bluuebunny/crossref_metadata_2025 huggingface dataset:
ULTRASTRUCTURAL ASPECTS OF THE DEVELOPMENT OF FIBRES FROM THE FLOWERING STEM OF LOLIUM TEMULENTUM L.
Authors: LAWTON J. R. , HARRIS P. J. , JUNIPER B. E.
Published: May 2006

Summary

Fibres develop from initially elongated cells with a large proportion of cytoplasm containing many ribosomes, relatively few, but large, mitochondria, proplastids, Golgi bodies and either several small vacuoles or one central vacuole. During cell elongation the central vacuole enlarges and the cytoplasm forms only a thin lining except at the fibre tips. At this stage the ribosomes are present as polysomes and associated with the endoplasmic reticulum as rough ER(RER). The number of Golgi bodies apparently increases and there are both electron transparent vesicles of various sizes and small vesicles with an electron dense core. Lomasomes and inclusions between the wall and the plasmalemma are seen at this stage. Increase in cell wall thickness is associated with an increase in the number of Golgi bodies with large vesicles and also those vesicles with an electron dense core. Wall thickening is also accompanied by the appearance of many microtubules parallel to the long axis of the cell adjacent to the plasmalemma. Even in a well developed inflorescence axis bearing ripening grains there is still visible cytoplasm in the majority of the fibre cells.
CLONAL VARIATION IN POPULATIONS OF RANUNCULUS REPENS
Authors: SOANE I. D. , WATKINSON A. R.
Published: May 2006

Summary

A computer simulation model is developed to examine the relationship between the population flux of ramets, the recruitment of seedlings and genet diversity in populations of Ranunculus repens in a North Wales pasture. The study is based on a continuous monitoring of the flux of ramets and recruitment of seedlings in eight populations over a period of 4 years. A simple flow diagram, which describes the life‐cycle of R. repens and which incorporates the field census data, is used as the basis for a series of computer simulations. The computer model simulates the actual flux of ramets in each of the eight populations and, assuming no selection between families, is used to follow the fates of ramets and families of ramets. Comparisons between the numbers of families of ramets in the real and simulated populations provide little evidence for selection between families of ramets or against new seedling recruits. With no selection the number of original families present within a population declines at an approximately exponential rate and the contribution made by these families to the total genet diversity of the population rapidly becomes subordinate to the role of new seedling inputs. It is suggested that although the contribution of seedlings to maintaining the total number of individuals, Nη, in populations of plants which spread clonally may be very small, the occasional establishment of seedlings may nevertheless play a significant role in determining the number of clones or genets, N.
PROTEIN BODY MEMBRANES OF PHASEOLUS VULGARIS L. COTYLEDONS: ISOLATION AND PRELIMINARY CHARACTERIZATION OF CONSTITUENT PROTEINS
Authors: PUSZTAI A. , CROY R. R. D. , STEWART J. S. , WATT W. B.
Published: May 2006

Summary

Membrane preparations (1·16 g ml−1 average density) produced by osmotic shock from cotyledonary protein bodies of Phaseolus vulgaris were isolated and purified by sucrose density centrifugation. The constituent polypeptides of these membranes were characteristic and different from those of storage proteins and were shown by SDS gel electrophoresis to consist of, in addition to low mol. wt glycolipid‐type material, polypeptides of 16000, 20000, 25000, 30000 and 78000. Of these, the 25000 and the 78000 components appeared to be more tightly associated with the membrane structure than other polypeptides. The 20000, 25000 and 30000 polypeptidea were separated by preparative SDS gel electrophoresis, freed from SDS and extraneous carbohydrates by phenol‐borate (pH 8) partitioning and further purified by chromatography on Bio Gel A 5 m in 5 M guanidine HC1. The 30000 polypeptide was identified by chemical, physical and immunochemical methods as a haemagglutinating globulin lectin. The 25000 polypeptide component bore a superficial resemblance to the so‐called structural protein generally distributed in a great variety of plants and animal membranes. The 20000 polypeptide has not yet been identified with any known Phaseolus vulgaris protein.
STORAGE OF DETACHED LEAVES AND TWIGS WITHOUT CHANGES IN WATER POTENTIAL
Authors: KARLIC HEIDRUN , RICHTER HANNO
Published: May 2006

Summary

Several different methods were investigated for storing conifer twigs and tree leaves for prolonged periods without changing their water status, as assessed by the pressure chamber. Whereas simple procedures (keeping between wet foam‐rubber mats or even immersion in water) were sufficient for gymnosperms, the leaves of angiosperma had to be protected more carefully. With deciduous leaves the best method was to store them in completely airtight bags made from aluminium foil; sclerophyllous evergreen leaves may alternatively be covered with a layer of Vaseline and stored in polythene bags between wet foam‐rubber sheets. It proved possible to keep leaves for periods of up to several days without significant changes in either their total water potential or their osmotic relations as determined by the pressure‐volume technique.
LIGHT AS A FACTOR OF GROWTH AND MORPHOGENESIS II. EFFECT OF VARYING PHOTOPERIODS ON CROTALARIA JUNCEA L. AND C. SERICEA RETZ
Authors: PANDEY B. N. , SINHA R. P.
Published: May 2006

