bluuebunny/crossref_metadata_2025 huggingface dataset:
SAMPLING SYSTEMS TO ASSESS VARIABILITY IN THE NEEDLES OF TWELVE MEXICAN PINES
Authors: WOOD P. J.
Published: May 2006

Summary

The needle characteristics were studied of twelve Central American and Caribbean pines planted in a 3‐year‐old trial at Chati, Zambia, using a multistage sampling system with four levels. Variation patterns are given graphically for seven traits for each species, showing the effects of varying the sampling intensity at different levels. The practical aspects of the patterns found are discussed.
STUDIES IN THE VEGETATIONAL HISTORY OF MID‐WALES
Authors: MOORE P. D.
Published: May 2006

Summary

Pollen analysis has been conducted upon a mire site at an altitude of 312 m on the Mynydd Bach region of western Cardiganshire. The sediments subjected to analysis began forming at the close of the post‐Allerød cold phase (zone III sensu Godwin) and document vegetational history in the area up to the time of the elm decline, after which deposits appear to have suffered interference by peat cutting.

A number of the features present at this westerly site are of particular interest, especially the early rise of Corylus in the Flandrian. Corylus pollen (expressed as % arboreal pollen) began to rise at this site before the zone III/IV Juniperus peak. As one moves progressively north in western Britain, so the Corylus rise is delayed until well after the juniper peak. This time lag is considered to reflect the migration rate of Corylus as well as offering an opportunity to trace its route up the western edge of Britain, gradually extending eastwards and into regions of higher altitude.

Pine values are low at Gwarllyn throughout the early Flandrian, in contrast to the upland areas of Cardiganshire, where pine increases to a maximum in zone VIc, It is postulated that Pinus was less successful in the western lowlands as a consequence of the greater competitive ability of Quercus under the prevailing climatic and edaphic conditions in those regions.
NUMERICAL METHODS IN QUATERNARY PALAEOECOLOGY I. ZONATION OF POLLEN DIAGRAMS
Authors: GORDON A. D. , BIRKS H. J. B.
Published: May 2006

Summary

The concept of the pollen zone as a fossil assemblage zone is discussed, and the advantages of numerical approaches to the recognition and delimitation of such zones are considered. Existing procedures are reviewed, and original constrained agglomerative and divisive procedures are advanced. The results of these procedures are discussed in relation to existing zonation schemes for three sets of data, and the limitations and potentialities of the procedures are considered. The initial zonations suggested by visual inspection are, in general, confirmed by the numerical procedures. The application of these procedures to the subdivision of both pollen and macro‐fossil data in the same stratigraphical sequence is also discussed. Details are given of the computer time and storage required for the analyses.
A SIMPLE METHOD OF ISOLATING STOMATA ON DETACHED EPIDERMIS BY LOW pH TREATMENT: OBSERVATIONS OF THE IMPORTANCE OF THE SUBSIDIARY CELLS
Authors: SQUIRE G. R. , MANSFIELD T. A.
Published: May 2006

Summary

Most previous studies of stomatal behaviour on isolated epidermis of Commelina communis have been carried out in media of pH 6.5‐7.0. In the present investigation we have used a wide range of pH values obtained with several different buffers, and have paid special attention to the response of the epidermis to incubation in media of pH 4.0‐5.0. Within this region of pH, all the cells of the epidermis apart from the guard cells were severely damaged, a condition leading to considerably enhanced stomatal openings even in media containing low concentrations (1 mM) or completely lacking inorganic cations. The guard cells appeared to continue to function normally, with stomatal apertures changing in response to light and CO2, and the cells showing the expected solute potential changes and potassium accumulation as opening occurred. The stimulation of opening might, in part, be attributable to the removal of pressure from the surrounding cells.

