bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURAL VARIATIONS IN PEAT
Authors: STEWART J. M. , DURNO S. E.
Published: May 2006

Summary

The macro‐ and microscopic structure of an upland bog in north‐east Scotland was examined at two sites, where four main horizons were recognized according to dominant botanical constituents, degree of decomposition and texture after weathering. The botanical composition varied most markedly in the first and second horizons, decomposition in the second and third horizons, and texture in the third and fourth horizons. Microscopic examination of profiles from both sites was based on identifiable leaf cuticular patterns, assorted plant tissues (mainly roots and stems), and the pollen and spore record. The macro‐ and microfossil records from both sites differed in the distribution of Sphagnum spp., Hypnum cupressiforme, Calluna vulgaris and Betula spp., within certain horizons. Regional palynological data, supplemented by radiocarbon dating, placed the initiation of peat accumulation about the Atlantic Sub‐Boreal transition (N.P.L. 94. 5020 ± 95 B.P.). The results of this investigation indicated that isolation of the cuticular components of peat can provide useful supplementary data in the study of upland bogs, in which the regional pollen record is often poorly represented.
THE ACTIVITIES OF THE PHOTOSYNTHETIC CARBON CYCLE ENZYMES OF GREENING BEAN LEAVES
Authors: BRADBEER J. W.
Published: May 2006

Summary

After the transfer of 14‐day old dark‐grown bean seedlings into continuous illumination the etioplasts of the primary leaves develop into chloroplasts in a synchronous manner. Levels of activity in the leaves of most of the enzymes which have been implicated in the photosynthetic carbon cycle have been determined during the first 45 hours of chloroplast development. All of the enzymes investigated were present in etiolated leaves and the activities of most of them increased in response to illumination. One of the early effects of illumination was a rise in the protein content of the leaves, the level of which continued to rise throughout the 45 hours of illumination. Increases in the activity of some of the enzymes, notably phosphoglycerate kinase, fructosediphosphate aldolase, transketolase, NAD‐linked triosephosphate dehydrogenase and triosephosphate isomerase, appeared to begin soon after the commencement of illumination. The onset of light‐induced increases in the activities of ribosephosphate isomerase, phosphori‐bulokinase and ribulosediphosphate carboxylase, showed lag periods of similar duration to the ‘positive’ photoresponse described by Mohr (1966). The longer lag period before an increase of NADP‐Iinked triosephosphate dehydrogenase occurred is consistent with the suggestion of Ziegler and Ziegler (1965) that photosynthetically formed ATP and NADPH may be essential prerequisites for the synthesis of this enzyme. Possible mechanisms of control of the enzyme levels are discussed.

The data do not provide any evidence in support of the participation of phosphopyruvate carboxylase, hexosediphosphatase and transaldolase in an important role in connection with the photosynthetic carbon cycle of bean leaves.
LEAF RESISTANCE IN A GLASSHOUSE TOMATO CROP IN RELATION TO LEAF POSITION AND SOLAR RADIATION
Authors: HURD R. G.
Published: May 2006

Summary

Leaf resistances were measured in a glasshouse tomato crop, using a mass flow porometer. With plants of different age the sixth to eleventh leaf from the top of the plant had the lowest leaf resistance, both within the stand and at its perimeter. Full leaf expansion occurred at the twelfth to fourteenth leaf. Older leaves had high leaf resistances, especially within the crop.

Raising the CO2 concentration of the glasshouse to approximately 1000 vpm tended to increase leaf resistance but this increase was seldom significant and was sometimes not observed at all.

On sunny days, leaf resistances were higher for much of the day than resistances on dull days. This was believed to be due to a form of the midday stomatal closure observed in some plants under high insolation.
INTERACTION OF INDOLYL ACETIC ACID AND GIBBERELLIC ACID IN THE SYNTHESIS OF α‐AMYLASE BY BARLEY ALEURONE
Authors: MACLEOD ANNA M. , PALMER G. H.
Published: May 2006

Summary

When slices of barley endosperm were supplied with a mixture of 10−4 M gibberellic acid and indolyl acetic acid (10−4 or 10−10 m) continuously for 36 hours the amount of α‐amylase formed was significantly less than that formed in response to gibberellic acid alone. However, pre‐treatment of slices with a mixture of 10−10 M indolyl acetic acid + gibberellic acid for 8 hours followed by incubation in gibberellic acid alone resulted in enhanced levels of production of α‐amylase.

Removal of coleoptile tips from germinating grains was followed by diminished synthesis of α‐amylase in the endosperm, but the level of α‐amylase formed could be restored to that found in the intact grain by supplying 10−7 M indolyl acetic acid to the coleoptile stump.

It is suggested that indolyl acetic acid, migrating from the coleoptile tip, is involved not only in the process of lignification in the scutellum but also in the preliminary stages of gibberellin‐mediated α‐amylase formation in the aleurone.
TEMPERATURE RESPONSES IN ALTITUDINAL POPULATIONS OF EUCALYPTUS PAUCIFLORA SIEB. EX SPRENG
Authors: GREEN J. W.
Published: May 2006

Summary

The effects of temperature variation on germination and seedling growth in populations from different altitudes of Eucalyptus pauciflora were investigated by means of experiments in controlled environments and under natural conditions in the field.

Germination and seedling growth showed no statistically significant variation in optimum temperature according to altitude. On the other hand, there was strong evidence of differential resistance to freezing temperatures whereby seedlings from high‐altitude seed proved considerably more resistant than those from low‐altitude seed. This was reflected, to a certain extent, in the survival of reciprocal transplants over winter.