Summary

The growth of Crotalaria juncea L. and C. sericea Retz. under 8, 10, 12, 14 and 16 h daylengths was studied with respect to dry wt accumulation, leaf area increase, RGR, LAR, SLA, LWR, NAR, the value of a (ratio of mean relative growth rate to mean relative rate of leaf area increase) and S/R ratio. In both species, dry wt and leaf area increased up to 14 h daylength above which these features of C. juncea declined. The higher trend maintained in C. sericea suggests this is of selective value to a ruderal. C. sericea is characterized by a narrower range of values under the varying photoperiods. Strict comparison in terms of LAR is not possible owing to ontogenetic drift. In terms of RGR and NAR, C. sericea shows greater uniformity in all photoperiodic regimes. Values of a for this species also show a narrower range. All these are suggestive of its greater capacity than C. juncea to survive ecological vicissitudes in natural habitats.
THE DEVELOPMENT OF ENDOMYCORRHIZAL ROOT SYSTEMS II. EFFECT OF AGRONOMIC FACTORS AND SOIL CONDITIONS ON THE DEVELOPMENT OF VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION IN BARLEY AND ON THE ENDOPHYTE SPORE DENSITY
Authors: Black R. , Tinker P. B.
Published: May 2006

Summary

The percentage of roots with vesicular‐arbuscular mycorrhizal fungi and numbers of spores were measured over 2 years in a field experiment with different crop rotations of barley, kale and fallow. Spore numbers, and subsequent infections of barley crops, were largest following barley; both kale and fallow breaks reduced spore population and infection similarly. With all crop rotations there was a long delay before appreciable percentage infection of roots developed, followed by a rapid increase, and then a constant value. Such late infections appear unlikely to improve crop nutrition, and final yield was negatively related to per cent infection.

A survey of barley crops in 2 years on commercial fields following at least 3 years barley showed that infection was rather similar in most fields. There was a very slight correlation between infection percentage, clay content and pH, but no other soil factor had any influence. Early‐sown crops tended to have low infection.
MYCORRHIZAL STATUS OF ERICACEOUS PLANTS IN ALPINE AND SUBALPINE AREAS
Authors: Haselwandter K.
Published: May 2006

Summary

Mycorrhizal infection of Ericaceae is of considerable ecological significance in heathlands and may be of particular importance in alpine regions which experience short growing seasons and slow rates of mineralization of major nutrients. The extent of mycorrhizal infection has been determined by a chemical method based upon quantitative determination of fungal chitin. In five species of ericaceous plants selected from sites of different elevations in the alpine and subalpine zone, there is a relationship between extent of mycorrhizal infection and host vigour. Infection levels increase with decrease in altitude of sampling sites.
NUTRITIONAL STUDIES ON THE PARASITIC RED ALGA CHOREOCOLAX POLYSIPHONIAE
Authors: Callow J. A. , Callow M. E. , Evans L. V.
Published: May 2006

Summary

Choreocolax polysiphoniae Reinsch is a minute, cushion‐shaped, variably‐pigmented red alga forming a‘parasitic’association with Polysiphoma lanosa. Cortical cells of Choreocolax contain starch grains and small, poorly‐differentiated plastids. Through 14C labelling experiments it has been shown that 14C fixed by Polysiphonia as sodium mannoglycerate may be transferred to Choreocolax, although clear differentiation between host and parasite tissues is difficult due to displacement of some host cells within the thallus of the parasite. However, Choreocolax can also fix CO2 photosynthetically, an ability which appears to be partially repressed in the attached state since CO2 fixation progressively increases with time if Choreocolax plants are detached from the host. The products of Choreocolax photosynthesis may include mannitol and an unidentified complex carbohydrate.
HAUSTORIAL FREQUENCY OF SOME ROOT PARASITES IN CULTURE
Authors: MUSSELMAN L. J. , MANN W. F.
Published: May 2006

Summary

Seventeen root parasites representing nine genera in three families native to the southern United States were grown with 19 tree species to determine host preference and host susceptibility. Trees were grown in pots with a single parasite. After about 12 months the plants were removed and the number of haustoria noted. The number of haustoria or haustorial frequency were interpreted as a rough index of the suitability of that tree to serve as a host. All parasites showed a broad host range indicating little host specificity. In addition, none of the hosts were immune to parasitism. A few plants behaved as complete autotrophs, even though host roots were in physical contact with those of the parasite.
CARBOHYDRATE COMPOSITION AND INVERTASE ACTIVITY IN POPLAR LEAF TISSUES INFECTED BY MILLAMPSORA AECIDIOIDES (D.C.) SCHROETER
Authors: ROBERTS S. M. , MITCHELL D. T.
Published: May 2006

Summary

Qualitative analyses of ethanol‐soluble carbohydrates of rust‐infected poplar leaves were similar to those of other rust infections. Sucrose was the most abundant ethanol‐soluble carbohydrate in both healthy and infected leaf tissues. Mannitol, arabitol and trehalose were detected in low concentrations at the site of infection. Mannose formed a significant proportion of the insoluble carbohydrates in the pustule disc. Activities of both acid and alkaline invertase, assayed by two methods, were similar in both healthy and infected tissues. These results are discussed in relation to those of other biotrophic infections and it is suggested that the Populus canescens Aiton Sm./Melampsora aecidioides (D.C.) Schroeter relationship may be a benign one.
INTERGLACIAL POLLEN SPECTRA FROM SEL AYRE, SHETLAND
Authors: BIRKS H. J. B. , PEGLAR SYLVIA M.
Published: May 2006

