bluuebunny/crossref_metadata_2025 huggingface dataset:
FACTORS CONDITIONING DEVELOPMENT OF SEXUAL AND APOGAMOUS RACES OF PHASCUM CUSPIDATUM HEDW.
Authors: HUGHES J. G.
Published: May 2006

Summary

The effect of the intensity and composition of daylight and fluorescent light on vegetative growth and reproduction of the haploid sexual and diploid apogamous races of Phascum cuspidatum Hedw. has been investigated, using leaf number as an index of vegetative growth. Sown together in daylight at different seasons, both races proved to be summer annuals. In both races it was shown that leaf number is not conditioned by light intensity and that vegetative growth was prolonged in fluorescent light. The frequency of the vegetative development of sporangia in the diploid apogamous race was found to be low in daylight. Reduction in leaf number under coloured filters was not accompanied by increased development of sporangia; but under yellow‐filtered fluorescent light the frequency of sporangial development is greatly increased.

The low fertility of the diploid apogamous race of this and other species is discussed, and it is proposed that alternation of generations in mosses is based in part on a mechanism which ensures that neither sporophyte nor gametophyte alone can form sporangia.
THE OCCURRENCE OF SOUTHERN, STEPPE AND HALOPHYTE ELEMENTS IN WEICHSELIAN (LAST‐GLACIAL) FLORAS FROM SOUTHERN BRITAIN
Authors: BELL FRANCES G.
Published: May 2006

Summary

The southern element in Full‐glacial floras is thought to be primary except for a small number of derived species. The presence of southern plants in conjunction with northern and montane species is explained as the result of the special climate and advantageous open‐ground conditions of the Full‐glacial. A physiognomically steppe‐like vegetation may be recognized as part of the assemblages. The presence of halophytes is related to saline soils, probably developed over permafrost.
AUXIN, ETHYLENE AND KINETIN IN A CARRIER‐PROTEIN MODEL SYSTEM FOR THE POLAR TRANSPORT OF AUXINS IN PETIOLE SEGMENTS OF PHASEOLUS VULGARIS
Authors: OSBORNE DAPHNE J. , MULLINS MICHAEL G.
Published: May 2006

Summary

The capacity of bean petiole segments to transport 14C‐indole‐3‐acetic acid decreases to approximately half within 5 hours of excision and to less than one‐tenth after 10 hours. Exposure of the segments to ethylene enhances this loss in capacity, but pretreatment with an auxin completely protects the transport system from both the natural and ethylene‐induced fall. A decrease in synthesis of protein accompanies the natural loss of transport capacity, and treatments with auxin or kinetin which retain synthesis also retain transport. Only auxin treatments protect against the effects of ethylene. To correlate these results, a theoretical model for polar transport is developed in which it is proposed that auxin molecules are bound to a specific carrier protein sited at the plasmalemma. Transport capacity could be regulated by the rate of synthesis of the carrier protein, with a secondary regulation of the activity of the carrier by the binding of either auxin or ethylene molecules to specific sites on the protein.
GIBBERELLIN‐STIMULATED NUCLEIC ACID METABOLISM IN THE COTYLEDONS AND EMBRYONIC AXES OF CORYLUS AVELLANA (L.) SEEDS
Authors: PINFIELD N. J. , STOBART A. K.
Published: May 2006

Summary

Gibberellin treatment of intact hazel seeds stimulated 14C incorporation from [8‐14C] adenine into RNA and DNA of both cotyledons and embryonic axes compared with the corresponding water controls. This stimulation was apparent in the embryonic axes after only 12 hours treatment, but was not detected in the cotyledons until after 48 hours gibberellin treatment. The 14C incorporation into nucleic acids of cotyledons isolated from air‐dry seeds was also shown to be stimulated by gibbereliin treatment. It is concluded that the first effect of gibberellin on the intact hazel seed is on the embryonic axis, but that a second response occurs in the cotyledons, which is to some extent independent of the embryonic axis. It is suggested that the results for the cotyledons represent gibberellin‐stimulated nucleic acid synthesis, including the formation of specific mRNA required for the production of enzymes concerned with reserve lipid mobilization.
A STUDY OF THE ROOT SYSTEM OF BARLEY
Authors: HACKETT C.
Published: May 2006

Summary

Relationships between the number, length, surface area, volume and dry weight of the root members of two varieties of barley (Hordeum vulgare L. vars Maris Badger and Proctor) were examined over the first 4 weeks of growth in water culture. Plants given a complete nutrient supply were compared with plants deficient in potassium or phosphorus.

Although there were large effects of age, variety and nutrition on all the root dimensions, relationships between the dimensions varied comparatively little. In consequence, effects of age, variety and nutrition on the rate of nutrient uptake per unit of root were qualitatively similar whichever dimension of the root system was considered.

It is shown by reference to descriptions of root systems published elsewhere that constancy in relationships between root dimensions occurs in solid media also. This property of root systems, which appears to result quite straightforwardly from the contrasting morphological characteristics of root axes and laterals, may help to simplify some aspects of the study of nutrient absorption by roots.
STUDIES ON THE METABOLISM OF EUCALYPTUS OBLIQUA
Authors: CARRODUS B. B.
Published: May 2006

Summary

Both ammonia and nitrate are available forms of nitrogen for uninfected roots of Eucalyptus obliqua. Glutamine and glutamate increase in quantity when ammonia is absorbed from solution. The effect of temperature on uptake of ammonia is complex. External sources of carbon skeletons do not stimulate the uptake of ammonia from solution. Uptake of ammonia is insensitive to the presence of DNP and KCN, although glycolysis is inhibited by these compounds.
SIMPLE AUTOMATIC SCANNING AND RECORDING SYSTEM FOR THE MEASUREMENT OF WATER POTENTIALS WITH DROPLET THERMOCOUPLE PSYCHROMETERS
Authors: BARRS H. D.
Published: May 2006

