bluuebunny/crossref_metadata_2025 huggingface dataset:
RESPONSE TO BORON DEFICIENCY: A COMPARISON WITH RESPONSES PRODUCED BY CHEMICAL METHODS OF RETARDING ROOT ELONGATION
Authors: ROBERTSON G. A. , LOUGHMAN B. C.
Published: May 2006

Summary

Seedlings of Vicia faba L. were subjected to treatments with IAA, 2,4‐D, tri‐iodobenzoic acid, kinetin, 2‐chloroethanephosphonic acid as well as those designed to prevent normal division in the primary meristem. Where division was inhibited with colchicine, trifluralin, dinitramine or surgical excision, a radial expansion of the root tip occurred. However, the anatomical aspects of the responses and their effects on phosphate absorption and incorporation were quite distinct from the effects produced in both boron deficiency and excess auxin treatments. Kinetin gave similar effects to mitotic inhibitors. The possibility that boron deficiency is associated with an excess level of endogenous auxin was examined. The effects of boron deficiency were compared with those associated with the presence of excess auxin.
DIFFERING EFFECTS OF WATER DEFICIT ON NET PHOTOSYNTHESIS OF INTACT AND EXCISED SORGHUM LEAVES
Authors: PASTERNAK D. , WILSON G. L.
Published: May 2006

Summary

Net photosynthesis and leaf resistances in turgid sorghum leaves were compared with those of intact leaves which underwent relatively slow loss of water, and with excised leaves which lost water rapidly. Reduced net photosynthesis in intact leaves can largely be accounted for by stomatal closure; this is not so for excised leaves. Stomata of excised leaves both started and completed closure at much lower leaf water contents than those of attached leaves.
GROWTH PHASES IN THE LIFE OF A LICHEN THALLUS
Authors: ARMSTRONG R. A.
Published: May 2006

Summary

The growth rates of thalli of foliose saxicolous lichens before and after the linear phase of growth were measured in 1973. Changes in the radial growth rate (measured as mm/year) with thallus size in the prelinear phase (thalli less than approximately 1.5 cm in diameter) were consistent with the hypothesis that early growth of these lichens is logarithmic. When growth in the prelinear phase was measured as a relative growth rate (measured as cm2/cm2/year) there was a rapid rise in growth rate until about 3 mm thallus diameter and then a decline in growth rate. The radial growth rate of non‐fragmenting thalli when compared with fragmenting thalli at different stages of fragmentation suggested that the radial growth rate does not significantly decline after fragmentation of the thallus. This result is not consistent with a postlinear phase in the radial growth of a lichen thallus.
THE INFLUENCE OF ENVIRONMENT ON LEAF WAX DEVELOPMENT IN BRASSICA OLERACEA VAR. GEMMIFERA
Authors: BAKER E. A.
Published: May 2006

Summary

The influence of environmental conditions on the epicuticular waxes of the normal and four mutant forms of brussels sprout (Brassica oleracea var. gemmifera) has been studied. An increase in radiant energy rate, a decrease in humidity or a decrease in temperature induces the largest deposits of wax. Environmental conditions have only a limited effect on the compositions of the waxes of the normal and mutant lines but modify the size, configuration and distribution of the surface wax structures. A mechanism for the transport and subsequent organization of the wax on the plant surface is discussed.
PLANT MACROFOSSILS FROM LATE‐DEVENSIAN DEPOSITS AT NANT FFRANCON, CAERNARVONSHIRE
Authors: BURROWS C. J.
Published: May 2006

Summary

The occurrence of plant macrofossils in Late‐Devensian sediments from the valley of Nant Ffrancon is described. The range of fossils present and their distribution relative to changes in the sedimentary sequence allow an interpretation to be made of the Late‐Devensian environments of the area. A time of barren landscape, as ice retreated from the valley and adjacent areas, was followed by a brief period of vegetation development in which some woody plants were present, then a brief return to colder conditions and devegetation. There then occurred a longer interval during which varied vegetation developed, beginning primarily with herbaceous communities and culminating in a period of predominance of birch woodland and scrub, which probably formed mosaics with herbaceous communities. Finally, there was a return to barren conditions as climate again became colder. No absolute dating is yet available for these events but, provisionally, they may be correlated with phases in the glacial history of the area and with changes recorded by pollen analysis by other workers.
THE VEGETATION HISTORY FROM 6000 b.p. TO PRESENT OF WILSONS PROMONTORY, VICTORIA, AUSTRALIA
Authors: HOPE G. S.
Published: May 2006

Summary

Pollen analysis of three sites on Wilsons Promontory provides a vegetation record from 6000 b.p. to the present day. No extensive changes in the vegetation have been found over this time period, but local and regional variations in the extent of communities may imply small climatic changes. Moister conditions than at present seem to have prevailed earlier than 4500 b.p., followed by a drier phase till less than 2000 b.p., when an increase in moisture gave conditions similar to those of today. Some evidence exists to support the theory of a relatively steady sea level close to the present level over the last 6000 years along the western Wilsons Promontory coastline.
AN ULTRASTRUCTURAL STUDY OF PIT CONNECTIONS AND PERCURRENT PROLIFERATIONS IN THE RED ALGA NEMALION HELMINTHOIDES (VELL. IN WITH.) BATT.
Authors: DUCKETT J. G. , BUCHANAN J. S. , PEEL M. C. , MARTIN M. T.
Published: May 2006

Nemalion helminthoides exhibits considerable diversity in pit connection morphology. Their diameter ranges from 1.5 μm between fusion cells and the gametophyte, down to 0.3 μm on spermatial branches. Highly asymmetrical pit connections occur in the septa at the base of hairs. The plugs between the vegetative cells of the cortex possess a central groove, but this is absent from those in the medulla and on spermatial branches. The plug cap is three layered except at the base of hairs where only the innermost stratum is present. This last layer also extends as the border to the sides of the plugs separating them from the cell membrane which is continuous between adjacent cells. Granular material occurs in the cytoplasm adjacent to the plug caps, and peripheral to this is a region lacking ribosomes.