Summary

The lithostratigraphy of a section exposed at Sel Ayre on the Walls Peninsula, Shetland Mainland is described. A peat bed 50 cm thick is overlain by 7·3 m of sands, gravels, and boulder clay. Pollen analyses of this peat bed and of peat laminae in the sands reveal three distinctive pollen assemblages. These assemblages are interpreted as reflecting a vegetational development from grass‐ and fern‐dominated communities an fertile brawn‐earths to dwarf‐shrub heaths dominated by ericaceous shrubs including Bruckenthatia spiculifolia. These heaths grew on acid humus‐rich podsols and were replaced by open, grass‐dominated communities. Numerical comparisons of the Sel Ayre pollen spectra with pollen data from other sites on Shetland using principal components analysis suggest that three interglacial stages are represented on Shetland Mainland –Fiandrian, Ipswichian and Hoxnian. On the basis of the composition of the presumed long‐distance tree‐pollen rain, the Sel Ayre sequence is correlated with the Ipswichian stage. A basic interglacial cycle is proposed for the Shetlands.
PINOCYTOSIS IN PLANTS
Authors: CRAM W. J.
Published: May 2006

Summary

The question considered is whether pinocytosis is the principal means of transporting major nutrients across the plasmalemma.

It is argued that ultrastructural evidence previously advanced in favour of pinocytosis in plant cells can be interpreted in other ways and does not uniquely support the hypothesis of pinocytosis. Physiological evidence ‐ particularly, selectivity in uptake, competition between substances, differential effects on influx of changes in internal states, and the associated electrical currents ‐ is incompatible with the characteristics of pinocytosis in animal cells. The suggestion that pinocytosis in plants involves selective binding prior to uptake cannot be accepted because the required density of binding sites is at least three orders of magnitude greater than is possible.

On theoretical grounds it is shown that the water flow that would be associated with pinocytosis would generate high values of turgor which are not observed and probably could not be sustained. Further, it is calculated that during pinocytosis the probable energy to overcome turgor would be needed at a rate greater than the cell could supply. Thus it appears not only that pinocytosis does not occur, but also that it could not occur in plant cells.
THE INFLUENCE OF TEMPERATURE ON THE ABSCISIC ACID STIMULATED WATER FLOW FROM EXCISED MAIZE ROOTS
Authors: COLLINS J. C. , MORGAN MAUREEN
Published: May 2006

Summary

The stimulatory effect of ABA on fluid exudation from excised maize roots has been confirmed. The maximum stimulation of water flow by ABA occurred at about 20 °C, and was enhanced by low concentration of the bathing medium. ABA increased the hydraulic conductivity of the root and the activation energy of water permeability was greater in the presence of ABA. It is believed that ABA acts directly at the membrane level, where it forms pores or channels in the membrane; these increase permeability to ions and water.
REPRODUCTIVE AND VEGETATIVE PERFORMANCE IN TWO WINTER ANNUAL GRASSES, CATAPODIUM RIGIDUM (L.) C.E. HUBBARD AND C. MARINUM(L.) C. E. HUBBARD
Authors: CLARK S. C.
Published: May 2006

Summary

Demographic analysis of the leaf population of three populations of Catapodium rigidum and one of C. marinum grown throughout their life‐cycles in a growth‐room showed that the factors affecting the age‐structure and life‐expectancies of the leaf‐populations were in the order, temperature and/or photoperiod > soil‐type > populations. Winter conditions produced an uneven‐aged, long‐lived leaf population, in which maximum leaf‐age was c. 150 d. Summer conditions produced even‐ aged, short‐lived populations in which maximum leaf‐ age was c. 60 d. Leaves which developed in winter conditions had shorter expectancies in summer conditions than those which developed during summer. There were some significant differences between soils for parts but not the whole of the life‐ cycle. The result of late sowing was to reduce the differences in age‐structure and expectancies between stage of the life‐cycle and to reduce maximum leaf‐age by c. 35%. Differences between the leaf‐populations of the early‐and late‐ sown plants were apparently due to external and not ontogenetic factors. The relationship between leaf life‐expectancy and leaf and tiller numbers on the one hand and numbers and weights of caryopses on the other was investigated using a step‐wise multiple regression technique. Leaf life expectancy, especially late in the life‐cycle, was significantly (negatively) associated with caryopsis weights but not with numbers and it accounted for c. 80% of the variation. Leaf numbers, especially late in the life‐cycle, were significantly positively associated with caryopsis‐numbers and accounted for 100% of the variation. Leaf‐numbers early in the life‐cycle were also associated (negatively) with caryopsis‐weights, when they accounted for c. 40% of the variation. Tiller‐numbers were not as closely associated with caryopsis production and accounted for < 40 % only of the variation. Possible effects on seed production of alterations in the demographic parameters of leaf‐populations are discussed.
THE INHIBITION OF GERMINATION OF BIDENS PILOSA SEEDS BY LEAF CANOPY SHADE IN SOME NATURAL VEGETATION TYPES
Authors: FENNER M.
Published: May 2006

Summary

The inhibition of germination by leaf canopies was investigated in Bidens pilosa, a widespread tropical colonizing weed species. Seeds of this species were sown in the shade of four natural vegetation types: early colonizing stage of an old field succession, a later stage of the same sere, short grass, and long grass. There were four control treatments: full sunlight on open soil, banana‐leaf shade, ‘neutral’ shade under white paper, and darkness. Since the temperature regimes under the canopies differed, the effect of temperature on the germination of the seeds was investigated. The results show that the leaf canopies of the vegetation types investigated are markedly effective in inhibiting germination of this species in the field. Inhibition by unfavourable temperatures could have been only a contributory factor. It is suggested that seed sensitivity to leaf canopy shade may be of importance in effecting changes in species composition in early successional stages, and in excluding open‐habitat species from closed vegetation generally.
THE BIOLOGY OF AMBROSIA TRIFIDA L. V.RESPONSE TO FERTILIZER, WITH GROWTH ANALYSIS AT THE ORGANISMAL AND SUB‐ORGANISMAL LEVELS
Authors: HUNT RODERICK , BAZZAZ F. A.
Published: May 2006

Summary

Giant ragweed, Ambrosia trifida L., was grown over a period of 36 days in a glasshouse at two levels of soil fertility. Growth was investigated both by the conventional (whole‐plant) techniques of growth analysis and by these same techniques applied to data obtained on the growth of roots, stems and each of the successive leaves.