Summary

A simple, automatic scanning and recording system designed specifically to receive the output from up to twenty‐five droplet thermocouple psychrometers is described. Essential components are a solenoid‐operated, low‐level switch, a high grade preamplifier and a potentiometric chart recorder capable of remote operation. Chart traces show noise level is low even on a 10 μV range. Provision is made to correct psychrometer readings for temperature effects due to heat of respiration. Statistical comparison of psychrometer calibrations obtained with this system and with manual switching into a reflecting galvanometer show the former system is at least as accurate as the latter. Parallel leaf water potential measurements made with the two systems agreed closely.
A NOTE ON THE MEASUREMENT OF STOMATAL APERTURE
Authors: LESHEM Y. , THAINE R.
Published: May 2006

Summary

Cellulose acetate replicas were made from silicone rubber impressions of the abaxial surfaces of perennial ryegrass leaves. Apertures between 1 μ and 4 μ (mean 2 μ) were measured in replicas from leaves which had been exposed to conditions expected to close the stomata. This discrepancy is explained by observations of the ventral walls of guard cells in transverse sections of stomata, and by Araldite impressions of the cut ends of ryegrass leaves. These show that when a stoma is closed the ventral walls make contact below the paradermal walls of the guard cells and consequently a small depression is left between the cells. These depressions are similar in width to the apparent apertures in the cellulose replicas which may be wrongly interpreted as slightly open stomata. In some species the silicone impression method is incapable of giving an accurate measurement of stomatal aperture. Consequently, in attempts to relate such measurements to stomatal function or rate of transpiration it should be established that small apertures shown in cellulose acetate replicas are not the result of depressions between the external surfaces of guard cells in closed stomata.
EFFECT OF TEMPERATURE DURING GROWTH ON LEAF ANATOMY AND SUBSEQUENT LIGHT‐SATURATED PHOTOSYNTHESIS AMONG CONTRASTING LOLIUM GENOTYPES
Authors: WILSON D. , COOPER J. P.
Published: May 2006

Summary

The effect of temperature during growth of ten Lolium genotypes from contrasting populations on subsequent light‐saturated photosynthesis and on leaf mesophyll and stomatal characteristics was examined. Most genotypes grown at 9° and 15° C had faster rates of photosynthesis at 15° than those grown at 21° C. Photosynthetic activity at 21° C was also greater when plants were grown at 15° Compared with 21° C. This temperature effect was not associated with changes in the observed mesophyll or stomatal characteristics. Plants grown at 21° usually had smaller mesophyll cells than those grown at 15° C. Among plants grown at 9° and 15° C, and among those grown at 21° C, light‐saturated photosynthesis was negatively correlated with mesophyll cell size.
NOTE ON THE CYTOLOGY OF AN F1 HYBRID BETWEEN SILENE DICLINIS (LAG.) M. LAINZ AND S. HEUFFELII SÓO
Authors: MORISSET PIERRE , BOZMAN GABRIELLE V.
Published: May 2006

Summary

This paper describes the meiotic cytology of an artificial F1 hybrid (2n= 24) between Silene diclinis (Lag.) M. Lainz (2n= 24) from Spain and S. heuffelii Sóo (2n= 24) from Rumania.

The hybrid was intermediate between the two parents in most of its morphological characters. It had a pollen fertility of 31%. At meiosis, it formed bivalents except for an association of three or four chromosomes which revealed the presence of an heterozygous reciprocal translocation. The extent of pairing showed that the chromosomes of S. diclinis are homologous with those of S. heuffelii. Anaphase bridges occurred at both meiotic divisions; this phenomenon is discussed and interpreted as the result of spontaneous chromosome breakage. This breakage is tentatively explained as a consequence of minute structural differences between paired chromosomes.

It is suggested that spontaneous chromosome breakage at meiosis may be a common but overlooked effect of diclinis in plants.
LIME CHLOROSIS IN SEEDLING ESTABLISHMENT ON CALCAREOUS SOILS
Authors: HUTCHINSON T. C.
Published: May 2006

Summary

A comparison has been made amongst a number of species as to the ability of green and chlorotic foliage to fully reverse induced leaf water‐deficits. In all cases it was found that chlorosis conferred a reduction in the ability of the affected leaf to resaturate, compared with green leaves of the same species. Three distinct patterns of behaviour of chlorotic leaves were found in this respect. Permanent damage was caused by leaf water‐deficits as low as 10% in some species, whilst chlorotic leaves of others could withstand 60% water‐deficits before irreversible damage was detected. Green foliage of chlorosis‐resistant species were able to tolerate deficits of from 60 to 85% before resaturation ability was impaired. The ecological implications of these findings are considered, with respect to the establishment and survival of chlorosis‐resistant and susceptible seedlings on calcareous soils subject to periodic droughts.
DIFFERENTIATION OF RESPONSE TO CALCIUM WITHIN THE SPECIES FESTUCA OVINA L., USING ETHYLENEDIAMINE TETRAACETIC ACID
Authors: URQUHART C.
Published: May 2006

Summary

A method was described by which differentiation of response to calcium within plant species could be rapidly detected. Festuca ovina tillers were used as the experimental material, and the method consisted of measuring root extension‐growth in 10−3m disodium ethylenediamine tetraacetic acid (Na2‐EDTA). A significant correlation (r=−0.86) was obtained between root growth in Na2‐EDTA and the calcium content of soil from the plants' natural habitats. The action of Na2‐EDTA on plant tissue was discussed and it was concluded that calcium deficiency was induced.
CHANGE OF APPARENT WEIGHT OF PLANT TISSUES IN SOLUTIONS
Authors: BLYTH D. F. , BRIGGS G. E.
Published: May 2006

