bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE INFLUENCE OF THE ROOT SYSTEM ON THE RELATIONSHIP BETWEEN THE RATE OF TRANSPIRATION AND DEPRESSION OF LEAF WATER POTENTIAL
Authors: STOKER R. , WEATHERLEY P. E. 
Published: May 2006

SummaryThe relationship between rate of transpiration and depression of water potential of the leaves (δψ1) was investigated with Gossypium hirsutum and Heliantlnis annum grown in water culture. (δψ1) was measured with a thermocouple psychrometer over a wide range of transpiration rates. The different transpiration rates were obtained by altering the environmental conditions in a climatological wind tunnel. At zero transpiration rate δψ1 was found to be 5.5 atm in H. annuus and 6.0 atm in Gossypium hirsutum. As the transpiration rate was raised, δψ1 rose steeply to a plateau in both species and remained at near to 9 atm within the transpiration range 0.4–2.4 g/dm2/hour. Thus within this range resistance in the plant declined in proportion to the transpiration rate. With transpirational fluxes greater than 2.4 g/dm2/hour, δψ1 rose, indicating little further decline in resistance.That the variable plant resistance is located in the roots was confirmed since plants with killed roots had a constant resistance, δψ1 exhibiting a linear relationship with transpiration. The resistance of the dead root system was much lower than that of living roots at low transpiration rates, but at high transpiration rates the resistance of living roots fell to about the same level as the dead roots. The implications of these findings are discussed.
Studies IN POTENTILLA L.
Authors: SMITH GORDON L. 
Published: May 2006

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

SummaryReference pollen slides have been made from twenty‐three samples of material identified as Tilia platyphyllos Scop., T. cordata Mill., or T. × vulgaris Hayne. Up to 100 grains in each slide have been microscopically examined and each opposing face has been classified as of ‘cordata’ or ‘platyphyllos’ type. The survey showed that grains of T. platyphyllos material were homopolar and consistently of ‘platyphyllos’ pattern. Some material of T. cordata was also homopolar and consistently of ‘cordata’ pattern. There was, however, an extreme degree of heteropolarity in most of the hybrid material and also in much of that attributed to T. cordata, a large proportion of the grains having ‘cordata’ pattern on one face and ‘platyphyllos’ on the other.The results show the extreme importance of adequate authentication of pollen type‐material and suggest that in Britain both T. cordata and T. platyphyllos are native, but that much hybridization has occurred between them, giving progeny in which the somatic phenotypes show less indication of ‘platyphyllos’ parentage than the pollen seems to do.
CYTOLOGICAL STUDIES IN DORMANCY
Authors: VILLIERS T. A. 
Published: May 2006

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

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

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

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

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

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

SummaryAnalysis of the growth of seedlings of Urtica dioica on a woodland soil shows that in well‐illuminated situations, the large response to addition of phosphate is caused by a high rate of absorption which allows a short period of high relative growth rate related to a rapid, but transient, increase of leaf area ratio. Without addition of phosphate, both relative growth rate and leaf area ratio remain almost constant over this same period. The relative increase of leaf area ratio caused by addition of phosphate is greatly reduced in shade.Neither in the rate of absorption of phosphate from dilute solutions, nor in the production of dry matter relative to the quantities of phosphate absorbed, does Urtica appear to differ significantly from species which show a much smaller response to phosphate on this type of soil.
THE CONTRIBUTION OF MICRO‐ORGANISMS TO THE APPARENT ABSORPTION OF IONS BY ROOTS GROWN UNDER NON‐STERILE CONDITIONS
Authors: BARBER D. A. , FRANKENBURG U. C. 
Published: May 2006

SummaryMicro‐organisms can make a considerable contribution to the apparent absorption of inorganic nutrients by excised roots. The microbial component of uptake has been studied by comparing the absorption of phosphate and rubidium by seedling roots of barley grown prior to excision under sterile and non‐sterile conditions.Although relative to the quantities taken up by sterile roots more phosphate than rubidium was absorbed by micro‐organisms, for both ions over the range 0.001‐1.0 mM, the relationship between absorption and increasing external concentration followed the kinetics of a first order reversible reaction. No simple kinetic relationship could, however, be derived to describe the uptake of either phosphate or rubidium by the roots.The significance of these findings is considered in the light of the postulate, derived from experiments under non‐sterile conditions, that the absorption of ions by roots is mediated by two distinct‘carrier’mechanisms, one of which dominates at low and the other at high external concentrations. It is concluded that experiments designed to investigate the nature of the uptake process should be carried out under sterile conditions.
GROWTH FACTORS PRODUCED BY GERMINATING SPORES OF POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M. 
Published: May 2006

