bluuebunny/crossref_metadata_2025 huggingface dataset:
CAVITATION AND OSMOTIC POTENTIALS OF SORDARIA ASCOSPORES
Authors: MILBURN JOHN A.
Published: May 2006

Ascospores of Sordaria fimicola have been separated into two distinct kinds on the basis of colour, structure and physiology, which may represent different degrees of maturation.

The osmotic potential of the darker spores has been found to vary considerably (22–45 atm).

Cavitation occurs in ascospores and the cavitation potentials of a number of individual spores Were measured. There is considerable variation between different spores even from the same ascus (18–71 atm). Cavitation could neither be detected by vibration techniques depending on electronic amplification, nor could spore recoil be seen when detached spores cavitated under the microscope.

Estimates of the permeability coefficients of mature ascospores have been made with respect to water entering the spores osmotically. The osmotic pressure generated in hyphal germ tubes of Sordaria ascospores is discussed.
HORMONAL REGULATION OF NITRATE REDUCTASE ACTIVITY IN LEAVES
Authors: ROTH‐BEJERANO NURIT , LIPS S. HERMAN
Published: May 2006

The level of nitrate reductase activity in leaves of tobacco is not determined only by nitrate availability. Kinetin and gibberellin interact, affecting the activity of the enzyme. Kinetin seems to modulate the effectivity of gibberellin on the determination of nitrate reductase activity: the larger the amount of kinetin added the smaller the concentration of GA3 required to obtain maximal activity of nitrate reductase. The effect of both growth substances on the enzyme is not due to a general protein synthesis stimulation.
NATURAL AND EXPERIMENTAL HYBRIDIZATION IN POTENTILLA
Authors: MATFIELD B. , JONES J. K. , ELLIS J. R.
Published: May 2006

Three natural hybrids have been reported in Potentilla subseries Tormentillae: Potentilla Y. suberecta, P. ×mixta and P. × italica. This paper presents results of morphological and cyto‐logical studies and experimental crosses made to clarify the origins and taxonomy of the hybrids, and to investigate the possibility of introgression.

All natural hybrids examined were hexaploid (2n= 42). Experimental crosses confirmed that P. × suberecta is the hybrid between P. erecta (2n= 28) and P. anglica (2n= 56), but the origin of the other hybrids is less clear. It is suggested that the names P. ×mixta and P. ×italica have been applied to different forms of a single variable taxon, and that P. × italica should be regarded as a synonym of P. ×mixta. The origin of this natural hybrid remains uncertain. It is generally considered to be P. reptans (2n= 28) ×P. anglica, but numerous attempts to hybridize these species have failed, although one unpublished, successful hybridization is cited. Experimental crosses have indicated an alternative origin for P. ×mixta, by hybridization between P. reptans and P. erecta, in which the former either contributes an unreduced gamete or occurs as an autopolyploid cytotype.

Vigorous backcross progenies were raised from both P. ×suberecta and P. ×mixta and the importance of backcrossing and introgression in natural populations is discussed.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE B. , HAYMAN D. S.
Published: May 2006

Summary

The benefits of mycorrhizal infection were compared in four irradiated and unsterilized soils containing little soluble phosphorus. Mycorrhizal infection was produced in onion seedlings by pre‐planting in a heavily infected soil and transplanting into the test soil, or by sowing in situ on a cushion of Endogone inoculum. In all soils, irradiated or not, mycorrhizal seedlings grew very much better than non‐mycorrhizal ones. In two of the soils natural infectivity was very low and most uninoculated seedlings remained non‐mycorrhizal even after 16 weeks. In the other two soils most plants became mycorrhizal in the unsterilized soils. In one of them the indigenous mycorrhizal fungi aided phosphorus uptake of the host plant, in the other they did not. Infections produced by the indigenous fungi in the two soils were anatomically different, though both were typical VA mycorrhiza.

It is concluded that inoculation may have practical significance in some low phosphate soils containing either few indigenous mycorrhizal fungi or ineffective strains.
STOMATAL RESPONSE TO CHANGING LIGHT BY FOUR TREE SPECIES OF VARYING SHADE TOLERANCE
Authors: WOODS DAVID B. , TURNER NEIL C.
Published: May 2006

Summary

Stomatal opening and closing was followed with a diffusion porometer in beech (Fagus grandi‐folia Ehrh.), maple (Acer rubrum L.), oak (Quercus rubra L.) and yellow poplar (Liriodendron tulipifera L.) in a situation where illuminance could be changed by placing shades over the trees. In all four species the stomata opened quicker than they closed. The time to reach an equilibrium stomatal resistance was constant for a species but varied between species, for all changes in illuminance greater than 3000 ft‐candles. To open to a constant leaf resistance took from 3 minutes in beech to 20 minutes in yellow poplar; oak and maple were intermediate at 12 minutes. Beech required 12 minutes to close to a constant leaf resistance, maple 18, oak 20, and yellow poplar 36 minutes. When the change in illuminance was less than 3000 ft‐candles, the stomata took longer to reach a new equilibrium in all species except yellow poplar. Also beech stomata opened and closed in dimmer light than yellow poplar. The rates of stomatal opening and closing correlated well with the known shade tolerance of the species.
BIOLOGICAL EFFECTS OF SURFACTANTS
Authors: ERNST ROBERT , ARDITTI JOSEPH , HEALEY PATRICK L.
Published: May 2006

Summary

Relative phytotoxicity of purified, biodegradable surfactants was determined by observing their effects on the growth of orchid seedlings in vitro. Pronounced phytotoxic effects occurred on culture media containing high concentrations of surfactants. Concentration of ionies above 100 ppm were most damaging and also caused a 90% or greater reduction of interfacial tension. Nonionic ethoxylates reduced growth and viability at lower concentrations than ionies, but larger percentages of seedlings survived at 1000 ppm levels of these agents, which were less efficient in reducing interfacial tension. No correlation was found between biological effects and surface tension data but a coincidence may exist between interfacial tension reduction by ethoxylates and increased phytotoxicity.

