bluuebunny/crossref_metadata_2025 huggingface dataset:
THE INFLUENCE OF THE ROOT SYSTEM ON THE RELATIONSHIP BETWEEN THE RATE OF TRANSPIRATION AND DEPRESSION OF LEAF WATER POTENTIAL
Authors: STOKER R. , WEATHERLEY P. E.
Published: May 2006

Summary

The relationship between rate of transpiration and depression of water potential of the leaves (δψ1) was investigated with Gossypium hirsutum and Heliantlnis annum grown in water culture. (δψ1) was measured with a thermocouple psychrometer over a wide range of transpiration rates. The different transpiration rates were obtained by altering the environmental conditions in a climatological wind tunnel. At zero transpiration rate δψ1 was found to be 5.5 atm in H. annuus and 6.0 atm in Gossypium hirsutum. As the transpiration rate was raised, δψ1 rose steeply to a plateau in both species and remained at near to 9 atm within the transpiration range 0.4–2.4 g/dm2/hour. Thus within this range resistance in the plant declined in proportion to the transpiration rate. With transpirational fluxes greater than 2.4 g/dm2/hour, δψ1 rose, indicating little further decline in resistance.

That the variable plant resistance is located in the roots was confirmed since plants with killed roots had a constant resistance, δψ1 exhibiting a linear relationship with transpiration. The resistance of the dead root system was much lower than that of living roots at low transpiration rates, but at high transpiration rates the resistance of living roots fell to about the same level as the dead roots. The implications of these findings are discussed.
Studies IN POTENTILLA L.
Authors: SMITH GORDON L.
Published: May 2006

Summary

British material of Potentilla tabemaemontani Aschers. and P. crantsii (Cr.) Beck ex Fritsch consists of pseudogamous apomicts with chromosome complements at the hexaploid level (2n =c. 42) or higher. Some detailed information is given on the distribution of the various cytodemes, and the morphological variation is described. An ‘apomictic hybrid’ origin is suggested for certain topodemes of intermediate morphology. Comparison is made with Continental European studies on the two species.
EXINE PATTERN IN THE POLLEN OF BRITISH SPECIES OF TILIA
Authors: ANDREW R.
Published: May 2006

Summary

Reference pollen slides have been made from twenty‐three samples of material identified as Tilia platyphyllos Scop., T. cordata Mill., or T. × vulgaris Hayne. Up to 100 grains in each slide have been microscopically examined and each opposing face has been classified as of ‘cordata’ or ‘platyphyllos’ type. The survey showed that grains of T. platyphyllos material were homopolar and consistently of ‘platyphyllos’ pattern. Some material of T. cordata was also homopolar and consistently of ‘cordata’ pattern. There was, however, an extreme degree of heteropolarity in most of the hybrid material and also in much of that attributed to T. cordata, a large proportion of the grains having ‘cordata’ pattern on one face and ‘platyphyllos’ on the other.

The results show the extreme importance of adequate authentication of pollen type‐material and suggest that in Britain both T. cordata and T. platyphyllos are native, but that much hybridization has occurred between them, giving progeny in which the somatic phenotypes show less indication of ‘platyphyllos’ parentage than the pollen seems to do.
CYTOLOGICAL STUDIES IN DORMANCY
Authors: VILLIERS T. A.
Published: May 2006

Summary

During the period of maturation after imbibition by the seed, but before the administration of the dormancy‐breaking stimulus, changes observed in the radicle meristem cells included the disappearance of lipid bodies accompanied by a decrease in extractable lipid from 20% to 4% of the dry weight of the embryo, an increase of protein from 14% to 24% and the appearance of starch. The development of plastids into amyloplasts, during which they became associated with the ER, is described. Originally, a tubular network of rough ER was present but an additional, localized system of parallel arrays of sheet‐like rough ER appeared in each cell. A system of multivesicular and other paramural bodies developed, together with microbodies possessing crystalline cores. Golgi bodies, originally rare, became very numerous and appeared to be connected with the tubular ER system. Thus, food interconversions, wall development and the appearance and proliferation of cellular organelles all occurred during deep embryo dormancy, when actual germination was not possible.
WOOD ANATOMY AND SYSTEMATIC POSITION OF STREPHONEMA
Authors: VENKATESWARLU J. , RAO P. S. PRAKASA
Published: May 2006

Summary

The wood anatomy of Strephonema peudocola A. Chev. has been compared with the known members of Lythraceae and the Combretaceae in which this genus has been allied by some authors. The comparison shows that this species has little in common with Lythraceae but that certain xylotomical features point to a relationship between Strephonema and a few of the Combretacean taxa. Nevertheless the distinctiveness of the wood structure when considered together with half inferior condition of the ovary probably merit separation of Strephonema from the Combretaceae into a separate monogeneric family, the Strephonemataceae; this family is to be considered allied to Combretaceae.
Studies ON MUTUALISTIC SYMBIOSIS BETWEEN SYCONIA AND SYCOPHILOUS WASPS IN MONOECIOUS FIGS
Authors: GALIL J. , EISIKOWITCH D.
Published: May 2006

