bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF TEMPERATURE AND LIGHT ON SEED GERMINATION OF TWO ECOTYPES OF PORTULACA OLERACEA L.
Authors: SINGH K. P. 
Published: May 2006

SUMMARYThe effect of various temperature and light conditions on the germination of freshly harvetesd and 1‐year‐old seeds of obovate leaf and narrowly obovate leaf ecotypes of Portulaca oleracea L. is reported. These plants are common weeds of moist cultivated fields in the Upper Gangetic Plain. Freshly harvested seeds showed insignificant germination in darkness at any temperature between 10–40° C, and required specific photoperiodic and thermoperiodic conditions for germination. In contrast 1‐year‐old seeds showed significant temperature‐dependent dark germination, and almost complete germination with a single light exposure given at high temperatures; they thereby exhibited the loss of photo‐thermoperiodic requirement. In general the seeds of the narrowly obovate leaf ecotype were more sensitive to light than those of the obovate leaf ecotype. The possible significance of the germination requirements in relation to the success of the plant in Nature and to its essentially tropical distribution is discussed.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE: I. THE ISOLATION OF THE ENDOPHYTE AND SYNTHESIS OF MYCORRHIZAS IN ASEPTIC CULTURE
Authors: PEARSON V. , READ D. J. 
Published: May 2006

SUMMARYTechniques are described for the isolation of fungi inhabiting ericaceous roots and for the culture of mycorrhizas under aseptic conditions. The mycorrhizal status of a range of isolates is assessed and the distinctive features of the true endophyte are described. The biology of this fungus is considered with special reference to host specificity and its occurrence as a free living soil micro‐organism.
BASIDIOCARPS ASSOCIATED WITH ERICOID MYCORRHIZAS
Authors: SEVIOUR R. J. , WILLING R. R. , CHILVERS G. A. 
Published: May 2006

SUMMARYA species of basidiocarp has been seen in constant and specific association with mycorrhizal Ericaceae. These basidiocarps are shown to be serologically related to pelotons of the mycorrhizal fungus.
SYMBIOTIC GERMINATION OF SOME AUSTRALIAN TERRESTRIAL ORCHIDS
Authors: WARCUP J. H. 
Published: May 2006

SUMMARYIn symbiosis tests on an agar medium with powdered cellulose as carbon source, isolates of several species of Tulasnella and of Ceratobasidium cornigerum were compared on seven species of Thelymitra and two each of Diuris and Pterostylis. The Pterostylis species were stimulated to germinate only by Ceratobasidium cornigerum, the Diuris species only by Tulasnella calospora but, in general, the Thelymitra species were stimulated by more than one species of Tulasnella, but not markedly by Ceratobasidium cornigerum. These results correlate well with specificities noted in isolations from the roots of mature orchids of these genera in nature.It was found that different isolates of Tulasnella calospora differed markedly in the efficiency with which they stimulated germination of the species of Diuris and Thelymitra. The most efficient isolates were not necessarily those isolated from these orchids.
HYBRIDS BETWEEN LOLIUM PERENNE L. AND FESTUCA PRATENSIS HUDS. I. CROSSING AND INCOMPATIBILITY
Authors: GYMER P. T. , WHITTINGTON W. J. 
Published: May 2006

SUMMARYNatural hybrids between Lolium perenne and Festuca pratensis occur in old grassland; diploids and two types of triploids, festucoid and loloid, may occur. Attempts were made to produce similar hybrids experimentally, both by crossing in the glasshouse, and in mixed plots in the field. It was found very difficult to produce F1 hybrids, except for the production of festucoid triploids by crossing diploid Lolium with tetraploid Festuca. No triploids were obtained from diploid‐diploid crosses, but there was evidence of unreduced gametes in the appearance of tetraploid progeny from diploid–tetraploid crosses within Lolium perenne.The hybrids were found to be nearly sterile, but attempts to backcross in the glasshouse yielded a few progeny, both from diploids and triploids. Lolium was a much more successful pollen parent than Festuca. The progeny from diploids were mostly diploid, but included a few triploids and aneuploids. Triploid hybrids produced a wide range of progeny, varying from fourteen to twenty‐eight chromosomes.The difficulty of crossing, and reciprocal differences in compatibility which occur are apparently due to seed incompatibility, probably controlled by the relationship between the genomes and the plasmon in the endosperm.It is concluded that the abundance of hybrids in natural populations must be explained ecologically.
THE EFFECT OF ROOT PRUNING AND 6‐BENZYL‐AMINOPURINE ON THE CHLOROPHYLL CONTENT, 14CO2 FIXATION AND THE SHOOT/ROOT RATIO IN SEEDLINGS OF PISVM SATIVUM L.
Authors: McDAVID C. R. , SAGAR G. R. , MARSHALL C. 
Published: May 2006