A number of purification procedures for surface active agents are presented as an Appendix.
THE EFFECT OF DESICCATION ON SUBSEQUENT ASSIMILATION AND RESPIRATION OF THE BRYOPHYTES ANOMODON VITICULOSUS AND PORELLA PLATYPHYLLA
Authors: HINSHIRI H. M. , PROCTOR M. C. F.
Published: May 2006

Summary

Anomodon viticulosus (Hedw.) Hook. & Tayl. and Porella platyphylla (L.) Lindb. show evidence of a consistent pattern in the course of net assimilation following moistening after various periods of desiccation. In the early stages of desiccation (up to 22 days at 50% RH in Anomodon viticulosus; up to 60 days in Porella platyphylla), recovery is rapid and apparently complete within c. 3–4 hours. After longer periods of desiccation the net assimilation rate is initially negative, but becomes positive after lengths of time increasing progressively to several days. This is partly a consequence of delayed (and probably incomplete) recovery of photosynthesis, and partly of an enhanced initial rate of respiration. After prolonged desiccation (more than 70 days) respiration in Anomodon viticulosus builds up to very high values over a period of about 24 hours following moistening and then falls to more normal levels, but subsequent recovery is problematical.
RAPID MEASUREMENTS OF RELATIVE TURGIDITY IN MAIZE (ZEA MAYS L.)
Authors: DOWNEY LLOYD A. , MILLER J. W.
Published: May 2006

Summary

Two rapid methods of assessing relative turgidity in maize are described. The first involved measuring the water uptake by discs of leaf tissue but omits the oven dry weight from the calculation. Where the position on the leaf was standardized, the relationship was linear (r = 0.99***) over a wider range than normally encountered in field conditions. The regression relationship held for plants grown under a wide variety of environmental conditions and at various stages of development.

The second method utilized a series of photographic standards of plants at different relative turgidities. Relative turgidity could then be estimated visually by comparing the plant and the photographic standards.

Accuracy with either method was similar to the experimental error of relative turgidity measured by normal means. Both offer a considerable saving in time, especially the photographic standard method which allows instantaneous readings to be made. This should permit field workers to assess rapidly the water status of their crop without the labour involved in conventional measurements.
MORPHOGENETIC STUDIES ON CULTURED MATURE ENDOSPERM OF CROTON BONPLANDIANUM
Authors: BHOJWANI S. S. , JOHRI B. M.
Published: May 2006

Summary

The mature endosperm of Croton bonplandianum proliferated profusely on White's medium (WM) + 2 ppm 2,4‐D + 5 ppm kinetin + 2500 ppm yeast extract. Association with the embryo was essential for initiation of proliferation of mature endosperm. Tracheidal cells usually differentiated. Twelve‐month‐old callus contained predominantly triploid and hexaploid cells. When the callus obtained on WM + 2,4‐D + kinetin + yeast extract was subcultured on WM triploid roots formed in 25% of the cultures. At 10−7 M, IBA, IAA, or NAA, in WM, promoted rooting; IBA was most effective. Attempts to induce shoot differentiation failed.
FUNGUS–ALGA ASSOCIATION IN LICHENS OF THE TELOSCHISTACEAE: AN ULTRASTRUCTURAL STUDY
Authors: GALUN MARGALITH , BEN‐SHAUL Y. , PARAN NAVAH
Published: May 2006

Summary

The ultrastructure of the physical contact between fungus and alga has been examined in six species of the lichen family Teloschistaceae. The relation between the fungus and living algal cells was found to be merely one of very close proximity of their cell walls. Only a few distorted algal cells were found to be intracellularly invaded by the fungus. The association between the symbionts was compared with that previously observed in lichens of the Lecanoraceae and Lecideaceae.
STELAR EVOLUTION IN VASCULAR PLANTS
Authors: SLADE BRENDA F.
Published: May 2006

Summary

Recently Namboodiri and Beck (1968c) and Beck (1970) in proposing a new hypothesis of stelar evolution in the gymnosperms failed to mention its possible application to angiosperms. This paper, by showing the close similarity of the primary vasculature of gymnosperms with that of the ‘parastichous type’ (Philipson and Balfour, 1963) in dicotyledons, shows that the hypothesis applies equally to both groups. Brief reference is made to other instances of stelar structure where application of the leaf‐gap theory (Jeffrey, 1902, 1917) has failed. Here Namboodiri and Beck's new concept, that parenchymatous areas may arise having no association with leaf gaps, is most helpful.
CONTRIBUTIONS TO THE ECOLOGY OF BRACKEN (PTERIDIUM AQUILINUM)
Authors: WATT A. S.
Published: May 2006

Summary

The phenomena of change from the marginal belt to the hinterland on the acid sandy podsol of area E are regarded as symptoms of senescence (increase in age of the frond population and in patchiness: reduction in height and number of fronds, in size of plant and its rate of growth). They are considered in relation to causes, primary and secondary.

The primary cause is the plant's reaction on itself: in the invading marginal plant increasing competition until the maximum number is reached (at 30–40 ft; 9–12 m) and reaction on the root and rhizome system through the amount and kind of litter. Once started a chain of reactions is set up in which frost and drought are important but secondary causes.