Up to four successive spermatia and up to twelve hairs may be produced by percurrent proliferations in Nemalion. Absence of pit connections in the walls remaining after spermatium discharge suggests that pit connection displacement may be important in the liberation of the male gametes. Pit connections may also have a mechanical role in anchoring the cytoplasm and providing cross‐bridges between adjacent cells.
THE LATE‐GLACIAL DEPOSITS AT GLANLLYNNAU, CAERNARVONSHIRE
Authors: SIMPKINS KATHLEEN
Published: May 2006

Late‐glacial deposits from two kettleholes at Glanllynnau, Caernarvonshire, are described and the lithological units and their stratigraphical relationships are discussed. The pollen analytical procedure and the method of zonation are outlined. The characteristics of each pollen assemblage zone are described, and a correlation is made between pollen zones and lithostratigraphic units: the environmental implications are stated. An attempt is made to determine the relative pollen concentration within each pollen zone/lithological type, in order to assess the relevance of statements deduced from the Blelham Bog comparison of absolute and percentage pollen data (Pennington and Bonny, 1970). The pollen record at Glanllynnau is interpreted in terms of (i) the terrestrial vegetation history, and (ii) the aquatic vegetation and palaeoecology of the sites. The significance of the Glanllynnau 14C dates is examined and a brief comparison is made with similarly dated lithostratigraphic horizons at other British sites. The inconsistency between the coleopteran and floral evidence for the beginning of the Late‐glacial interstadial at Glanllynnau is noted, but no explanation can be given. The status of the Bölling–Alleröd interval is also considered.
THE EFFECTS OF FLOWERING AND FRUIT FORMATION ON THE SUPPLY OF PHOTOSYNTHETIC ASSIMILATES TO THE NODULES OF PISUM SATIVUM L. IN RELATION TO THE FIXATION OF NITROGEN
Authors: LAWRIE ANN C. , WHEELER C. T.
Published: May 2006

Both nitrogenase activity and the accumulation of 14C‐labelled photosynthates in the nodules of pea plants in nitrogen‐free culture reached maxima shortly before flowering and fruit development. During the period from flowering to fruiting, nitrogenase activity and accumulation of 14C‐photosynthates in the nodules declined by 60%, whereas the photosynthesis of the plant doubled. Studies of the translocation of the photosynthates within the plant during this period suggested that this might be due to an increase from 17% to 50% of the photosynthates which accumulated at the shoot apex. Consistent increases in nitrogenase activity over the 24 hours following removal of the shoot apex were only achieved in fruiting plants, however, although vegetative, flowering and fruiting plants all showed increased accumulation of photosynthates in the nodules. Continuous removal of flowers as they were formed over a 2‐week period resulted in a large increase in accumulation of photosynthates in the nodules and in nitrogenase activity.

Other factors which may regulate nitrogenase activity in these plants are discussed.
ARBUSCULAR MYCORRHIZAS IN PLANTS COLONIZING COAL WASTES IN SCOTLAND
Authors: DAFT M. J. , NICOLSON T. H.
Published: May 2006

All the grasses and nearly all the dicotyledonous plants growing on three coal tips in Scotland were infected by vesicular‐arbuscular mycorrhizal fungi. Infection levels ranged from 20 to 90%. Three main types of fungal endophytes were identified, two being Endogone spp. and one with very narrow hyphae. Mixed infections were present in some plants and there was some evidence that the endophytes occurred in different areas of the tips. The ecological importance of the mycorrhizas in these habitats is discussed.
PHOTOSYNTHETIC 14C FIXATION BY THE LICHEN UMBILICARIA MUHLENBERGH (ACH) TUCK. FOLLOWING SHORT EXPOSURES TO AQUEOUS SULPHUR DIOXIDE
Authors: PUCKETT K. J. , RICHARDSON D. H. S. , FLORA W. P. , NIEBOER E.
Published: May 2006

Photosynthetic 14C fixation by the lichen Umbilicaria muhlenbergii was reduced within 15 min of exposure to aqueous sulphur dioxide (75 ppm, pH 3.0), but no changes were observed in the spectra of extracted chlorophyll pigments. Exposed lichen samples maintained under moist, sulphur‐dioxide‐free conditions in the light for 24 h were able to fix 14C at pre‐exposure levels. Partial recovery was observed when samples were kept under moist dark conditions but little when the lichens were maintained dry in the light or dark. When samples were exposed repeatedly to sulphur dioxide, but with a recovery period between each exposure, they gradually lost the ability to regain their photosynthetic activity. After the third cycle of exposure and recovery, little 14C fixation was observed while changes in the spectra of extracted pigments was evident. Increased potassium levels were found in the medium during exposure. These levels reverted to control values after a suitable recovery period. In vitro studies showed that 10‐20 ppm sulphur dioxide was found to deactivate both staphylococcal nuclease and lysozyme. Possible explanations as to the mode of SO2 toxicity on lichen metabolism and suggestions as to recovery mechanisms are fully discussed.
SOME EFFECTS OF SULPHITE ON PHOTOSYNTHESIS IN LICHENS
Authors: HILL D. J.
Published: May 2006