SUMMARYPruning the roots of light‐grown pea seedlings every 4 days accelerated senescence of older leaves and reduced their rate of fixation of 14CO2. Application of 6‐benzylaminopurine to the shoot largely compensated for root removal and increased the shoot/root ratio of both pruned and intact plants. It is suggested that the supply of cytokinins from root to shoot may affect leaves by delaying senescence and maintaining their capacity for photosynthesis; it may also alter the distribution of dry matter within the plant by influencing the proportion of assimilates and other metabolites retained by the shoot.
PERMEABILITY TO WATER OF THE ROOTS OF FIVE HERBACEOUS SPECIES
Authors: NEWMAN E. I. 
Published: May 2006

SUMMARYThe permeability to water of whole detopped root systems of five herbaceous species, all grown under the same conditions, was determined by the solution‐change method of Arisz, Helder and van Nie (1951). Measurements of root dimensions allowed permeability to be expressed per unit of (a) root surface area, (b) endodermis area, (c) root volume, and (d) root length. By any of these four methods of calculation there were large differences in permeability between the species. Per unit surface area the permeabilities were: broad bean, 0·54; dwarf bean, 0·56; sunflower, 0·71; maize, 2·2; tomato, 6·1 nm second‐1 bar‐1. These differences cannot be explained by any obvious difference in root morphology. The permeability values fit with two previously proposed theories; (1) that much of the root resistance lies in the endodermis; and (2) that the resistance of the soil in the rhizosphere is small compared with that of the plant until the soil has dried to near or beyond the permanent wilting point.
INTERACTIONS OF LIGHT AND TEMPERATURE ON THE GERMINATION OF PLANTAGO MARITIMA L.
Authors: ARNOLD SYLVIA M. 
Published: May 2006

SUMMARYThe percentage of seeds of Plantago maritima which germinated in the light increased linearly with temperature between 8 and 18° C. The response to fluctuating temperatures could be accounted for entirely by this linear relation. Germination was inhibited when seeds were kept in darkness during ihibition and percentage germination was shown to depend on the temperature of the seeds as well as the length of the dark period. Exposure to light at 25° C released the inhibition of some of the dark treated seeds but exposure to low temperature was ineffectual. Most of the seed came from Upper Teesdale but seed from Devon responded to germination tests in the same way. The germination of seeds of Kobresia simpliciuscula from Teesdale was also inhibited by darkness during imbibition. This type of response may promote the survival of seedlings in their natural environment.
APPARATUS TO MEASURE THE RATE OF FALL OF WIND‐DISPERSED SEEDS
Authors: SHELDON J. C. , LAWRENCE J. T. 
Published: May 2006

SUMMARYApparatus is described for accurately measuring the rate of fall of wind‐dispersed seeds over known distances. The detection system consists of photo‐electric beams at the open ends of a Perspex tube. The apparatus was connected to an automatic timing counter which was switched on by the released seed breaking the uppermost photo‐electric beam, and switched off as the seed passed through the lower beam. A simplified circuit diagram of the detection system is given.
THE ROLE OF TAXIMETRICS IN ANGIOSPERM TAXONOMY II. PARALLEL TAXIMETRIC AND ORTHODOX STUDIES IN CROTALARIA L.
Authors: BISBY F. A. , POLHILL R. M. 
Published: May 2006

SUMMARYThis paper indicates one way in which taximetrics can contribute to the taxonomic work currently being carried out in herbaria and universities. Taximetric and orthodox studies of African species of Crotalaria L. (Leguminosae) carried out separately by the two authors produced classifications which were similar in essential features. It was possible to resolve twenty discrepancies between the two classifications which varied from the delimitation of major groupings to the placing of individual species and the treatment of outliers. In some cases Polhill's orthodox scheme was upheld and in others Bisby's taximetric results provided evidence for making improvements. The outcome was an amended classification for which the nomenclatural changes are set out.The authors suggest that parallel studies of this sort may prove one of the most useful contributions that taximetrics can make. Not only is maximum use made of both types of procedure but also such studies contribute to knowledge of the relative performance of the taximetric and orthodox procedures. Only when there is much more confidence and experience in using taximetric procedures will it be useful to apply them in situations where there is no immediate check from orthodox work.
THE HOST‐PARASITE RELATIONSHIP BETWEEN ZIZANIA CADUCIFLORA TURCZ. AND USTILAGO ESCULENTA P. HENN. I. STRUCTURE AND DEVELOPMENT OF THE HOST AND HOST–PARASITE COMBINATION
Authors: CHAN YUK‐SIM , THROWER L. B. 
Published: May 2006