Litter (s.l.) acts in two ways with opposing effects on the welfare of bracken but with no hard and fast line between them and the effect varying with the conditions. Litter (s.s. = the L layer) when abundant, as in the mid‐region of the marginal belt, means protection from winter frost and drought and by delaying emergence of the fronds reduces liability to spring frost and in its F and H forms induces a concentration of roots in them, a rise in the general level of the shoot system and greater vulnerability of the growing points to frost and drought. With age of the population the F and H layers increase relatively to the L (s.s.).

Data on the vigour and vertical distribution of the rhizome system from an area (Blaxhall Heath) vacated by bracken and from the live bracken marginal to it show a similar robust but dead system in both, which in the latter has a younger, superficial, attenuated system, consisting mostly of intermediate and short shoots above it and lying almost wholly in the F layer. Details show that the process of degeneration has not only been checked but recently reversed.

Response to fluctuations in weather show that the hinterland plant is not inherently weak, but its attainment of a size and vigour similar to that of the marginal plant depends on conditions enabling it to reach that status and to maintain it on the continued provision of open conditions with little competition.

The interpretation of degeneration (regression) advanced here does not invoke the presence of a pathogen.

The results are considered briefly in relation to the status of bracken in a man‐controlled environment.
A METHOD FOR THE GROWTH OF LARGE BATCHES OF PLANTS IN AN ASEPTIC ENVIRONMENT
Authors: WILDON D. C. , WONG DOREEN , BRYANT J. A.
Published: May 2006

Summary

A method for growing large numbers of seedlings under aseptic conditions is described. The method makes use of peracetic acid for the initial sterilization of the seeds, followed by transfer of the seeds to a flexible film sterile isolator for germination and growth in an aseptic environment.
DISTRIBUTION OF THE LICHEN CHONDROPSIS SEMIVIRIDIS IN RELATION TO ITS HEAT AND DROUGHT RESISTANCE
Authors: ROGERS R. W.
Published: May 2006

Summary

The distribution of Chondropsis semiviridis (FvM. ex Nyl.) Nyl. was mapped for Australia. Studies in gas exchange physiology demonstrated that length of drought is likely to limit distribution of the species. Similarly, it is shown that sensitivity to heat when wet is likely to prevent the species from establishing in arid areas with a summer rainfall seasons The surge of respiration upon wetting of lichen thalli noted by other workers was so short for C. semiviridis that it could not affect the limits of its distribution.
FREEZING RESISTANCE OF RELICTS FROM THE ARCTO‐TERTIARY FLORA
Authors: SAKAI A.
Published: May 2006

Summary

The freezing resistance of winter twigs of genera which became extinct in Japan during Tertiary time, such as Sequoia, Metasequoia, Taxodium, Glyptostrobus, Pseudolarix, Keteleeria and Liquidambar, has been investigated. Except for Taiwania, Sequoia, Cunninghamia lanceolata, most of the genera were found to survive freezing down to – 20° to – 25°C, and Metasequoia and Taxodium to resist freezing down to – 25° to – 30°C. Most of the typical temperate deciduous genera native to Japan, such as Carpinus, Zerkova, Castanea, Acer and Cercidiphyllum, which lived together with the extinct genera during the Tertiary as common members of the Arcto‐Tertiary Forest, were also found to survive freezing down to –20° to – 25°C. From the standpoint of freezing resistance, it therefore seems likely that most of the Arcto‐Tertiary genera which became extinct in Japan could winter in the deciduous forests in Japan during late Tertiary time, unlike evergreen broad‐leafed trees and some conifers such as Taiwania, Sequoia and Cunninghamia lanceolata. To clarify the reason of their distinction from the standpoint of cold injury, a further study on their resistance to winter desiccation is required.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: HOLLIGAN P. M. , JENNINGS D. H.
Published: May 2006

Summary

Cultures of Dendryphiella salina, grown in a liquid glucose‐tryptone medium, were transferred to a similar but more dilute medium until the mycelial soluble carbohydrates had been depleted. These so‐called starved cultures were then placed in various defined (regrowth) media, differing particularly with respect to concentrations of glucose and nitrate. The changes in mycelial carbohydrates, which occurred during starvation, and afterwards, in the regrowth media, were determined by gas chromatography.

Mannitol and arabitol were the major products of glucose assimilation. When this sugar was depleted from the medium, mannitol was readily catabolized. By contrast, accumulation of arabitol continued for several hours after the exhaustion of substrate glucose and the maximum levels attained were dependent upon the nitrogen source.

Microscopical observations on the mycelium during starvation and regrowth are reported. The results are discussed in relation to other studies on the growth of fungi in stirred liquid culture.
THE EFFECTS OF WATER STRESS ON NITROGEN‐FIXING ROOT NODULES
Authors: SPRENT JANET I.
Published: May 2006

Summary

Water stress reduced nitrogen fixation of soybean plants grown in pots of sand. Provided that the nodules retained some activity, recovery on watering was normally complete in an hour. Using tritiated water (3HOH) it was confirmed that water could be withdrawn by nodules en route from the root to the shoot system.

A field trial with Vicia faba showed a high degree of correlation between soil‐water content and nitrogen‐fixing activity. Slow natural drying over a 6‐week period resulted in progressive reduction of activity, which was restored by irrigation. Maximum nitrogen fixation occurred at about field capacity; above this, activity was reduced due to water logging. Under the conditions of the experiment, water supply was the major environmental factor affecting nitrogen fixation.