Results showed that the superior performance of the fertilized plants was due to their higher leaf‐area ratio rather than to an enhanced unit leaf rate. Here, the rates of dry‐matter commitment to leaves at nodes 2, 3 and 4, expressed per unit of whole plant dry wt, were initially around 0‐04 g g−1 day−1 ‐about twice the values obtained for the same leaves in the unfertilized plants.

There was a heavy early commitment to root growth especially in the unfertilized plants. Stem production was moderately high throughout in both treatments. The large response to fertilizer application would be expected of the species since it colonizes arable land and flood‐plains both of which experience nutrient pulses. This behaviour, together with the flexibility of material allocation contribute to the high success of the species.

The study provided the opportunity to assess the techniques of growth analysis when applied at the sub‐organismal level. The value of this approach was discussed in relation to the parallel activity of leaf demography.
MORPHOLOGICAL VARIATION BETWEEN SOME ISOLATED POPULATIONS OF SILENE MARITIMA WITH. IN THE BRITISH ISLES WITH PARTICULAR REFERENCE TO INLAND POPULATIONS ON METALLIFEROUS SOILS
Authors: BAKER A.J. M. , DALBY D. H.
Published: May 2006

Summary

The present distribution of Silene maritima in the British Isles is discussed in relation to the phylogenetic history of the bladder campions and the status of the inland populations. An experimental study of morphological variation between geographically isolated populations of S. maritima is described. Large‐scale divergence in a number of quantitative and qualitative vegetative and floral characters was apparent. The populations studied included coastal, arctic‐alpine and inland, heavy‐metal mine types, together with one mine population of S. vulgaris. Populations from mine sites proved distinct from coastal and arctic‐alpine populations in their growth habit and leaf morphology. Similar, but smaller, differences in floral morphology were apparent. For every quantitative character scored, significant inter‐population variation was detected. The qualitative characters scored also showed great inter‐population differences. The possible evolutionary significance of morphological divergence between these S. maritima populations is discussed.
FACTORS CONTROLLING THE DISTRIBUTION OF TILIA CORDATA AT THE NORTHERN LIMITS OF ITS GEOGRAPHICAL RANGE
Authors: PIGOTT C. D. , HUNTLEY JACQUELINE P.
Published: May 2006

Summary

Pollen originating from small populations of Tilia cordata is largely deposited within a few hundred metres of the trees, so that their presence can only be detected by pollen analysis at sites within distances of this order. Pollen diagrams from such sites show a continuous curve for Tilia pollen extending to the present surface, although the values may be only about 1 % of arboreal pollen. Pollen analysis shows that T. cordata was present in the Lake District by about 5000 to 4800 B.C.; it then became plentiful in the southern valleys and extended to reach its present north‐western limit, or just beyond, by 3100 B.C., when migration ceased. While the tree was extending its range, it must have been able to produce frequent large crops of fertile seed but subsequently regeneration from seed ceased. After 3100 B.C. the proportion of its pollen initially may increase but then generally decreases. Although there are small recoveries at several horizons, these are not certain evidence of reproduction by seed. Failure to produce fertile seed renders the species particularly sensitive to woodland clearance and has resulted in a decrease in abundance within the Lake District and its virtual extinction in west Yorkshire and south Lancashire.
A CONTRIBUTION TO THE PHYTOGEOGRAPHY OF SHETLAND
Authors: HULME P. D. , DURNO S. E.
Published: May 2006

Summary

Peat and lacustrine deposits from a basin mire in Mainland Shetland have been analysed for plant macrofossils and a number of species of particular phytogeographical interest recorded. Results of macrofossil and pollen analyses indicate that deposition started during Late Devensian times.
THE TOLERANCE OF TREE ROOTS TO WATERLOGGING
Authors: PHILIPSON J. J. , COUTTS M. P.
Published: May 2006

Summary

Internal oxygen movement was demonstrated in woody roots of both Sitka spruce and Lodgepole pine by partially submerging detached roots in reduced indigo‐carmine solution and noting the appearance of the blue halo due to re‐oxidisation of the dye.

Transport in the Hood‐tolerant pine occurred in both wood and bark and was greater than that in spruce where it was confined to the bark.

The pathways of oxygen movement within the tissues are discussed and the results are considered in relation to the survival of tree roots when waterlogging of both primary and woody roots occurs.
NITROGEN FIXATION AND BIOMASS PRODUCTION IN CLONES OF ALNUS INCANA
Authors: HUSS‐DANELL KERSTIN
Published: May 2006

Summary

Nitrogen fixation, growth, biomass production and nitrogen content of seven clones from grey alder (Alnus incana (L.) Moench) were compared. Rooted green cuttings, inoculated with a root nodule suspension, were grown without combined nitrogen in a growth chamber for nine weeks. Nitrogenase activity (C2H2 reduction) was repeatedly measured in intact plants, and biomass and nitrogen content were measured at the end of the growth period.