The relative uniformity of temperature optima suggested that in the field germination and early seedling growth would occur later with increasing altitude, thus bearing out casual field observations. The marked altitudinal variation in tolerance to low temperatures suggested that natural selection may have operated under the influence of winter temperature gradients to bring about adaptive changes related to altitude of occurrence.
SOFTWOOD STRUCTURE AND THE CLASSIFICATION OF CONIFERS
Authors: YOUNG D. J. , WATSON L.
Published: May 2006

Summary

Computational analysis of anatomical data for 113 species and forty‐two genera of Coniferae shows a marked distinction between Pinaceae and the rest, not reflected in taxonomic systems but consistent with other information. Most accepted genera and families, and the sections of Pinus, have anatomical support. Cupressaceae, however, fall into two widely separated groups, southern members joining the Podocarpaceae and Araucariaceae and the rest associating with northern families. The order Taxales is not distinguished by wood structure.
AEROPALYNOLOGY IN BRITAIN—AN OUTLINE
Authors: HYDE H. A.
Published: May 2006

Summary

The author reasserts his original definition of palynology as the study of plant spores and their dispersal and applications thereof, and here considers aeropalynology as that branch of palynology which is concerned with the dissemination of plant spores in both theory and practice. During the present century important advances in methods of sampling atmospheric spores have been made and have been applied at a limited number of locations in England, Wales and Scotland either with a view to assessing the general (outdoor) aerospora of the region concerned or of various special habitats. Variation both ‘circadian’and annual in the incidence of various spore types has been studied. The atmospheric transport of microbes (dispersal in the wider sense) which embraces take‐off (liberation), free flight (dispersion proper) and landing (deposition) has occupied the attention of several workers. Advances have been made also in intramural palynology. The fact that the aerospora is a reflex of the vegetation has been recognized but not worked out in detail despite the abundant data available. Finally the author claims that the many applications of aeropalynology both potential and actual, would amply justify further long‐term observation and assessment of the aerospora.
THE FINE STRUCTURE OF GYMNODINIUM FUSCUM (DINOPHYCEAE)
Authors: DODGE J. D. , CRAWFORD R. M.
Published: May 2006

Summary

The large freshwater dinoflagellate Gymnodinium fuscum (Ehrenberg) Stein, which is the type species of the genus, has flagella, chloroplasts, mitochondria, golgi bodies and chromosomes with typically dinophycean fine structure. It has an elaborate pusule with a large central vesicle, into which numerous small vesicles open, and a spiral canal which connects the central vesicle to the exterior. The nuclear envelope is complex with many flattened vesicles built into it which are perforated only towards the nucleus. The theca consists of three membranes, enclosing beneath the outer two a thin plate‐like structure homologous with the plates of armoured dinoflagellates. Beneath the third membrane numerous microtubules are found. G. fuscum does not possess pyrenoids or trichocysts.
PARTIAL IDENTIFICATION OF DARK 14CO2 FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)
Authors: KNAUFT ROBERT L. , ARDITTI JOSEPH
Published: May 2006

Summary

Following exposure of Cattleya leaves to 14CO2 in the dark, labelled malate, citrate and an unidentified compound were detected by thin layer chromatography. This is interpreted to suggest the existence in Cattleya leaves of a dark CO2 fixation pathway which may be similar to that found in other plants which can fix large amounts of carbon in the dark.
GIBBERELLIN ANTAGONISM BY MATERIAL FROM A BROWN ALGA
Authors: JENNINGS R. C.
Published: May 2006

Summary

The ethyl acetate‐soluble, acidic fraction extracted from sporophytes of Ecklonia radiata contains material inhibitory to the growth of dwarf maize plants treated with gibberellic acid, but which did not affect the growth of maize plants not treated with gibberellic acid. Saturation concentrations of gibberellic acid did not overcome the inhibition. It is concluded that the inhibitory material was functioning as a specific antagonist to gibberellin‐controlled growth in maize and that a non‐competitive component was present.

The inhibitory extract was shown to reduce the growth of gametophytes of Ecklonia when applied to cultures at physiological concentrations. This suggests an endogenous growth regulatory function for the active material, perhaps as a gibberellin antagonist. Higher levels were extracted from blade tissue than from stipe plus transition region tissue.
THE ECOLOGICAL DISTRIBUTION OF MYCORRHIZA OF BEECH
Authors: MEJSTRIK V. , DOMINIK T.
Published: May 2006

Summary

The following conclusions may be drawn from the determination of mycorrhizal spectra on beech at eight localities in Czechoslovakia. Altogether thirty‐three sub‐subtypes of ectotrophic mycorrhiza on beech were described in Czechoslovakia, of which seven are entirely new, namely: De, Df, Ed, Ee, Ek, Ih and Ik (see Dominik, 1959). Maximum frequencies of ectotrophic mycorrhizas were found down to a depth of 15–30 cm. With increasing depth the number of short roots and mycorrhizas decreased and the mycorrhizal spectrum narrowed. The quantities and types of humus were a decisive factor influencing mycorrhiza formation. Subtype E was the most frequent (20.26%) of all mycorrhizas. The richest mycorrhiza spectrum of four comparable localities was at Albrechtice in the Ore Mountains where fourteen sub‐subtypes of ectotrophic mycorrhiza were found despite a heavy deposition of industrial ash from power plants and a high concentration of SO2 in the atmosphere. No differences were found in the mycorrhiza variety between beech saplings (5–10 years) and older trees (over 100 years), nor was the occurrence of individual mycorrhiza strains characteristic of beech trees of different age.
AN IPSWICHIAN PEAT RAFT IN GLACIAL TILL AT HUTTON HENRY, CO. DURHAM
Authors: BEAUMONT P. , TURNER J. , WARD P. F.
Published: May 2006