Details of the effect of sulphite on H14CO3‐ fixation in the light were studied. The reduction of fixation by sulphite was rapid, taking place within 30 min of contact with the lichen. Parmelia physodes recovered in 24 h from almost total reduction of fixation caused by 1 h treatment with 0.4 mM sulphite but Usnea sp. did not. Studies with [35S] sulphite indicated that sulphite was taken up nonlinearly with time and that it was bound to protein. Algae isolated from Usnea sp., Parmelia physodes and Lecanora conizaeoides were similar in their response to sulphite, although the intact lichen L. conizaeoides is known to be more resistant. L. conizaeoides did not seem to be resistant to sulphite by causing rapid oxidation of sulphite to sulphate. There was no marked effect of temperature on the concentration of sulphite required to reduce fixation in Usnea sp.
PSEUDOGAMY IN THE GENUS POTENTILLA L.
Authors: GOSWAMI D. ACHARYA , MATFIELD B.
Published: May 2006

Three closely related pseudogamic species, Potentilla argentea L., P. recta L. and P. cf. hirta L. were pollinated by other species of Potentilla and observations were made on pollen germination, pollen tube growth, ovule development and seed set. The three pseudogamic species stimulated seed set in each other, but no seeds were formed after pollination by ten other species although well‐developed pollen tubes were observed in a number of cases. The offspring from the successful pollinations were mainly maternal but a few deviant individuals were also produced.
FACTORS INFLUENCING NITRATE REDUCTION IN SOYBEAN FOLIAGE
Authors: TINGEY DAVID T. , FITES ROGER C. , BAHARSJAH JUSTIKA
Published: May 2006

Summary

Optimum conditions for the in vivo nitrate reductase assay in soybean (Glycine max (L.) Merr.) foliage were determined. The in vivo and in vitro nitrate reductase assays correlated highly but exhibited differential decay rates with increasing leaf age. Nitrate reduction could be coupled to the oxidation of either frustose‐I,6‐diphosphate or 6‐phosphogluconate. Compounds, such as glucose, 2,4‐dinitrophenol or phosphate, which stimulate glycolysis also stimulated nitrate reduction. Citrate stimulated nitrate reduction in young expanding leaves but was inhibitory in mature, expanded leaves. Caffeic acid was inhibitory in young but not in mature leaves.
EFFECT OF WATER STRESS UPON ENDOGENOUS ETHYLENE LEVELS IN VICIA FABA
Authors: EL‐BELTAGY A. S. , HALL M. A.
Published: May 2006

Summary

Conditions of drought or waterlogging lead to greatly increased internal ethylene concentrations in Vida faba L. These increases appear to be due partly to decreased diffusion and partly to increased synthesis and are superimposed on normal diurnal fluctuations in internal ethylene concentration. The higher concentrations observed are correlated with a reduction in growth rate and increased leaf and flower abscission and senescence. The role of ethylene in the mediation of developmental responses to water stress is discussed.
VERTICAL AND RADIAL MOVEMENT OF AUXIN IN YOUNG SYCAMORE PLANTS
Authors: ZAMSKI E. , WAREING P. F.
Published: May 2006

Summary

Three‐year‐old active and dormant sycamore plants were treated with labelled auxin solution applied to the outer bark or the inner xylem in order to establish the rate of transport of radioactive materials in longitudinal and radial directions.

The velocity of auxin transport in the vertical direction within the bark was 0.4–0.6 cm/h in active plants and 0.1–0.2 cm/h in dormant plants. It was found that auxin can move from bark to xylem or vice versa. Autoradiography shows that radial transport takes place within the rays. Auxin is translocated from xylem to bark at a higher rate and in greater amounts than in the reverse direction both in active and dormant plants, but the radial transport from bark to xylem in dormant plants is greater than in active plants. The slower the vertical transport within the bark the faster the radial one in the centripetal direction. On the other hand, the rate of the transport in the centrifugal direction was found to be slower for dormant plants. A higher level of auxin may be maintained in the cambium of active plants because of the centrifugal movement of auxin within the xylem.
THE EFFECT OF MICRO‐ORGANISMS ON THE ABSORPTION OF MANGANESE BY PLANTS
Authors: BARBER D. A. , LEE R. B.
Published: May 2006

Summary

The uptake of manganese by barley plants grown in solution culture is stimulated in the presence of micro‐organisms, irrespective of whether they originated as casual laboratory contaminants or as rhizosphere micro‐organisms in the soil. The microbial effect is mediated by a watersoluble substance but neither its identity nor its mode of action has yet been established.

When manganese is supplied as EDTA chelates these appear to be broken down at or near the surface of the roots and this process is accelerated in the presence of micro‐organisms. Under the conditions of these experiments EDTA was absorbed by the plants much less readily than manganese.
KARYOTYPE VARIATION AND EVOLUTION IN THE VICIA SATIV A AGGREGATE
Authors: HOLLINGS E. , STACE C. A.
Published: May 2006

Summary

Previous accounts of the chromosome complement of members of the Vicia sativa aggregate and of V. lathyroides are reviewed, and the results of a new survey of 122 strains belonging to four taxa presented. Significant variation in chromosome morphology within each of the three segregates of V. sativa agg. was found; in V. segetalis both 2n= 10 and 2n= 12 was encountered among the cultivated material. In wild V. lathyroides also both 2n = 10 and 2n= 12 populations were found. Reasons are given for considering that this group of vetches shows a reductional evolutionary series 2n= 14 2n= 12 2n= 10, and the inter‐relationships of these three karyotypes are discussed. In addition two counts of 2w = 14 are reported for wild Turkish strains of V. amphicarpa.
POPULATION VARIATION AND TAXONOMY IN ARMERIA MARITIMA WITH SPECIAL REFERENCE TO HEAVY‐METAL‐TOLERANT POPULATIONS
Authors: LEFÈBVRE C.
Published: May 2006

