Tutin T. G.
Published: May 2006

Summary

Samples of the modern pollen rain, some from lake sediment and some from moss polsters, were taken in two regions of West Greenland in which the climate is respectively low arctic continental and low arctic oceanic: (1) round the head of Söndre Strömfjord at 67° N; and (2) the south‐west of Disko Island at 70° N. The vegetation has been described and analysed by Böcher (1954, 1959, 1963). In Region 1 where the vegetation is a mosaic of xerophilous grassland with Artemisia borealis (steppe) and Betula nana heath, mean pollen percentages from 11 polsters corresponded quite closely with percentage cover for those taxa in the vegetation. Polsters from steppe could be distinguished from heath polsters by higher values for Artemisia in steppe and Ericales (Ledum, Empetrum, Vaccinium, Rhododendron) in heath, but Betula nana and grasses, with the highest values in both pollen and vegetation, showed no consistent difference between polsters of different origin‐presumably showing good pollen dispersal. In four lake samples B. nana was over‐represented by pollen values and Artemisia had a lower mean than in terrestrial samples. In Region 2 where the vegetation is a more oceanic heath in which B. nana is infrequent and Artemisia absent, the pollen samples differ from those of Region 1 in consistently higher values for Cyperaceae and lower values for Gramineae and B. nana: Artemisia is here represented by only the same few grains as the exotic taxa Pinus and Picea. When compared with vegetation cover in Region 2, sedges and B. nana appear to be over‐represented in pollen samples, especially from lakes, and Salix herbacea and the herbs of snow‐bed and heath‐mat communities to be under‐represented.

These findings can be used in interpretation of Late Devensian pollen spectra which lack arboreal pollen, and make it probable that: (i) samples from the earliest Late Devensian pollen zones represent an oceanic dwarf‐shrub vegetation in which there was more Salix herbacea and fewer sedges than pollen values suggest; (ii) Betula nana did not at any time form an appreciable part of the vegetation cover; and (iii) Artemisia pollen values provide an index to local vegetation cover, which implies a vegetation mosaic correlated with snow cover during the period of the Loch Lomond Advance (c. 11000 to 10500 B.P.).
COMPARISON OF THE ONION PLANT (ALLIUM CEPA) AND ONION TISSUE CULTURE III. FEEDING OF 14C LABELLED PRECURSORS OF THE FLAVOUR PRECURSOR COMPOUNDS
Authors: TURNBULL A. , GALPIN I. J. , COLLIN H. A.
Published: May 2006

Summary

Callus and onion leaf tip material were exposed to [14C]cysteine, [14C]serine or [14C]valine and the distribution of labelling in the amino acids and cysteine derivatives assessed after two to fourteen days. With [14C]cysteine and serine radioactivity was found in the callus in a range of amino‐acids and in the flavour precursor compounds, S‐methyl‐L‐cysteine sulphoxide and S‐trans‐prop‐1‐enyl‐L‐cysteine sulphoxide, particularly in the former precursor. [14C]valine was much more metabolically inert and little distribution of radioactivity occurred. In comparison the shoot tip showed a more active metabolism of [14C]serine and cysteine than callus but again much less activity with [14C]valine. With all three compounds, however, the heaviest labelling in the shoot tip was in the cysteine derivatives, particularly the main flavour precursor of the intact onion, S‐trans‐prop‐1‐enyl‐L‐cysteine sulphoxide. When unlabelled cysteine derivatives were fed to callus, S‐trans‐prop‐1‐enyl‐L‐cysteine sulphoxide was formed. The presence of this precursor compound in callus showed that the callus was capable of synthesizing 5‐trans‐prop‐l‐enyl‐L‐cysteine from early intermediates, such as the amino‐acids, and by a pathway similar to that in the intact plant.
ACTION OF GROWTH REGULATORS ON LUCERNE GERMINATION AND GROWTH UNDER WATER STRESS
Authors: ROSS HEATHER A. , HEGARTY T. W.
Published: May 2006