There were considerable, often significant, differences between clones in most of the studied parameters. Within each clone a very close correlation between various parameters was found. It was suggested that the value of any one variable which was easy to measure, such as shoot length, may be used for the prediction of the response of other variables when clones are grown together under the same conditions.
ECTOMYCORRHIZAL ASSOCIATIONS OF AUSTRALIAN INDIGENOUS PLANTS
Authors: WARCUP J.H.
Published: May 2006

Summary

Besides species of Eucalyptus, Leptospermum, Casuarina and Pomaderris which are known to form ectomycorrhizas, many other Australian native plants may form ectomycorrhizal associations. The plants include many legumes, especially in the tribe Podalyrieae of the Fabaceae and Acacia in the Mimosaceae, all members of the Rhamnaceae examined, and species of such diverse genera as Opercuhria, Poranthera, Platysace, Goodenia and Stylidim. Many, perhaps most, of these ectomycorrhizal plants may also form endomycorrhizas of the VA type.

The ectomycorrhizal species range from large forest trees to small non‐woody herbs. The associations vary from well‐defined mycorrhizas of the beech type to looser ones of a continuous or partial sheath, with or without a Hartig net. In soil low in available phosphate both typical and looser ectomycorrhizal associations markedly increased plant growth compared with that of uninoculated plants.
ON THE PHYCOBIONTS OF THE CYCAD CORALLOID ROOTS
Authors: GRILLI CAIOLA MARIA
Published: May 2006

Summary

The structure, ultrastructure and the developmental cycle of the phycobionts living in the coralloid roots of various cycads growing in different Italian Botanical Gardens were studied. The phycobionts were examined in the various zones of the coralloids from the top towards the base. All the phycobionts observed have the characteristics typical of Nostoc. Eucaryotic algae, fungi or bacteria have never been observed. Nostoc present in the coralloid roots of various cycads differ from each other in the trichomes and the organization of vegetative cells and heterocysts. Three main types of phycobionts have been distinguished, each having preference for a group or species of cycad. In the coralloid roots the heterocystous phase prevails with vegetative cells and heterocysts. The latter differ from the heterocysts reported in other cyano‐bacteria. Their frequency increases towards the basal parts of the coralloid roots and concomitantly they undergo changes until they become empty and stiff. Heterocysts releasing gonidia or dividing were not observed. In the sporogenous phase akinetes were not found. In the oldest coralloid roots few vegetative cells and numerous heterocysts in various stages were found.
NH4+ ASSIMILATION AND NITROGENASE REGULATION IN THE LICHEN PELTIGERA APHTHOSA WILLD
Authors: RAI A. N. , ROWELL P. , STEWART W. D. P.
Published: May 2006

Summary

The lichen Peltigera aphthosa consists of a green alga Coccomyxa, a fungus, and a N2‐fixing Nostoc which is located in superficial packets (cephalodia). In symbiosis the Nostoc shows only low activities of glutamine synthetase, but the cephalodia show very high activities of glutamate dehydrogenase. Alanine dehydrogenase activity is rather similar in all components. The Nostoc liberates over 95% of the N2 which it fixes as NH4+, and fungal glutamate dehydrogenase in the cephalodia appears to be important in the assimilation of this NH4+. Exogenous NH4+ (5 mM) has no effect on acetylene reduction activity by excised cephalodia but completely inhibits acetylene reduction by cephalodia attached to lichen discs (of fungus +Coccomyxa) within 24 h. This inhibition can be overcome by inhibiting main thallus glutamine synthetase activity by adding the glutamate analogue, L‐methionine‐SR‐sulphoximine (MSX). On adding exogenous NH4+ to main thallus discs with cephalodia, giutamine accumulates in the cephalodia when main thallus glutamine synthetase is active but not when it is inactivated by MSX. Exogenous glutamine also specifically inhibits nitrogenase activity by the cephalodia although exogenous alanine and glutamate (all 5 mM) have no such effect. The data indicate that glutamine produced in the main thallus may be involved in the regulation of nitrogenase activity by the cephalodial Nostoc.
EFFECTS OF OXYGEN, TEMPERATURE AND OTHER FACTORS ON THE REDUCTION OF ACETYLENE BY ROOT NODULES FORMED BY RHIZOBIUM ON PARASPONIA ANDERSONII PLANCH
Authors: TRINICK M. J.
Published: May 2006

Summary

Test tube grown Parasponia plants formed nodules on the surface of the agar and reduced acetylene at a constant rate for a mimimun of 5.5 h at 25°C. Nitrogenase activity increased with pC2H2 to maximum activity at levels higher than 0.1 atm. No diurnal rhythm, attributable to the supply of photosynthate, was detected and decapitation of the plant had no effect on nitrogenase activity although nodule detachment lowered activity by 32 % with fürther diminution when nodules were sliced. Nitrogenase activity decreased from the tip to the base of the nodule. Soaking for 30 min did not affect activity. Repeated acetylene reduction assays made on plants adversely affected their activity. Maximum activity occurred at 25° to 35 °C. Below 20 °C nitrogenase activity ceased within minutes. Unlike that in legumes, acetylene reduction recovered slowly when plants were returned to favourable temperatures. Activity was lowered by 50% at 40 °C and to zero at 45 °C. The pO2 optimum for nitrogenase activity, in contrast to that in legume and many non‐legume nodules, was narrow and activity fell rapidly above and below 0.2 atm O2. Restoration of nitrogenase activity after inhibition by 0.4 and 0.9 atm pO2 was slow.
A BIOCHEMICAL AND ULTRASTRUCTURAL EVALUATION OF THE TAXONOMIC POSITION OF GLAUCOSPHAERA VACUOLATA KORSH.
Authors: McCRACKEN D. A. , NADAKAVUKAREN M. J. , CAIN J. R.
Published: May 2006