Summary

A peat raft found in a sequence of glacial deposits at Hutton Henry, Co. Durham, is described. The peat contained quantities of Carpinus pollen and is therefore Jpswichian in age. From the position of the peat it is concluded that the Upper Till sheet of eastern Durham is of Weichselian age.
POLLEN DIAGRAMS FROM THE NORTH YORK MOORS
Authors: SIMMONS I. G.
Published: May 2006

Summary

Four pollen diagrams from the Egton High Moor watershed of the North York Moors are described. Two are from infilled sub‐glacial meltwater channels and two from blanket peat. The channel mires developed from woodland through fen peats (dominated by Thelypteris) to acidic bogs during Post‐glacial times. The uplands started to accumulate peats in late zone VI or early zone VIIa. The stratigraphy suggests that fire as well as paludification was involved in the inception of blanket peat. Clearance phenomena are observed in pre‐Ulmus decline times and some of these are tentatively assigned to Mesolithic activity. In the upper portions of the diagrams massive forest clearance is seen and this is probably due to Bronze Age occupation. The representation of Tilia is discussed in its regional context and the possible significance of the Fagus percentages in the light of Tauber's work is briefly mentioned.
VARIATION IN CERCOCARPUS IN SOUTHERN CALIFORNIA
Authors: SEARCY KAREN B.
Published: May 2006

Summary

Present‐day Cercocarptis leaves are compared with fossil leaf impressions from Miocene, Pliocene and Pleistocene floras of California and adjacent states in order to interpret the present pattern of geographic variation in leaf size in southern California. The various taxa described have had separate histories since at least the Miocene, and have remained morphologically stable despite changes in the climate and topography in the region.
ZOSTEROPHYLLUM FROM THE LOWER OLD RED SANDSTONE OF SOUTH WALES
Authors: EDWARDS DIANNE
Published: May 2006

Summary

The plant is found in the Senni Beds of the Lower Old Red Sandstone of South Wales (= Siegenian‐Emsian). Details of the morphology and anatomy of both sterile and fertile parts are given, together with an account of the spores. The plant is thought to be closely related to Zosterophyllum fertile erected by Leclercq in 1942, but as this species is known from a single fructification, it is concluded that the new plant, for the moment, should be called Z. cf. fertile.
A NOTE ON TRACE ELEMENTS FOR THE GROWTH OF NIGROSPORA ORYZAE (B. AND BR.) PETCH
Authors: RAWLA G. S.
Published: May 2006

Summary

Out of sixteen trace elements tested for the growth of this fungus, only Fe, Zn and Mn are found essential whereas the rest of the trace elements are not found essential for its growth. The fungus requires an optimum concentration of 1–10 ppm Fe and Zn and of 100 ppm Mn for its growth. Concentrations of the essential trace elements beyond the optimum level inhibit the growth of this fungus progressively. However, 200 ppm Zn completely inhibits the growth of this fungus.
THE EFFECT OF TEMPERATURE ON THE TRANSLOCATION OF PHOSPHORUS BY RHIZOPUS STOLONIFER
Authors: LYON A. J. E. , LUCAS R. L.
Published: May 2006

Summary

The effect of temperature on the rate of phosphorus translocation, on the uptake and metaholism of phosphate and on respiratory rate of Rhizopus stolonifer, has been studied. Over the temperature range 20–30° C the rate of phosphorus translocation is greatest at 20° C and lowest at 30° C. The rate of oxygen uptake is greatest at 25° C. The rate of phosphate uptake does not vary significantly over this temperature range, but the proportion of ahsorhed phosphate present as orthophosphate bears a direct relationship to the rate of phosphorus translocation. These results are consistent with the view that phosphorus may be translocated in the form of orthophosphate.
UPTAKE OF IONS BY ROOTED WILLOW CUTTINGS
Authors: BOVIS C. P. , BRIGGS G. E.
Published: May 2006

Summary

The uptake of radioactive ions from solutions into the root, wood and bark of the stem, and leaves of rooted willow cuttings has been investigated. The salts used were Na82 Br, K131 I, 42KCl and 86RbCl. In none of the experiments did the amount of isotope even in the lowest part of the stem reach the value to be expected if its concentration in the water‐free space there was equal to that outside the roots. After 9 days when 520 ml had been transpired hy a plant weighing 34 g the estimated concentration of 86Rb in the water‐free space of the wood was less than one‐seventh of that outside the roots. Transport to the bark appears to be via the wood. For the stems plus leaves the ratio of uptake of an ion to that of water was less than the concentration outside except in one experiment, which was exceptional in other respects. The gradient of concentration in the wood and the contribution of diffusion to uptake are discussed.
THE UPTAKE AND ACCUMULATION OF COPPER BY BECIUM HOMBLEI (DE WILD.) DUVIG. & PLANCKE
Authors: REILLY C.
Published: May 2006

Summary

Becium homblei, a flowering plant of the family Labiatae indigenous to Zambia, has been found to grow on soils contaminated with high levels of copper. The plant is capable of accumulating more than 100 ppm of the metal in its leaves and roots. Serial extraction of the plant tissue with various solvents has shown that much of the accumulated metal is tightly bound within the plant and is not in free solution in ionic form. The finding that increased copper content is accompanied by an increase in total nitrogen suggests that the metal may be bound as a complex with protein in the plant tissue.
THE SIGNIFICANCE OF CLINAL VARIATION IN DACTYLIS MARINA BORRILL†
Authors: BENSON MAUREEN , BORRILL MARTIN
Published: May 2006

Summary

Clinal variation was studied in four populations of Dactylis marina Borrill from the Portuguese coast. Differences in the balance of leaf epidermal characters are found to be associated with differences in climatic conditions. In particular, the presence of epidermal papillae was found to affect the association between frequency of epidermal cells and stomata.