Exposure of epidermis to a pH of 4.5 for 1 1/2 hours proved to be a highly effective method of destroying all the cells apart from the guard cells, which apparently remained fully functional. This is a quick and reliable way of‘isolating’ stomata which could prove invaluable in future studies of their physiology and metabolism. A comparison of stomatal responses to solutes in the medium for epidermis with all cells intact and for epidermis with isolated stomata suggests a role for the subsidiary cells in regulating solute entry into the guard cells.
LIFESPAN AND BUDDING POTENTIAL OF LEMNA AS A FUNCTION OF AGE OF THE PARENT– A GENEALOGIC STUDY
Authors: CLAUS WALTER D.
Published: May 2006

Summary

Experiments tested claims that, in Lemna, increasing age of the parent reduces lifespan and reproductivity of the offspring. Successive cultures of nth buds (‘nth‐bud lines’, n= 1–10), and also of late‐buds and last‐buds, were observed for size and number of the buds they produced, and lifespan. Advancing age of the parent frond affected bud size, but had little or no effect on either lifespan or budding capacity of the offspring. First, second, and third buds of all lines were larger than their parents; successive buds then decreased in size approximately linearly with bud number or time of separation. Small, late buds, as parents, have smaller buds than do their early siblings. Numbers of buds produced by late buds, as parents, differ little from the numbers produced by their earlier siblings. Both groups vary randomly; together, their productivity is well represented by a normal distribution curve. Lifespans of early and late buds do not, on the average, differ markedly. ‘Survival curves’ indicate that early buds are more likely to survive into middle age (to produce nine‐ten buds), but late buds are more likely to survive into very old age and to produce thirteen‐fifteen buds. Bud production by late offspring is somewhat slower than that by early offspring.
ELECTROPHORETIC CHARACTERIZATION OF EUCALYPT MYCORRHIZAS
Authors: SEVIOUR R. J. , CHILVERS G. A.
Published: May 2006

Summary

Disc electrophoresis of extracts from mycorrhizas synthesized with different eucalypts, produces similar protein patterns when the same fungal symbiont is involved. Consequently, where sufficiently large homogeneous clusters of mycorrhizas can be collected, the technique is a valuable adjunct to anatomical classification of naturally occurring mycorrhizas.
BREEDING SYSTEMS IN COTULA L. (COMPOSITAE, ANTHEMIDEAE)
Authors: LLOYD DAVID G.
Published: May 2006

Summary

Five classes of sex expression are distinguished in Cotula on the basis of the degree of separation of male and female gametes on different flowers and plants. These classes are divided into sexually monomorphic and dimorphic systems. The order–monocliny, gynomonoecy, monoecy, subdioecy, dioecy–places the five classes in a linear sequence of increasing dependence for fertilization on the transfer of pollen between flowers and plants. Four of the five major taxonomic groups in Cotula and five species have more than one class of sex expression. The four monoecious and gynomonoecious species tested are self‐compatible. The morphology of hermaphrodite, male and female florets are compared.

Seven additional characters are associated with sex expression in New Zealand species. In general, the extent of protogyny, brightness of flowers, degree of retraction of stigmas and anthers, floret length, head diameter, peduncle length and the number of pollen grains increase from gynomonoecious through monoecious to dimorphic (dioecious or subdioecious) populations. But within each kind of sex expression there is considerable variation in these ancillary characters. A MAS (measurements associated with sex expression) index is calculated from the four quantitative characters for each New Zealand species (or part‐species where there are two kinds of sex expression in a species). The MAS index reflects the expenditure of energy on adaptations to cross‐pollination and provides an approximate measure of the relative frequency of outbreeding. The MAS indices of the species and part‐species indicate a continuous array in the expression of adaptations to cross‐pollination and the frequency of outbreeding. The different kinds of sex expression occupy characteristic but overlapping segments of this array and ought to be considered as convenient classes which only specify the breeding system approximately.
VARIATION IN GENTIAN A VERNA L.
Authors: ELKINGTON T. T.
Published: May 2006

Summary

The British populations of Gentiana verna are clearly distinguishable morphologically into two groups by both calyx and leaf characters. These groups are coincident with the geographical areas of the species, Teesdale in north England and Galway Bay in west Ireland. On the Continent, populations from the Alps and Pyrénées are indistinguishable in calyx characters, but are significantly different from English and Irish populations. Leaf length and length/ breadth ratio are correlated and the leaf length/breadth ratio of the Continental populations is clinally correlated with their altitude. Leaf characters of British populations are similar to those Continental populations from higher altitudes, those from Teesdale being indistinguishable from those at the highest altitudes. It is considered that these differences may either be the result of random drift or genecological differentiation. The possibility of variation in leaf morphology being related to heat transfer properties is discussed.
POSSIBLE PHANTOM HYBRIDS IN EUCALYPTUS
Authors: PARSONS R. F. , KIRKPATRICK J. B.
Published: May 2006