Summary

The ultrastructure and carbohydrate chemistry of Glaucosphaera vacuolata Korsh. were studied to clarify the uncertain taxonomic position of this alga. Serial thin sections reveal that the double membrane bounded photosynthetic apparatus of Glaucosphaera, described by previous investigators to consist of many chromatophores or cyanelles, is a single, highly lobed chloroplast without a pyrenoid. Thylakoids are single and bear phycobilisomes. The single nucleus is centrally located and surrounded by Golgi bodies. Starch granules are located outside the chloroplast and are not membrane bounded. Chemical analysis of the solubilized starch granules by butanol precipitation, iodine staining, and enzymatic digestion indicates the presence of both amylose and amylopectin. It is concluded that Glaucosphaera is a red alga and should be assigned to the order Porphyridiales.
FLORAL MORPHOLOGY AND REPRODUCTIVE BIOLOGY OF FOUR SPECIES OFCYANELLA(TECOPHILAEACEAE)
Authors: DULBERGER RIVKA , ORNDUFF ROBERT
Published: May 2006

Summary

In the South AfricanCyanella alba, C. lutea, C. hyacinthoidesandC. orchidiformisthe androe‐cium consists of an upper group of five or three stamens and one or three low stamens. Anthers of the upper and lower stamens differ in size and shape, and lower anthers produce much more pollen than upper ones. Pollen is released only when the poricidal anthers are forcibly beaten. The configuration of the androecium suggests that ‘feeding’ and ‘pollinating’ stamens are present; the manner of pollen discharge suggests vibratile pollination by heavy‐bodied bees. According to the direction in which the style is deflected,C. albaandC. luteahave right‐handed and left‐handed flowers. In these two species, the lower stamen is deflected in a direction opposite to that of the style. Artificial pollinations were carried out with plants sampled from various field populations of the four species. The seed set data obtained indicate the presence of physiological self‐incompatibility. No significant differences have been found in fertility of pollen from lower and upper anthers. InC. albaandC. lutea, the floral dimorphism together with a low number of flowers open at any time may be effective in promoting outbreeding. The ratio of pollen grains per flower to the number of seeds produced is much smaller inC. albaandC. luteathan in the other two species. It is possible that smaller numbers of pollen grains are required here, because the floral dimorphism enhances pollinations between flowers of different types.
DIVERSITY OF METAL TOLERANCES IN PLANT AGO LANCEOLATA L. FROM THE SOUTHEASTERN UNITED STATES
Authors: POLLARD A. J.
Published: May 2006

Summary

Populations of Plantago lanceolata L. from a variety of habitats in the southeastern United States contaminated with zinc, copper or arsenic (from mining), or lead (from motor vehicle exhaust fumes) were found to be more tolerant to the metals present at the collection site than was a control population from uncontaminated soil. This is the first record of copper or arsenic tolerance in this species. Testing was based on root growth of young seedlings in aqueous solutions of metal salts. In the case of arsenic, there was extremely high tolerance in seedlings from plants in contaminated soils, but the seedlings from plants growing on uncontaminated soil, although severely inhibited on average, contained a few individuals of high tolerance, suggesting a potential for rapid evolution of tolerance to this contaminant.
RELATION OF INTERNAL PHOSPHORUS CONCENTRATION AND PLANT WEIGHT IN PLANTS INFECTED BY VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: STRIBLEY D. P. , TINKER P. B. , RAYNER J. H.
Published: May 2006

Summary

Our own results and a search of the literature have shown that shoots of plants infected with vesicular‐arbuscular mycorrhiza normally contain higher internal concentrations of P than those of uninfected plants of equal size, over wide ranges of external P supply and of host plants. Increased demand for carbon by infected roots is a possible explanation for this, and simple graphical methods of estimating the resulting dry wt loss are suggested.
ALLELOPATHIC ACTIVITY OF CAMELINA SATIVA (L.) CRANTZ IN RELATION TO ITS PHYLLOSPHERE BACTERIA
Authors: LOVETT J. V. , JACKSON HELEN F.
Published: May 2006

Summary

In the presence of phyllosphere bacteria, aqueous washings of foliage of Camelina sativa stimulate early growth of several species of higher plants. At least two bacteria can promote the observed effects, however, suitable substrates for bacterial activity may be limited to cruciferous plants.

The stimulatory principle is produced rapidly by bacterial activity and is probably an organic chemical produced by bacterial degradation of more complex compounds commonly found in the Cruciferae.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: STRIBLEY D. P. , READ D. J.
Published: May 2006

Summary

Young mycorrhizal plants of Vaccinium macrocarpon could utilize amino acids as a nitrogen source as readily as ammonium whereas aseptically grown plants and plants inoculated with common soil saprophytic fungi were unable to utilize the organic nitrogen compounds. Seedlings of Festuca ovina grown as controls in the sterile condition and in the presence of the ericaceous endophyte also failed to utilize the amino compounds. The capacity of the ericaceous plant to exploit these compounds is therefore dependent upon mycorrhizal infection. In contrast to cultures of Marasmius oreades, the endophyte failed to grow on complex nitrogenous humic and fulvic acids extracted from soils under ericaceous plants. The capacity to utilize simple organic nitrogen compounds could be of importance for mycorrhizal ericaceous plants in mor‐humus soils which are characterized by slow rates of nitrogen mineralization.
SYMPLASTIC CONTINUITY DURING HARTIG NET FORMATION IN NORWAY SPRUCE ECTOMYCORRHIZAE
Authors: NYLUND JAN‐ERIK
Published: May 2006