Summary

The constituents of a normal monoecious fig, namely the male and female flowers, the short‐and long‐styled female flowers and the male and female wasp galls, are arranged in definite spatial and numerical relations. The normal development of the syconium depends on a balance of these different elements. Occasionally various types of aberrant figs are found in nature, differing from normal figs in development and in final structure. These are purely gall figs, seed figs and male wasp or female wasp figs. Such abnormal figs were obtained experimentally by introducing specially treated female wasps into receptive young syconia at the receptive B phase. Treatments of the wasps involved one of the following: shortening of their ovipositor, preventing contact of wasps with pollen, preventing wasp fertilization or their sterilization by irradiation with gamma rays at various doses. In some of the already inhabited figs, the wasp larvae were killed by insecticidal sprays. Analysis of the development and structure of naturally‐found aberrant syconia, taking into account also the conditions under which they may be produced experimentally, provides data for elucidating various aspects of the mutualistic symbiosis in figs.
EXPERIMENTAL STUDY OF THE EFFECT OF SULPHITE ON LICHENS WITH REFERENCE TO ATMOSPHERIC POLLUTION
Authors: HILL D. J.
Published: May 2006

Summary

The effect of sulphite solutions on the incorporation of H14CO3− in the light in Usnea subfloridana, Parmelia physodes and Lecanora conizaeoides was studied. The sulphite concentration which prevented incorporation was least in Usnea subfloridana and greatest in Lecanora conizaeoides. These differing sensitivities to sulphite were correlated with the known sensitivities of these lichens to atmospheric pollution. Sulphate was less toxic than sulphite. Sulphite was toxic at pH 4 and below but not toxic at pH 5 and above.
CARBON DIOXIDE AND THE FORMATION OF HEARTWOOD
Authors: CARRODUS B. B.
Published: May 2006

Summary

The state of knowledge of the transition of sapwood into heartwood in trees is reviewed, and attention is drawn to the composition of the gas mixture available to such cells as remain alive in wood. The probable effect of such a mixture is postulated and experiments indicate that the high concentrations of carbon dioxide known to exist inside wood are conducive to formation of compounds known to be typical of the heartwood of Acacia mearnsii.
PHOSPHATE ABSORPTION BY PLANTS FROM HABITATS OF DIFFERENT PHOSPHATE STATUS
Authors: NASSERY H.
Published: May 2006

Summary

Deschampsia flexuosa and Scabiosa columbaria, species with low relative growth rate and small growth response to phosphate concentration contain a greater proportion of inorganic phosphate than organic phosphate. By contrast, Urtica dioica and Rumex acetosa with high relative growth rates and high phosphate response contain more organic phosphate, particularly organic insoluble phosphate, especially when grown in low phosphate concentrations. It is concluded that the evidence from the present and previous work indicates that the growth response to phosphate is a reflection of relative growth rate, that is, demand for phosphate in growth.
ANALYSIS OF THE RESPONSE OF URTICA DIOICA TO PHOSPHATE
Authors: PIGOTT C. D.
Published: May 2006

Summary

Analysis of the growth of seedlings of Urtica dioica on a woodland soil shows that in well‐illuminated situations, the large response to addition of phosphate is caused by a high rate of absorption which allows a short period of high relative growth rate related to a rapid, but transient, increase of leaf area ratio. Without addition of phosphate, both relative growth rate and leaf area ratio remain almost constant over this same period. The relative increase of leaf area ratio caused by addition of phosphate is greatly reduced in shade.

Neither in the rate of absorption of phosphate from dilute solutions, nor in the production of dry matter relative to the quantities of phosphate absorbed, does Urtica appear to differ significantly from species which show a much smaller response to phosphate on this type of soil.
THE CONTRIBUTION OF MICRO‐ORGANISMS TO THE APPARENT ABSORPTION OF IONS BY ROOTS GROWN UNDER NON‐STERILE CONDITIONS
Authors: BARBER D. A. , FRANKENBURG U. C.
Published: May 2006

Summary

Micro‐organisms can make a considerable contribution to the apparent absorption of inorganic nutrients by excised roots. The microbial component of uptake has been studied by comparing the absorption of phosphate and rubidium by seedling roots of barley grown prior to excision under sterile and non‐sterile conditions.

Although relative to the quantities taken up by sterile roots more phosphate than rubidium was absorbed by micro‐organisms, for both ions over the range 0.001‐1.0 mM, the relationship between absorption and increasing external concentration followed the kinetics of a first order reversible reaction. No simple kinetic relationship could, however, be derived to describe the uptake of either phosphate or rubidium by the roots.

The significance of these findings is considered in the light of the postulate, derived from experiments under non‐sterile conditions, that the absorption of ions by roots is mediated by two distinct‘carrier’mechanisms, one of which dominates at low and the other at high external concentrations. It is concluded that experiments designed to investigate the nature of the uptake process should be carried out under sterile conditions.
GROWTH FACTORS PRODUCED BY GERMINATING SPORES OF POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M.
Published: May 2006

Summary

The greater the density that spores are sown the greater the inhibition of spore germination and of protonema development in Polypodium vulgare L. The factor mainly responsible for the inhibition of germination apparently also promotes cell elongation. It does not persist in culture filtrates and is probably a volatile substance. Three other factors have been separated from culture filtrates by means of paper chromatography. All three cause a delay in germination and inhibit cell division but the evidence available suggests that at low concentrations they have a promotive effect on these processes. None of them appears to affect cell elongation.
PARTICLES AND MICROTUBULES IN VASCULAR CELLS OF PINUS STROBUS L. DURING CELL WALL FORMATION
Authors: MURMANIS LIDIJA
Published: May 2006

Summary

Particles in the plasmalemma‐cell wall area are reported in fixed and sectioned material of differentiating vascular cells of Pinus strobus L. The particles, from 13 nm to 16 nm in diameter, arise from the superficial layer of cytoplasm and reach the plasmalemma‐cell wall area apparently by a‘membrane flow.’Frequently the particles are in close spatial association with microtubules at the plasmalemma‐cell wall area. The particles observed here are thought identical with those observed on the outer surface of plasmalemma by the freeze‐etching method.
THE CHLOROPLASTS OF EQUISETUM TELMATEIA ERHR.: A POSSIBLE DEVELOPMENTAL SEQUENCE
Authors: WHATLEY JEAN M.
Published: May 2006

Summary

Parenchyma cells in the leaf sheath of Equisetum telmateia form linearly arranged series of maturing and senescing cells. These series of cells contain chloroplasts showing a progressive sequence of developmental stages easily recognizable because of the spatial relationships involved. The cell sequence may be classified into four successive zones, characterized by the typical structure of the chloroplasts present in the cells of each zone.