It is suggested that water stress affects nodule activity directly, but that this effect may be aggravated by reduced supplies of photosynthate from wilted leaves.
THE EFFECT OF VESICULAR‐ARBUSCULAR MYCORRHIZAL ASSOCIATIONS ON GROWTH OF CEREALS
Authors: KHAN A. G.
Published: May 2006

Summary

The subsequent growth of maize seedlings which were already mycorrhizal when planted in the field was improved compared with non‐mycorrhizal controls. Mycorrhizal plants removed more phosphorus from the soil and had greater dry matter and phosphorus. There were positive correlations between spore number in the soil and mycorrhizal development, and between extent of root infection and increased growth. Root infection decreased with an increase in phosphorus level of the soil. The onset of the reproductive process in non‐mycorrhizal plants growing without added fertilizer was delayed and, even in those cases where ears did form, their quality was poor. Number of grains per ear and grain weight were increased almost twelve times by the fungus.
THE ACCUMULATION OF ZINC BY SUBCELLULAR FRACTIONS OF ROOTS OF AGROSTIS TENUIS SIBTH. IN RELATION TO ZINC TOLERANCE
Authors: TURNER R. G. , MARSHALL C.
Published: May 2006

Summary

Zinc tolerance in the grass, Agrostis tennis Sibth., was investigated by comparing the uptake of radiozinc by the cell wall and mitochondrial fractions from the roots of sixteen different populations. Large differences in tolerance between populations were found. There was a significant correlation between zinc accumulation by each subcellular fraction and the index of zinc tolerance but the cell wall fraction accumulated a greater quantity of zinc. There was no correlation between the nitrogen content of the cell wall fraction and zinc tolerance. The importance of metal accumulation by the cell wall fraction is discussed and it is suggested that it is a major feature of the mechanism of tolerance to heavy metals in A. tenuis.
AFTER‐EFFECTS OF NIGHT TEMPERATURES ON STOMATAL BEHAVIOUR AND PHOTOSYNTHESIS OF SORGHUM
Authors: PASTERNAK DOV , WILSON G. L.
Published: May 2006

Summary

Exposure of whole sorghum plants to cold (5° C) or hot (30° C) nights, or exposure of shoots only to a range of low night temperatures (5—15° C) reduced both the rate and extent of stomatal opening during the succeeding day. Photosynthesis was correspondingly reduced. The reduction in the rate of stomatal opening could be attributed to a development of water deficits in the leaves.
IDENTIFICATION OF ABSCISIC ACID IN YOUNG STEMS OF PINUS RADIATA D. DON
Authors: JENKINS P. A. , SHEPHERD K. R.
Published: May 2006

Summary

An inhibitor from Pinus radiata was separated using paper chromatography from an acidic ether fraction of a stem tissue extract. Using electrophoresis the inhibitory activity was resolved into two parts. One part remained at the origin. The second part behaved similarly to ABA, in electrophoresis and was investigated further.

The inhibitor has similar properties to ABA in electrophoresis; TLC using a number of solvent systems; UV fluorescence spectra: UV absorption; ORD spectra and gas chromatography. Final proof of the identity of the natural inhibitor as ABA was obtained by gas chromatography‐mass spectrometry.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A.
Published: May 2006

Summary

An unusual pattern of senescence occurs in the root caps of embryos of Zea mays subjected to an artificial ageing treatment. After an initial reversal of membrane damage in the first stages of germination, precocious senescence was observed in the zone of differentiation of the root cap at the 48‐hour stage of germination. These senescent changes occurred suddenly, with apparently normal cells being found immediately adjacent to cells in which the entire protoplast had degenerated. Acid phosphatase activity was confined to lysosome‐like organelles in the still‐organized cells, but was distributed throughout the ground cytoplasm of the adjacent senescent cells. The degenerative changes appeared to progress from the outermost cells proximally towards the chronologically younger cells. Thus the precipitous senescent changes were probably caused by the release of hydrolases normally confined within lysosomes, and the precocious senescence was due to an acceleration of a genetically‐controlled process of ageing.
POLLEN TUBE GROWTH AND THE SITE OF THE INCOMPATIBILITY REACTION IN BRASSICA OLERACEA
Authors: OCKENDON D. J.
Published: May 2006

Summary

Unpollinated, cross‐pollinated and self‐pollinated stigmas of Brussels sprouts and kale were examined in a scanning electron microscope as fresh uncoated specimens. The stigmatic papillae are closely appressed in young stigmas, but are held apart in the mature stigma by the swollen bases of the papilla cells. Some self‐pollen tubes show obvious signs of inhibition by being very short, or by coiling over the surface of the papilla without penetrating it. Other self‐pollen tubes appear to behave like cross‐pollen tubes by producing tubes which penetrate papillae directly. The implications of these observations for the identification of the site of the incompatibility reaction are discussed.
THE EFFECT OF PRE‐TREATMENT WITH GIBBERELLIC ACID ON THE DISTRIBUTION OF PHOTOSYNTHATE IN INTACT AND DISBUDDED PLANTS OF SOLANUM TUBEROSUM L.
Authors: BOOTH A. , LOVELL P. H.
Published: May 2006