Summary

Lucerne seeds (Medicago sativa L.) were germinated in a range of polyethylene glycol (PEG) and sodium chloride (NaCl) solutions in the presence and absence of kinetin with ethrel. In addition, seeds were germinated in water and transferred to PEG and NaCl solutions, and root growth was measured. The water potentials at which there was 50% germination inhibition and at which 50 % of the germinated seeds failed to grow after transfer were determined. Kinetin and ethrel together completely removed the block to germination through osmotic stress, allowing germination to proceed at the same water potential as growth. The action of kinetin and ethrel was studied by following the processes of cell expansion and division during germination and early growth. The control of germination by water stress was through cell expansion, and the initiation of this process was shown to be stimulated in the presence of the growth regulators. Cell division although initially permitted in their presence, was later inhibited causing a decline and finally cessation of seedling growth.
ADAPTATION OF VESICULAR‐ARBUSCULAR MYCORRHIZAE TO EDAPHIC FACTORS*
Authors: LAMBERT D.H. , COLE H. , BAKER D. E.
Published: May 2006

Summary

In three field soils, birdsfoot trefoil (Lotus corniculatus L.) transplants infected with mycorrhizal fungi from 42 soils showed no clear superiority of strains from these individual soils after a year's growth. Differences among strains decreased with time and were only significant for all three soils at the first cutting. There were low‐level correlations between yield and various chemical properties of the soils from which the cultures were derived. In the greenhouse, with sterilized soils low in P, trefoil yield was always greatest when the inoculum used was indigenous to the soil in which the plants were grown as compared to inocula from five different soils. These results suggest that indigenous strains of mycorrhizal fungi may possess an adaptation to edaphic factors and that the performance and persistence of strains otherwise more efficient in nutrient uptake may be limited by their lack of adaptation.
THE ULTRASTRUCTURE OF COLEOPTILE CELLS IN DRY RICE (ORYZA SATIVA L.) GRAINS AFTER ANHYDROUS FIXATION WITH OSMIUM TETROXIDE VAPOUR
Authors: ÖPIK HELGI
Published: May 2006

Summary

Coleoptiles from dry rice grains were prepared for electron microscopy by anhydrous fixation with OsO4 vapour. The cells were much shrunken, with highly folded walls; nuclei, plastids, mitochondria and lipid bodies all showed irregular outlines indicative of shrinkage and mutual compression. Some membranes were represented only by an electron‐transparent lamella, but in the plasmalemma a tripartite structure could be discerned. A significant finding was that the plasmalemma was continuous and unbroken (as were other cellular membranes), in complete contrast to the situation seen after aqueous fixation, when many breaks occur in the plasmalemma. Such breaks must be attributed to stresses set up between the plasmalemma and the cell wall as the cells are hydrated during fixation. Difficulties were encountered in identifying organeiles, contrast being low and less detail being visible than after aqueous fixation.
REPRODUCTIVE BIOLOGY OF STELLARIA LONGIPES GOLDIE AS REVEALED BY A CULTIVATION EXPERIMENT
Authors: PHILIPP M.
Published: May 2006

Summary

In cultivation experiments with Stellaria longipes sensu lato. from Greenland, the life history has been thoroughly studied, in order to find out how female plants in this gynodioecious/gynomonoecious breeding system are favoured in relation to the hermaphrodite plants. It seems that the maintenance of the female plants is determined by a combination of differences in length of the reproductive cycle, number of flowers per plant, number of seeds per capsule, and the sex segregation in the populations. Other factors, which might be sex linked, such as the area of cotyledons and germination pattern, may be important.
PLEISTOCENE FOREST HISTORY IN EAST ANGLIA
Authors: WEST R. G.
Published: May 2006