The presence of a cline in papillosity, a character known to be recessive, suggests that this type of epidermal cell may play an important physiological role in the life of the plant.

The effects of epidermal morphology are discussed, and suggestions made for further study.
STOLON INITIATION AND DEVELOPMENT IN SOLANUM TUBEROSUM L.
Authors: LOVELL P. H. , BOOTH A.
Published: May 2006

Summary

Plants of cv. Majestic were grown in solution culture in tanks so designed that the development of the normally subterranean stolons could be followed individually by daily observation and measurement. An analysis is made of the pattern of stolon emergence, elongation, branching and tuber initiation. The effects on stolon development of reduced mineral nutrient supply, decapitation of the main shoot apex and exclusion of light from the developing shoot were also examined.
A TAXIMETRIC STUDY OF AN ANGIOSPERM FAMILY: GENERIC DELIMITATION IN THE CHRYSOBALANACEAE
Authors: PRANCE G. T. , ROGERS D. J. , WHITE E.
Published: May 2006

Summary

This is an account of how some taximetric techniques were used in a study of generic delimitation in the Hirtelleae, one of the two tribes of an Angiosperm family, the Chrysobalanaceae. It is probably the first account of a study in which the use of such techniques has formed part of an original monographic study of a sizable group of higher organisms above the species level.

A preliminary study based on an examination of herbarium material of all 254 species suggested considerable departures from previously accepted generic concepts, chiefly involving the splitting of Parinari into four, possibly as many as eight, smaller, more clearly defined units. The character‐states of twenty‐one characters were recorded for all species (140) for which the material was sufficiently complete. These data were subjected to four taximetric analyses—two principal component analyses and two clustering analyses—which are described and discussed. All four clearly confirmed the heterogeneous nature of Parinari. Most of the tentative groupings were confirmed by all or most of these analyses. Accordingly the following segregates from Parinari are recognized: Bafodeya, Cyclandrophora, Kostermanthus, Exellodendron, Maranthes and Neocarya. For a few species the results obtained by the taximetric analyses are less unanimous; the reasons for this are discussed. Indecisive results were obtained for only two species.

All four analyses yielded taxonomically meaningful results and provided insights into the taxonomic situation, though to different degrees. The Wirth, Estabrook and Rogers model gave the most useful results and displayed them in the most informative way. Since much confusion exists concerning the aims and methods of taximetrics, we have attempted to explain our own position. Rather than expect the reader to take on trust our statements concerning the contribution of taximetrics to our study, we have given a full account of the history of the problem and of our tentative taxonomic conclusions before the analyses were done, and have shown how they were confirmed or modified in the light of the results of the different methods.
SUCCINATE METABOLISM IN RELATION TO TUBER STORAGE AND TUBER DEVELOPMENT IN SOLANUM TUBEROSUM
Authors: LOVELL P. J. , BOOTH A.
Published: May 2006

Summary

Freshly‐cut slices of mature tubers liberated little 14CO2 from [2–3 14C] succinate even when sprouting after 9 months storage at 5° C. Output from 24‐hour washed slices was considerable; it increased in amount with increasing length of storage period and was enhanced when light was excluded during washing and incubation in succinate.

A comparison was made between non‐tuberizing stolon tips and young tubers taken within a day or so of tuber initiation. The fresh stolon tips released an appreciable quantity of CO2 from succinate, much less after washing. Fresh young tubers liberated much less 14CO2, slightly more after washing. Although this indicated that the tricarboxylic acid‐ (TCA‐) cycle block might arise soon after initiation, the qualitative distribution of the label in tissue extracts showed stolon tips and young tubers to be similar to each other and distinct from mature tuber tissue.
MERISTEMS AND GROWTH CONTROL IN ASCOPHYLLUM NODOSUM (L.) LE JOL.
Authors: MOSS BETTY
Published: May 2006

Summary

From a study of young plants of Ascophyllum nodosum raised from fertilized eggs it has been shown that an apical cell differentiates from the basal cell of one of a group of apical hairs. This apical cell builds up an active meristem around itself. This meristem and its subsequent products function throughout the life of the thallus. Generally the apical meristem dichotomizes once a year. Behind it a succession of lateral nodes develop during spring and summer. These originate from the meristoderm in a similar way to the conceptacles. The branches, whether vegetative or fertile, which are produced from the lateral nodes, are superficial in origin.

The apical cell of a meristem exerts apical dominance and inhibits the development of branches from nearby lateral nodes. Meristems from lateral nodes will inhibit the development of branches from a wound callus. Lateral branches, gametangia in conceptacles and branches from a wound callus all require some interruption of the dominating effect of the apical cell before they can complete their normal development.
DURATION OF THE MITOTIC CYCLE IN THE APICAL BUD OF RUDBECKIA BICOLOR
Authors: JACQMARD A.
Published: May 2006

Summary

Duration of the mitotic cycle and its component phases is estimated in the different regions of the apical bud of Rudbeckia bicolor by means of pulse‐labelling with tritiated thymidine and autoradiographic techniques. The average length of the mitotic cycle is around 30–33 hours in all regions of the bud, except in the central zone where it is far longer.
SHADE TOLERANCE IN TREE SEEDLINGS
Authors: LOACH K.
Published: May 2006