SUMMARYInfection of the flowering culm of Zizania caduciflora by the smut fungus, Ustilago esculenta, results in a swollen structure named‘gau sun’This host‐parasite combination is culivated as a vegetable in eastern Asia. The structure and development of gau sun is described and terms are denned to describe developmental stages. The swollen culm (gau sun) has a volume 517 × that of the unswollen culm and contains 2‐9 × the number of cells which are 14‐9 × the volume of those in the unswollen culm. Mucilaginous cavities, absent from the unswollen culm, make up 16% of the total volume of the swollen culm.
FLORAL SEX RATIOS IN ANDROMONOECIOUS UMBELLIFERAE
Authors: DOUST J. LOVETT 
Published: May 2006

SUMMARYThe distribution of hermaphrodite and male flowers was determined in the inflorescences of three andromonoecious species of Umbelliferae, Smyrnium olusatrum, Pastinaca sativa and Anthriscus sylvestris. Despite wide differences in the number of flowers produced per plant by the three species the floral ratio 4 male to 1 hermaphrodite was remarkably constant and except in an extreme environment 55 to 70 % of hermaphrodite flowers produced ripe seeds. The constancy in floral ratio per plant was maintained by quite different distributions of flower type between umbels in the three species. The apparent contradiction between protandry in flowers but protogyny within umbels is interpreted as an avoidance of simultaneous competition for resources within the plant.
SEASONAL OCCURRENCE OF AN ANTIMICROBIAL FLAVANONE, SAKURANETIN, ASSOCIATED WITH GLANDS ON LEAVES OF RIBES NIGRUM
Authors: ATKINSON P. , BLAKEMAN J. P. 
Published: May 2006

SUMMARYSakuranetin, a flavanone aglycone, was present in glands on the adaxial surfaces of leaves of most varieties of Ribes nigrum L. These glands senesce early in the season, releasing their contents on to the surface of the leaf. Glands on the abaxial surfaces of leaves, which are different in structure from those of adaxial surfaces, do not contain sakuranetin. Conidia of Botrytis cinerea Pers. ex Fr. were inhibited from germinating on adaxial but not on abaxial surfaces of leaves at the time of adaxial gland senescence. Later in the season there was no inhibition of germination of conidia on either leaf surface. Because of the low activity of sakuranetin in vitro it was concluded that other factors were also likely to affect germination of conidia on adaxial leaf surfaces.
GENETIC DIFFERENTIATION OF THE MICROSPECIES SALICORNIA EUROPAEA L. (SENSU STRICTO) AND S. RAMOSISSIMA, J. WOODS
Authors: JEFFERIES R. L. , GOTTLIEB L. D. 
Published: May 2006

SUMMARYElectrophoretic variability was examined in 15 natural populations of Salicornia europaea and Salicornia ramosissima, two nearly indistinguishable, diploid, annual plant species common in salt marshes in England and Europe. All of the 800 plants examined were homozygous at the 30 loci which were scored and the number of isozymes for each of the enzyme systems was the same in all individuals. The electrophoretic mobilities of 24 of the enzymes were identical in all plants. With respect to the gene loci coding the other six enzymes, only two classes of individuals were detected: a plant possessed either one set of alleles, or an alternate set for the sis loci. One electrophoretic pattern was found primarily in individuals from the upper levels of salt marshes, whereas the other pattern was common in plants from the lower levels. The two patterns are characteristic of Salicornia ramosissima and Salicornia europaea respectively. The electrophoretic evidence confirms the reproductive isolation of the species, indicates an apparent lack of genetic variability in both of them and simplifies the interpretation of the ecological differentiation.
SEASONAL VARIATION IN NITROGEN AVAILABILITY AND UTILIZATION IN AN ACIDIC AND CALCAREOUS SOIL
Authors: TAYLOR A. A. , DE‐FELICE J. , HAVILL D. C. 
Published: May 2006