Summary

The East Anglian Pleistocene succession records eight temperate stages with forest and also interstadials with forest in two of the intervening cold stages. The forest histories of these temperate stages and interstadials are described. The records through the Pleistocene of the tree genera involved are considered. The forest assemblages in each of four substages of the temperate stages (pre‐temperate, early‐temperate, late‐temperate, post‐temperate) are compared. The development of heath in the temperate stages is also examined. Floristic and phytogeographic changes indicated by the palaeobotanical evidence give information on Tertiary‐relic genera and on extinctions, and have a bearing on the problem of the history of cold stage refugia. The success or failure of particular genera in response to the stress of climatic change is discussed. Finally, comparisons are made with Pleistocene forest history in north‐west Europe.
PLASTID GROWTH AND DIVISION IN PHASEOLUS VULGARIS
Authors: WHATLEY JEAN M.
Published: May 2006

Summary

The sizes and numbers of plastids were determined in the cells of the upper epidermal and upper palisade layers during development of the primary leaf of Phaseolus vulgaris. Plastids of both epidermal and palisade cells divide at all stages of plastid development, but division ceases soon after the plastids become mature. The process of plastid division involves both extension growth and fission. During growth of the primary leaf within a seed developing on the parent plant, plastids in both the epidermal and the palisade cells show little overall growth in size. During germination epidermal cell plastids remain small but plastids in palisade cells increase considerably in size as the leaf expands. Populations of potentially dividing plastids can be identified by the characteristic distribution of their size classes which, when set out graphically, give curves of distinctive shape.

Cell division takes place during development of the primary leaf both prior to and following dormancy. Plastid division also occurs during these two periods. However, within each cell the plastids do not divide in synchrony. Nor are the periods of cell and plastid division synchronized, for the plastids continue to divide during the phase of maximum leaf expansion, when cell division has ceased but while cell extension continues. In the primary leaf of Phaseolus the overall number of cycles of plastid division exceeds that of cell division by between two and three cycles.
SEXUAL STRATEGIES IN PLANTS
Authors: LLOYD DAVID G.
Published: May 2006

Summary

It is postulated that in one reproductive session the level of maternal expenditure of an angiosperm plant is determined by a temporal series of controls on the number of potential fruit in which an investment is made. The serial adjustment hypothesis has three parts:

A. The amount of maternal expenditure is regulated at many developmental units, particularly single flowers and fruit, at three principal sequential stages – the determination of flowers, the development of ovaries and the maturation of fruit.

B. At each stage, the initiation or continuation of an investment requires an amount of available resources above a certain threshold. Hence maternal expenditure is continually adjusted to the resources available at each developmental site.

C. The pattern of controls that maximizes the maternal fitness of a plant is selected. Many factors affect the relative advantages of regulation at the three stages, therefore species and sexual morphs appear to vary widely in their proportional use of the three stages.

Regulation of flower determination has the general advantages of offering bidirectional adjustment of maternal investment, maintaining a constant ratio of maternal to paternal investment, and reducing wasted expenditure. The later stages, ovary and fruit regulation, allow secondary adjustments of maternal investment in unpredictable circumstances and permit adjustment of the relative numbers of polliniferous and seminiferous flowers. The relative advantages of restricting the numbers of developing ovaries, or of maturing fruit, depend principally on the extent to which differences in the capacity of flowers to mature fruit are evident before anthesis.
SEXUAL STRATEGIES IN PLANTS
Authors: LLOYD DAVID G. , WEBB C. J. , PRIMACK RICHARD B.
Published: May 2006