Summary

Seedlings of five tree species of different shade tolerance were raissed in 100, 44, 17 and 3% of natural daylight. Growth analysis was carried out on data obtained from two harvests during the growing season. The net assimilation rates (E) of the more tolerant species were little higher in 100% daylight than in slight shade (44% daylight), but thereafter E decreased as shade increased. The intolerant species had greatest E in 100% daylight, but this high E fell sharply with increasing shade, and in Populus tremuloides was negative in 3% daylight. Even in this deep shade, however, the intolerant Liriodendron tulipifera had as high a net assimilation rate as the shade‐tolerant species. Decreased E was offset by increased leaf area ratio (leaf area/plant weight), but in contrast to previous studies with herbaceous species, the magnitude of this increase gave no indication of the relative shade tolerance of the different species. In L. tulipifera and Acer rubrum, the increased leaf area ratio resulted from an increase in the proportion of assimilates diverted into leaf production (i.e. increased leaf weight ratio), together with a relatively greater increase in specific leaf area (leaf area/leaf weight). The more tolerant Fagus grandifolia and Quercus rubra showed less increase in specific leaf area, and leaf weight ratio increased only in the deepest shade. No clear‐cut distinction can be drawn between tolerant and intolerant species on the basis of the relative size or efficiency of their photosynthetic systems in low light; factors other than those relating to carbohydrate economy in shade, also play a role.
AN ELECTRON MICROSCOPE STUDY OF EXOGENOUSLY DORMANT SPORES, SPORE GERMINATION, HYPHAE AND CONIDIOPHORES OF ALTERNARIA BRASSICICOLA
Authors: CAMPBELL RICHARD
Published: May 2006

Summary

Freeze‐etching and chemical fixation techniques were used to study exogenously dormant spores, spore germination, hyphae and conidiophores of Alternaria brassicicola (Schw.) Wiltshire. Dormant spores have very thick, heavily pigmented, mclanized walls with plugged septal pores. The small amounts of endoplasmic reticulum and the few mitochondria lie near the plasmalemma. The germ‐tube walls arise from the inner layers of the spore walls; lomasomes and endoplasmic reticulum vesicles are probably concerned with this wall formation. During germination mitochondria and ribosomes increase in numbers, first in the germinating cell and then in the germ tube. As the hyphae age they produce lipid droplets and vacuoles; the latter finally fill most of the cell as the cytoplasm degenerates. Conidiophores have a similar structure to mature hyphae except that they have, after spore production, a pore in the tip and an annulus.
A BASIC STAINING MATERIAL ASSOCIATED WITH THE PENETRATION PROCESS IN RESISTANT AND SUSCEPTIBLE POWDERY MILDEWED BARLEY
Authors: EDWARDS H. H.
Published: May 2006

Summary

A possible mechanism for resistance has been observed in powdery mildewed barley (Erysiphe graminis f. sp. hordei on Hordeum vulgare). A substance which stains with basic protein staining procedures occurs in papillae of susceptible and resistant powdery mildew infected barley. It is first detectable after the infection peg penetrates the host cell wall. In susceptible host cells this substance is confined to the papilla, whereas in resistant host cells this substance spreads throughout the penetrated cell and to adjacent mesophyll cells beneath the infected cell. The spread of this substance correlates with the expression of resistance in the host cells.
OBSERVATIONS ON THE STRUCTURE AND BIOLOGY OF HAPLOMITRIUM AND TAKAKIA, HEPATICS WITH ROOTS
Authors: GRUBB P. J.
Published: May 2006

Summary

The gametophytes of certain species of Haplomitrium and of Takakia have organs that may be called roots. These normally grow downward, are almost colourless and, unlike flagella‐shoots, have no leaf rudiments. They may have up to two orders of branching; they have no root‐caps but are covered by mucilage if grown in dry conditions.

The axes of most species have a central cylinder of elongated cells. In the aerial shoots these cells generally appear ‘empty’ like the hydroids of mosses. The leaf cells have an outer layer which is relatively impermeable to water and solutes. Shoots of Haplomitrium mnioides are able to maintain their water balance more effectively than those of Plagiochila asplenioides under marginally drying conditions. The endohydric habit of Haplomitrium and Takakia appears to confer little advantage in the field because it is not coupled with a protoplasmic resistance to desiccation.
PHOTOINDUCED CHANGES IN RICE SHOOT APEX
Authors: MISRA G. , KHAN P. A.
Published: May 2006

Summary

A late‐winter variety of indica rice was subjected at the age of 28 days to one to twelve consecutive cycles, each of 8 hours natural daylength plus 16 hours darkness. Changes in the shoot apex in its transition from the vegetative to the reproductive condition under each photo‐inductive cycle were noted. Seven consecutive photoinductive cycles played the master role and brought about panicle initiation 50 days earlier and panicle emergence 61 days earlier than in the controls grown under natural daylengths in the open field.
STUDIES IN THE VEGETATIONAL HISTORY OF MID‐WALES
Authors: MOORE P. D.
Published: May 2006

Summary

Sediments of Late‐glacial origin from the Elan Valley in Cardiganshire have been subjected to close‐interval pollen, spore and macrofossil analysis. From the results of this analysis an attempt has been made to reconstruct contemporary plant species assemblages and to follow the changes in these communities during the climatically unstable Late‐glacial period. Conventional zonation required some modification for adequate representation of the dynamic state of both environment and vegetation at the time, hence a series of transitional zones has been constructed. Certain species are found to reach their greatest abundance in these transitional periods and are considered to be relatively thermophilous yet intolerant of competition.