Summary

Populations of Armeria maritima growing in various ecological situations were studied in northwestern and central Europe. In their typical ecogeographical areas populations of ssp. maritima, ssp. elongata and ssp. alpina are well differentiated. These three subspecies are nevertheless interconnected by transitional populations related to ssp. intermedia and ssp. halleri s.1. Populations from mines of heavy metals (ssp. halleri s.1.) show endemic frequencies of morphological traits from one site to another. This variation which can occur in neighbouring areas is random and may be due to genetic drift associated with the founder principle. Mixed populations of ssp. intermedia originated from hybridization between ssp. maritima and ssp. elongata in their overlapping area (west part of the Baltic). Morphological differences between populations are not correlated with sterility barriers so that there is discordance between morphological units and biosystematical units. Taxonomic treatments of the group of metal‐tolerant populations is misleading.
PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: BRADBEER J. W. , IRELAND H. M. M. , SMITH J. W. , REST J. , EDGE H. J. W.
Published: May 2006

Summary

By the use of light and electron microscopy a quantitative investigation has been made of plastid membrane formation in the primary leaves of bean plants, during germination and growth in the dark. From 4 to 14 days of dark growth there was an eleven‐fold increase in cell number and a twenty‐six‐fold increase in plastid number per leaf. Formation of plastid envelope membrane between 6 and 14 days of dark growth amounted to 98 cm2 of membrane per leaf while the corresponding formation of internal plastid membrane was 272 cm2 per leaf. This internal plastid membrane appears to be formed, at least during the early stages of leaf growth, by the invagination of the inner envelope membrane. When a substantial amount of the thylakoid membrane has accumulated in the plastid a condensation process takes place to give the pro‐lamellar body, which is a structure composed of branching membrane tubules. Calculations based on the dimensions of these tubules have established that 1 μ3 of prolamellar body contains about 44 μ2 of membrane.

Dark‐grown leaves have been found to contain all of the enzymes of the photosynthetic carbon cycle. The course of development, during dark growth, has been determined for the activities of eight enzymes of the photosynthetic carbon cycle and for two enzymes of the cytoplasm.
PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: BRADBEER J. W. , GYLDENHOLM A. O. , SMITH J. W. , REST J. , EDGE H. J. W.
Published: May 2006

Summary

The effects of short exposures to low intensities of red, far‐red, blue and white light, applied separately and in certain combinations, have been studied with respect to plastid development in dark‐grown beans. ‘Rapid’ effects, occurring within a few hours of illumination, were the transformation and loss of the prolamellar bodies together with changes of the thylakoid area per plastid. All light treatments except blue, effectively transformed the prolamellar body and all the light treatments induced falls in prolamellar body volume. Red light, or illumination treatments containing red light, gave a ‘rapid’ stimulation to thylakoid development while blue and far‐red given alone were inhibitory.

‘Slow’ effects on plastid development appeared to be primarily controlled by phytochrome, in addition to which there was some indication that low intensity treatments with blue light partially reversed the phytochrome effects. These ‘slow’ effects were on plastid expansion, plastid division and the formation of the internal membranes of the plastids.
NUMERICAL ZONATIONS OF FLANDRIAN POLLEN DATA
Authors: BIRKS H. J. B.
Published: May 2006

Summary

Five numerical zonation methods have been applied to two sets of pollen data from deposits of Flandrian age at Scaleby Moss, Cumberland and Red Moss, Lancashire. The zonations suggested by these methods generally correspond to the conventional Flandrian pollen zones with the exception that the ‘elm‐decline’ is not consistently distinguished as a zone boundary. Reasons for this omission are discussed in terms of the weightings implicit in the various numerical methods.
EFFECTS OF VITAMINS AND NITROGEN SOURCES ON ASYMBIOTIC GERMINATION AND DEVELOPMENT OF ORCHIS LAXIFLORA AND OPHRYS SPHEGODES
Authors: MEAD J. W. , BULARD C.
Published: May 2006

In order to assess the role of endophytic fungi in the germination and growth of wild European orchids, Orchis laxiflora Lamk. and Ophrys sphegodes Mill, were tested on asymbiotic strictly defined media. In spite of minor differences between the two species, a good development was obtained with both, if sucrose, organic nitrogen and vitamins were added to a basic mineral medium containing ammonium nitrate. Casein hydrolysate as an organic nitrogen source could be replaced successfully by a reconstitution of its amino acids or by glutamine. Among the vitamins tested thiamine proved to be necessary to Orchis laxiflora.
REGENERATES FROM EXCISED PSEUDOLATERAL BRANCHES OF HETEROSIPHONIA PLUMOSA (ELLIS) BATT.
Authors: BONEY A. D.
Published: May 2006

Excised pseudolaterals of Heterosiphonia plumosa showed rhizoid formation from surviving basal cells and regenerate formation either from the region of the rhizoid in close proximity to a basal cell, or directly from the basal cell. Survival of pseudolaterals and regenerate formation was obtained with fluorescent illuminations of 205 and 270 lux, but the majority of detached filaments failed to survive in illuminations of 320 lux and above, and at 105 lux and in the dark.
THE EFFECTS OF SPORE AGE ON GERMINATION AND GAMETOPHYTE DEVELOPMENT IN POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M.
Published: May 2006