Summary

The distribution of Eucaiyptus cypellocarpa, E. goniocalyx and four populations apparently morphologically intermediate between these two but isolated from them is described in an area near Melbourne, Victoria. Scatter diagrams of various characters from both mature trees and progeny document and confirm that the four populations are intermediate. However, the variability of their progeny is not markedly different from that of the‘pure’ species and is not as high as that of recent hybrids between the two species. It is suggested that the four populations represent either old hybrid swarms now stabilized by selection from which the parents have disappeared, or that they arose without hybridization (a) by selection from a single species or (b) as a former cline between both species. The difficulties in interpreting the origins of such stands are pointed out.
THE DISTRIBUTION OF INTRASPECIFIC CHROMOSOME RACES OF HIPPOCREPIS COMOSA L. AND THEIR PHYTOGEOGRAPHICAL SIGNIFICANCE
Authors: Fearn Gillian M.
Published: May 2006

Summary

Results of a cytological survey of Hippocrepis comosa are reported and the geographical and ecological distribution of the three chromosome races, two of which occur in Britain, is described. Reasons for the restricted distribution of the diploid race are proposed and the probable post‐glacial history of both British races is discussed. This intraspecific polyploidy is related to the evolution of a polyploid complex.
AN IMPROVED CATHODE FOR THE MEASUREMENT OF PHOTOSYNTHETIC OXYGEN EVOLUTION BY ISOLATED CHLOROPLASTS
Authors: DELIEU T. , WALKER D. A.
Published: May 2006

Summary

The construction, operation and calibration of an improved form of a Clark oxygen electrode are described in detail. The electrode shows a rapid response (1–5 seconds) to change in oxygen concentration and is capable of measuring rates of oxygen evolution (or uptake) of up to 4 μmoles oxygen per minute. The use of a pair of electrodes to measure the oxygen evolution of choloroplasts at high intensity of illumination is described.
NITROGEN METABOLISM OF HALOPHYTES
Authors: STEWART G. R. , LEE J. A. , OREBAMJO T. O.
Published: May 2006

Summary

The present paper reports a study into the activity of nitrate reductase in plants of Suaeda maritima. The growth of S. maritima in the upper salt‐marsh appears nitrogen limited, going from the upper to lower marsh there is a three‐fold increase in total nitrogen of the plants. Nitrogen status and the activity of nitrate reductase are related. Plants from the lower marsh contain a fifty times higher level of enzyme than those from the upper marsh. By feeding nitrate to plants at different sites in the marsh it was possible to induce high nitrate reductase activity in plants that previously contained low levels of the enzyme. At all sites there is an equal potential to induce nitrate reductase. The induction experiments with plants in situ suggest that in this marsh nitrate availability is the main factor limiting the growth of S. maritima in the upper marsh.
THE LOSS OF POTASSIUM AND SODIUM FROM EXCISED BARLEY AND BEAN ROOTS
Authors: NASSERY H.
Published: May 2006

Summary

The loss of potassium and sodium from preloaded excised barley and bean roots was compared under identical experimental conditions. In barley roots, metabolic inhibitors stimulated the potassium loss but inhibited that of sodium, indicating an active mechanism for sodium extrusion. In excised bean roots, such a mechanism could not be demonstrated and the losses of potassium and sodium were both stimulated by DNP and cold‐treatment.
STUDIES ON THE LIGNOTUBERS OF EUCALYPTUS OBLIQUA L'HERIT.
Authors: BLAKE T. J.
Published: May 2006

Summary

Seasonal variations in apical dominance, maximal in summer and minimal during winter, were noted in eucalypt lignotubers. Temperature variation was more important than photo‐period in affecting seasonal variation of apical dominance. The concentrations of growth‐promoting and growth inhibiting substances in the leaves were correlated with seasonal variation suggesting that both have a role in apical dominance. Decapitation studies indicate that amounts of mineral nutrients and carbohydrate do not prevent dormant bud development.
STUDIES IN DACTILIS
Authors: PARKER P.F.
Published: May 2006

Summary

Samples of populations of Dactylis smithii native to Madeira were collected for studying seed set and morphological characteristics. The analysed data showed two main groupings, the reasons for these groupings and the resultant classification are discussed.
THE DIATOM FLORA OF THE HOXNIAN DEPOSITS AT MARKS TEY, ESSEX
Authors: EVANS G. H.
Published: May 2006