SUMMARYPronounced seasonal trends were observed in nitrogen availability and utilization in an acidic soil supporting Deschampsia flexuosa and a calcareous soil supporting Zerna erecta. In both soils, mineralization rates and instant inorganic nitrogen concentrations were maximum in late winter/early spring after which a rapid decline occurred. A similar seasonal pattern was evident in the levels of several nitrogen‐assimilating enzymes and soluble nitrogen pools in both grasses. Fertilizer experiments indicated that in both soil types nitrate formation was limited by the ammonium supply. Despite differences in the major form of inorganic nitrogen supplied to the plants, Deschampsia and Zerna showed similar capacities to utilize ammonium and nitrate. It is suggested that the observed seasonal enzymic response in these native species may be an adaptation to the fluctuating and low nitrogen status of natural soils.
REPLACEMENT OF LEAF PRIMORDIA WITH IAA IN THE INDUCTION OF VASCULAR DIFFERENTIATION IN THE STEM OF COLUCUS
Authors: BRUCK D. K. , PAOLILLO D. J. 
Published: May 2006

SummaryRemoval of a leaf of Coleus before or early in the differentiation of leaf traces severely reduced vascular differentiation in the subjacent internode. Auxin (IAA) in anion exchange beads (applied on 2 out of every 3 d for 2 to 4 weeks) restored normal structure with respect to arrangement of leaf traces and their composition, size, and rate of development. That IAA is the likely leaf‐limiting factor for vascular differentiation in situ is suggested by the formation of normal quantities of procambium, phloem and xylem under the influence of IAA after leaf excision. However, some peculiarities were induced as well. Plants treated with IAA showed earlier xylem maturation in side bundles, earlier and more frequent differentiation of xylem opposite putative phloem‐only bundles, and corner‐trace xylem connections at the node of IAA application. These can be accounted for by a lack of well‐defined channelling of IAA through petiolar tissues when IAA was applied to the cut surface after leaf excision. Phloem‐only bundles are regarded as an early auxin‐deficient stage in collateral bundle formation, which depends on auxin availability to the bundle for fulfillment.
SENSITIVITY OF FOREST PLANT REPRODUCTION TO LONG RANGE TRANSPORTED AIR POLLUTANTS: IN VITRO AND IN VIVO SENSITIVITY OF OENOTHERA PARVIFLORA L. POLLEN TO SIMULATED ACID RAIN
Authors: COX R. M. 
Published: May 2006

SummaryEffects of simulated acid precipitation on pollination in Oenothera parviflora L. from different populations were examined both in vitro and in vivo. The responses of pollen to acidity (pH 5.6 to 2.6) in standing drop cultures and the stigma receptivity of flowers under field simulations of acid rain were observed. The response of pollen in vitro indicated significant inhibitory effects of pH, and demonstrated that pH values ≤ 3.6 were inhibitory to both germination and tube growth, when compared with the treatment of pH 5.6. Dosages of LD50 for in vitro pollen germination, taken as the initial pH of cultures for the different pollens, ranged from pH 3.49 to 3.72. Stigma receptivity assessed by germination and initial tube growth on the stigmatic surface also declined significantly (P < 0.01) in response to acid rain simulation prior to hand pollinations. Again simulants ≤ pH 3.6 significantly reduced stigma receptivity compared with the treatment at pH 5.6. Here LD 50, dosages, taken as the pH of the simulant, were pH 3.45 and 4.66 for the failure of potentially viable pollen to germinate, or produce tubes three times the length of the grain, respectively. These results are discussed in relation to rain chemistry in Southern Ontario, Canada.
SEED PROTEIN QUANTITIES OF FIELD‐GROWN SOYBEANS EXPOSED TO SIMULATED ACIDIC RAIN
Authors: EVANS LANCE S. , DIMITRIADIS LEANDROS , HINKLEY DEBORAH A. 
Published: May 2006

SummaryAnalysis of seeds harvested from field‐grown soybeans demonstrated that simulated acidic rainfalls from two experimental protocols can significantly decrease total protein contents of soybeans. Statistically significant differences in protein content per seed mass were obtained in three of four experiments at the field site. Mean protein contents of control plants for the three experiments reported herein were 33.0, 39.3 and 43.8 % and were comparable to protein yields obtained by commercial growers. When results were expressed as protein content per seed mass the changes were independent of reduction in seed mass per plant due to increased rainfall acidity. When results were expressed as protein contents per plant, decreases in protein of 20 % were common in plants exposed to rainfalls similar to ambient (pH 4.1) compared with experimental controls (pH 5.6).
PRODUCTION OF PROTONEMAL GEMMAE IN CULTURE BY THE MÓSS, DIDYMODON RECURVUS (GRIFF.) BROTH.
Authors: VASHISTHA B. D. , CHOPRA R. N. 
Published: May 2006