Summary

Before tuberization, the radiocarbon from 14CO2 fixed by single leaves of Solanum tuberosum cv. Majestic was distributed fairly uniformly throughout the plant and treatment with gibberellic acid prior to 14CO2 fixation bad little effect on the distribution of labelled assimilates. After tuberization, the tubers imported the majority of the 14C supplied. Pretreatment with gibberellic acid greatly reduced accumulation of assimilate in, and growth of, tubers, particularly in the 7‐day period following pretreatment. This effect was manifest in plants from which all aerial shoot‐apices had been removed, suggesting that gibberellic acid acted directly on the tubers. The reduced import by tubers in gibberellic acid‐treated plants was associated with a substantial decrease in the ratio, 14C in the ethanol‐insoluble fraction to 14C in the ethanol‐soluble fraction. It is proposed that the main effect of gibberellic acid is to decrease starch accumulation and increase sugar levels in the tubers, and that these changes are associated with the characteristic‘growing‐out’ of the tubers and a ‘switching‐off’ of the tuber sink.
STOMATAL‐DIFFUSION RESISTANCE AND WATER POTENTIAL OF SOYBEAN AND SORGHUM LEAVES
Authors: TEARE I. D. , KANEMASU E. T.
Published: May 2006

Summary

Hourly trends in stomatal resistance and water potential of the upper leaves of sorghum and of soybean canopies (measured with diffusion porometer and thermocouple psychrometer) tended to parallel each other. Vertical profiles (both canopies) indicated that the stomatal resistance of the lower leaves usually was greater than that of the upper leaves. The position of minimum resistance varied with time of day. The profiles of temperature and water‐vapour pressure were consistent with the profile of canopy transpiration resistance. The upper sorghum leaves had a lower water potential than the lower leaves. In the morning a strong gradient of water potential existed from lower to upper leaves in plants in both canopies; in the afternoon the gradients continued in sorghum but disappeared in soybean plants.
THE PATTERN OF DISTRIBUTION OF AGROSTIS AND FESTUCA PLANTS OF VARIOUS GENOTYPES IN A SWARD
Authors: SMITH A.
Published: May 2006

Summary

Samples from a population of plants present in a grazed hill sward were isolated and grown as spaced individuals at a lowland site. The predominant taxa present were Agrostis, chiefly A. tenuis Sibth., and Festuca rubra L. Within each species, there was considerable variation between plants obtained from a relatively small area of sward. From an examination of morphological characters and tests of self‐ and cross‐compatibility among plants, an indication of the number of genotypes present was obtained. Eighty‐four putative genotypes of Agrostis and forty of Festuca were identified. A map is given showing the position of each putative genotype in the original population and the structure of Agrostis‐Festuca swards is discussed.
EFFECTS OF DAYLENGTH AND CHILLING ON THE RESPONSES OF DOUGLAS‐FIR (PSEUDOTSUGA MENZIESII (MIRB) FRANCO) SEEDLINGS TO ROOT DAMAGE AND STORAGE
Authors: LAVENDER D. P. , WAREING P. F.
Published: May 2006

Summary

A series of experiments designed to identify the factors responsible for reduced seedling vigour and survival in Douglas‐fir seedlings following lifting and cool, dark storage in the fall, is described. Although pretreatment under short days leads to reduced root activity and less ability to regenerate new roots, this response does not account for the adverse effects of lifting and dark storage in the fall, since these latter effects are, in fact, greater after pretreatment with long days than short days. A period of chilling, following short‐day pretreatment, greatly increases the seedlings' resistance to the adverse effects of root damage and dark storage. The deleterious effects of dark storage can be greatly reduced by a daily exposure to several hours of low intensity illumination. The adverse effects of dark storage at cool temperatures appear to be exerted primarily through the roots, since maintenance of the roots at 15° C and of the shoots at 2° C largely removes the adverse effects of storage. The regeneration of roots by chilled seedlings is dependent on the presence of needles. If the needles are removed their effect on root regeneration cannot be replaced by application of naphthalene‐acetic acid, niacin or pyridoxine.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A.
Published: May 2006

Summary

Embryos of Zea mays that had lost viability were still able to continue certain metabolic processes. Radicle emergence and cell division did not occur, and mitochondria and plastids appeared to be degenerate. However, ER synthesis and delayed polysome formation occurred, 3‐uridine and 3H‐leucine were incorporated, and certain cells were able to take up 3H‐thymidine. From the sequence of events, it is concluded that loss of viability was due to general damage to macromolecules, including nucleic acids, membrane components, and enzymes.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A.
Published: May 2006

Summary

Following an accelerated ageing treatment, the radical cells of non‐viable embryos of Zea mays were found to be disorganized. Organelles were swollen and did not differentiate into functional structures. During inhibition the cells deteriorated progressively and their cytoplasm lysed. Acid phosphatase activity, normally confined to lysosomal vacuoles, spread to the cytoplasm during inhibition, and this was presumed to indicate general release of hydrolytic enzymes. Loss of viability is considered to be a consequence of the deterioration of membrane systems.
FEATURES OF MYCORRHIZAL INFECTION IN SOME MALAYAN ORCHIDS
Authors: HADLEY G. , WILLIAMSON B.
Published: May 2006

Summary

In the roots of most species of terrestrial and epiphytic Malayan orchids examined, mycorrhizal infection was spasmodic and confined to a small proportion of the root cortex cells. Only a few terrestrial species exhibited the pattern of dense infection seen in north temperate orchids. Chlorophyllous tissue in the roots of some terrestrial and epiphytic species was invaded and cytological changes, including fragmentation and disappearance of the chloroplasts, occurred in some instances.

Measurements of host cell nuclei indicated that nuclear hypertrophy occurred not only in infected cells but also in many non‐infected cells localized around pockets of infection.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: HOLLIGAN P. M. , JENNINGS D. H.
Published: May 2006

Summary

The incorporation of radioactivity into polyols and carbon dioxide was measured for cultures of Dendryphiella salina incubated in media containing [i‐14C]‐ or [6‐14C]‐glucose, with nitrate, ammonium or glutamate as nitrogen sources.