Certain of the types found, e.g. Artemisia c.f. norvegica, Linnaea borealis, Tofieldia and Scleranthus perennis are of particular interest, both because of the infrequency with which they have been recorded in British quaternary deposits in the past, and because of their present day disjunct and sometimes anomalous distributions. Their presence in mid‐Wales during Late‐glacial times throws further light upon these distributions.
PERIDERM DEVELOPMENT AND PHELLOGEN ACTIVITY IN THE SHOOTS OF ACACIA RADDIANA SAVI
Authors: ARZEE TOVA , WAISEL Y. , LIPHSCHITZ NILI
Published: May 2006

Summary

The origin and the seasonal activity of the phellogen in Acacia raddiana were investigated. The phellogen is initiated from collenchyma cells of one of the three outermost layers of the cortex. The first phellogen persists for several years. The activity is periodic and slow. The phelloderm consists of several crystal‐containing cell layers, which eventually become sclerified. The activities of the phellogen and of the cambium were found not to be correlated.
EFFECTS OF ASPERMY VIRUS INFECTION ON THE WATER STATUS OF TOMATO LEAVES
Authors: TINKLIN R.
Published: May 2006

Summary

The effect of aspermy virus infection on the water status of tomato leaves was studied. Infected leaves had a higher relative water content than controls, the increase being related to inoculum concentration. This was shown to be caused by an inability to take up water rather than a truly higher water content. It is suggested that this may be the result of a reduction in the permeability of cell membranes.
THE QUALITATIVE AND QUANTITATIVE PHOTO‐PERIODIC RESPONSE OF INDIAN POTATO VARIETIES
Authors: PUROHIT A. N.
Published: May 2006

Summary

Plants of Solanum tuberosum L. vars. Kufri Sindhuri, Kufri Shakti, EM/B‐1399 and OT‐No. were grown under short day (SD) and long day (LD) (continuous light) at identical temperature and humidity. Observations on haulm growth, number and shape of leaves, and number of tubers produced per plant and their fresh weight were recorded.

Plants grow taller under LD in all the varieties. The early maturing varieties (Kufri Shaki and EM/B‐1399) die earlier, but more or less simultaneously under SD and LD conditions, whereas the growth period of the other two varieties is lengthened considerably under LD conditions. The heteroblastic development of leaves is considerably influenced by photoperiod.

All the four varieties are quantitative long‐day with respect to floral initiation but in all of them floral buds drop before they open into flowers. One of the four varieties, OT‐No., is quantitative whereas the others are qualitative short‐day in tuber initiation. Yield per plant is considerably influenced by the photoperiod. Long days during tuber enlargement increase the yield.

The significance of these results in evaluating the seasonal and regional adaptability of potato varieties and the mechanism of tuberization is discussed in the light of available literature on the subject.
INWASHED POLLEN SPECTRA AT LOCH FADA, ISLE OF SKYE
Authors: BIRKS H. J. B.
Published: May 2006

Summary

Pollen and macrofossil analyses of contiguous 1 cm samples have been made through a band of terrestrial bryophyte remains interstratified in Late‐Weichselian limnic silts. Various forms of pollen deterioration were distinguished and scored for the different sediment types. The fossil assemblage in the moss band suggests derivation by inwashing from a montane moss‐dominated spring. This is supported by comparison with a modern pollen spectrum from such a community in Scotland. Pollen in the bryophyte band is largely corroded, due to aerial oxidation and microbial attack, while pollen in the silts is broken and degraded, resulting from mechanical damage. The silts also contain pre‐Quaternary microfossils, largely of Jurassic origin. Two forms of redeposited microfossils are distinguished: secondary types redeposited from erosion of older strata, and inwashed types redeposited from contemporary materials.
POLLEN AND DIATOM ANALYSES OF LATE‐QUATERNARY DEPOSITS IN THE BLELHAM BASIN, NORTH LANCASHIRE
Authors: EVANS G. H.
Published: May 2006

Summary

Investigations have been made of Late‐Weichselian and Flandrian deposits in Blelham Tarn, Lancashire and other parts of its basin. Pollen and diatom analyses have been made of several cores and samples taken from the inflows. Pollen analysis has been used as a basis for chronology. The vegetational history of the region and past diatom flora of the tarn and ‘kettle‐hole’ are discussed. During the Late‐Weichselian, in pollen zones I and III, the vegetation was dominated by herbs of open habitats, whilst in pollen zone II birch woodland developed. The diatom flora consisted mainly of non‐planktonic forms with Fragilaria spp. dominant. In the Early‐Flandrian (pollen zones IV–VI) birch woodland developed and was succeeded by a mixed oak forest. Differences are shown in the pollen spectra from the ‘kettle‐hole’, marginal and open water regions of the tarn. The planktonic/non‐planktonic (P/NP) diatom ratio slowly increased in the tarn. However, dominance was retained by the non‐planktonic forms. This increase in P/NP ratio did not occur in the ‘kettle‐hole’ region. A new diatom variety Melosira distans var. blelhamensis appeared in the flora. At the opening of pollen zone VIIa Alnus rapidly increased, and for the first time planktonic diatoms became dominant in the open waters of the tarn. In littoral regions non‐planktonic forms, in particular Achnanthes minutissima var. cryptocephala, remained dominant. Sphagnum‐sedge peat accumulated in the ‘kettle‐hole’. Diatoms are scarce in this peat. During the Late‐Flandrian (pollen zone VIIb to the present day) the local vegetation was an older mixed oak forest. However, more open vegetational conditions gradually developed as shown by the increase in herbaceous pollen. Dominance was held in the open waters by the planktonic diatoms. The littoral regions favoured the growth of Achnanthes minutissima var. cryptocephala. Sphagnum‐sedge peat continued to accumulate in the ‘kettle‐hole’. Other limnological aspects considered include the tarn's trophic condition, productivity, alkalinity, the transparency of its waters and tarn level changes. In the past the tarn covered a much wider area. Field evidence shows that man has interfered with the drainage system.
THE USE OF COMPUTERS IN THE PRESENTATION OF POLLEN DATA
Authors: SQUIRES R. H. , HOLDER A. P.
Published: May 2006