Summary

Samples from cores taken in the central and marginal areas of Hoxnian lacustrine beds at Marks Tey have been analysed for diatoms. Diatoms are extremely scarce in samples from the marginal areas. Non‐planktonic diatoms dominated the early parts of the interglacial. The change to planktonic dominance took place during the early‐temperate zone HoII. Stephanodiscus astraea var. minutula was the leading planktonic diatom. No diatoms have been found in deposits of post‐temperate age (zone HoIV), nor in the succeeding glacial deposits (Gipping Early‐glacial zone). In the Lowestoftian Late‐glacial deposits diatoms are scarce and corroded.
NITROGEN METABOLISM IN LICHENS IV. THE NITROGENASE ACTIVITY OF THE NOSTOC PHYCOBIONT IN PELTIGERA CANINA
Authors: MILLBANK J. W.
Published: May 2006

Summary

The content of the blue‐green alga phycobiont, Nostoc sp. in the lichen Peltigera canina has been estimated using various techniques and represents on average 2.7% of the total thallus nitrogen. Expressed in terms of cell numbers, this represents approximately 3 × 106 cells cm2, mature thallus. The nitrogenase activity, expressed as nil ethylene evolved/minute/mg Sostoc protein, varies considerably with the thallus sample, but a mean value of 10, considerably greater than that in free‐living Nostoc, has been found. The nitrogenase activity of the algal cells is particularly sensitive to disturbance of the thallus structure and the implications of these findings are discussed.
THE FREQUENCY OF HETEROCYSTS IN THE NOSTOC PHYCOBIONT OF THE LICHEN PELTIGERA CANINA WILLD.
Authors: GRIFFITHS H. BRONWEN , GREENWOOD A. D. , MILLBANK J. W.
Published: May 2006

Summary

A reliable estimate of 3.27% for the frequency of heterocysts in the cell population of the Nostoc phycobiont present in the thallus of the lichen Peltigera canina has been obtained by electron microscopy at low magnification.
LICHEN PHYSIOLOGY XII. THE ‘INHIBITION TECHNIQUE’
Authors: HILL D. J. , SMITH D. C.
Published: May 2006

Summary

During photosynthetic fixation of 14C by lichens, 14C‐carbohydrate moves from alga to fungus. If the 12C‐form of this mobile carbohydrate is added to the external medium, then the 14C‐form is released from the lichen. This observation forms the basis of the, inhibition technique', used to study movement of carbohydrates between symbionts within intact lichen thalli. The effect is specific since 14C is released from the lichen only if the 12C‐carbohydrate in the medium is identical or structurally very similar to that moving between the symbionts.

This paper examines the usefulness of the technique in the study of carbohydrate movement. Lichens were exposed to a short pulse of NaH14CO3 before transfer to carbohydrate media. Relatively high concentrations of carbohydrate (20 mM–80 mM) were needed for maximum ‘inhibition’. More than half the lichens examined released over 50%, of a pulse of fixed 14C during maximum ‘inhibition’ Using 2‐desoxy‐glucose as an ‘inhibitor’ of glucose movement in Peltigera polydactyla, it was shown that the supply of glucose from the alga was more than sufficient for the metabolic requirements of the fungus. The rate release of 14C during ‘inhibition’ varied widely between different lichens, but it was not clear if this was due to differences in pool sizes of mobile caibohydrates, or to real differences in rates of carbohydrate supply. Much less carbohydrate movement between the symbionts occurred in the dark, than in the light. The effect of pH on 14C release during ‘inhibition’ contrasted sharply with effects of pH on release from freshly isolated algae. This raised further doubts whether the behavior of freshly isolated algae is similar to those in the thallus. The explanation of ‘inhibition’ on the basis of a competition between the high concentration of external carbohydrate and the much lower concentration of 14C‐carbohydrate released from the alga at fungal uptake sites may require modification in at least some lichens. Competition or exchange between 12C and 14C carbohydrates may begin at stages before the fungal uptake sites.
SOME OBSERVATIONS ON OXYGEN TRANSPORT IN CONIFER SEEDLINGS
Authors: ARMSTRONG W. , READ D. J.
Published: May 2006

Summary

The diffusive flux of oxygen from the roots of intact conifer seedlings was measured by a polarographic technique. With an anaerobic solution bathing the roots maintained at 23° C and with their aerial parts in air, flux rates were appreciable from eight of the twenty‐five seedlings tested. When the aerial parts were placed in oxygen, there was a large increase in flux from each pine seedling. While their general response was barely measurable, a significant but much smaller increase occurred from eight of the spruce. Oxygen transport through the plants appeared to be by diffusion chiefly in the gas phase and significant flux rates from the roots with aerial parts in air might indicate some capacity for wet soil tolerance in the seedlings concerned.