Summary

Pits with plasmodesmata were observed by scanning and transmission electron microscopy in cortical cells of uninfected short roots, grown in vitro, and ectomycorrhizal roots grown in vitro and in vivo, of Norway Spruce, Picea abies (L.) Karst. The ectomycorrhizal fungus, Piloderma bicolor (Peck) Jülich, while forming a Hartig net during mycorrhiza synthesis in vitro, did not separate the host cell walls in the pit zones. In natural spruce ectomycorrhizae with P. bicolor and an unidentified ascomycete, the cortex symplast remained continuous by means of frequent pits with plasmodesmata. The tanniferous cells bordering the fungal mantle were never pitted.

The symplastic continuity, which has not been previously demonstrated in the cortical cells of the host of ectomycorrhizae, is essential for the exchange of substrates between the fungus and the host.
DIAMOND‐BARK DISEASES OF SYCAMORE IN BRITAIN
Authors: BEVERCOMBE GAY P. , RAYNER A. D. M.
Published: May 2006

Summary

Outbreaks of disease in sycamore (Acer pseudoplatanus) characterized by development of variously sized diamond‐shaped patches of necrotic bark (diamond‐cankers) are described. It is suggested that apparently similar symptoms may be caused by a variety of agencies. The fungus Dichomera saubinetii was closely associated with diamond‐cankers in many localities but it was sometimes absent and other fungi were then present, e.g. Cryptodiaporthe lebiyesi.

Callous tissue frequently develops at the margin of diamond‐cankers, allowing their time of origin to be determined by an annual ring count. The most recent, major development of the disease, associated with particularly large cankers, occurred following the drought summer of 1976. There was also evidence of previous disease outbreaks from which trees had recovered, for previously wounded surfaces had often been completely sealed over by overgrowth and fusion of callous tissue.

During the 1976 outbreak, callus often failed to form effectively around diamond‐cankers, and this was associated with death of the whole, or upper part of the tree. In the most severe cases (generally not associated with D. saubinetii) this resulted in considerable numbers of often quite large trees being destroyed within an area. Here the largest trees affected were as much as 15 to 25 m high and 0.5 to 0.75 m diameter near the base and in excess of a hundred separate cankers might be present on an individual trunk.
THE SECRETORY CYCLE OF DIONAEA MUSCIPULA ELLIS IV. THE ENZYMOLOGY OF THE SECRETION
Authors: ROBINS R. J. , JUNIPER B. E.
Published: May 2006

Summary

The proteolytic activity of the secretion is examined using inhibitors and site‐specific substrates. The major protease present is not peptic, tryptic or chymotryptic, but may be a thiol protease as activity is inhibited by alkylation with iodoacetamide. Acetylation causes an inhibition of activity, suggesting that one of the major proteases may have an amide group involved in its action. Carboxypeptidase A is found to be present. The secretion is shown to contain chitinolytic and peroxiditic activities but not N‐acetyl‐β‐d‐glucosaminidase. The possible origin of the secretion is discussed.
GROWTH ANALYSIS OF MAIZE VARIETY HYBRIDS OBTAINED FROM TWO RECURRENT SELECTION PROGRAMMES FOR GRAIN YIELD*
Authors: FAKOREDE M. A. B. , MOCK J. J.
Published: May 2006

A reciprocal recurrent selection programme was initiated in 1949 to improve the grain‐yield performance of Iowa Stiff Stalk Synthetic [BSSS(R)] and Iowa Corn Borer Synthetic no. 1 [BSCB(R)] maize (Zea mays L.) populations. In the same year, a half‐sib selection programme was initiated in an open‐pollinated maize variety, ‘Alph’ (i.e. BS12), with the same objective. Inbred B14 was the tester variety in the half‐sib programme. Previous studies showed that significant grain‐yield increases resulted from seven cycles of reciprocal recurrent selection and six cycles of half‐sib selection. Growth analysis was used to examine productivity and distribution of dry matter by the unimproved and improved variety hybrids of BSSS(R) × BSCB1 (R)and BS12 × B14A.

Only leaf area, leaf‐area duration, leaf‐area index, and leaf‐area index duration were significantly larger in the improved than the unimproved hybrids. These differences occurred mostly during grain filling. Evidently, increased grain yields from recurrent selection in these programmes were consequences of prolonged photosynthetic activity, increased production of photosynthate during grain filling, and increased translocation of photosyntheate from source to sink, in both BSSS(R) × BSCBl(R) and BS12 × B14A.
A RE‐INVESTIGATION OF CHARACTER CORRELATIONS AMONG DICOTYLEDONS
Authors: SPORNE KENNETH R.
Published: May 2006

A computerized analysis of the occurrence among 291 dicotyledon families of 107 morphological or biochemical characters is described. The results confirm earlier work and increase the number of characters that are shown to be statistically associated from 26 to 39. Many of these occur more often in rain‐forest floras than in the rest of the world. They also occur more often in families that are represented in the fossil record than they do in the present‐day world flora, and are therefore regarded as primitive.