Summary

The volume in carrot tissue apparently not penetrated, AOV, by a plasmolysing solution of cane sugar, potassium nitrate, potassium chloride or calcium chloride is a linear function of the reciprocal of the osmotic pressure of the solution over the range of the concentration used. This AOV, which includes the solids in the cell walls, is practically independent of the nature of the electrolytes but appears to be greater for cane sugar. There is no clear evidence for any active transport of water into the vacuoles of the cells.
POLLINATION IN FICUS RELIGIOSA L. AS CONNECTED WITH THE STRUCTURE AND MODE OF ACTION OF THE POLLEN POCKETS OF BLASTOPHAGA QUADRATICEPS MAYR
Authors: GALIL J. , SNITZER‐PASTERNAK YEHUDIT
Published: May 2006

Summary

Blastophaga quadraticeps, the legitimate pollinator of Ficus religiosa, possesses two thoracic pockets in which pollen is stored for subsequent introduction into the young figs. In nature, pocket‐loading takes place in the nearly ripe fig at the male phase. Impregnated female wasps leave their galls, approach the ripe anthers, and load the pockets by very swift movements of the forelegs. Then they leave the fig via narrow channels bored by the males. Upon entering young receptive figs, the female wasps begin oviposition, during which pocket‐emptying and pollination take place.

The pollen pocket of Blastophaga quadraticeps is a complex and highly specialized structure rather than a mere depression or fold of the body wall. Each pocket is a small saccular organ with well‐defined openings. The two marginal exits are very narrow. The third opening is the largest. It gaps widely when the adjacent sternite is touched parallel to the inner border of the pocket and closes shortly afterwards.

Loading of the pocket is achieved by two separate actions, which follow each other: The legs transfer the pollen to the thorax and then the pollen is absorbed by some inherent mechanism of the pocket itself, through the wide entrance which opens at the touch of the legs. A technique for artificial loading with various materials (spores, iron particles, etc.) affords good means of studying the inner structure of the pocket.

As yet no satisfactory explanation can be offered as to which forces are responsible for the opening of the pocket and the mechanism of pollen absorption.
SITES OF EXUDATION OF14C‐LABELLED COMPOUNDS FROM WHEAT ROOTS
Authors: McDOUGALL BARBARA M. , ROVIRA A. D.
Published: May 2006

Summary

The combination of autoradiography and a filter paper ‘sandwich’technique using wheat plants labelled with14C has shown that roots of wheat exude two types of compounds, viz. (a) non‐diffusible material released from the apices of both primary and lateral roots and (b) diffusible material released along the whole length of the roots. The high amount of non‐diffusible material compared with diffusible material suggests that the former may be more significant than previously anticipated in relation to root functions and microorganisms in the rhizosphere.
STUDIES ON THE LIGNOTUBERS OF EUCALYPTUS OBLIQUA L'HERI.
Authors: BLAKE T. J. , CARRODUS B. B.
Published: May 2006

Summary

A growth inhibiting substance has been extracted from mature tissues of Eucalyptus obliqua in which apical dominance occurs, but is absent in juvenile tissues of very young seedlings which show weak apical dominance. Sprouting from lignotubers in decapitated E. obliqua seedlings is correlated with a reduction in the level of inhibitory properties. Reapplied inhibitory substance, but not abscisic acid, reduced sprouting. The inhibitory substance has been partially purified and some of its properties tested, suggesting that it is not abscisic acid.
FURTHER REMARKS ON THE ‘LEAFLET THEORY’ OF THE OVULE
Authors: GUEDES M. , DUPUY P.
Published: May 2006

Summary

The study of teratological flowers of Coriaria ruscifolia L. (Coriariaceae) gives evidence which supports the ‘leaflet theory’ (foliolar theory) of the ovule. The latter appears to be homologous with a leaflet of the carpellary blade, as put forward by certain previous authors and more recently confirmed by the present writers. The fairly complete series of terata here studied support the somewhat theoretical final view of Čelakovský, that the nucellus is fundamentally terminal on the ovular leaflet. The ovule considered has only one integument; its significance may be easily determined. The appearance of an extra nucellus upon an ovular leaflet already provided with the usual nucellus is also described and interpreted.
THE TROPICAL FOREST AND SPORNE'S ADVANCEMENT INDEX
Authors: WOOD D.
Published: May 2006

Sporne found certain characters of dicotyledonous plants were correlated and also well represented in fossil Tertiary floras. He showed that this correlation could be explained by assuming the characters to be primitive and proposed an advancement index based on the proportion of these characters found in each family. By measuring the average advancement index of vegetation from different habitats and of the London Clay Flora, which is the Tertiary flora taken by Sporne as an ancestral standard, it is shown here that there is a clear relationship between the supposed primitive characters and woody habitats. As an alternative to Sporne's hypothesis that the correlated characters are primitive it is suggested that the correlations are a result of the adaptive nature of the characters, the supposedly primitive characters being adaptive to the woody habit, the supposedly advanced characters being adaptive to the herbaceous habit.
METABOLIC CHANGES AND SENESCENCE IN CULTURED PEA ROOT TISSUE
Authors: HABESHAW D. , HEYES J. K.
Published: May 2006

Summary

The changes occurring during the maturation, senescence and death of cells in pea roots grown in sterile culture were followed for 30 days after growth by cell extension had ceased. Gross analysis of DNA content and various enzyme activities, analyses of several nitrogen fractions showed that complex changes occurred between the cessation of cell expansion and the death of the root cells. Although the tissue analysed was not homogeneous in cell type, histochemical and anatomical investigations of the distribution and number of nuclei within the root, DNA content of these nuclei and acid phosphatase distribution enabled gross changes to be correlated with changes in the cells of various regions within the root cortex.