Zone I. Meristematic cells contain immature chloroplasts with little internal lamellar structure.

Zone II. Adjacent to the above are cells containing mature chloroplasts with a well‐developed internal lamellar system.

Zone III. Next in sequence are cells in which the chloroplasts retain a mature internal lamellar system but are distinguished from the previous group by the presence of irregular osmiophilic deposits around the outer double membranes.

Zone IV. Finally there occur cells with usually rounded chloroplasts which show the osmiophilic deposits described above, but in which the outer double membrane is often difficult to distinguish. Internally the lamellar system is highly sinuous, and contains many swollen locules.

In spite of a general similarity in appearance between chloroplasts of Equisetum and those of angiosperms, Equisetum plastids are characterized by a distinctive feature more commonly associated with algae than with higher plants. Young chloroplasts are almost completely surrounded by rough endoplasmic reticulum. This very close relationship between reticulum and chloroplast is retained as the chloroplast matures, though the degree of envelopment becomes less with increasing age.
VEGETATION OF THE MARITIME CLIFF‐TOPS OF THE LIZARD AND LAND'S END PENINSULAS, WEST CORNWALL
Authors: MALLOCH A. J. C.
Published: May 2006

Summary

The maritime cliff‐top vegetation of the Lizard and Land's End, West Cornwall, is described in a traditional phytosociological manner. Six new associations are described, together with a number of other noda. The noda are related to environmental factors and the zonation on the cliffs is found to be determined by the amount of exposure to maritime influence, with further variation due to differences in soil depth and moisture content and to the geology of the underlying rocks. A strongly marked relationship between the percentage of maritime species in a nodum and the sodium‐organic ratio is noted.
STIMULATION OF CHLORIDE TRANSPORT IN CHARA BY EXTERNAL PH CHANGES
Authors: SMITH F. A.
Published: May 2006

Summary

Transport of Cl− into cells of Char a corallina is greatly reduced when the cells are bathed in solutions of high pH. Under these conditions there is no difference between the influx in the light and in the dark. When cells are pretreated at high pH in light and then transferred to low pH and darkness, the rate of Cl− transport is greatly stimulated. This is the reverse of the normal effect when cells are transferred from light to dark. An increase in Cl− transport is also produced by pretreatment of cells at high pH in the dark. Addition of (NH4)2SO4 to the solutions produces even larger stimulations of Cl− transport under these conditions.

The results suggest that CI− transport is controlled by the pH gradient across the plasma‐lemma, and that the pH gradient (normally produced by metabolic processes) is altered by the treatments described above. The results are consistent with the hypothesis that charge transfer across the plasmalemma results in H+ extrusion, and that Cl− is taken up in exchange for OH−. Other possible effects of pH changes on ion transport are also considered.
LEAF ABSCISSION IN COLEUS
Authors: HALLIDAY M. B. W. , WANGERMANN ELISABETH
Published: May 2006

Summary

Autoradiographs of sections of explants treated distally with [14C]indolylacetic acid (IAA) for 48 hours showed that radioactivity was higher in the abscission zone than in the neighboring distal and proximal zones at all stages of its development. Higher activity in the abscission zone compared with the distal zone (about 4 to 1) was confirmed by liquid scintillation counting and scanning of paper chromatograms of extracts. The chromatograms also showed that a large part of the activity from abscission zones was due to unchanged IAA. This was confirmed by showing that a large part of the radioactivity in the abscission zone could be removed by treating the explants with unlabelled IAA.
GERMINATION OF ACHENES OF BIDENS PILOSA L.
Authors: VALIO I. F. M. , KIRSZENZAFT SIMONE L. , ROCHA ROSELY F.
Published: May 2006

Summary

The germination of achenes of Bidens pilosa L. was enhanced by light. Under continous fluorescent light germination was 80–90%. Germination was also induced by brief exposures (2 minutes or longer) to blue, green, red and far‐red light. The promotive effect of an irradiation with red was not reversed by far‐red. Cold treatments also enhanced germination. A low concentration (5 ppm) of 6–benzyladenine stimulated germination of the achenes in darkness and also enhanced the proportion of germination in combination with red and far‐red irradiation.
EFFECTS OF PHOTOPERIOD ON EARLY PERIDERM AND XYLEM DEVELOPMENT IN FRAXINUS PENNSYLVANIA, ROBINIA PSEUDOACACIA AND AILANTHUS ALTISSIMA SEEDLINGS
Authors: BORGER G. A. , KOZLOWSKI T. T.
Published: May 2006