In the fern Polypodium vulgare L. increasing spore age leads to a decline in spore viability. It is suggested that the sigmoidal form of the survival curve is related to the fact that the spores of the cytotype used in the investigation are probably triploid. The other effects of increasing age include an increasing delay in germination, a decrease in the rate of germination, and an increase in the proportion of abnormal gametophytes. To some extent these effects are alleviated by high population density and low light intensity. Evidence is presented that the effects of age may be partly attributable to the declining ability of the spores to synthesize metabolites essential for germination and gametophyte development.
BREEDING SYSTEMS IN COTULA III. DIOECIOUS POPULATIONS
Authors: LLOYD DAVID G.
Published: May 2006

Some male and female plants of dioecious populations of seven Cotula species are strictly unisexual, or constant; other plants of the same populations are inconstant, with a low proportion of florets of the opposite sex (minority‐sex florets) which function normally. The distribution of minority‐sex florets among heads of male and female plants is shown by rank‐frequency curves. The average inconstancies of males and females are quantified as the proportions of genes transmitted via gametes of the minority‐sex florets, estimated by the proportions of minority‐sex florets. The average inconstancy of males is 9.9 × 10−4; that of females is 4.3 × 10−4. The Primary Sex Index, 0.9993, is the average constancy (1—inconstancy) of all individuals. This provides a measure of the degree of separation of male and female gamete functions in the two sexes, on a scale from 0.5 (sexual monomorphism) to 1.0 (complete separation of the sexes).

The sex Asymmetry Index, male inconstancy–female inconstancy/male inconstancy + female inconstancy, + 0.39, measures the relative magnitude of inconstancies of the two sexes on a scale from –1.0 (androdioecy) to + 1.0 (gynodioecy). Male and female heads differ in several secondary characters. The progeny of experimental crosses show that females are heterogametic and males are homogametic for sex‐determining chromosomes. Males and females occur in equal numbers in the progeny of male × female crosses and in natural populations.

The distribution and experimental manipulation of sex inconstancies provide considerable information on the origin and genetic maintenance of dioecy. The evolution of dioecy in Cotula has been accomplished by divergence in the sexes of the timing of the switch from male floret to female floret formation during head development, rather than by the introduction of male‐ and female‐sterility genes. No genes essential for female reproduction are restricted to the Y chromosome. A polyploid series in the dioecious populations (2n= 52 to 2n=c.312) indicates an ‘active Y’ mechanism, and may have been facilitated by the regeneration of sexual dimorphism from inconstant females with new chromosome numbers.
BREEDING SYSTEMS IN COTULA IV. REVERSION FROM DIOECY TO MONOECY
Authors: LLOYD DAVID G.
Published: May 2006

In both Cotula dioica and C. dispersa there are dioecious populations and simple‐monoecious populations (in which all heads of all plants are bisexual, with numerous male and female florets.) In addition, in C. dioica and also in C. rotundata, there are complex‐monoecious populations in which all plants have both male heads and bisexual heads with one or a few female florets and many male florets; the plants resemble inconstant males of dioecious populations in their sex expression, secondary sex characters and genetical behaviour, but they are not associated with females and are therefore equisexual (contribute equally via male and female gametes during sexual reproduction). In C. dispersa, there are also ‘unisexual male’ and ‘unisexual female’ populations resembling one or other sex of dioecious populations. ‘Unisexual’ populations sometimes have a small proportion of florets of the opposite sex and hence may produce a few seeds; when they reproduce sexually, the plants are functionally equisexual. One population of C. dispersa has a single patch of males in a large area of females.

It is postulated that ‘unisexual female’ populations arise by the loss of males from a dioecious population. Rare seeds produced on these females (the heterogametic sex in dioecious populations) may lead to the reappearance of males, producing a dimorphic population. Further male × female crosses regenerate normal dioecy by equalizing the numbers of males and females. Following the loss of females from a dioecious population, ‘unisexual male’ populations may restore seed production by selection for increased proportions of female florets. In this way, dioecy reverts to simple‐monoecy via ‘unisexual male’ populations and complex‐monoecy. Reversion to monoecy has probably occurred independently in the three species.
NITROGEN FIXATION IN THE ROOT NODULES OF VICIA FABA L. IN RELATION TO THE ASSIMILATION OF CARBON
Authors: LAWRIE ANN C. , WHEELER C. T.
Published: May 2006

Nitrogenase activity of the root nodules of field‐grown Vicia faba increased during plant growth until 3–4 weeks after the onset of flowering. The subsequent decline in activity was never greater than to 20% of the maximum, until finally plants were killed by frost. Nodules of medium size (100–200 mg fresh weight) showed greatest nitrogenase activity.

After photosynthesis in 14CO2 for 30 min, maximum accumulation of 14C‐assimilates in the nodules occurred within 90 min of synthesis. The relatively low levels of radioactivity associated with the organic acid fraction of the nodules, the absence of sucrose which is present in large quantities in the roots and the appearance of radioactivity in the nodule amino acids within 30 min of feeding the shoot 14CO2 show that photosynthates are rapidly metabolized on arrival in the nodules. The distribution of radioactivity among the constituents of the basic fraction confirms the importance of glutamate, glutamine and aspartate as early products of the metabolism of the fixed nitrogen in broad bean nodules receiving ample supplies of new photosynthates.
DEVELOPMENTAL STAGES IN A NONHETEROCYSTOUS FILAMENTOUS CYANOPHYTE
Authors: LADHA JAGDISH K. , KUMAR H. D.
Published: May 2006