From the changes observed in the root segment as a whole, two types of process were associated with changes in the cells of the root cortex. The first was a rise in the DNA and protein content of certain areas of the root cortex. It is suggested that this is a consequence of the interaction between the older and younger regions of the root and is not a general characteristic of senescence in cells. The majority of the changes observed were, in general, very similar to those already found in other higher plant systems such as ageing fruits and starving leaves, and were associated with the senescence and death of cortical cells.
QUINONES AND α‐TOCOPHEROL IN GREENING CALLUS CULTURES OF KALANCHOË CRENATA
Authors: THOMAS D. R. , STOBART A. K.
Published: May 2006

Summary

Dark‐grown Kalanchoë callus tissue subcultured into 16‐hour days produce chlorophyll only after several generations. Plastoquinone: chlorophyll molar ratios in extracts from green callus indicate that the level of plastoquinone is somewhat lower than in leaf tissue. This was confirmed in purified chloroplast preparations from callus and leaves. Hill reaction activity was lower in green callus chloroplasts than in those from mature leaves.

α‐Tocopherol, although present in non‐green callus, increased with chlorophyll synthesis. D, L[214C]‐mevalonate feeding experiments seem to indicate active sites of α‐tocopherol synthesis other than the mature chloroplast.

Changes in ubiquinone and α‐tocopherol content were observed during the growth of dark‐grown callus. Such changes may be due to an increase in mitochondrial populations and to the onset of senescence.
CARPEL PELTATION AND SYNCARPY IN CORIARIA RUSCIFOLIA L.
Authors: Guédès M.
Published: May 2006

Summary

The gynoecium of Coriaria ruscifolia is made up of five carpels joined in their lower parts. It is interpreted as syncarpous, not apocarpous, and is considered to represent five peltate carpels free above a very short ventral split and joined narrowly below the split along their median parts, as by so many longitudinal strips. The free part of each carpel consists of the unifacial style (without ventral split) and its short junction with the associate part of the carpel at the level of the ventral split. The joined parts are the ascidiate regions of the carpels with their solid basal union.

The study of phyllodic gynoecia enables us to discover the homologies between carpel and leaf in Coriaria and to explain more clearly the peltation concept, which appears to have been misunderstood by English‐speaking botanists.
A SIMPLE METHOD FOR THE DETERMINATION OF CONDUIT LENGTH AND DISTRIBUTION IN STEMS
Authors: MILBURN J. A. , COVEY‐CRUMP P. A. K.
Published: May 2006

Summary

A simple method for the determination of the lengths and distribution of conduits in plant stems and petioles is described using graphical and algebraic methods. The method proposed by Skene and Balodis (1968) is shown to give improper probability distributions. The data presented by these workers for Eucalyptus‘vessels’ is reinterpreted, giving different results, so far as the accuracy of the data will show. The need for great accuracy in determination of conduit lengths from injection profiles is emphasized.
BIOLOGICAL EFFECTS OF SURFACTANTS
Authors: HEALEY PATRICK L. , ERNST ROBERT , ARDITTI JOSEPH
Published: May 2006

Summary

Effects of a nonionic surface active agent (lauroyl/myristoyl di (2‐hydroxyethyl) amide) and one anionic surfactant (sodium (linear) dodecylbenzene sulphonate) on cell ultrastructure were determined using Phalaenopsis protocorms. There were no observable effects after 5 days exposure to 1000 ppm of the nonionic. However, the anionic caused severe damage. Drastic changes in morphology, loss of membranes, swelling of thylakoids and appearance of dense osmophilic granules were evident in chloroplasts. Other effects include disintegration of polysomes into monosomes; swelling of mitochondria; dispersion of chromatin in the nucleus; appearance of unidentified vesicles in the cytoplasm and plasmolysis of cells. These ultra‐structural changes can be attributed to the possible emulsification of membrane lipids as well as precipitation and dispersion of cellular proteins.
THE BARNWELL STATION ARCTIC FLORA: A REAPPRAISAL OF SOME PLANT IDENTIFICATIONS
Authors: BELL FRANCES G. , DICKSON CAMILLA A.
Published: May 2006

Summary

The plant macrofossils described by Chandler from the classic site of the Barnwell Station beds of Cambridge have been re‐examined. A number of identifications, including all those of strictly Alpine and of extinct species, have been rejected. Some new finds have been added to the list. The changes made do not substantially alter Chandler's ecological interpretation of the flora.
SCANNING ELECTRON MICROSCOPY OF TILIA POLLEN
Authors: CHAMBERS T. C. , GODWIN H.
Published: May 2006

Summary

A method is described for studying simultaneously the intact and the sectional view of pollen walls. Scanning electron micrographs of such fractured pollen grains of Tilia platypliyllos Scop., T. cordata Mill, and the putative hybrid T.×vulgaris Hayne assist in the interpretation of a number of observations made by light microscopy on the differences between these taxa and confirm and amplify our interpretation of T. platyphyllos made from early transmission electron microscopy of embedded and sectioned grains. The new information makes imperative the distinction between two types of exine reticulation, one bacula‐bordered and the other baculacentric (the Tilia type).
FOSSIL POLLEN OF TILIA FROM THE EAST ANGLIAN FENLAND
Authors: MITTRE VISHNU
Published: May 2006