Summary

Seventeen angiosperm species were examined to determine the degree to which the plants of each sexual morph limit their maternal investment during one reproductive session at three successive floral stages (flower determination, pre‐anthesis ovary development, and post‐anthesis fruit maturation). The results indicate that species and sexual morphs differ dramatically in the relative use they make of the three stages. Both the flower number per inflorescence and the proportion of flowers with developed ovaries are generally less variable in species with inflorescences which have well denned sequences of flower development. In most species, the variability among the plants of one morph is greater in the frequency of fruit maturation than in the frequency of ovary development. Much of the intra‐morph variation in both the frequency of ovary development and the frequency of fruit maturation appears to be non‐genetic. In most of the morphs examined, the frequencies of ovary development and fruit maturation are not correlated with the number of flowers per plant or with each other. The results provide circumstantial evidence in support of the hypothesis of serial adjustment of maternal investment.
PERFECT STATES OF RHIZOCTONIAS ASSOCIATED WITH ORCHIDS. III
Authors: WARCUP J. H. , TALBOT P. H. B.
Published: May 2006

Summary

Further Rhizoctonia isolates from Australian orchids have been induced to fruit in culture. The perfect states obtained include three new species of Ceratohasidium, C. angustisporum, C. globisporum, and C. papillatum, a new species of Tulasnella, T. irregularis, and a new species of Ypsilonidium Donk emend. Talbot, Y. anomalum Talbot.
THE SECRETORY CYCLE OF DIONAEA MUSCIPULA ELLIS
Authors: ROBINS R. J. , JUNIPER B. E.
Published: May 2006

Summary

Autoradiography has been used to track the path of secretion in the digestive glands of Dionaea muscipula. Neither the dictyosomes nor dictyosomal vesicles appear to be involved, but radio‐label is lost rapidly from the endoplasmic reticulum and small osmiophilic vacuoles directly into the cell wall. Radiolabel is subsequently lost from the large osmiophilic vacuoles and accumulates in the small vacuoles. The effects of colchicine and cytochalasin B are complex. Both decrease the enzymatic activity of the secretion, but not the protein content, suggesting effects on the synthesis and discharge of secretion not directed against microtubules or microfilaments. It is proposed that the discharge of secretion occurs by direct fusion of ER to the plasmalemma or via vesicles and vacuoles derived from the ER.
AUTECOLOGICAL STUDIES OF TRIFOLIUM MOLINERII AT THE LIZARD PENINSULA, CORNWALL
Authors: MARTIN M. H. , FROST L. C.
Published: May 2006

Summary

Trifolium molinerii (T. incarnatum ssp. molinerii) is shown to be a strongly maritime plant growing typically in head deposits on schistose cliffs and a member of the Thero‐Sedetum anglici Association of Malloch, (1971). Principle co‐ordinates analysis of quadrat data separated eight groupings, which are interpreted in terms of environmental factors in particular in relation to position on the cliff profile. The status of the clover is discussed and, although biotic influences and human interference are important factors in its present distribution, the plant is considered to be native.
THE REQUIREMENT OF AQUATIC BRYOPHYTES FOR FREE CO2 AS AN INORGANIC CARBON SOURCE: SOME EXPERIMENTAL EVIDENCE
Authors: BAIN JANET T. , PROCTOR M. C. F.
Published: May 2006

Summary

Twenty bryophyte species were tested for photosynthetic uptake of bicarbonate by immersing plants in 2.0 mM and 0.2 mM NaHCO3 and monitoring rise in pH. Equilibrium values were clustered around pH 9.0 and pH 8.0 in the two solutions, indicating limitation by free CO2 and inability to use bicarbonate. Anthoceros husnotii reached a maximum pH value of 9.5 in 2.0 mM NaHCO3, suggesting possible, although inefficient, bicarbonate uptake. Four species of bicarbonate‐using plants tested for comparison gave final pH values in the range of 10.1 to 10.9. Field measurements gave results consistent with the laboratory experiments. Availability of CO2 to bryophytes growing in different aquatic habitats is discussed and their ecology is considered in light of the results.
Studies IN FESTUCA 12. MORPHOLOGY, DISTRIBUTION AND CYTOGENETICS OF F. DONAX, F. SCARIOSA AND THEIR HYBRIDS, AND THE EVOLUTIONARY SIGNIFICANCE OF THEIR FERTILE AMPHIPLOID DERIVATIVE
Authors: BORRILL MARTIN , KIRBY MADELEINE , MORGAN GARETH
Published: May 2006

Summary

The morphology and distribution of the phenotypically dissimilar diploid species Festuca donax and F. scariosa have been examined.

