bluuebunny/crossref_metadata_2025_split huggingface dataset:
ULTRASTRUCTURAL OBSERVATION OF THE SURFACE COAT OF DUNALIELLA TERTIOLECTA FROM STAINING WITH CATIONIC DYES AND ENZYME TREATMENTS*
Authors: OLIVEIRA LUIS , BISALPUTRA THANA , ANTIA NAVAL J. 
Published: May 2006

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

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

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

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

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

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

SUMMARYThe seed weight of individual perennial ryegrass seeds was measured prior to recording their date of emergence and subsequent growth in experimental populations raised in the glasshouse and sown at different initial densities. Seed size did not correlate with time to emergence although lighter individuals had a slightly lower probability of emergence. Seed size had no statistically significant effect on subsequent tillering up to 27 weeks, or on the dry wt attained by this time.The time from sowing to emergence was significantly related to subsequent tillering of the grass plants for a number of weeks in populations sown at different densities. After some 20 weeks the effect of emergence time became non‐significant. This coincided with the onset of tiller mortality in the population. Even after 27 weeks individual emergence time was inversely related to dry wt but was not related to mean tiller weight.
NITROGEN FIXATION BY MEMBERS OF THE STICTACEAE (LICHENES) OF NEW ZEALAND
Authors: GREEN T. G. A. , HORSTMANN J. , BONNETT H. , WILKINS A. , SILVESTER W. B. 
Published: May 2006

SUMMARYForty‐four species of New Zealand lichens, including 22 species of Pseudocyphellaria and seven of Sticta, were assayed for nitrogenase activity by acetylene reduction. Nitiogen fixation was confirmed by 15N enrichment studies. Ten species, all with green algal phycobionts, showed no detectable nitrogenase activity; the remainder, including all species of Pseudocyphellaria and Sticta, assayed positively. Fixation rates were found to be species specific ranging from 0·2 to 52 nmol g‐1 min‐1. Nitrogen fixing lichens showed a species specific range of total nitrogen content and all had greater values than non‐fixing species. Further analysis of nitrogen fixation in Sticta and Pseudocyphellaria species by plotting a graph of acetylene reduction against nitrogen content showed a highly significant positive relationship; also species of like chemical strain grouped together, and in any one chemical strain lichens with solely blue‐green phycobionts possessed higher rates. The possibility exists that these lichens could provide a significant input of nitrogen into some native forests in New Zealand.
THE EFFECT OF ORTHOPHOSPHATE CONCENTRATION AND EXOGENOUSLY SUPPLIED SUGARS ON THE DISTRIBUTION OF NEWLY FIXED CARBON IN SUGAR BEET LEAF DISCS
Authors: HEROLD A. , McGEE E. E. M. , LEWIS D. H. 
Published: May 2006

SUMMARYThe apportioning of newly fixed carbon in leaf discs of sugar beet (Beta vulgaris L.) is dependent on the incubation medium. Concentration of orthophosphate (Pi) influences the distribution of carbon between chloroplast starch and the cytoplasm, and the proportion of 14C incorporated into sucrose. In the presence of exogenous sucrose and glucose, starch synthesis is enhanced and gross changes in cytoplasmic metabolite pools occur. These observations are discussed in relation to sink/source interactions of whole plants. In the presence of mannose, which sequesters cytoplasmic Pi in leaves of sugar beet as mannose‐6‐phosphate, sucrose synthesis is severely inhibited and maltose accounts for up to 30 % of the fixed carbon. This is related to earlier reports of unusual accumulation of maltose.
GROWTH OF PARASPONIA IN AGAR TUBE CULTURE AND SYMBIOTIC EFFECTIVENESS OF ISOLATES FROM PARASPONIA SPP.
Authors: TRINICK M.J. 
Published: May 2006