Summary

Analysis of a large number of fossil pollen grains of Tilia from the East Anglian Fenland, led to examination of the characters that might be employed to separate T. platyphyllos from T. cordata. Certain characters were discarded but mesh structure and size in surface reticulation, characters since accepted by other authors, were regarded as satisfactory and made the basis for classifying fossil grains. The results indicated native British status for both species of lime from pollen‐zone Vila onwards, with T. cordata much the commoner, and very high relative frequencies of Tilia pollen in zone Vila and diminution zone by zone thereafter to levels below 0.5% of total tree pollen.
CARBOHYDRATE METABOLISM IN CHAETOMIUM GLOBOSUM
Authors: ADOMAKO D. , KAYE A. G. , LEWIS D. H.
Published: May 2006

Summary

Specific ATP‐phosphotransferases for glucose, fructose and mannose, and glucosephosphate and mannosephosphate isomerases have been extracted from Chaetomium globosum. The fructokinase is stabilized by potassium whereas the glucokinase is activated by this cation, but is, otherwise, more stable than the former. The less‐studied mannokinase showed no requirement for potassium. The inhibition of the fructokinase by glucose and mannose, and of the glucokinase by mannose are detailed, together with pH optima, Km values and other properties of the enzymes. The level of glucosephosphate isomerase was found to be higher in fructose‐grown than in glucose‐grown mycelium. The role of the enzyme systems in the absorption and utilization of exogenous hexoses is discussed.
THE METABOLISM AND RADIAL MOVEMENT OF GROWTH REGULATORS AND HERBICIDES IN WILLOW STEMS
Authors: FIELD R. J. , PEEL A. J.
Published: May 2006

Summary

The metabolism of IAA, NAA, MCPA, 2.4‐D, 2.4.5‐T, MH, TCA and paraquat was investigated in bark strips and stem segments. Both IAA and NAA were extensively metabolized (up to 80% and 40% respectively of the applied compound was converted into other compounds in 24 hours). The principal metabolite of IAA appears to be IAA asp. 2.4‐D, paraquat, TCA and MH were metabolized to a small extent (maximum of 2% in 24 hours), whilst no metabolites were detected from MCPA‐i‐14C and 2.4.5‐T‐I‐14C. The decarboxylation rate of I‐14C‐labelled IAA, NAA and the phenoxyacetic acids was low, IAA having the greatest rate (maximum of 4% of the total activity applied given off as 14CO2 during 48 hours).

Investigation of the relative mobilities of the non‐metabolized compounds from xylem to phloem, and from phloem to the xylem stream, revealed that MH, MCPA and 2.4‐D were the most mobile in both directions, TCA and paraquat the least mobile. A comparison of the mobilities of IAA and its metabolites, and NAA and its metabolites, centrifugally and centripetally across the wood was also made. NAA appears more mobile than its metabolites in both directions. In contrast, IAA seems to be more mobile than its metabolites only in a centripetal direction, the converse being found in centrifugal movement.
THE EMPETRUM POLLEN RECORD AS A CLIMATIC INDICATOR IN THE LATE WEICHSELIAN AND EARLY FLANDRIAN OF THE BRITISH ISLES
Authors: BROWN A. P.
Published: May 2006

Summary

The climatic patterns, in terms of relative oceanicity and continentality, of the British Isles, for the Late Weichselian and early Flandrian periods, may be derived from palynological records of Empetrum L. Climatic fluctuations in south‐western England in these periods differ dramatically from those of other western areas of the British Isles. A possible reason for the differences is the position of south‐western England in the boundary zone of the activity of the Atlantic and continental European air masses and the consequent increased sensitivity to movements of this boundary zone compared with other regions of the British Isles.
PLANT MICROFOSSILS FROM TERTIARY DEPOSITS OF THE ISLE OF WIGHT
Authors: MACHIN JANE
Published: May 2006

Summary

Pollen and spores have been examined from deposits of presumed Oligocene age occurring in the northern half of the Isle of Wight (southern England). A brief review of the geology and method of investigation is given. The plant microfossils identified are listed and it is shown that they represent a predominantly subtropical swamp vegetation comparable with the more calcareous areas of modern south‐east U.S.A., with an additional strong affinity to the modern swamp and more dry ground flora of subtropical/warm temperate south‐east Asia. In the highest beds investigated an increase in more temperate genera, qualitatively and quantitatively, is found. Comparisons are made with southern English Tertiary macrofossil floras, especially the Bembridge flora. It is shown that some separation within this series of beds can be made on the basis of pollen and spore assemblages and that it is possible to correlate one of these assemblage changes, namely that between the top of the Bembridge Beds and the base of the Hamstead Beds, with a boundary denned on pollen/spore change in the German Tertiary.
A SECTORIAL GREEN‐YELLOW LEAF CHIMERA IN THE POTATO
Authors: HOWARD H. W.
Published: May 2006

Summary

The distribution of green and yellow parts in the foliage of a mericlinal chimera suggested that there are six initial cells for layer 2 (L2) in potatoes. The L2 of leaves traces back to only two cells, resulting in some leaves which had green leaflets on one side and yellow on the other; other leaves were all green or all yellow. Layer 3 (L3) showed a behaviour similar to L2 in one year but in the following year a more complex pattern of sectors, leaves having light green as well as normal green and yellow parts, was found suggesting that cell divisions in L3 do not follow so regular a plan as do those in L2.
THE INFLUENCE OF TEMPERATURE ON THE PROCESS OF WATER UPTAKE BY DETACHED LEAVES AND LEAF DISCS
Authors: MILBURN J. A. , WEATHERLEY P. E.
Published: May 2006

Summary

When a water deficit was induced in a mature fully turgid leaf of Ricinus communis L. the tissues could completely regain full turgidity by absorption of water at around 1° C. This was true of large water deficits (40%) which greatly exceeded the cell wall volume (12%). This uptake therefore included movement into the protoplasts and was not restricted to the cell walls alone as had been previously supposed (Weatherley, 1963).