The labelling patterns show that mannitol is synthesized partly via a direct route from substrate glucose and partly from hexose‐phosphate derived from the pentose‐phosphate pathway. Rapid turnover of the mannitol pool and the redistribution of radioactivity caused by the symmetry of the mannitol molecule lead to the synthesis of labelled arabitol from both forms of radioactive glucose. After a 6‐hour incubation period, the proportion of mannitol synthesized via the pentose‐phosphate pathway ranges from 36% in nitrate media to 19% in glutamate media.

C1/C6 ratios for yields of 14CO2 also indicate that the activity of the pentose‐phosphate pathway is greatest in the nitrate media and least in the presence of glutamate. Furthermore, there is an increase in the C1/C6 ratio when nitrate or methylene blue is added to cultures in ammonium media.

The results are discussed in relation to previous studies of the pentose‐phosphate pathway in fungi containing mannitol.
MORPHOLOGY AND TAXONOMY OF THE OOMYCETES, WITH SPECIAL REFERENCE TO SAPROLEGNIACEAE, LEPTOMITACEAE, AND PYTHIACEAE
Authors: DICK M. W.
Published: May 2006

Summary

Problems of intraspecific variability and the delimitation of taxa are discussed in relation to the patterns of inheritance in Oomycetes made possible by the combination of a haplobiontic‐B life cycle with multinucleate gametangia.
ENDOGENOUS INORGANIC CARBON SOURCES IN PLANT PHOTOSYNTHESIS
Authors: RAVEN J. A.
Published: May 2006

Summary

The biochemical evidence concerning the rate of production of CO2 by dark respiratory pathways in illuminated green plant cells is reviewed.

Pyruvate decarboxylation and the TCAC are important sources of biosynthetic intermediates in the light as well as in the dark. The rate of CO2 release required to synthesize these carbon skeletons from pyruvate in the light approaches the rate of dark CO2 production. Oxidative phosphorylation, the second important role of the TCAC in the dark, is supplemented and partly replaced by photophosphorylation in the light, and some sort of ‘physiological uncoupling’ may be required to stop the rate of generation of reductant in the TCAC in the light from exceeding the rate of its consumption in oxidative phosphorylation. The decarboxylations of pyruvate and TCAC metabolism occur, in the light as in the dark, in the mitochondria (except possibly in Acetabularia, where they may also occur in the choroplasts). All the decarboxylations produce unhydrated CO2.

The oxidative PPP has no obligatory role to play in carbon skeleton synthesis, and it is supplemented in its dark rôle of NADPH2 synthesis by photoproduction of reductant when the cell is illuminated. Evidence as to whether light stimulates or inhibits the oxidative PPP is contradictory. This pathway occurs in at least some illuminated green cells; the decarboxylation reaction produces unhydrated CO2, and occurs in both the cytoplasm and the chloroplast.

The situation with regard to carbon flux through the dark respiration pathways in various groups of plants is considered quantitatively. Even without taking into account the contribution from light‐dependent pathways of CO2 production (photorespiration), it would appear that the absence of net CO2 release to a CO2‐free gas stream in the light in a green cell or tissue cannot entirely be attributed to inhibition of respiration. The absence of CO2 release must also reflect the capacity of the tissue for reassimilation of endogenous CO2.
‘DUAL ISOTHERMS’ FOR THE ABSORPTION OF IONS BY PLANT TISSUES
Authors: BARBER D. A.
Published: May 2006

Summary

It has frequently been demonstrated that when plant tissues of the same initial ionic status are transferred to solutions of a sufficiently wide range of concentration, two absorption isotherms are observed. They have been widely interpreted as evidence for the existence of two independent physiological mechanisms for the absorption of nutrients. The experiments here described on the uptake of phosphate and rubidium ions by excised barley roots and discs of beetroot tissue from solutions ranging in concentration between 0.001 and 50.0 mM were conducted by procedures similar to those on which the foregoing conclusions had been reached, except that sterile procedures were used to eliminate any effects of micro‐organisms. The two absorption isotherms were evident under sterile conditions. However, evidence was obtained that only uptake observed at low concentrations (below 0.2–0.5 mM) is attributable to plant metabolism. The isotherm observed over the higher concentration range is accountable to passive diffusion and may thus be regarded as a consequence of the experimental procedures.
THE INFLUENCE OF PHOSPHORUS DEFICIENCY ON THE TRANSPIRATION OF ARCTIUM MINUS BERNH.
Authors: ATKINSON D. , DAVISON A. W.
Published: May 2006

Summary

The effect of phosphorus deficiency on the transpiration of Arctium minus was investigated. The transpiration rate of the phosphorus‐deficient plants was lower than that of the controls. This situation was reversed after wilting which depressed the transpiration rate of the control plants. The ratio of light to dark transpiration was higher in the control plants, and covering the abaxial surface of their leaves with petroleum jelly caused a proportionately greater reduction in their rate of transpiration. The leaves of the deficient plants were composed of smaller cells than those of the controls. An examination of leaf surfaces showed that those of the deficient plants were covered by a much denser layer of hairs. It was concluded that the difference in the rate of transpiration was probably connected with stomatal functioning.
IONIC RELATIONSHIPS OF ENTEROMORPHA INTESTINALIS
Authors: BLACK D. R. , WEEKS D. C.
Published: May 2006