SummaryProduction of protonemal gemmae in Didymodon recurvus varies according to the conditions of culture. Low light and high temperature favour gemma formation, whereas high light and low temperature promote development of gametophytic buds on the protonema.
A POLLEN DIAGRAM FROM ST KILDA, OUTER HEBRIDES, SCOTLAND
Authors: WALKER M. J. C. 
Published: May 2006

SummaryPollen‐stratigraphic data supported by four radiocarbon dates are presented from a site on Hirta in the St Kilda archipelago, western Scotland. The pollen spectra in the basal sediments reflect an open tundra environment and are considered to be of Loch Lomond (Younger Dryas) Stadial age. Although no evidence of early Flandrian vegetation is preserved in the stratigraphy, the middle and upper levels of the profile contain a record of landscape changes throughout the middle and late Flandrian. During the period from about 6000 B.P. to the present, wood and scrub cover on the island was minimal and the vegetation consisted of a mosaic of grassland and heathland communities. Changes in the composition of the vegetation, involving in particular the role of maritime plant communities, are discussed principally in terms of regional climatic changes in the north‐west Atlantic province.
ROOT DEVELOPMENT IN THE SEAGRASS HALOPHILA OVALIS (R. BR.) HOOK F. (HYDROCHARITACEAE), WITH PARTICULAR REFERENCE TO ROOT LACUNAE
Authors: ROBERTS D. G. , McCOMB A. J. , KUO J. 
Published: May 2006

SummaryThe roots of Halophila ovalis are sheathed by root cap cells up to 2 mm above the meristem tip, and carry prominent root hairs. Air lacunae differentiate schizogenously close to the apex, where they are first occluded by material which stains heavily with toluidine blue, but some appear empty within 300 μ of the apex, offering a path for gaseous diffusion to the apical region. As a root matures the lacunae, which differentiate centripetally, contribute approx. 22 % of the root cross sectional area, as compared with about 65 % due to cortical cells.Sieve tubes differentiate before xylem elements. Casparian strip formation and xylem differentiation are approximately synchronous, suggesting that these structures are involved in the uptake and transport of materials.
THE EFFECT OF SALINITY ON LEAF ULTRASTRUCTURE AND NET PHOTOSYNTHESIS OF TWO VARIETIES OF RICE: FURTHER EVIDENCE FOR A CELLULAR COMPONENT OF SALT‐RESISTANCE
Authors: FLOWERS T. J. , DUQUE E. , HAJIBAGHERI M. A. , McGONIGLE T. P. , YEO A. R. 
Published: May 2006

SummaryThe effects of sodium chloride on the leaf ultrastructure and net photosynthesis of two varieties of rice (Oryza sativa L.), the land race Amber and the elite breeding line IR2153.26.3.5.2, were examined. Similar concentrations of salt in the leaf tissue had a greater effect in bringing about a disorganization of cellular structure and of decreasing net photosynthesis in Amber than in IR2153.26.3.5.2. It is argued that these data support the view that rice varieties differ with respect to a cellular component of salt resistance.
STUDIES ON THE TOLERANCE TO SO2 OF GRASS POPULATIONS IN POLLUTED AREAS
Authors: WILSON G. B. , BELL J. N. B. 
Published: May 2006

SummaryThe development of acute and chronic sulphur dioxide (SO2) tolerance in lawn grass populations was studied by two approaches: the minimum time for tolerance to appear in Festuca rubra L., Lolium multiflorum Lam., L. perenne L., Phleum pratense L. and Poa pratensis L., was determined by comparison annually of plant samples from monoculture plots sown at a polluted site, with plants grown from the seed originally sown; the long term development of tolerance in F. rubra, D. glomerata L. and Agrostis tenuis Sibth. was also investigated by comparison of five lawns of different ages (1–c. 200 years) at a polluted site.Tolerance to acute SO2 injury was detected in L. perenne and Phleum pratense only three and four years after sowing, respectively. However, population samples of these two species, collected from the field three years later, showed no significant SO2 tolerance. An analysis using morphological and isozyme variation as criteria showed that the tolerant population consisted of a large number of different individual genotypes. The populations experienced a state of evolutionary flux with rapid selection first of the tolerant, and subsequently of the non‐tolerant phenotypes. The disappearance of tolerance coincided with declining ambient SO2 concentrations.The lawns of different ages were shown to represent an evolutionary series of increasing acute SO2 tolerance with age of lawn in F. rubra and A. tenuis. This demonstrated the continuing development of acute SO2 tolerance in grass populations over a prolonged period.The significance of the occurrence and rate of development of SO2 tolerance for grasslands in polluted areas is discussed.