Production of the fertile amphiploid hybrid F. donax×F. scariosa, by colchicine treatment of hybrid seeds, and of triploids by backcrossing the amphiploid to the parents, has made possible a study of preferential pairing in these genotypes. The S and D genomes had considerable and approximately equal ability to pair preferentially in the SSD and SDD hybrids. The amphiploid had marked bivalent pairing, segregated little, and was seed and pollen fertile.

These results put in perspective previous studies based on diploid hybrids between sections Scariosae and Montanae, and suggest a greater degree of differentiation of the genomes of these two sections than previously supposed. They are nevertheless more closely related to one another, than to F. pratensis.

The caryopsis apex in diploids of Scariosae and Montanae sections is pubescent. The presence of this pubescence has therefore been surveyed in broad‐leaved fescue polyploids. It occurs only in polyploid species of the Moroccan Atlas mountains and is apparently another of the features they inherited from F. scariosa. Pubescence of the leaf auricle region is absent from diploid F. scariosa, from F. pratensis and related Lolium species, but present in diploid Montanae species. Enhanced auricle‐zone pubescence occurs in the fertile Cl and C2 amphiploids of F. scariosa (glabrous) and F. donax (pubescent). This suggests that diploids of section Montanae could be the gene source of the auricle pubescence present in broad leaved fescue polyploids exemplified by hexaploid tall fescue.
THE RESPONSES OF CONIFERS TO SOME OF THE ADVERSE FACTORS ASSOCIATED WITH WATERLOGGED SOILS
Authors: SANDERSON P. L. , ARMSTRONG W.
Published: May 2006

The effect in solution culture of iron(II), acetic and butyric acids and ethylene on rooted cuttings of Sitka spruce and Lodgepole pine has been studied and compared with the effects of anoxia. A relative growth rate parameter is employed to reveal changes in the rate of root growth. Possible mechanisms of toxicity and detoxification are suggested and the greater tolerance of Lodgepole pine is discussed in relation to its superior gas transport system. Conclusions are drawn concerning the role played by each of the toxic factors in the field situation.
CUTICLE DEVELOPMENT IN THE STOMATAL REGION OF POPULUS CLONES
Authors: PALLARDY S. G. , KOZLOWSKI T. T.
Published: May 2006

Cuticle development and degree of stomatal occlusion of three Populus clones varied with growth environment and leaf type (early or late leaves). Whereas stomatal occlusion by cuticular components was negligible in plants of all clones grown in a moist controlled environment, heavier cuticle deposition and stomatal occlusion were found on abaxial surfaces of early, but not late leaves, of field‐grown clones. Hence these Populus clones responded adaptively to the more xeric field conditions in a fashion that would restrict both stomatal and cuticular water loss. The cuticle around the stomatal apparatus of all clones was ridged, with elaborate stranded patterns emanating from the stomata. Stomatal ledges were found in all clones studied, and ledge aperture was not closely related to pore aperture of the guard cells because of variation in the point of attachment of the ledges to the outer lateral wall of the guard cells. Because stomatal pore and ledge apertures are independent, stomatal impressions (which reproduce ledge aperture only) should not be used to estimate stomatal aperture unless it can be shown that ledges are not present.
COMPOSITION OF LIPIDS IN ROOTS OF SIX CITRUS CULTIVARS INFECTED WITH THE VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS, GLOMUS MOSSEAE
Authors: NAGY S. , NORDBY H. E. , NEMEC S.
Published: May 2006