Developmental stages broadly similar to those previously reported in Nostoc have been seen in an Oscillatoria‐like cyanophyte isolated from nature and grown in unialgal cultures. Apparent cell fusions and anastomoses occurred in cultures raised from single filaments.
SOME OBSERVATIONS ON F2 AND BACKCROSS PLANTS DERIVED FROM HYBRIDS BETWEEN PAPAVER DUBIUM L. AND P. LECOQII LAM.
Authors: HUMPHREYS M. O.
Published: May 2006

Plants of the F2 and backcross generations derived from F1 hybrids between Papaver dubium L. (2n= 42) and P. lecoqii Lam. (2n= 28) were studied. It was deduced from the chromosome numbers of the F2 and backcross plants that the successful F1 gametes possess high chromosome numbers. This phenomenon is explained in terms of‘genomic buffering’, i.e. F1, gametes with large numbers of chromosomes are better buffered than those with small numbers of chromosomes to withstand the effects of a mixture of alien chromosome material resulting from meiosis in F1 hybrids between polyploids. The importance of this phenomenon is discussed in relation to the evolution of polyploid species of Papaver in Section Orthorhoeades.
CRITERIA OF INTACTNESS AND THE PHOTOSYNTHETIC ACTIVITY OF SPINACH CHLOROPLAST PREPARATIONS
Authors: LILLEY R. McC. , FITZGERALD M. P. , RIENITS K. G. , WALKER D. A.
Published: May 2006

Chloroplast preparations capable of rapid rates of photosynthesis contain large numbers of intact (Class A) chloroplasts and smaller numbers of ruptured (Class C) chloroplasts. It is suggested that there is also a third or intermediate class in which the envelope has re‐sealed following rupture and release of stromal protein. The number of re‐sealed chloroplasts seems to be lowest in preparations containing the largest proportion of Class A chloroplasts. Assays for intactness based on the ability of Class C chloroplasts to utilize ferricyanide as a Hill oxidant are quick and convenient but do not distinguish between Class A and re‐sealed chloroplasts. If it is assumed that there is an inverse linear relationship between percentage intactness and ability to react with ferricyanide, such assays over‐estimate the proportion of intact chloroplasts and, therefore, underestimate their photosynthetic activity and protein content when these are expressed on a chlorophyll basis.
SOURCES OF ATP FOR ACTIVE PHOSPHATE TRANSPORT IN HYDRODICTYON AFRICANUM: EVIDENCE FOR PSEUDOCYCLIC PHOTOPHOSPHORYLATION IN VIVO
Authors: RAVEN J. A. , GLIDEWELL S. M.
Published: May 2006

Active, ATP‐dependent phosphate influx in Hydrodictyon africanum can occur when pseudo‐cyclic photophosphorylation is the only plausible source of ATP. The conditions used for the elimination of other ATP sources involve illumination in air in the presence of cyanide and antimycin; the inhibitors prevent oxidative photophorylation, cyclic phosphosphorylation and non‐cyclic photophosphorylation with carbon dioxide or nitrate as electron acceptor. The relationship between phosphate influx and oxygen concentration under these conditions indicates a lower affinity for oxygen in pseudocyclic electron flow than that found for electron flow via cytochrome oxidase. Experiments with salicylhydroxamic acid, an inhibitor of the ‘alternate oxidase’ pathway of plant mitochondria which also has a low oxygen affinity and is cyanide‐insensitive, suggest that this oxidase is not involved in pseudocyclic photophosphorylation. This evidence for pseudocyclic photophosphorylation in vivo is consistent with measurements reported elsewhere on tracer oxygen uptake in. H africanum.
THE INFLUENCE OF ASPECT ON THE PATTERN OF SEASONAL GROWTH IN THE LICHEN PARMELIA GLABRATULA SSP. FULIGINOSA (FR. EX DUBY) LAUND
Authors: ARMSTRONG R. A.
Published: May 2006

The radial growth of samples of thalli of Parmelia glabratula ssp. fuliginosa were measured in situ on a south‐facing and a northwest‐facing rock surface each month from August 1973 to July 1974. In the periods August to October 1973 and March to July 1974 the radial growth of thalli in the northwest population was greater than in the south population. In the period November 1973 to February 1974 the radial growth of thalli in the south population was greater than in the northwest population. A physiological basis for the differences in seasonal growth in the two populations was suggested. The mean annual radial growth rate (in units of mm/year) was not significantly different in the two populations. However, the variability in radial growth rate between thalli was significantly larger in the northwest than in the south population. These results may be explained by genetic differences between the populations and environmental differences between the rock surfaces.
ENDOPOLYPLOIDY IN MAIZE SMUT NEOPLASMS INDUCED BY THE MAIZE SMUT Fungus, USTILAGO MAYDIS
Authors: CALLOW J. A.
Published: May 2006

Infection of maize seedlings by Ustilago maydis results in neoplasia. The response of host nuclei and nucleoli to infection in these neoplasms has been examined in detail by Feulgen microspectrophotometry and quantitative interferometry. Seven days after infection, two distinct tissue zones could be recognized within the neoplastic leaf sheaths. Small cells around the vascular stele contained nuclei of 2C and 4C DNA content suggesting a meristematic function. Larger, vacuolate cells that form the bulk of the tissue contained nuclei of 16C, 32C, and 64C DNA levels, indicating substantial endopolyploidy. Nucleolar dry mass was substantially increased in infected cells (up to ten‐fold compared with controls), indicating enhanced ribosome synthesis. These results are discussed in relation to the hormonal control of DNA synthesis and mitosis.
THE GIANT LOBELIAS: TOXICITY, INFLORESCENCE AND TREE–BUILDING IN THE CAMPANULACEAE
Authors: MABBERLEY D. J.
Published: May 2006