Summary

Problems associated with comparing pollen diagrams can be partly avoided by using a computer to draw diagrams in a standard form. A program which may be used to produce comparative diagrams is described. The input specifications and limitations and examples of the output are presented and discussed in the light of the increasing volume of pollen data which are available.
THE MECHANISM OF CHLORIDE TRANSPORT IN CHARACEAN CELLS
Authors: SMITH F. A.
Published: May 2006

Summary

Active chloride uptake by cells of Chara corallina decreases as the pH of the bathing solution is increased, using a range of buffers. Superimposed on this effect, large stimulations of Cl− uptake can be obtained by the addition of imidazole and tris buffers or ammonium sulphate. ‘Stimulated’ or ‘normal’ Cl− influxes respond similarly to the presence of metabolic inhibitors.

It is suggested that these effects are not due to changes in photosynthesis or respiration, but reflect the dependence of Cl− transport on the pH gradient across the plasmalemma. Possible ways in which Cl− transport might be linked to H+ or OH− fluxes are discussed. It is proposed that the pH gradient across the plasmalemma is controlled by charge‐separating reactions which produce an active H+ efflux, and that Cl− uptake is linked to OH− efflux by ion‐exchange reactions.

The metabolic implications of this scheme are discussed in detail, with reference to previous work on Characean and other plant cells.
AUTORADIOGRAPHIC LOCALIZATION OF SOLUBLE AND INSOLUBLE 14C FROM [14C]INDOLYLACETIC ACID SUPPLIED TO ISOLATED COLEUS INTERNODES
Authors: WANGERMANN ELISABETH
Published: May 2006

Summary

Methods for localizing soluble label in Plant tissues using frozen sections and stripping film are discussed. After 24 hours' application, 14C derived from radioactive indolylacetic acid (IAA) is heavily concentrated in the phloem, less so in the xylem, and very weak in the cortex and pith. The 14C cannot be ‘chased’ out of the tissues by non‐radioactive IAA, but nearly all of it is removed by leaching sections in water or methanol. The small amount which remains after leaching is attached to the walls of vessel elements.

Chromatograms of extracts of treated internodes show that very little of the label seen in the tissues remains attached to IAA, and that most of it is present associated with substances which remain near the origin.
STUDIES ON THE EFFECT OF CERTAIN ENZYMIC POISONS ON THE METABOLISM OF STORAGE ORGANS
Authors: YOUNIS M. E. , YOUNIS A. E. , GABR M. A.
Published: May 2006

Summary

Glucose and fructose fed to radish slices were taken up at different relative rates with marked accumulation of carbohydrates; a possible working mechanism is presented to explain the differential rates of uptake. Addition of iodoacetate to the sugar media decreased both the uptake of sugars and the accumulation of carbohydrates.

Although there was synthesis of proteins in the presence of iodoacetate, the synthesis both in iodoacetate and in iodoacetate plus sugar was less than in the absence of iodoacetate.

Sugars and iodoacetate either alone or in combination increased the rates of CO2 output; a possible explanation of the different rates observed is given. Moreover, iodoacetate increased the permeability of the cell membranes as is evident from the increased leakage of nitrogen compounds from the tissues into the media.
SUBAQUEOUS TRANSPIRATION IN NEW PERSPECTIVE
Authors: POTTER A. W. , MILBURN J. A.
Published: May 2006

Summary

Dixon's original observation that the submerged shoots of terrestrial plants continue to take up water through the cut stems for considerable periods has been confirmed. His observations were not due to artifacts, as suggested by others. His interpretation, that the uptake was in response to a loss of water from the leaves, termed ‘subaqueous transpiration’, caused by metabolic activity of the mesophyll cells, was not supported by experiments with shoots of the same genus he used.

The possibility that minute amounts of water can be actively excreted by shoots cannot be eliminated, but none could be detected under paraffin by microscopy. A more satisfactory explanation is that uptake was due to incorporation of water into cells during growth whilst ‘fully turgid’. This postulated growth uptake seems sufficiently large to explain all experimental observations to date and active water secretion need not be presumed.
THE PARTITIONING OF RESISTANCES TO PHOTOSYNTHETIC CO2 UPTAKE IN THE LEAF
Authors: KOLLER DOV
Published: May 2006

Summary

A theoretical analysis is presented of the partitioning of overall resistance to photosynthetic CO2 uptake in the leaf. This is based on the existence of a resistance to gaseous diffusion between the upper and lower layers of the chlorenchyma (Ri). It takes into account the anisolaterality of the leaf with respect to resistance to diffusion (Rw) through the upper and lower surfaces, and with respect to the (residual) resistance to CO2 uptake and fixation (Rm, the ‘mesophyll resistance’) in the upper and lower chlorenchyma. When Ri exists in conjunction with epidermal anisolaterality, mesophyll resistance of the whole leaf (R¯m) is over‐estimated by subtracting the diffusion component resistance (R¯w) from the total resistance to CO2 uptake (R). This over‐estimation increases with epidermal and mesophyll anisolaterality, as well as with increase in Ri and R¯w, but decreases as R¯m becomes relatively greater. A method is presented and discussed, by which Ri and the Rm values of the two sides of the leaf can be simultaneously estimated, using simultaneous measurement of their transpiration and photosynthesis and of diffusion porometry through the leaf.
THE ACCUMULATION AND BINDING OF COPPER IN LEAF TISSUE OF BECIUM HOMBLEI (DE WILD.) DUVIGN. & PLANCKE
Authors: REILLY C. , ROWEL JANE , STONE JANE
Published: May 2006