Summary

Seedlings of Fraxinus pennsylvanica, Robinia pseudoacacia, and Ailanthus altissima were grown from seed for 30 days in different daylengths and used to investigate early periderm and xylem formation. Periderm and secondary xylem did not develop in dark‐grown seedlings. Xylem increments of Fraxinus pennsylvanica and Robinia pseudoacacia seedlings increased significantly with each increase in daylength from 8 to 24 hours. Xylem increment in seedlings of Ailanthus altissima showed a slight but non‐significant response to daylength. Phellogen formation and activity were stimulated in all three species as daylength was increased. Periderm was not present in 30‐day‐old Ailanthus altissima seedlings grown on 8–hour days, but phellem increased significantly as daylength was increased from 16 to 24 hours. In Fraxinus pennsylvanica seedlings periderm was formed earlier and phellem increment was greater in seedlings grown on 24‐hour daylengths than in those grown on 16‐hour daylengths. In the latter regime phellogen was formed sooner and was more active than in seedlings grown on 8‐hour daylengths. Periderm increment in Robinia pseudoacacia seedlings could not be measured because of crushing of phellem, but it formed sooner and appeared to proliferate faster in seedlings grown on 16 or 24 hour days than on shorter daylengths. Differences in time to formation of the vascular cambium and phellogen and in production of xylem and phellem indicated differences in physiological controls.
WOUND PERIDERM ONTOGENY IN FRAXINUS PENNSYLVANICA SEEDLINGS
Authors: BORGER G. A. , KOZLOWSKI T. T.
Published: May 2006

Summary

In Fraxinus pennsylvanica seedlings which were injured by epidermal scraping, wound periderm was initiated before callus formation. Wound periderm was formed before normal periderm and stimulated formation of normal periderm in uninjured tissue near the wound.
VARIABILITY IN THE PROPORTION OF HEARTWOOD FORMED IN WOODY STEMS
Authors: CARRODUS B. B.
Published: May 2006

Summary

Data on the proportion of heartwood formed in a conifer (Pinus radiata D. Don) and an angiosperm (Acacia mearnsii de Willd.) are presented. A statistical relationship between diameter and amount of sapwood is derived, and a possible causal relationship between the ratio of wall material to space and the formation of heartwood, is discussed. Selective attack by defoliating insects on a physiological strain of A. mearnsii is recorded.
THE ASSIMILATION OF NITRATE AND AMMONIUM BY CHLAMYDOMONAS REINHARDI
Authors: THACKER ANN , SYRETT P. J.
Published: May 2006

Summary

Chlamydomonas reinhardi did not assimilate nitrate or ammonium unless a suitable source of carbon was provided. Suitable sources were CO2 in light or, in darkness, acetate or the carbon reserves accumulated in nitrogen‐starved cells. Illuminated cells in which CO2, assimilation was prevented by DCMU did not assimilate either nitrate or ammonium but did so when acetate was added; the rate of nitrogen assimilation was faster than with acetate in darkness and it is suggested that light promoted nitrogen assimilation by photophosphorylation. The assimilation of nitrate was inhibited by addition of either ammonium or nitrite and that of nitrite by addition of ammonium. Experimental evidence indicated that products of ammonium assimilation, rather than ammonium itself, were inhibiting.
THE EFFECTS OF WATER STRESS ON NITROGEN‐FIXING ROOT NODULES
Authors: SPRENT JANET I.
Published: May 2006

Summary

The fine structure of the non‐infected (outer) region of a soybean root nodule is described. Apart from vascular traces, the cells are mainly vacuolate, with active cytoplasm. They are connected with each other and to cells of the infected region by numerous plasmodesmata. A network of air spaces runs throughout the nodule. Atmospherically applied water stress affects the outer cells of the nodule more quickly and more severely than the inner cells. In any region, vacuolate cells are more susceptible to stress than nonvacuolate cells. Loss of about 30% of their fresh weight results in breakdown of the cytoplasm into approximately spherical sub‐units, some of which are coated with ribosomes. Organelles such as nuclei and mitochondria retain their structure longer than the rest of the cytoplasm. More severe stress is needed to affect infected and pericycle cells, which are nonvacuolate.

It is concluded from the fine structure of stressed and unstressed nodules that the vacuolate cells of the cortex play an integral part in the nitrogen‐fixing activities of the whole nodule.
DESICCATION INJURY IN MOSSES
Authors: STEWART G. R. , LEE J. A.
Published: May 2006

Summary

The effects of desiccation on the activity of several enzymes from Acrocladium cuspidatum were investigated; with the exception of glyceraldehyde 3‐phosphate dehydrogenase prolonged desiccation had little effect on the enzymes studied. The response of the NADP+‐dependent glyceraldehyde 3‐phosphate dehydrogenase to sulphydryl compounds changes during desiccation; when extracted from desiccated shoots it showed a six to twenty times stimulation of activity in the presence of reduced glutathione, that from fresh shoots showed only a twofold stimulation. The effects of glutathione on the enzyme's activity were examined in species with varying resistance to desiccation. It is suggested that the decline in photosynthesis during desiccation may be explained in part by the oxidation of sulphydryl residues essential for the catalytic activity of the NADP+‐glyceraldehyde 3‐phosphate dehydrogenase.
A TEMPORARY SECTION THROUGH LATE‐DEVENSIAN SEDIMENTS AT GREEN LANE, DALTON‐IN‐FURNESS, LANCASHIRE
Authors: JOHNSON R. H. , TALLIS J. H. , PEARSON M.
Published: May 2006

Summary

The glacial geomorphology of the Furness region is described in relation to the sequence of events during the Last (Devensian) Glaciation. Towards the close of this period melt‐streams formed parallel to the upland margins of the wasting ice‐sheets, and a complex network of melt‐water channels was eroded on the lower hill‐slopes. In one such channel at Dalton‐in‐Furness two organic layers interbedded in clay were temporarily exposed during building operations in 1970. Pollen analysis revealed a sequence of Late‐Devensian (Late‐glacial) deposits, interrupted near the top by a layer of soliflucted grey clay. Seven sub‐zones, covering Zones I to early Zone IV are recognized, based on differing representations of seven major pollen assemblages. The affinities of the pollen diagram to other published Lake District diagrams are discussed.
ORGANIC FLUORINE IN TROPICAL SOILS
Authors: HALL R. J. , CAIN R. B.
Published: May 2006