However, resaturation of leaf tissues taken from plants which had suffered from drought for more prolonged periods, could be separated into two fractions. An uptake at 1° C was attributable as before to recovery of turgor; an extra uptake at 25° C seemed to be a growth phenomenon inhibited at the lower temperature. This represented a rapid cell expansion following a period of growth arrestment due to water stress.

The implications of these findings for the measurement of relative water content are discussed.
α‐N‐MALONYL‐D‐TRYPTOPHAN IN SEEDLING WHEAT ROOTS
Authors: ELLIOTT M. C.
Published: May 2006

Summary

The most prominent Ehrlich reactor present in the acid ethyl acetate fraction of extracts of seedling wheat roots is identified as α‐N‐malonyl‐D‐tryptophan. This compound is synthesized by roots fed with 14C‐labelled D‐tryptophan. The compound was without a significant effect on the growth of cultured excised wheat roots over the range 3.45 × 10−12 to 3.45 × 10−6 M.
GROWTH OF ANDROPOGON SCOPARIUS (LITTLE BLUESTEM)IN PHOSPHORUS DEFICIENT SOILS
Authors: WUENSCHER M. L. , GERLOFF G. C.
Published: May 2006

Summary

The capacity of a native prairie grass, Andropogon scoparius (little bluestem), to grow successfully in an extremely P deficient soil of central Wisconsin was investigated. This grass is invading ridges, but not depressions, of abandoned fields of Poa pratensis (Kentucky bluegrass). Ridge soils contain less available phosphorus than depression soils. The yield and P absorption of Andropogon and Poa were compared when grown in the low P soil and in nutrient sand culture at various levels of added P. The former consistently outyielded the latter at all levels of P in both soil and sand cultures. Andropogon, which exhibited less yield response to increasing P supply than did Poa when grown in the P deficient ridge soil, was able to absorb much more P from ridge soil. It also utilized absorbed P more efficiently in producing plant dry matter when grown under extreme P stress in sand culture. The critical P concentration for Andropogon was lower than for Poa.
POST‐POLLINATION PHENOMENA IN ORCHID FLOWERS
Authors: ARDITTI JOSEPH , JEFFREY DAVID C. , FLICK BRIGITTA H.
Published: May 2006

Summary

NAA, in concentrations exceeding 0.01 μg/flower, initiates post‐pollination phenomena in Cymbidium (Orchidaceae) flowers similar to those brought on by pollination. These include stigmatic closure, swelling and loss of curvature of the column, wilting of the perianth, deformation of the calli, and anthocyanin production. Applications of relatively high concentrations of GA3 induce post‐pollination effects which, except for anthocyanin production, are less intense than those brought about by auxin. Kinetin does not induce post‐pollination phenomena, but in concentrations of 10 μg and 100 μg/flower causes slight stigmatic closure, and in some combinations with NAA it inhibits wilting. Stigmatic closure, loss of column curvature and changes in calli, all of them NAA induced, cannot be prevented by simultaneous applications of kinetin, GA3 or ABA. Some combinations of NAA and GA3 lowered anthocyanin content relative to separate treatments with either hormone. Flowers treated with GA3 plus kinetin wilted slightly in most cases, but columns did not swell and retained their curvature; calli did not develop colour and anthocyanin content was generally equal to that of flowers given only kinetin. GA3 and ABA when applied together brought on symtoms which were similar to those caused by ABA only but anthocyanin content was lower than in flowers treated with either hormone alone. This is also true for ABA‐kinetin mixtures, but intensities of the effects are different and, with certain concentration ratios, stigmatic closure occurs. The phenomena are discussed relative to fruit‐set, seed formation, anthocyanin production, senescence, orchid biology and the possible mode of action of each hormone.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: IIOLLIGAN P. M. , JENNINGS D. H.
Published: May 2006

Summary

Starved cultures of Dendryphiella salina were transferred to defined liquid media containing different carbon sources. Mannitol was accumulated in the mycelium in all except arabitol media. By contrast, the rapidly utilized carbon sources gave high to moderate yields of arabitol whereas, with mannitol or carbon sources that were less readily assimilated, there was little or no increase in the level of pentitol.

Variation of the nitrogen source in media containing glucose had a significant effect on the accumulation of arabitol but not of mannitol. The results indicate that the quantity of arabitol synthesized is related to the activity of the pentose‐phosphate pathway which in turn is influenced by the form of nitrogen supplied to the fungus.

The activities of certain enzymes were determined and these are discussed in relation to Polyol synthesis.
FACTORS CONTROLLING STOLON DEVELOPMENT IN THE POTATO PLANT
Authors: KUMAR D. , WAREING P. F.
Published: May 2006

Summary

The development of the basal axillary shoots of Solanum andigena as stolons is dependent upon their being subject to apical dominance. Normally, stolons develop only from axillaries located below the soil surface and it is shown that darkness and a moist atmosphere favour stolon emergence. However, all axillaries subject to apical dominance are potentially capable of emerging as stolons, as shown by the fact that maintaining the axillaries of aerial shoots under conditions of darkness and humidity by ‘aerial layering’ results in their emergence as stolons. In rooted stem cuttings, basal axillaries not subject to apical dominance grow as leafy shoots, but if the roots are removed they develop as stolons. Thus, axillary shoots not subject to apical dominance are converted from stolons into leafy shoots by some influence of the roots.