The lipid compositions of infected (Glomus mosseae) and noninfected fibrous roots of sweet orange, sour orange, rough lemon, Carrizo citrange, Cleopatra mandarin and Rangpur lime were studied. Infected roots of all cultivars contained significantly more phospholipids and triglycerides than did their noninfected controls. Campesterol was found at significantly higher percentages of free sterols, whereas cholesterol and β‐sitosterol were detected at lower percentages in infected roots when contrasted to their respective controls. Three unknown fatty acids (A, B, and C) were detected in infected roots but not in noninfected roots. Unknowns A, B and C made up 46 to 52 % of the fatty acids in the triglycerides, 31 to 41 % in the total lipids and 7 to 20 % in the phospholipids.
ULTRASTRUCTURAL OBSERVATION OF THE SURFACE COAT OF DUNALIELLA TERTIOLECTA FROM STAINING WITH CATIONIC DYES AND ENZYME TREATMENTS*
Authors: OLIVEIRA LUIS , BISALPUTRA THANA , ANTIA NAVAL J.
Published: May 2006

The surface coat of the cell‐wall‐lacking alga Dunaliella tertiolecta has been examined with the use of the cationic dyes, alcian blue and ruthenium red. The previously undetected existence of a glycocalyx‐type cell envelope is described. The results from enzymic digestions suggest a gross similarity in the biochemical nature of the coat of Dunaliella with that reported for other eukaryotic cell types. The biological significance of this surface coat is discussed in relation to the absence of a rigid cell wall and the known ability of such algae to withstand extreme changes in the osmotic potential of the growth medium.
A CYTOLOGICAL STUDY OF THE MALE AND FEMALE SPOROCARPS OF THE HETEROSPOROUS FERN AZOLLA FILICULOIDES LAM.
Authors: LUCAS R. C. , DUCKETT J. G.
Published: May 2006

Cytochemistry and transmission electron microscopy reveal that the mature megaspores of Azolla filiculoides contain protein bodies, lipid globules, polysaccharide vacuoles and amylo‐plasts whereas the microspores are packed with saturated lipid. The megaspore indusium is lignified but the flotation apparatus, capture mechanism, massulae and glochidia are heavily impregnated with sporopollenin. Ultrastructurally the walls of the massular pseudocells are closely similar to those of the flotation collar, from which filaments, identical to those in fossil taxa, extend. The microspore glochidia usually become attached to this region of the megaspore and the capture mechanism around the latter's blunt end is a misnomer. New details of distinctive internal surfaces of the sporocarps are demonstrated from fractured resin embedded specimens, a technique which may permit more accurate diagnosis of fragmentary fossil remains. The unsculptured exine around the megaspore is overlain by a two layered perine. The inner stratum, or endoperine, has a granular texture and expands to make up the bulk of the notation collar and the excrescences (tubercles) of the capture mechanism, whereas the outer, or exoperine forms a thick continuous layer between the tubercles and an anastomosing network above them. Since the filaments around the flotation apparatus have a similar homogeneous texture these are also assigned to the exoperine.
TRANSLOCATION INTO MATURE LEAVES‐THE PATHWAY OF ASSIMILATE MOVEMENT
Authors: THROWER STELLA L. , THROWER L. B.
Published: May 2006

Possible routes of assimilate movement from younger into mature leaves of Vigna sesquipedalis have been investigated. The presence of label is not the result of redistribution of root amino acids. No evidence could be found for movement in the xylem. The lack of direct phloem connections between successive leaves suggests that the only possible route is via parenchyma cells between adjacent sieve tube strands of the node, and subsequent movement in the phloem of the petiole and leaf. The implications for normal upward movement in the plant are discussed.
SENESCENCE IN SUBMERGED AQUATIC ANGIOSPERMS: CHANGES IN INTACT AND ISOLATED LEAVES DURING AGING
Authors: JANA S. , CHOUDHURI M. A.
Published: May 2006