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

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

SummaryParenchyma cells in the leaf sheath of Equisetum telmateia form linearly arranged series of maturing and senescing cells. These series of cells contain chloroplasts showing a progressive sequence of developmental stages easily recognizable because of the spatial relationships involved. The cell sequence may be classified into four successive zones, characterized by the typical structure of the chloroplasts present in the cells of each zone. Zone I. Meristematic cells contain immature chloroplasts with little internal lamellar structure. Zone II. Adjacent to the above are cells containing mature chloroplasts with a well‐developed internal lamellar system. Zone III. Next in sequence are cells in which the chloroplasts retain a mature internal lamellar system but are distinguished from the previous group by the presence of irregular osmiophilic deposits around the outer double membranes. Zone IV. Finally there occur cells with usually rounded chloroplasts which show the osmiophilic deposits described above, but in which the outer double membrane is often difficult to distinguish. Internally the lamellar system is highly sinuous, and contains many swollen locules.In spite of a general similarity in appearance between chloroplasts of Equisetum and those of angiosperms, Equisetum plastids are characterized by a distinctive feature more commonly associated with algae than with higher plants. Young chloroplasts are almost completely surrounded by rough endoplasmic reticulum. This very close relationship between reticulum and chloroplast is retained as the chloroplast matures, though the degree of envelopment becomes less with increasing age.
VEGETATION OF THE MARITIME CLIFF‐TOPS OF THE LIZARD AND LAND'S END PENINSULAS, WEST CORNWALL
Authors: MALLOCH A. J. C. 
Published: May 2006

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

SummaryTransport of Cl− into cells of Char a corallina is greatly reduced when the cells are bathed in solutions of high pH. Under these conditions there is no difference between the influx in the light and in the dark. When cells are pretreated at high pH in light and then transferred to low pH and darkness, the rate of Cl− transport is greatly stimulated. This is the reverse of the normal effect when cells are transferred from light to dark. An increase in Cl− transport is also produced by pretreatment of cells at high pH in the dark. Addition of (NH4)2SO4 to the solutions produces even larger stimulations of Cl− transport under these conditions.The results suggest that CI− transport is controlled by the pH gradient across the plasma‐lemma, and that the pH gradient (normally produced by metabolic processes) is altered by the treatments described above. The results are consistent with the hypothesis that charge transfer across the plasmalemma results in H+ extrusion, and that Cl− is taken up in exchange for OH−. Other possible effects of pH changes on ion transport are also considered.
LEAF ABSCISSION IN COLEUS
Authors: HALLIDAY M. B. W. , WANGERMANN ELISABETH 
Published: May 2006

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

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

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

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

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

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

SummaryThe fine structure of the non‐infected (outer) region of a soybean root nodule is described. Apart from vascular traces, the cells are mainly vacuolate, with active cytoplasm. They are connected with each other and to cells of the infected region by numerous plasmodesmata. A network of air spaces runs throughout the nodule. Atmospherically applied water stress affects the outer cells of the nodule more quickly and more severely than the inner cells. In any region, vacuolate cells are more susceptible to stress than nonvacuolate cells. Loss of about 30% of their fresh weight results in breakdown of the cytoplasm into approximately spherical sub‐units, some of which are coated with ribosomes. Organelles such as nuclei and mitochondria retain their structure longer than the rest of the cytoplasm. More severe stress is needed to affect infected and pericycle cells, which are nonvacuolate.It is concluded from the fine structure of stressed and unstressed nodules that the vacuolate cells of the cortex play an integral part in the nitrogen‐fixing activities of the whole nodule.
DESICCATION INJURY IN MOSSES
Authors: STEWART G. R. , LEE J. A. 
Published: May 2006

SummaryThe effects of desiccation on the activity of several enzymes from Acrocladium cuspidatum were investigated; with the exception of glyceraldehyde 3‐phosphate dehydrogenase prolonged desiccation had little effect on the enzymes studied. The response of the NADP+‐dependent glyceraldehyde 3‐phosphate dehydrogenase to sulphydryl compounds changes during desiccation; when extracted from desiccated shoots it showed a six to twenty times stimulation of activity in the presence of reduced glutathione, that from fresh shoots showed only a twofold stimulation. The effects of glutathione on the enzyme's activity were examined in species with varying resistance to desiccation. It is suggested that the decline in photosynthesis during desiccation may be explained in part by the oxidation of sulphydryl residues essential for the catalytic activity of the NADP+‐glyceraldehyde 3‐phosphate dehydrogenase.