Axillaries in the aerial part of the shoot may be stimulated to grow out as stolons by applying gibberellic acid to the stem. The role of indole acetic acid (IAA) in stolon development appears to be related to its effects on apical dominance. It is shown that application of the cytokinins, kinetin and benzylamino purine to the tips of stolons (both natural and experimentally induced) causes them to develop into upwardly directed leafy shoots. The development of an axillary into a leafy shoot or a stolon can be experimentally regulated by manipulation of the levels of applied gibberellin, IAA and cytokinin, stolon development requiring high gibberellin and low cytokinin levels. It is suggested that normal stolon development is regulated by interaction between endogenous hormones, and it is postulated that the apical dominance necessary for stolon development involves the monopolization of cytokinins produced in the roots by the main apex, so that only low cytokinin levels are available to the axillary shoots. The effect of darkness on stolon emergence may be mediated through increased endogenous gibberellin levels.
EFFECTS OF COTYLEDONS, LEAVES AND STEM APEX ON EARLY PERIDERM DEVELOPMENT IN FRAXINUS PENNSYLVANICA SEEDLINGS
Authors: BORGER G. A. , KOZLOWSKI T. T.
Published: May 2006

Summary

Seedlings of Fraxinus pennsylvanica were grown from seed and subjected to various treatments which removed leaves, cotyledons, stem apices or buds at periods up to 35 days after cotyledon emergence. In addition, portions of the stems of several seedlings were kept in darkness during the experiments. Periderm did not form in seedlings from which all foliage was removed as it emerged. Seedlings with any foliage developed periderm, but periderm‐stimulatory substances were not released from foliage until it reached a certain stage of development. Both cotyledons and leaves exported periderm‐stimulatory substances, but leaves appeared to export more. Substances produced in the apical meristem or actively growing buds had no effect on phellogen formation and activity, but appeared to regulate the kind of periderm cells produced, their differentiation, and their anti‐clinical divisions. The stimuli for periderm formation and subsequent development were strongly basipetal and only weakly acropetal. However, darkening the stem below the foliage appeared to moderate the polar transport of periderm‐stimulatory substances. Foliar products increased wound‐periderm formation and were essential for wound‐stimulated formation of normal periderm.
EFFECT OF SELECTION FOR STOMATAL Length AND FREQUENCY ON THEORETICAL STOMATAL RESISTANCE TO DIFFUSION IN LOLIUM PERENNE L.
Authors: WILSON D.
Published: May 2006

Summary

A population of Lolium perenne L.‘Grasslands Ruanui’ grown in a controlled environment, exhibited much phenotypic variation in stomatal resistance to diffusion (rs) as calculated from stomatal dimensions and frequency. Direct selection for rs was comparatively ineffective and the heritability was low (about 0.22) because of a negative correlation between stomatal length and stomatal frequency. However, selection for frequent and infrequent stomata resulted in a marked correlated genetic shift in the F1 generation toward respectively low and high rs at a given pore opening. Further selection for stomatal frequency did not affect rs and response by frequency itself was much reduced in the F2. Selection for stomatal length had no effect on rsin the F1 but there was a slight reduction in rs in the F2 long stomata selection.
A COMPARISON OF THE UPTAKE OF NITRATE, CHLORIDE AND PHOSPHATE BY EXCISED BEECH MYCORRHIZAS
Authors: SMITH F. A.
Published: May 2006

Summary

Rates of uptake of nitrate and chloride by excised beech mycorrhizas are much smaller than those of phosphate. With solutions containing 1 mM KCl or KH2PO4, about 45% of the chloride absorbed is found in the fungal sheath, compared with about 85% of the phosphate. The uptake of both chloride and phosphate is increased when the roots are cut into thin slices. The results show that direct uptake of chloride and phosphate into the host cells is limited by diffusion through the sheath, but in the case of chloride the diffusion gradient is not greatly affected by uptake into the sheath. It is suggested that, in the absence of nitrate reduction by the fungus, the processes controlling nitrate uptake and chloride uptake are likely to be similar. Effects of ageing excised mycorrhizas in dilute CaSO4 solutions are discussed.
THE INFLUENCE OF A MATURE LEAF ON XYLEM DIFFERENTIATION
Authors: HESS TAMAR , SACHS T.
Published: May 2006

Summary

The general problem studied in this work was the control of the formation of different types of cells from the cambium in ordered spatial arrangements. Young Phaseolus vulgaris plants were used, and the cells which were studied were the vessels and fibres of the secondary xylem. It was possible to control the type of xylem which was formed in the stem by selectively removing leaves of different ages. Many vessels were formed below young leaves while a single mature leaf caused the formation of a large volume of xylem, often more than that formed in an intact plant, and this xylem consisted almost entirely of fibres. Evidence is presented that the stimuli of young and mature leaves differ by at least one component. Quantitative results show that young leaves can be imitated, in terms of the xylem which is formed, by a source of auxin while a mature leaf can be imitated by a combination of auxin and gibberellin.
THE LONGITUDINAL MOBILITY OF GROWTH REGULATORS AND HERBICIDES IN SIEVE TUBES OF WILLOW
Authors: FIELD R. J. , PEEL A. J.
Published: May 2006

Summary

Using the dual chambered bark strip system described by Peel et al. (1969), the relative longitudinal mobilities of MCPA, 2,4‐D, 2·4·5‐T, MH, paraquat and TCA in the sieve tubes of willow have been measured. It was possible to measure the quantity of a compound which entered one end of the sieve tube system and to compare this with the mass which moved to the other end of the same system. We have termed the ratio of these two masses the relative mobility.