Summary

A number of tropical soils growing toxic plant species which contain organically combined fluorine have been studied with a view to establishing the relationship between plant and soil in terms of fluorine. The analyses of the soils for total fluorine and water‐soluble fluoride showed that there was no correlation with the levels of total and organically‐combined fluorine in the leaves of the plant species. Some of the most toxic plants grew in soils having low levels of mineral fluorine. Examination by electrodialysis, gas‐liquid chromatography and infra‐red spectroscopy, supported by chemical analysis, has revealed the presence in significant amounts of what appears to be fluoroacetate in several of the soils supporting species known to contain toxic fluorinated fatty acids. The origin of the naturally‐occurring fluoroacetate in these soils is discussed.
ION ABSORPTION BY ROOTS: THE ROLE OF MICRO‐ORGANISMS
Authors: EPSTEIN EMANUEL
Published: May 2006

Summary

Theoretical considerations and experimental evidence are adduced to the effect that ion absorption by plant tissue from solutions in the range of low concentrations (< 1 mM) is due to the type 1 mechanisms of ion transport of the plant cell membranes, not to bacteria associated with the tissue.
VARIABILITY IN THE WILD RASPBERRY
Authors: KEEP ELIZABETH
Published: May 2006

Summary

Surveys of wild raspberries in Europe and Britain, and of progenies raised from seed collected in the wild, showed widespread polymorphism for the gene H (hairy/subglabrous canes) and less frequent polymorphism for P (spine colour intensifier). No yellow fruited (t), spineless (s) or sepaloid (sx3) plants were seen. Breeding experiments snowed there was no close linkage between H and the incompatibility S locus. Male sterility occurred in three out of nineteen progenies and partial female sterility, accompanied by abnormalities affecting vegetative characters, segregated in three out of eleven progenies from sibbing four seedlings. This condition was due to a semi‐lethal gene, gr.

Progenies varied widely in response to powdery mildew (Sphaerotheca macularis (Fr.) Jaczewski), from 0 to 100% of seedlings proving resistant. The incidence of resistance in progenies tended to increase with increasing altitudinal origin of the parent, total percentage resistance in all progenies being 6.6, 59.6, 64.3 and 97.2 for parental altitudes of less than 500 m, 500–1000 m, 1000–1500 m and over 1500 m, respectively. It is suggested that higher mildew resistance may be a secondary effect of greater cold hardiness at high altitudes.

Resistance to the aphid Amphorophora rubi occurred in seventeen out of twenty‐eight wild progenies. Resistance to strain 3 of the aphid was more common than to strain 2; in both cases, the incidence of resistance tended to decrease with increasing altitude of the parent. Only one very small progeny was homozygous for resistance. Resistant and susceptible classes were usually sharply differentiated, indicating the segregation of major resistance genes. Genes conferring, respectively, strain 2 resistance alone, strain 3 resistance alone and resistance to both strains, were isolated.
THE INTERACTION BETWEEN GROWTH PROMOTERS IN APICAL DOMINANCE
Authors: WOOLLEY D. J. , WAREING P. F.
Published: May 2006

Summary

The effects of light intensity, day length and nitrogen status on lateral bud growth and endogenous levels of gibberellins and cytokinins were investigated. Low light intensity had little effect on gibberellin levels in the leaves of long–day plants but greatly increased acidic gibberellin levels in short‐day leaves. Both short days and low nitrogen status reduced cytokinin levels in the roots. The correlation between lateral shoot development and endogenous cytokinin levels was consistent with results obtained using exogenous hormones: this correlation strongly suggests that lateral shoot development is controlled by a delicate balance between auxins, gibberellins and root–produced cytokinins.
THE PHASE‐RESPONSE OF THE DARK STOMATAL RHYTHM IN TRADESCANTIA VIRGINIANA TO LIGHT AND DARK TREATMENTS
Authors: MARTIN E. S. , MEIDNER H.
Published: May 2006

Summary

In continued darkness following a standard pretreatment of 12 hours light and 12 hours dark, the stomata of Tradescantia virginiana did not reveal a truly repeating rhythm, but only a single opening cycle which matched the opening phase of the rhythm in light. An investigation of the phase response of this dark opening cycle to light and dark treatments revealed that the phase of the dark opening cycle could be manipulated as follows. When light commenced during that phase characteristic of darkness in nature, the dark opening cycle showed phase‐shift, but little or no phase‐shift occurred when light commenced during that phase characteristic of light in nature. The fact that the rhythms can be manipulated in this manner may indicate the plant's ability to adapt to different day lengths.
THE DISTRIBUTION AND ROLE OF CYTOPLASMIC MEMBRANE‐BOUNDED VESICLES DURING THE DEVELOPMENT OF BOTRYOSE SOLITARY BLASTOSPORES OF TWO FUNGI
Authors: COOK BERYL E.
Published: May 2006

Summary

During a study of the fine structure of developing conidiophores and spores of Oedocephalum roseum it was found that two kinds of wall growth existed: (a) growth and extension involving addition of wall material, i.e. wall synthesis; (b) extension only, i.e. growth without synthesis but involving instead plasticizing of the wall. The latter type of growth occurred only during denticle formation. Associated with these two types of growth were two different kinds of cytoplasmic organization. During growth involving extension and synthesis, membrane‐bounded vesicles of two different sizes were present, but during growth involving extension alone, only the smaller vesicles were present. Observations of Fomes annosus showed a similar pattern. The implications of the observations are discussed.
CORRELATED LIGHT AND ELECTRON MICROSCOPE STUDIES ON BROWN ALGAE I. LOCALIZATION OF ALGINIC ACID AND SULPHATED POLYSACCHARIDES IN DICTYOTA
Authors: EVANS L. V. , HOLLIGAN M. SUSAN
Published: May 2006

Summary

By electron microscopy and light microscope histochemical techniques, alginic acid and sulphated polysaccharides (probably largely fucoidan) have been located in the cell walls of Dictyota dichotoma.