SUMMARYThe symbiosis between Rhizobium and Parasponia andersonii was examined under a range of nutrient regimes in agar tube culture. Nodule initiation and nitrogen fixation were stimulated with ‘starter’ nitrogen. Nitrogenase activity of plants in tubes was similar to plants in Leonard jars or pots and resembled, when expressed on a nodule weight basis, the activity of other non–legumes rather than legumes.Fifteen isolates of Rhizobium from Parasponia were compared for effectiveness in nitrogen fixation in controlled environment cabinets. All rhizobia produced nodules and only one failed to fix nitrogen. The others varied in their degree of effectiveness, the least effective yielded only 70 % of the plant top weight of the best symbiotic combination. A few ineffectively nodulated plants occurred in all rhizobial treatments. Their presence was considered to be a result of host variability rather than environmental factors.
GERMINATION OF THE LIGHT‐SENSITIVE SEEDS OF CUCUMIS ANGUR1A AND RUMEX OBTUSIFOLIUS: EFFECTS OF TEMPERATURE
Authors: Felippe G. M. 
Published: May 2006

SummaryThe effect of temperature and exposure to far red light were compared using positively photoblastic seeds of Cucumis and negatively photoblastic seeds of Rumex. Short exposure of Cucumis seeds to 45°C was without effect but exposure at 0°C for 1 to 3 h promoted subsequent germination in white light at a constant temperature of 25°C. In contrast, white light alternating temperatures 25/10 and 25/5°C fully counteracted the inhibitory effect of light on germination of Cucumis seeds.The temperature pairs 15/35, 20/35, and 25/35°C were tested with both Rumex (in darkness) and Cucumis (in light). Seeds of both species had their germination strongly promoted by the 15/35°C pair. The pair 25/35°C had a promotive effect in Rumex and no effect in Cucumis, while the pair 20/35°C was very effective for Rumex but much less so for Cucumis.In experiments in which the alternating pair 25/5°C was combined with far red (followed by darkness and white light), Rumex and Cucumis seeds behaved similarly. With both, when far red was given during the 5°C period followed by light or darkness at 25°C germination was promoted (but the inhibitory effect was completely reversed only where far red was followed by white light). When far red was given at 25°C followed by white light or darkness during the 5°C period germination was not promoted. Thus, both positively and negatively photoblastic seeds show the same behaviour in relation to light and temperature when exposed to far red.
THE GERMINATION OF FOUR ANNUAL STRAND‐LINE SPECIES
Authors: IGNACIUK R. , LEE J. A. 
Published: May 2006

SummaryThe germination of four strand‐line annuals, Atriplex glabriuscula, Atriplex lacimata, Cakile maritima and Salsola kali, was studied in the field and laboratory. Germination in the field began approximately 1 month after the spring equinox. Thus, seedling establishment was not directly affected by high spring tides. The relative importance of the various biological and environmental factors influencing the timing of germination of these species is discussed.The effects on germination of salinity and temperature and various interactions between these two factors were characterized. From experiments designed to determine the nature of the inhibition of germination by saline solutions, it was concluded that, in the Atriplex spp., the inhibition was purely osmotic but, in C. maritima and S. kali, ionic toxicity is important. The potential for dispersal of strand‐line species by sea‐currents depends upon the buoyancy of the fruit and the ability of the seed to survive prolonged immersion in seawater. Laboratory experiments showed that the four species differed considerably in these characteristics.
SOME CHARACTERISTICS OF PHOSPHOENOLPYRUVATE CARBOXYLASE ACTIVITY FROM LEAF EPIDERMAL TISSUE IN RELATION TO STOMATAL FUNCTIONING
Authors: WILLMER C. M. 
Published: May 2006