An hypothesis on the origin of (i) the distribution of alkaloids and thorns, (ii) the position of the inflorescence, and (iii) arborescent forms in the Campanulaceae, considered in the light of recent studies onLobeliasect.Rhynchopetalum(Fres.) Benth. & Hook, f., is proposed. It is suggested that the primitive Campanulaceae were pachycaul forest plants and that it is possible to argue that on the continents those with alkaloids (Lobelioideae) were tolerant of browsing herbivores until the rise of alkaloid tolerance in herbaceous mammals when only armed forms could survive in lowland rainforest. In theLobelioideae., the terminal inflorescence is considered more primitive than the lateral which can be derived from the lowermost branches of the terminal with the onset of periodic inception of fertile primordia. In this way, non‐hapaxanthic shoots and the capacity for ‘tree‐building’ arise.
CALCULATION OF THE PRIMARY TRAJECTORIES OF DUST SEEDS, SPORES AND POLLEN IN UNSTEADY WINDS
Authors: BURROWS F. M.
Published: May 2006

The movement of dust seeds, spores and pollen released into winds which fluctuate in both speed and direction is considered in terms of the aerial mechanics of a small spherical particle moving under the Stokes' law of resistance and in a gravitational field. Equations of motion are established from which the aerial paths followed may be determined whenever it is possible to specify the movement of the environment accurately and in sufficiently fine detail. Example calculations show how deposition may arise on account of wind fluctuations, in addition to the normal process of gravitational sedimentation, and how very complicated trajectory geometry can result in quite simple flows which vary in both time and in space and time. It is also shown that very different positions of ultimate migration may be occupied at a particular time by particles released from positions quite close to one another in space and into unsteady winds.
COMPARISON OF THE EFFECTS OF A LOCALISED SUPPLY OF PHOSPHATE, NITRATE, AMMONIUM AND POTASSIUM ON THE GROWTH OF THE SEMINAL ROOT SYSTEM, AND THE SHOOT, IN BARLEY
Authors: DREW M. C.
Published: May 2006

Barley plants were grown for 21 days in sand culture, continuously irrigated with nutrient solution. The rooting depth was divided into three compartments, one above another, such that different zones of the root system could be supplied with very low or high concentrations of a single inorganic nutrient, all other nutrients being maintained at a high concentration.

Exposure of parts of the main seminal roots (axes) to high concentrations of phosphate caused a localized promotion of the initiation and subsequent extension of both first and second order laterals, compared with zones receiving very low concentrations of phosphate. This resulted in considerable modification to root form, but with only a small depression in shoot growth, compared with control plants receiving an ample supply to all parts of the root system. The extension of seminal axes was little affected by the concentration of phosphate to which they were exposed.

Similar responses to those described for phosphate occurred with variation in concentration of nitrate or ammonium, but with potassium a localized supply promoted the growth of laterals to approximately the same extent as controls throughout the entire root system.

The experiments show that adequate external concentrations of nitrogen and phosphorus are required by any part of the root system for optimal growth of laterals, but not axes. Possible mechanisms which compensate shoot growth when nutrients are supplied to only part of the root system, and agronomic implications, are discussed.
THE ROLE OF SEED PARTS IN THE INDUCTION OF DORMANCY OF HAZEL (CORYLUS AVELLANA L.)
Authors: JARVIS B. C.
Published: May 2006

Embryo dormancy is induced during the dry storage of hazel seed. During this inductive dry storage, it appears that inhibitors of germination move from the testa and pericarp through the cotyledons and into the embryonic axis. Microdrop applications of GA3 and ABA suggest that both have early affects on stimulation and inhibition of axis growth respectively. However, since both are transported in the seed affects on the cotyledons cannot be discounted.
TEMPERATURE AND THE GROWTH OF IMPATIENS PARVIFLORA DC.
Authors: ELIAS C. O. , CAUSTON D. R.
Published: May 2006

The growth of Impatiens parviflora DC. under four temperature regimes (13°C, 16°C, 20°C and 23°C) and a constant 18 h photoperiod was analysed using the traditional methods of growth analysis. Temperature had a very marked effect upon the growth rate, but the net assimilation rate was not markedly temperature‐dependent. The results are discussed in the context of previous work on I. parviflora, notably that by Evans and Hughes in respect of light intensity and also in the light of a simple model presented by Warren Wilson (1972), in which the main growth analysis parameters were related to source and sink activities in the plant.
BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)
Authors: BAKER N. R. , HARDWICK K.
Published: May 2006

A quantitative study is made of the changes in the soluble sugar content of developing cocoa leaves. Fructose, glucose, inositol and sucrose were the major sugars present. The possibility that endogenous sucrose concentration can affect chloroplast development is considered.

Estimates of the net daily sucrose synthesis in a developing cocoa leaf are made from photo‐synthetic and respiration rate measurements, and it is shown that the leaf does not become self‐dependent for respiratory substrate until after the termination of leaf expansion.
ULTRASTRUCTURE AND RECRYSTALLIZATION OF PLANT EPICUTICULAR WAXES
Authors: JEFFREE C. E. , BAKER E. A. , HOLLOWAY P. J.
Published: May 2006

A wick feed method was used to recrystallize a range of different plant epicuticular waxes from solutions in organic solvents. Using the scanning electron microscope the ultrastructure of the recrystallized wax from each species was compared with that of the wax on the corresponding intact plant surface and in many cases was found to be similar. It is concluded that the crystal structure of epicuticular waxes is greatly influenced by their inherent chemical and physical properties rather than by properties of the underlying cuticular membrane or by any mechanism of extrusion or transport of the wax to the plant surface.
CORRELATION BETWEEN THE BREEDING SYSTEM AND RECOMBINATION INDEX IN FIVE SPECIES OF SENECIO
Authors: GIBBS P. E. , MILNE C. , CARRILLO M. VARGAS
Published: May 2006