The cell walls of the vegetative thallus and those of mature reproductive cells (tetrasporangia, tetraspores, antheridia and oogonia) are composed of three to four well‐defined layers, mainly of alginic acid, sulphated polysaccharide or a mixture of these substances. Prior to their secretion the two types of polysaccharide can generally be detected in conspicuous, peripheral, intra‐cellular cytoplasmic vesicles. Alginic acid is liberated from vesicles through the plasma membrane by reversed pinocytosis.

The results are discussed in relation to other work on the polysaccharides and histochemistry of brown algae.
CORRELATED LIGHT AND ELECTRON MICROSCOPE STUDIES ON BROWN ALGAE
Authors: EVANS L. V. , HOLLIGAN M. SUSAN
Published: May 2006

Summary

The physodes or fucosan vesicles abundant in vegetative and reproductive cells of the brown seaweed Dictyota originate in the plastids. Precursor material expelled from the chloroplast matrix, may run together to produce the large physodes in the cell cytoplasm. Staining reactions indicate that the physodes are phenolic or tannin‐like in nature. They may be products of photosynthesis. Physodes in the apical region of thalli are exceedingly resistant and stable compared with those in older parts of thalli; the latter are lost during glutaraldehyde fixation.
BREEDING SYSTEMS IN COTULA L. (COMPOSITAE, ANTHEMIDEAE) II. MONOECIOUS POPULATIONS
Authors: LLOYD DAVID G.
Published: May 2006

Summary

The distribution of male and female florets in heads of monoecious populations is represented by a curve joining points on a graph of percentage of female florets against rank in the same percentage. Comparison of curves for samples from different origins in Cotula minor and C. atrata subsp. atrata shows that sex expression is not greatly influenced by macro‐environmental differences. Much of the total intra‐population variation in sex expression appears in the heads collected at one time from a single plant. The rank‐frequency curves show marked differences between species in the percentages of male and female florets. The average percentage of female florets in seventeen monoecious species is negatively correlated with the floret length, a measure of adaptation to outbreeding. In three species, the seed set and subsequent germination percentages are slightly lower after self‐pollination than after cross‐pollination. Self‐fertilization probably occurs in varying degrees in the monoecious species. Monoecy has arisen independently in sections Leptinella and Strongylosperma.
A DATA BANK OF QUATERNARY PLANT FOSSIL RECORDS
Authors: DEACON JOY
Published: May 2006

Summary

A data bank of British Quaternary plant fossil records has been established in the Subdepartment of Quaternary Research, Cambridge. The bank is based on an exhaustive survey of the literature and includes both fossil pollen and macrofossil records. The information entered on each record card includes, whenever possible: grid reference of site; zone, stage and radiocarbon date of sediment; average frequency of pollen type; details of stratigraphy and archaeological correlations. Examples of how the bank can be used are given.
LATE‐GLACIAL DEPOSITS NEAR CAPEL CURIG, CAERNARVONSHIRE
Authors: CRABTREE K.
Published: May 2006

Summary

Investigations into former lake basins in the region to the north of Capel Curig (SH 721581) in Caernarvonshire have revealed deposits of Late‐glacial age. Pollen analysis of the deposits permits subdivision of the sequence into the standard Late‐glacial zones I, II and III together with some sub‐zones based upon recurring pollen assemblages. Some of the ecological implications of these assemblages are discussed, in terms of vegetation, climate and soils. High Rumex* pollen values characterize pollen zone I. A wide range of herbs and Betula pollen dominate in zone II. Zone III is characterized by high Artemisia pollen values. A transition zone III–IV is included to cover the Empetrum and Juniperus pollen peaks, prior to the rapid rise in Betula pollen values in zone IV.
THE CELLULAR LOCATION OF LEAD AND POTASSIUM IN THE LICHEN CLADONIA RANGIFORMIS (L.) HOFFM.
Authors: BROWN D. H. , SLINGSBY D. R.
Published: May 2006

Summary

The cellular location of lead and potassium has been studied in the lichen Cladonia rangiformis, collected from a lead‐rich site. Elution of ions by dilute acid or their replacement by other ions has demonstrated that lead is ionically bound, most probably within the cell wall. The same techniques have shown a proportion of the total potassium to be also bound ionically in the cell wall. In addition potassium is present as freely diffusible material retained within the permeability barriers of the intact cell and also firmly bound in an insoluble form. The reported tolerance of lichens to heavy metals is discussed in relation to the demonstrated location of lead.
IDENTIFICATION OF FOSSIL SEEDS OF ERICA AND CALLUNA BY SCANNING ELECTRON MICROSCOPY
Authors: HUCKERBY E. , MARCHANT R. , OLDFIELD F.
Published: May 2006