Over a 24‐hr application period, TCA and paraquat had the highest relative mobilities, 2·4‐D and 2·4·5‐T the least. However, the total mass of TCA and paraquat which was moved along the sieve tube system was less than certain of the other compounds, notably MH and MCPA. These differences in relative mobility are thought to be due to variations in the removal of the compounds from the sieve tubes as they are being transported. In experiments of 36‐hour duration in which sieve tube exudate was sampled at 12‐hour intervals, the relative mobility changed with time. After 36 hours the order of relative mobility was different from that after a 24‐hour application time.

The relative mobilities of IAA and IAA asp were also studied, either by allowing the IAA asp to be produced by metabolism from applied IAA, or by simultaneous application of 3H‐IAA and 14C‐IAA asp. IAA asp had the greater relative mobility, though the mobility of IAA increased with time to approach that of the IAA asp after a 12‐hour application period.
ENZYMATIC QUANTITATIVE DETERMINATION OF HEXOSES, SINGLY AND IN MIXTURES WITH THEIR OLIGOSACCHARIDES
Authors: ERNST ROBERT , ARDITTI JOSEPH
Published: May 2006

Summary

Quantitative determinations of a number of naturally occurring D‐hexoses and their oligosaccharides can be accomplished by combinations of enzymatic methods without prior separation of the sugars. These spectrophotometric methods employ readily‐available enzymes and commercial reagents. The procedures are particularly useful for the quantitative analysis of fructofuranosides, such as raffinose or stachyose, in the presence of sucrose, glucose and/or fructose; maltose or lactose mixed with galactose and/or glucose; melibiose in mixtures with raffinose, and other combinations.
SEASONAL VARIATIONS IN THE SECONDARY PHLOEM OF SOME FOREST TREES FROM NIGERIA
Authors: LAWTON JUNE R.
Published: May 2006

Summary

The appearance of the phloem is described for the trees Albizia adianthifolia, Bombax buono‐pozense, Antiaris africana, Holarrhena floribunda, Ricinodendron heudelotii, Sterculia tragantha, and Tectona grandis. Measurements of the percentage sieve tube area, the sieve tube number per unit and the diameters of the sieve tubes have been made throughout one year. Changes in structure and composition of the phloem occurred in different ways in the several species at different times of the year. Increase in length of sieve tube elements with age was found in four of the species. In the three species with compound oblique sieve plates the pores were less than μm diameter, and the percentage sieve tube area was lower than that of the trees with phloem with simple sieve plates. The variety of phloem structure and the quantitative changes in phloem dimensions are discussed; the need for thorough investigation of phloem structure for each species as a prelude to physiological studies of the phloem is emphasized.
AN ASSESSMENT OF INTER‐SPECIFIC RELATIONSHIPS IN EQUISETUM SUBGENUS EQUISETUM
Authors: PAGE C. N.
Published: May 2006

Summary

The use of the scanning electron microscope to survey the surface relief of Equisetum reveals with clarity the existence of hitherto little known fine surface features. These patterns of sculpturing are characteristic and distinct from species to species, and form a valuable basis on which to construct taxonomic and phylogenetic ideas independently of the features of habit and gross morphology used currently but known to be highly variable. A new taxonomic layout for the species of subgenus Equisetum is suggested on this evidence, and the interrelationships and evolution of the species concerned are considered.
THE EFFECT OF ABSCISIC ACID ON STOMATAL BEHAVIOUR IN FLACCA, A WILTY MUTANT OF TOMATO, IN DARKNESS
Authors: TAL M. , IMBER DOROT
Published: May 2006

Summary

Young plants of the wilty tomato mutant, flacca, in which the stomata resist closure, were sprayed with abscisic acid eight times over a period of 24 hours in light and darkness. The hormone induced closure of stomata similarly in leaves treated either in light or in darkness. Abscisic acid does not appear to induce stomatal closure in darkness by increasing the internal CO2 concentration in the leaf, since this concentration should already be very high in darkness. A considerable and rapid decrease of CO2 assimilation and increase of CO2 evolution were demonstrated in mutant as well as in normal plants transferred from light to darkness.
THE CONTROL OF GERMINATION IN STACHYS ALPINA (L.)
Authors: PINFIELD N. J. , MARTIN M. H. , STOBART A. K.
Published: May 2006

Summary

Seeds of Stachys alpina are dormant, but can be induced to germinate either by treatment with gibberellin or by the removal or perforation of the integuments. Incubation of intact seeds and seeds with punctured integuments in increased oxygen tensions failed to stimulate germination above that observed in air, while after‐ripening in dry storage, incubation in continuous illumination and exposure to alternating temperatures were not effective in inducing germination of intact seeds. However, chilling treatments of up to 20 weeks' duration resulted in 20–30% germination. The significance of the response to gibberellin and of the role of the integuments in controlling dormancy are discussed.
OESTROGENS IN THE LONG‐DAY PLANTS HYOSCYAMUS NIGER AND SALVIA SPLENDENS GROWN UNDER INDUCTIVE AND NON‐INDUCTIVE LIGHT CONDITIONS
Authors: KOPCEWICZ JAN
Published: May 2006

Summary

An increased biosynthesis of oestrogen‐like substances occurs in plants growing under inductive photoperiods. Oestrogens appear at the time of flower bud formation and reach a maximum at the time of flower development. Three oestrogen‐like substances were found in extracts from flowering plants of both Hyoscyamus niger L. and Salvia splendens Sellow. These substances differed both from one another and from the standard substances they were compared with except that one substance in Hyoscyamus may be oestrone.