SummaryPEP carboxylase from Commelina communis leaf epidermis was characterized. Activity was optimal at concentrations of 2 to 3 mM bicarbonate and 5 mM PEP at pH 8·3. The temperature optimum was between 35 and 40°C and the activation energy was 9·1 kcal mol‐1. At saturating substrate concentrations and at pH 8·3, malate inhibited PEP carboxylase activity; slight inhibition occurred at 2·0 mM (the lowest concentration tested) while 13·5 mM caused 50% inhibition. At saturating substrate concentrations KC1 and mannitol, both up to concentrations of 250 mM, had no significant inhibitory effect upon PEP carboxylase activity although, thereafter, marked inhibition occurred in the KC1 medium (concentrations of mannitol higher than 250 mM were not tested). 10 ‐4 M ABA had no effect on PEP carboxylase activity from Tulipa gesneriana leaf epidermis.The effects of a number of factors were tested both on PEP carboxylase activity and also on stomatal opening in epidermal strips of C. communis. After 1 h, maximum apertures and maximum opening rates occurred at 35°C. The activation energy for stomatal opening was 9·3 kcal mol ‐1. The effects of malate on stomatal opening in C. communis epidermis were complex: At pH 4·1 to 4·3, 10 mM monosodium malate saturated the opening response; widest openings also occurred at pH 4·0 with no opening at pH 2·7 and some opening at pH 5·0, 6·0 and 7·0.PEP carboxylase from C. communis epidermal tissue behaved, in most respects, very similarly to PEP carboxylase from C4 leaves. Correlations between the effects of the factors on PEP carboxylase activity and stomatal opening were difficult to make. However, temperature effects were remarkably similar. The effects of osmotica on PEP carboxylase activity suggested that inhibition due to high K+, Cl‐ or other osmoticum in the guard cell cytoplasm would be negligible. It was also concluded that ABA does not control stomatal movements via its effect on PEP carboxylase.
SODIUM NUTRITION OF PASTURE PLANTS II. EFFECT OF SODIUM CHLORIDE ON GROWTH, CHEMICAL COMPOSITION AND THE REDUCTION OF NITRATE NITROGEN
Authors: SMITH G. S. , MIDDLETON K. R. , EDMONDS A. S. 
Published: May 2006

ABSTRACTThe effect of increasing concentrations of sodium chloride in the root zone on growth, chemical composition and nitrate reductase activity of perennial ryegrass and timothy was investigated in a glasshouse pot experiment. For ryegrass, a natrophile, sodium chloride had little effect on growth, whereas for timothy, a natrophobe, growth was severely depressed by comparatively low concentrations of salt. The result also indicate that translocation of sodium into the leaves of timothy took place readily only after the accumulation sites in the roots and lower stems had been saturated with this element. This means that relatively large quantities of sodium chloride were needed to produce concentrations of sodium in the leaves of timothy as high as those normally found in the leaves of ryegrass. Sodium chloride increased the uptake of total and nitrate‐nitrogen but, in contrast, depressed the uptake of potassium by ryegrass and timothy It was therefore concluded that the marked stimulation by sodium chloride of nitrate reductase activity in both species was more the result of the increased uptake of nitrates than a specific effect of this salt on the enzyme. The practical implications of these results are discussed.
MULTIPLE METAL TOLERANCES IN THE GRASS DESCHAMPSIA CESPITOSA (L.) BEAUV. FROM THE SUDBURY SMELTING AREA
Authors: COX R. M. , HUTCHINSON T. C. 
Published: May 2006

SummaryAn investigation was conducted into the multi‐element tolerance of the grass Deschampsia cespitosa growing around a nickel/copper smelting complex at Coniston, near Sudbury, Ontario. Tolerances for nickel, copper, aluminium, zinc, lead and cadmium in this population were compared with those of control populations growing on uncontaminated pastures. Distinctive population differences were found in distributions of copper and nickel tolerances, indicating that elevated tolerance to these elements had evolved in the Coniston population. More subtle differences between the populations in aluminium, zinc and lead tolerance were also noted, with increased tolerances showing in the smelter area population, despite a lack of elevation in zinc and lead levels in the soils. Various individuals in the Coniston population demonstrated a positive response to nickel and copper at levels as high as 0.3 μg cm‐3 in water culture. This ‘need’ for the metals was reflected in the seed population from Coniston which germinated and survived better in the copper/nickel‐contaminated soils than in the control soil. In contrast, germination of the control seed population was uniformly good, but seedling survival was poor on the metal contaminated soils compared with that of the Coniston seedlings. The relevance of these findings to evolution of multi‐metal tolerances and the possible uses of the species for reclamation are discussed. The occurrence of coincidental metal tolerances is considered.
RECIPROCAL TRANSFER OF NUTRIENTS BETWEEN ERICACEOUS PLANTS AND A CLAVARIA SP.*
Authors: Englander L. , Hull R. J. 
Published: May 2006