Summary

Concentrations of the major component ions (K, Na and Cl) of sea water and cells of Enteromorpha intestinalis (L.) Link, were determined. Measurements of the electric potential difference across the plasmalemma and the influx and efflux of each ion indicate that K and Cl are actively imported and Na actively exported. Estimates of membrane permeability to the passive diffusive fluxes of these three ions alone have been used to explain the origin of the cell membrane potential. Tracer ion exchange kinetics are taken as showing that the tonoplast is more permeable than the plasmalemma to each ion.
AGEING IN PLANT EMBRYOS II. AGE‐INDUCED DAMAGE AND ITS REPAIR DURING EARLY GERMINATION
Authors: BERJAK PATRICIA , VILLIERS T. A.
Published: May 2006

Summary

The rate of ageing of a batch of caryopses of Zea mays was accelerated by placing in a controlled environment of high temperature and humidity. Samples were withdrawn representing a sequence of increasing physiological ageing, and selected stages were subjected to ultrastructural and cytochemical investigation. Membrane aberrations increased with increasing age of the embryos. The damage was seen immediately upon imbibition, but there was much evidence of repair of this damage at later stages of germination. The existence and operation of mechanisms for the repair of such damage are discussed.
CYTOLOGY OF SIEVE ELEMENTS IN MINOR VEINS OF SUGAR BEET LEAVES
Authors: ESAU KATHERINE
Published: May 2006

Summary

In view of some questions raised in the literature on assimilate translocation regarding the degree of differentiation of sieve elements in minor veins of Beta vulgaris L. these elements were examined with light and electron microscopes. The sieve elements throughout the minor veins in the sugar beet leaf, including those in the free endings of the veins, have typically differentiated sieve plates, with pores usually lined with callose and containing P‐protein. The sieve plates occur in the end walls and the side walls. The sieve elements are connected with adjacent parenchyma cells (including the companion cells) by branched plasmodesmata. The protoplasts of the sieve elements undergo ontogenetic changes common for these cells in most vascular plants. The one to several sieve elements seen in transection of a minor vein attain maturity before the xylem is completely differentiated. No sieve elements are added after this stage, and the earliest mature sieve elements are not obliterated. The parenchyma cells (including the companion cells) of the phloem are generally several times wider than the sieve elements and constitute the major part of the tissue. However, the width of a parenchyma cell may vary at different levels so that in some sections a given parenchyma cell may not exceed a sieve element in width even if it does so in other sections.
THE ULTRASTRUCTURE OF GUARD CELLS OF PHASEOLUS VULGARIS
Authors: WHATLEY J. M.
Published: May 2006

Summary

The ultrastructure of mature guard cells of Phaseolus vulgaris L. grown under continuous light regime showed remarkable stability, remaining constant in appearance under a wide range of conditions of nutrient deficiency. The ultrastructure was quite unlike that of leaf parenchyma cells of normal plants, but had certain characteristics similar to those found in palisade parenchyma cells suffering from magnesium and potassium deficiency.
SOME OBSERVATIONS ON THE EVOLUTION OF POLLEN TYPES IN DICOTYLEDONS
Authors: SPORNE KENNETH R.
Published: May 2006

Summary

Sulcate pollen is shown statistically to be positively correlated with four primitive characters. There is some evidence that tricolpate pollen is more primitive than triporate. Polyporate pollen and polycolpate pollen are negatively correlated with two and six primitive characters, respectively, while multiaperturate pollen is negatively correlated with seven primitive characters. Evolution, therefore, has involved a progressive increase in the number of apertures. This conclusion is supported by the fossil record.
ULTRASTRUCTURE AND ION GRADIENTS IN THE SALT GLANDS OF AVICENNIA MARINA (FORSSK.) VIERH.
Authors: SHIMONY CARMELA , FAHN A. , REINHOLD LEONORA
Published: May 2006

Summary

The salt gland of Avicennia marina consists of two to four collecting cells, one stalk cell and usually eight secretory cells. The side wall of the stalk cell is completely impregnated with electron‐dense material. An amorphous substance appears between the upper walls of the secretory cells and the cuticle above them. The latter possesses many narrow channels.

The ultrastructure of the secretory cells was studied under various conditions. The protoplast is usually dense and poorly vacuolated. The nucleus is relatively large, and the cytoplasm rich in organelles, especially E.R. elements, Golgi bodies and mitochondria. There are many vesicles which appear to be derived from the Golgi bodies and from E.R. cisterns. Elongated vacuole‐like structures, apparently derived from Golgi cisterns, and membranous bands were also observed: it is suggested that both represent different stages of the same structure. In many glands the protoplast appeared to be contracted in one of the secretory cells and the space between it and the cell wall was filled with an amorphous electron‐dense substance.

Antimonate precipitation and electron probe analysis were employed to locate ions in the tissues. Both techniques indicated that the salt content of the gland cells was lower than that of the mesophyll. A downhill gradient appeared to exist from cells near the xylem, through the mesophyll to the gland, and was continued through the gland itself. The possible location of ion pumps is discussed in the light of this evidence.
AGEING IN EXCISED ROOTS OF TOMATO
Authors: WESTON GEOFFREY D.
Published: May 2006

Summary

Glucose pre‐treatment enhances ageing in excised roots of tomato on subsequent sub‐culture in sucrose medium to a much greater extent than pre‐treatment in sucrose or fructose. However, continual sub‐culture in glucose medium causes much less ageing than continual sub‐culture in sucrose or fructose. Sugar concentrations used were such as to preclude effects due to osmotic potential changes. Pre‐treatment in mixtures of glucose and sucrose caused less ageing than glucose alone, but this may be due to the demonstrated reduction in glucose absorption caused by sucrose. A two‐stage system for the development of ageing is proposed and this is discussed in the light of earlier studies on ageing in cultured tomato roots.
UPTAKE OF 32P BY PINUS RADIATA ROOTS INOCULATED WITH SUILLUS LUTEUS AND CENOCOCCUM GRANIFORME FROM DIFFERENT SOURCES OF AVAILABLE PHOSPHATE
Authors: MEJSTŘÍK V. K. , KRAUSE H. H.
Published: May 2006