Summary

A study of the surfaces of Erica and Calluna seeds by S.E.M. reveals a range of morphological characteristics, which can be used in conjunction with features more readily visible by conventional light microscopy to separate contemporary reference material of all the West European species. These fine morphological characteristics have also been detected on well‐preserved Pleistocene material from south‐west France and used to identify eight separate Erica species in the fossil record. Where the surface of fossil seeds has been sufficiently degraded an underlying regularly pitted layer is revealed which seems to be present in all the species recorded and has frequently been observed and used in identification by previous workers using transmitted light microscopy.
A METHOD FOR DETERMINING ABSOLUTE POLLEN FREQUENCIES IN LAKE SEDIMENTS
Authors: BONNY ANNE P.
Published: May 2006

Summary

A detailed account is given of the procedure required to obtain an estimate of fossil pollen per unit volume of sediment, using a method, outlined by previous workers, which involves the addition of a known number of exotic or ‘marker’ pollen grains. Sources of error in the method are discussed and statistical tests for certain errors are included. Details are given of calculations whereby confidence limits are obtained for the counting error of fossil pollen concentration. Absolute pollen counts obtained by means of this method from a Late‐Weichselian profile of lake sediments provide additional information for the expenditure of little extra time.
A SIMPLE INTEGRATING PHOTOMETER
Authors: DREW EDWARD A.
Published: May 2006

Summary

A selenium photovoltaic cell coupled to a mercury electrolytic coulometer makes a useful integrating photometer with the following features: linear response to a wide range of intensities; high sensitivity from 400 to 650 nm; cosine light collection; no power requirements, minimum circuitry; robust, resistant to all environmental conditions; small size, easy construction and low cost. Results from use underwater show good correlation with expected light attenuation and readings can easily be converted to absolute light energy units.
THE MOVEMENT OF CARBOHYDRATE FROM THE ALGA TO THE FUNGUS IN THE LICHEN PELTIGERA POLYDACTYLA
Authors: HILL D. J.
Published: May 2006

Summary

The pattern of incorporation of 14C into the thallus during incubation with H14CO3‐ in the light suggested that a substance in the 80% ethanol insoluble fraction, an unknown compound (probably a sugar phosphate) and glucose were intermediates in the transfer of carbon to the fungus. Results are presented which are consistent with the hypothesis that the alga releases a glucan which the fungus hydrolyses extra cellularly to form glucose. This glucose is then taken up by the fungus and converted to mannitol.
A RELATIONSHIP BETWEEN OXYGEN TRANSPORT AND THE FORMATION OF THE ECTOTROPHIC MYCORRHIZAL SHEATH IN CONIFER SEEDLINGS
Authors: READ D. J. , ARMSTRONG W.
Published: May 2006

Summary

The response of the mycorrhizal fungus, Boletus variegatus, to living coniferous roots and to hollow silicone rubber ‘roots’ in anaerobic media was investigated. Mycelial macerates were cultured in nutrient and non‐nutrient agar media in tubes. The roots of whole seedlings or silicone ‘roots’ were placed in the media to a depth of several centimeters below the air‐agar interface. The silicone ‘roots’ were either provided with access to the atmosphere by means of a capillary tube exposed above the agar surface, or were sealed.

In young seedlings with unsuberized roots a diffuse fungal growth occurred over the whole root surface. In older, suberized, root systems, colonization was restricted to areas of the main axis through which short laterals were appearing. It was demonstrated polarographically that the area stimulating fungal growth were the only areas of significant oxygen evolution along the root. Fungal growth occurred around the silicone ‘roots’ only when access to air was provided by the capillary. It took the form of a diffuse mycelial ball in non‐nutrient medium but, in mitrient agar, of a tight sheath with a distinct tendency for pseudoparenchyma formation. The possible role of oxygen evolution from roots is discussed both in terms of the initial stimulus to the symbiont and of the continued physiological activity of the mycorrhiza.
ROOTING OF HARDWOOD CUTTINGS IN RELATION TO BUD DORMANCY AND THE AUXIN CONTENT OF THE EXCISED STEMS
Authors: SMITH N. G. , WAREING P. F.
Published: May 2006

Summary

Experimental evidence is given for poplar cuttings (Populus x robusta Schneid.) of the role of dormant and nondormant buds to root initiation. Chilling treatments shortened bud dormancy and greatly increased the emergence of pre‐formed roots from stem cuttings, but caused a smaller increase in numbers of wound‐roots. With terminal popular cuttings greater root numbers were obtained when, after excision, a warm treatment preceded chilling. Chilling only induced a large increase in the number of wound‐roots on terminal apple cuttings (Malus cv. Mailing II), if steeped in indolyl butyric acid immediately after the chilling treatment.

A greater amount of auxin was found in chilled than in unchilled poplar cuttings five weeks after the end of chilling.

Endogenous auxin levels at the base of both intact and disbudded, chilled cuttings of poplar were high at the time when roots were about to emerge from the cortex, but were low 15 days later when the roots were several centimetres in length.
RNA‐DNA HYBRIDIZATION COMPETITION STUDIES ON SENESCING BARLEY LEAVES
Authors: SRIVASTAVA B. I. SAHAI
Published: May 2006

Summary

No detectable differences in RNA populations from 7‐day‐old (young) and 17‐day‐old (senescent) first seedling leaves of barley were found by RNA‐DNA hybridization competition experiments. It is suggested that enzymatic changes during senescence may result from minor changes at the transcription level or alterations at the translation level.
MEASUREMENT OF THE TRANS‐ROOT ELECTRICAL POTENTIAL OF PLANTS GROWN IN SOIL
Authors: ANSARI A. Q. , BOWLING D. J. F.
Published: May 2006