Summary

The flowering plant Beciutn homblei is able to accumulate copper and other heavy metals to a relatively high level in its leaves. Approximately 17% of the total copper is concentrated in cell walls where it is bound as an organic complex. Copper in water extracts of leaf tissue is not in free ionic form but is complexed with amino acids or peptides. In vitro experiments indicate the strong complexing powers with copper of certain substances in leaf tissue.
NON‐SPECIFICITY OF SYMBOTIC INFECTION IN ORCHID MYCORRHIZA
Authors: HADLEY G.
Published: May 2006

Summary

Symbiosis tests carried out between orchids from several geographical localities and thirty‐two Rhizoctonias isolated from orchids, non‐orchid hosts and soils of worldwide distribution, showed no evidence of any species‐to‐species relationship between orchid and fungus.

Dactylorhiza purpurella established a symbiotic relationship with most fungi tested while Coeloglossum wide, Goodyera repens and Cymbidium canaliculatum, although less frequently symbiotic, established compatible infections with many isolates. Among orchids with photo‐synthetic protocorms, Epidendrum radicans was compatible with several fungi but three other species of Epidendrum together with Spathoglottis plicata and a Laeliocattleya cultivar were symbiotic only with Tulasnella calospora and certain Ceratobasidium isolates.

Tulasnella calospora may be a universal orchid symbiont. Ceratobasidium cornigerum and Thanatephorus orchidicola commonly occur as root endophytes but are doubtfully symbiotic with most orchids. T. cucumeris is frequently symbiotic with Dactylorhiza purpurella but less commonly so with other orchids tested.
THE EFFECTS OF POPULATION DENSITY ON GAMETOPHYTE MORPHOGENESIS IN POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROGAN P. G.
Published: May 2006

Summary

Growth and development of gametophytes of Polypodium vulgare L. in culture are affected by population density. Increasing population density leads to an increase in gametophyte length and a delay in the transition to two‐dimensional growth. Cell number is at a maximum at an intermediate density. On the evidence presented it is concluded that the inhibition of development associated with high population density is attributable to the presence in the medium of a substance (or substances) secreted by the gametophytes. Although other explanations are possible, all the effects could be caused by a single, diffusible, volatile factor. It is suggested that the promotive effect of blue light on gametophyte development is due to the suppression of this factor by blue light.
A COMPARATIVE STUDY OF THE MORPHOLOGY AND ANATOMY OF LEUCOSTEGIA AND ARAIOSTEGIA
Authors: SEN T. , SEN U.
Published: May 2006

The anatomy and morphology of Leucostegia immersa (Wall.) Presl (type species of the genus Leucostegia) and Araiostegia pulchra (Don.) Copel. (a species which comes very near to the type species of the genus Araiostegia) are described in detail for the first time in order to determine whether the genus Araiostegia is distinct from Leucostegia. The present investigation reveals that Leucostegia differs from Araiostegia in many significant morphological and anatomical details. For example, in Leucostegia, both scales and hairs protect the rhizome, while on the rhizome of Araiostegia hairs are absent. Further, the basifixed scales of Leucostegia are sharply different from the strongly peltate scales of Araiostegia. Though the stelar cylinders in the two genera are basically similar in construction, they are markedly different in their modes of production of root‐traces and leaf‐traces. No tanniniferous cells which are found in Leucostegia, occur in the fundamental tissues of Araiostegia. Young fronds of Leucostegia produce delicate hairs, but in Araiostegia the fronds are glabrous throughout. The rachises and costae in Leucostegia are grooved on the upper surface and never show any raised median bands in sharp contrast to the rachises of Araiostegia which are at least in the upper part narrowly winged on either side of the raised upper surface. All these differences certainly show that these genera are well defined. The relationship between Araiostegia and other davallioid ferns is also discussed.
SPECIES DIFFERENTIATION IN PAPAVER DUBIUM
Authors: KOOPMANS ALIE
Published: May 2006

Summary

Papaver dubium seeds were obtained from several European countries. Two different chromosome numbers were found: 2n= 42 and 2n= 28. The forty‐two chromosome races are most widespread. Four races with 2n= 28 chromosomes can be distinguished.

From results of cytological investigation especially of chromosome pairing behaviour during meiosis, it is suggested that the two 2n= 28 chromosome races, Alb and Upps II, may be considered as subspecies whereas the other two (Cors II and Ca Sw) are best regarded as chromosome races of P. dubium L.
POLLEN ZONES IN THE PLEISTOCENE OF GREAT BRITAIN AND THEIR CORRELATION
Authors: WEST R. G.
Published: May 2006

Summary

The zonation of pollen diagrams in relation to the necessity for correct biostratigraphical subdivision is discussed, and a process of correlation of pollen diagrams to a chronostratigraphical framework is outlined.
THE ROOTED EXCISED COTYLEDON AS AN EXPERIMENTAL SYSTEM
Authors: LOVELL P. H. , BARRATT E. , MOORE K. G.
Published: May 2006

Summary

Techniques for the culture of excised cotyledons are briefly described and the advantages of using an excised rooted cotyledon as an experimental system are discussed.