Summary

The efficiency of the mycorrhizal fungi Cenococcum graniforme and Suillus luteus on young seedlings of Pinus radiata for phosphorus uptake from different sources was investigated using 32P. There was a stimulatory effect of mycorrhizas with Suillus luteus on uptake of phosphorus. Cenococcum graniforme had a stimulatory effect on incorporation of 32P only when most of the phosphorus was in organic form. In the other conditions this symbiont had an inhibitory effect. There was a greater accumulation of phosphate in the roots than in the green parts of the seedlings.
POLLEN‐RAIN FROM THE VEGETATION OF NORTH‐WEST INDIA
Authors: SINGH G. , CHOPRA S. K. , SINGH A. B.
Published: May 2006

Summary

A general survey of the pollen‐rain from the vegetation of north‐west India is described. The survey is based on the study of 114 modern pollen spectra from sixty‐four different sites. It is revealed that with certain qualifications the major aspects of the extant vegetation belts of north‐west India are reflected in the pollen‐rain falling within them. In the territory as a whole, the pollen of herbs dominates that of trees and shrubs except in close proximity to one of the latter. Amongst the woody plant pollen that of shrubs is commonest in the arid belts but tree Pollen asserts itself as rainfall increases. The long‐distance transport of pollen from one region to another does not affect the overall picture of the pollen‐rain to any significant degree except in the areas bordering the Himalayas where pine pollen is over‐represented. Cerealia type pollen usually occurs in areas where there is cereal cultivation but remains unrepresented in the very arid belt which is free of cereal agriculture. The pollen frequencies of Acacia, Prosopis, Zizyphus, Salvadora, Maytenus and the species belonging to Leguminosae, Labiatae and Geraniaceae are Under‐represented. On the other hand 5% pine pollen occurs even as far as 600 km from the source.
FACTORS INFLUENCING THE GROWTH OF THE ROOT SYSTEM OF ETIOLATED SEEDLINGS OF PISUM SATIVUM L.
Authors: MCDAVID C. R. , MARSHALL C. , SAGAR G. R.
Published: May 2006

The growth of the root system of dark grown dwarf‐pea seedlings ceases 10–12 days after germination, even though cotyledonary reserves continue to be used for shoot growth. The cessation of root growth was not due to competition between shoot and root for cotyledonary reserves, but appeared to be the result of a depletion of essential factors which are normally supplied to the root by the light‐grown shoot. These factors included auxin, the B vitamins (thiamine and nicotinic acid) and adenine. Application of IAA in lanolin to the cut stumps of de‐shooted seedlings plus a supply of thiamine, nicotinic acid and adenine in the culture solution substituted to some extent for an illuminated shoot.
AN IMPROVED BIO‐ASSAY FOR ABSCISIC ACID AND OTHER ANTITRANSPIRANTS
Authors: OGUNKANMI A. B. , TUCKER D. J. , MANSFIELD T. A.
Published: May 2006

A greatly improved method is described for the bio‐assay of abscisic acid (ABA) and other compounds that possess ‘antitranspirant’ activity. As in the previous method, the stomatal responses are observed on pieces of isolated epidermis of Commelina communis immersed in small volumes of solution containing the compounds to be assayed. In new media, it is now possible to obtain linear responses to ABA concentrations over the range 10‐4‐10‐8 M in PIPES buffer at pH 6.8, and over the range 10‐7‐10‐10 M in citrate buffer at pH 5.5. In citrate buffer, it is possible to detect as little as 26 pg of ABA. In both media, the assay is unaffected by the presence of six other growth regulators (auxin, gibberellic acid, kinetin, coumarin, xanthinin and scopoletin) but the stomata closed partially in response to 10‐3 M chlorogenic acid.
GROWTH AND WATER ABSORPTION OF WHEAT WITH PARTS OF THE ROOTS AT DIFFERENT WATER POTENTIALS
Authors: LAWLOR D. W.
Published: May 2006

The growth and water transport of wheat plants was measured with the root system divided into two equal parts and grown in solutions of different osmotic potential. Growth of roots decreased with decrease in osmotic potential and stopped at ‐10 bar, but solutions of high osmotic potential, available to part of the root system, did not significantly influence the growth of the other part of the root system when the osmotic potential was small. However, it did allow greater growth of leaves and faster transpiration rates, because plant water potential was not greatly decreased. The rate of water transport slowed with decreasing osmotic potential but with part of the root system under stress absorption from solutions of high potential increased. The resistance of the parts of the root system and plant increased, approximately logarithmically, with decreasing leaf water potential from ‐4 to ‐17 bar. Roots are influenced by the potential of water at their surface, but a decrease in water absorption by part of the root is compensated for by an increase in water absorption by other roots.
HYDROPHILIC GROWTH INHIBITORS FROM LAMINARIA AND ASCOPHYLLUM
Authors: HUSSAIN A. , BONEY A. D.
Published: May 2006

Water‐soluble compounds isolated from Laminaria digitata and Ascophyllum nodosum caused marked inhibition of lettuce hypocotyl growth. GLC analysis of these substances showed, in one case, properties similar to ABA (abscisic acid) but definite information on this must be deferred until the chemical nature of the seaweed compound is verified. The possible role of these compounds in seaweed growth and their possible significance as ectocrines in the sea, are discussed.