Summary

Electrical potential differences between the soil and the exuding xylem sap of detopped sunflower plants grown in potting compost were measured. The concentrations of some of the major nutrient ions in the soil water and in the xylem sap were determined, enabling the driving forces on the ions to be calculated. The anions, Cl, NO3 and SO4, appeared to be moving from the soil into the sap against the electrochemical potential gradient indicating active transport. There was also evidence that K and Na were actively transported into the xylem. These results are discussed in relation to those obtained with plants grown in water culture. They suggest that this could be a useful method for studying salt uptake by plants growing in the field.
EFFICIENCY TESTS ON THE TAUBER TRAP USED AS A POLLEN SAMPLER IN TURBULENT WATER FLOW
Authors: PECK R. M.
Published: May 2006

Summary

The Tauber trap was subjected to tests in the controlled water flow of a flume to assess its sampling efficiency for a range of pollen types and varying speeds of flow. The equipment and procedures of pollen preparation are described, and the method of trap efficiency calculation is explained, Results indicating numerical differences in amounts of pollen caught by two sizes of trap are attributed to scaling factors on the traps used, and the increased flow velocity near the floor of the flume. Similar pollen proportions from these traps in each experiment are obtained, indicating an even distribution of pollen within the flow. Collection efficiency for individual taxa are found to vary both according to size and weight of the grains and the velocity of flow. Within one experiment, other factors being constant, smaller grains arc trapped less efficiently than those larger. The total experimental evidence suggests that, with increasing water speed, differences in grain characteristics have Jess effect, though the overall trapping efficiency is lowered. Factors of weight rather than density are proposed as determining the final catch from water by this particular design of trap. The significance of under‐ and over‐representation of grains at low flow velocities is discussed in relation to the potential use of the trap as a pollen sampling mechanism in the field.
TISSUE CULTURE OF ORCHIDS I. METHODS FOR LEAF TIPS
Authors: CHURCHILL M.‐E. , BALL E. A. , ARDITTI J.
Published: May 2006

Summary

Leaf‐tips of Epidendrum and Laeliocattleya (Orchidaceae) have been cultured in vitro. Epidendrum seedling leaf‐tips form calli on Murashige‐Skoog medium (MS) or after being transferred to Knudson C agar following prior growth on MS. Plantlets also develop from tips of young leaves of mature Laeliocattleya plants cultured in Heller's medium or in a solution specifically devised for orchid shoot‐tip cultures. In Heller's medium plantlet development is preceded by callus formation whereas in the shoot‐tip medium protocorm‐like bodies are formed first. These tissues when subcultured from Heller's medium or the shoot‐tip solution to Knudson C agar also produce plantlets which resemble orchid seedlings. The results are discussed in relation to the components of each medium, the requirements of germinating orchid seeds and protocorms, and the difficulties encountered in attempts to culture tissues of mono‐cotyledonous plants.
PHOTOSYNTHETIC INDUCTION PHENOMENA AND THE LIGHT ACTIVATION OF RIBULOSE DIPHOSPHATE CARBOXYLASE
Authors: WALKER D. A.
Published: May 2006

Photosynthesis often reaches its maximal rate only after an initial induction period of some minutes. Simple induction phenomena in whole plants and intact chloroplasts have common features which imply that they are brought about by the same mechanism. The Osterhout–Haas Hypothesis explains induction in terms of light activation of a catalyst and building up of intermediates. This proposal is examined in the light of contemporary work and it is concluded that the major factor is the accumulation of metabolites brought about by the autocatalytic action of the Benson‐Calvin cycle. Light activation of ribulose diphosphate carboxylase is seen as an important factor in autocatalysis but normally too rapid a process, in itself, to account for delays of several minutes.
STUDIES ON TUBERIZATION IN SOLANUM ANDIGENA: I. EVIDENCE FOR THE EXISTENCE AND MOVEMENT OF A SPECIFIC TUBERIZATION STIMULUS
Authors: KUMAR D. , WAREING P. F.
Published: May 2006

Experiments were carried out with a clone of Solanum andigena, which requires short photo‐periods for tuberization, to investigate whether or not tuberization involves a specific stimulus. It was shown that a tuberization stimulus can be transmitted by grafting induced on to non‐induced shoots and that even small pieces of stem from induced plants are capable of transmitting the stimulus. The results of these and other experiments support the view that tuberization is determined by a specific stimulus, rather than by the availability of non‐specific photosynthates. It is shown that the stimulus can move both basipetally and acropetally, but tuber development occurs only at the physically lowest nodes of stem cuttings, whether these are normally orientated or inverted.
EFFECT OF TEMPERATURE AND LIGHT ON SEED GERMINATION OF TWO ECOTYPES OF PORTULACA OLERACEA L.
Authors: SINGH K. P.
Published: May 2006

The effect of various temperature and light conditions on the germination of freshly harvetesd and 1‐year‐old seeds of obovate leaf and narrowly obovate leaf ecotypes of Portulaca oleracea L. is reported. These plants are common weeds of moist cultivated fields in the Upper Gangetic Plain. Freshly harvested seeds showed insignificant germination in darkness at any temperature between 10–40° C, and required specific photoperiodic and thermoperiodic conditions for germination. In contrast 1‐year‐old seeds showed significant temperature‐dependent dark germination, and almost complete germination with a single light exposure given at high temperatures; they thereby exhibited the loss of photo‐thermoperiodic requirement. In general the seeds of the narrowly obovate leaf ecotype were more sensitive to light than those of the obovate leaf ecotype. The possible significance of the germination requirements in relation to the success of the plant in Nature and to its essentially tropical distribution is discussed.