Events during the senescence of intact and isolated leaves of two submerged aquatic angiosperms, Vallisneria spiralis L. and Hydrilla verticillata (L.F.) Royle, were studied. Mature leaves were the most active metabolically in both the plants. The decline in chlorophyll, protein and dry wt and increase in tissue permeability was, in general, age‐related in Vallisneria but not so in Hydrilla. Changes in the chlorophyll a: b ratio did not follow a consistent pattern as leaves aged. In general, an increase in the activities of protease, RNase, and acid pyrophosphatase and a decrease in alkaline pyrophosphatase activities were noted in aging leaves of Vallisneria. Catalase activity was, however, highest in mature and lowest in young leaves. In Hydrilla, a similar trend in the activities of the enzymes, with the exception of acid pyrophosphatase and catalase, was noted. Both acid pyrophosphatase and catalase activities showed a general decline with age of the leaves. A higher ratio of acid: alkaline pyrophosphatase was observed in both species as leaves aged. The senescence pattern of isolated leaves of the two species showed a general decline in cell components and dry wt, and an increase in tissue permeability. A rise in the activities of degradative enzymes and a decline in alkaline pyrophosphatase and catalase activities were also noted during aging of isolated leaves. The ratio of acid: alkaline pyrophosphatase increased with aging. Kinetin treatment delayed the loss of cell components and dry wt, and the rise in tissue permeability, and lowered the activities of catabolic enzymes and thus effectively deferred senescence in both the species.
RAY MORPHOLOGY AND CYTOLOGICAL INVESTIGATIONS OF SENECIO CAMBRENSIS ROSSER
Authors: WEIR JACQUELINE , INGRAM RUTH
Published: May 2006

Experimentally synthesized allohexaploids between Senecio vulgaris L. and S. squalidus L. allow the genomic constitution of S. cambrensis Rosser to be defined. Ray morphology in this synthesized allohexaploid is interpreted on the basis of the known location of the ‘rayed’ gene, and the relevance of this information to ray morphology in S. cambrensis is discussed. Meiotic studies of the raw allohexaploid show that meiotic regularity is likely to have been a feature of the species from its inception, and is not the result of recent selection.
ARE THERE INTER‐RELATIONS BETWEEN THE METABOLIC ROLE OF BORON, SYNTHESIS OF PHENOLIC PHYTOALEXINS AND THE GERMINATION OF POLLEN?
Authors: LEWIS D. H.
Published: May 2006

The similarities between the effects of wounding, microbial infection and boron deficiency in bringing about alterations in phenolic and hormone metabolism in vascular plants are emphasized and attention drawn to gaps in available information. It is proposed that the similarities are due to induction of localized or systemic sequestration of endogenous borate by β‐l,3 glucans or other carbohydrates including glycoproteins (microbial elicitors and wound callose). In view of the morphological, physiological and biochemical parallels between fungal infection and pollination, it is further argued that there are common metabolic links between the effects of boron deficiency, wounding and infection and the presence of callose in pollen grains and tubes, the stigmatic deposition of callose in response to some incompatible pollinations and the boron requirement for the germination of pollen. A highly speculative but experimentally testable scheme is proposed.
EFFECTS OF SEED SIZE AND EMERGENCE TIME ON SUBSEQUENT GROWTH OF PERENNIAL RYEGRASS
Authors: NAYLOR ROBERT E. L.
Published: May 2006

The seed weight of individual perennial ryegrass seeds was measured prior to recording their date of emergence and subsequent growth in experimental populations raised in the glasshouse and sown at different initial densities. Seed size did not correlate with time to emergence although lighter individuals had a slightly lower probability of emergence. Seed size had no statistically significant effect on subsequent tillering up to 27 weeks, or on the dry wt attained by this time.

The time from sowing to emergence was significantly related to subsequent tillering of the grass plants for a number of weeks in populations sown at different densities. After some 20 weeks the effect of emergence time became non‐significant. This coincided with the onset of tiller mortality in the population. Even after 27 weeks individual emergence time was inversely related to dry wt but was not related to mean tiller weight.