SummaryA close physiological relationship between some ericaceous plants, Rhododendron sp. and Pieris japonica, and a member of the genus Clavaria is indicated by radioisotope translocation studies. [14C] photosynthate from host leaves was detected in Clavaria fruiting bodies and 25P applied to Clavaria fruiting bodies was detected in plant roots. Possible transfer mechanisms, including that of a mycorrhizal association, are discussed.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS XI. SNOWCOVER AND NITROGENASE ACTIVITY
Authors: MacFARLANE J. D. , KERSHAW K. A. 
Published: May 2006

SummaryThe influence of a long term snowcover on the rates of nitrogenase activity in the lichens Peltigera canina var. praetextata and P. canina var. rufescens has been investigated. In accordance with the existing literature, only very low rates of nitrogenase activity could be detected after several months of snowcover. These low rates of activity result from prolonged darkness rather than an inactivation of the nitrogenase enzyme by low temperature. The subsequent recovery of nitrogenase activity after snowmelt is very largely controlled by the presence of radiant energy with temperature playing a subordinate role.
NITROGENASE ACTIVITY ASSOCIATED WITH THE RHIZOSPHERE OF AMMOPHILA ARENARIA L. AND EFFECT OF INOCULATION OF SEEDLINGS WITH AZOTOBACTER
Authors: WAHAB A. M. ABDEL , WAREING P. F. 
Published: May 2006

SummaryA marked gain in nitrogen was obtained when plants of Ammophila arenaria L. were grown in pots in dune sand and supplied with nitrogen‐free nutrient solution. Nitrogenase activity was associated with the roots but the estimated rates of nitrogen‐fixation based upon the acetylene reduction technique were less than one‐tenth of those obtained by the Kjeldahl method. Significant rates of acetylene reduction were also demonstrated both for detached roots taken from plants growing naturally in sand dunes and from measurements made in situ in the field, but the estimated rates of nitrogen fixation were much lower than calculated rates of nitrogen gain by actively‐growing plants. Some possible reasons for this discrepancy are discussed. Acetylene reduction was greatly stimulated by the addition of glucose, suggesting that nitrogen fixation by micro‐organisms in the rhizosphere is limited by the supply of root exudates. Seedlings of Ammophila grown under aseptic conditions and inoculated with Azotobacter showed greatly increased growth compared with that of uninoculated seedlings.
POLLEN ALLELOPATHY—A NEW PHENOMENON
Authors: KANCHAN SUKHADA , CHANDRA JAYA 
Published: May 2006

SUMMARYWhite dust spread on the leaves and stigmatic surface of Crotalaria pellida L. and Desmodium heteracarpon (L.) DC var. strigosum Meeuwen growing in the midst of a Parthenium hysterophorus L. stand was found to be clusters of Parthenium pollen. The fruit set in those species was poor. It was found that Parthenium pollen grains contained growth inhibitors which inhibited fruit set in many test species when artificially dusted on the stigmatic surface. In culture conditions the germination and pollen tube growth of the test species were inhibited in the presence of Parthenium pollen or their extract. The plant produces on an average 3375 million pollen grains per square metre areas of the stand. The pollen grains disperse in dusters of 600 to 800 each and are carried great distances by wind. Pollen grains deposited on leaves in large quantity also reduce the chlorophyll content in these species.