The species Senecio aetnensis Jan., S. joppensis Dinsm., S. squalidus L., S. viscosus L. and S. vulgaris L. have been compared for automatic selfing ability, capitulum conspicuousness, pollen yield, chromosome number and chiasma frequency. It has been established that the species S. aetnensis, S. joppensis and S. squalidus which have low automatic selfing ability have large, showy capitula, high pollen output and low recombination indices. The species S. viscosus and S. vulgaris which have a high selfing ability have relatively inconspicuous capitula, low pollen yields and a high recombination index. The differences in recombination index values are mainly due to the fact that the selfing species are polyploids but it may be significant that the highest average chiasma frequencies per bivalent were found in some S. vulgaris plants. The adaptive significance of a high recombination index in inbreeding taxa is discussed and it is suggested that a high chiasma frequency and/or polyploidy may have a preadaptive value in facilitating the change from outbreeding to inbreeding in some species.
PLANT REMAINS FROM THE GRAVENEY BOAT AND THE EARLY HISTORY OFHUMULUS LUPULUSL. IN W. EUROPE
Authors: WILSON D. GAY
Published: May 2006

Over sixty plant taxa are listed from four samples associated with a boat abandoned at Graveney, Kent, in the tenth century A.D. All samples contained the remains of plants which grow on mudflats and salt marshes, indicating the vegetation immediately around the site. A sample from a brushwood platform beside the boat yielded in addition macro‐fossils of plants that grow beyond the reach of salt water, including shrubs and a number of species that grow in waste places or as weeds of cultivation. Pollen from this sample shows the presence of mixed oak forest somewhere in the region. Parts of the female inflorescence ofHumulus lupulusL. (hop) were also found. They occurred abundantly in the brushwood sample and in one from within the boat, and were also present (though sparsely) in one from just above the floor of the boat. None occurred in the sample from beneath the boat, and no pollen of hop was found in the brushwood sample. It is argued that the boat was carrying a cargo of hops, and the possible implications of this theory are discussed, with reference to the early history of hops and brewing.
ROOT GROWTH AND THE ONSET OF MITOSIS IN GERMINATING VICIA FABA
Authors: ROGAN P. G. , SIMON E. W.
Published: May 2006

The length and fresh weight of the root of germinating Vicia seeds increase slowly until 46 h from the start of imbibition and then more rapidly. The dry weight of the root only begins to increase at about 55 h; mitosis starts at the same time.
THE CLIMATIC CONTROL OF THE ALTITUDINAL DISTRIBUTION OF SEDUM ROSE A (L.) SCOP. AND S. TELEPHIUM L.
Authors: WOODWARD F. I. , PIGOTT C. D.
Published: May 2006

When plants of Sedum rosea (L.) Scop, and

S. telephium L. ssp. fabaria Syme are grown in competition at different altitudes it is found that the growth of the species is affected differentially. This effect is such that at low altitudes S. telephium is a larger plant than S. rosea, while the reverse is the case at high altitudes. The observed differences are caused by a marked sensitivity of the growth of S. telephium to differences in altitude, while S. rosea is very insensitive.

The most probable cause of these responses would appear to be differences of climate. The influence of altitude in northern England on air temperature, saturation deficit and irradiance has been investigated in order to establish the magnitude of the differences which may cause these responses.
LONGITUDINAL AND LATERAL TRANSPORT OF [3, 4‐3H‐] GIBBERELLING A1 AND 3‐INDOLYL (ACETIC ACID‐2‐14C) IN UPRIGHT AND GEO‐TROPICALLY RESPONDING GREEN INTERNODE SEGMENTS FROM HELANTHUS ANNUUS
Authors: PHILLIPS I. D. J. , HARTUNG W.
Published: May 2006

Distribution of radioactivity from [3H] GA1 and [14C] IAA within the tissues of isolated 2.5 or 3 cm long segments cut from the first internodes of sunflower seedlings was unaffected by displacement from a vertical to horizontal position. This was true whether the agar donor blocks were applied uniformly across the apical cut end of the segments, or where asymmetric donors were used. Neither downward nor upward lateral transport of gibberellin or auxin was influenced. Similarly, use of a lateral donor technique failed to reveal any effect of gravity upon transport across the stem segment to a lateral agar receiver block on the opposite flank. Experiments on etiolated Zea mays coleoptile segments confirmed the existence in this organ of gravity‐induced lateral transport of [14C] IAA.

No growth curvatures occurred in upright sunflower stem segments incubated with GA1 or GA3 apical donor blocks applied uniformly or asymmetrically, although elongation growth was enhanced. Horizontally positioned segments exhibited only very weak negative geotropic curvatures when in contact with plain agar blocks, but [3H] GA1 (2 × 10‐6M) donors induced marked curvatures when applied either uniformly or asymmetrically to the apical ends. Asymmetric donor blocks containing IAA induced growth curvatures in both upright and horizontal stem segments.

It is concluded that the mechanism of geotropic response in sunflower stems is likely to involve the participation of both auxin and gibberellin, but that these experiments do not suggest that lateral displacement of these hormones is part of such a mechanism. Differences in levels of endogenous gibberellins that are correlated with direction of geotropic curvature may be a consequence of preferential hormone synthesis or transport in the lower or upper sides of horizontally positioned orthogeotropic organs.