Using 30 of these correlated characters, the percentage advancement index of the various families is calculated. Among the most advanced families are Dipsacaceae, Valerianaceae and Hippuridaceae. The most primitive ones are Aextoxicaceae and Degeneriaceae, with Stachyu‐raceae and Magnoliaceae also very primitive.
THE GENECOLOGY OF LAWN WEEDS VI. THE ADAPTIVE SIGNIFICANCE OF VARIATION IN ACHILLEA MILLEFOLIUM L. AS INVESTIGATED BY TRANSPLANT EXPERIMENTS
Authors: WARWICK S.I. , BRIGGS D.
Published: May 2006

The performance of 21 populations of Achillea millefolium L., originating from I lawns, II grazed sites, III grasslands seasonally reduced in height by cutting and/or grazing and IV grassy areas not seasonally reduced in height by cutting and/or grazing, was investigated by transplanting clone‐propagated material into a mature lawn. The response of a small number of contrasting populations was also studied in mown and tall grass plots of a reciprocal transplant experiment.

There was no evidence, from the mown treatment of either experiment, to support the hypothesis that A. millefolium populations originating from certain lawns or grazed sites, and notably dwarf in standard cultivation, were more successful than others in vegetative spread, dry wt yield or reproduction. In both experiments plants originating from lawns were not uniformly successful. Also, individuals from all four habitat groups proved to be vegetatively vigorous in mown plots. Six plants (three from lawns, two from pasture and one from waste ground) fruited successfully in the mown plots of the reciprocal transplant experiment.

Experiments with tall grass plots did not support the notion of tall grass races of A. millefolium. Such plots revealed considerable variability in all populations and plants from several habitat groups produced mature achenes in tall grass plots.

Fruiting of A. millefolium is very rare in well‐kept lawns and the apparent clones in such habitats are likely to be the result of achene dispersal from habitats where the intensity and/or periodicity of grazing and/or mowing is insufficient to prevent fruiting.
CLASSICAL DATA ON THE GROWTH OF MAIZE: CURVE FITTING WITH STATISTICAL ANALYSIS
Authors: HUNT RODERICK , EVANS G. CLIFFORD
Published: May 2006

A new method of fitting curves to long sequences of data from successive harvests from populations of growing plants is applied to the classical data of Kreusler and his co‐workers on the growth of maize, carried out near Bonn in 1875 to 1878. The method effectively divides the data into phases, which are fitted by splined cubic polynomials meeting in‘knots’where adjacent curves agree in position, slope and rate of change of slope, thus ensuring smooth transitions and minimizing loss of degrees of freedom. The phases can be chosen on some physiological or morphological criteria, or (as here) best positions for knots can be determined statistically by a method which minimizes sums of squares of deviates.

The curves are fitted to the natural logarithms of the primary data on dry wt and leaf area, and relative growth rates, leaf area ratios and unit leaf rates are derived by manipulating the equations of the original fitted curves. All these curves are presented for five varieties grown in 1875 and one variety grown from 1875 to 1878. A full statistical apparatus gives confidence limits for all the interpolated points along all these curves. The variances are homogeneous along any one of the sixteen original fitted curves, and taken as a whole the data show remarkable statistical uniformity, reflecting great credit on the experimental planning and execution a century ago.

The fitted curves and their derivates show a large measure of agreement on common developmental progressions, with differences from variety to variety and year to year. Detailed examination shows that a number of these differences, particularly cases involving only a short sequence of harvests, were almost certainly due to deficiencies in the original data, the fitted curves and their associated statistics being valuable in detecting these. At the same time no serious example was detected of the fitting program injecting features not present in the primary data; but one minor example, not affecting specific conclusions, shows how necessary it is always to be on guard.
EFFECT OF CHLORAMPHENICOL ON GROWTH, CHEMICAL COMPOSITION AND CHLOROPHYLL CONTENT OF INTACT PLANTS
Authors: SMITH G. S. , EDMONDS A. S. , MIDDLETON K. R.
Published: May 2006

The growth of perennial ryegrass and lucerne was inhibited by d‐threo‐chloramphenicol at concentrations generally considered safe for preventing bacterial contamination. Inhibition of growth was the result more of a reduction in photosynthetic activity than of a specific effect on ion absorption. Young plants were more susceptible to chloramphenicol than older plants and the cumulative effect of repeated applications of the bactericide at low concentrations depressed growth and chlorophyll content to the same extent as a single concentrated application. The present results have been related to known effects of chloramphenicol on protein synthesis, leading to the conclusion that its use to prevent bacterial contamination in studies on the growth of green plants is inadvisable. Recognition of this fact makes suspect much published work where chloramphenicol has been used for this purpose.
THE SERIAL OBSERVATION OF EMBRYOGENESIS IN A CARROT CELL SUSPENSION CULTURE
Authors: FUJIMURA TATSUHITO , KOMAMINE ATSUSHI
Published: May 2006

Serial observations were made of the early stages of somatic embryogenesis in a cell suspension culture of carrot (Daucus carota L. cv. ‘Kurodagosun’) using a series of cell clusters which divided synchronously. Three phases were recognized in each of which the rate of cell division was different: the first phase (0 to 3 days) during which cells divided slowly, the second phase (3 to 4 days) during which cells divided very rapidly in the determined locus of the cell cluster, leading to the formation of globular embryos, and the third phase (4 to 6 days) during which cell division occurred at a slower rate than the second phase. Three regions were distinguishable in the cell clusters at the end of the second phase: a transparent region destined to develop into the shoot, an opaque region destined to develop into the root and another opaque region which had ceased to grow, suggesting that the determination of differentiation had already occurred by the end of the second phase. The rapid cell division which occurred in the second phase is considered to be a characteristic event in embryogenesis.