When the external concentration of oxygen was increased five‐fold there was a disproportionate increase in oxygen flux from pine roots indicating that respiration in the plants might be affecting the flux rates. By cooling the bathing medium to 30 C a further demonstration of the respiratory effect‐a large increase in flux rate‐was obtained. With respiration reduced by cooling, the flux rates from the pine seedlings increased approximately five‐fold for a five‐fold increase in the external oxygen concentration. Cooling did not induce any pronounced response from the spruce seedlings.

Internal diffusional resistance and oxygen leakage from the sub‐apical parts of the roots may account for the absence of high apical flux rates in the pines and the extremely low readings recorded for the spruce seedlings.
CHANGES IN GROWTH AND METABOLISM OF EXCISED PEA ROOTS ASSOCIATED WITH IRON DEFICIENCY II. CHANGES IN NUCLEIC ACIDS
Authors: ABBOTT A. J.
Published: May 2006

Summary

The effects of iron deficiency on growth and metabolism of isolated pea roots grown in sterile culture have been further studied. Investigations at time intervals during a culture passage and by serial sectioning of roots at a critical stage of deficiency, have shown the distribution, concentration and composition of nucleic acids in relation to iron depletion. The significance of the results is discussed in relation to the primary role of iron in metabolism. It is suggested that the primary lesion resides in systems responsible for RNA synthesis. Formation of a soluble RNA fraction is inhibited, which in turn may cause failure to produce those enzyme proteins necessary for cell division and resulting in secondary disturbances which are a feature of the iron deficiency syndrome.
PHYTOCHROME AND SEED GERMINATION
Authors: HOLDSWORTH M.
Published: May 2006

Summary

Both tobacco ‘Virginia Gold’ and Plantago hirtella seed germinate on exposure to red light. During the first day or so after sowing, the response can be stopped by a following exposure to deep‐red, indicating phytochrome action. However, the effects of successive exposures to red are additive through intervening exposures to deep‐red. Moreover, after several days in the dark, both red and deep‐red induce germination.
CYTOLOGICAL STUDIES IN DORMANCY II. PATHOLOGICAL AGEING CHANGES DURING PROLONGED DORMANCY AND RECOVERY UPON DORMANCY RELEASE
Authors: VILLIERS T. A.
Published: May 2006

Summary

Seeds with a chilling requirement were maintained fully imbibed at 22–25° C for more than 6 years without germination. Similar seeds stored air‐dry at the same temperatures were dead by the second year. Cytological changes in the radicle meristem cells during the first year included the development of complex associations of ER with protein bodies. After 2 years imbibition, cytolysomes were formed, and by the fifth year membrane systems were extensively damaged. Upon release from dormancy, germination was delayed compared with that of normal, unaged embryos. During this delay, the vacuoles acted as lysosomes, engulfing and hydrolysing cytoplasmic organelles. Renewal was by sub‐division of existing organdies, separating damaged from apparently normal zones by the formation of partition membranes. The relationship between lysosomal systems and the plant cell vacuole is discussed. The extended viability of imbibed seeds compared with dry seeds is discussed in relation to the possibilities of running repairs to membrane and genetic systems whilst the tissue is hydrated.
CYTOLOGICAL STUDIES IN DORMANCY III. CHANGES DURING LOW‐TEMPERATURE DORMANCY RELEASE
Authors: VILLIERS T. A.
Published: May 2006

Summary

The cytological changes occurring in dormant embryo radicle meristem cells of Fraxinus excelsior during the period of chilling before germination are described. The only events observed to be dependent on low temperature occurred in the nucleolus, which increased in volume and complexity of structure. A large, low temperature‐dependent increase in total cellular RNA occurred during chilling, and autoradiography showed preferential incorporation of RNA precursor into the nucleolus during this treatment. Other changes observed included the formation of smooth ER, the development of plastid inclusion bodies, and the formation of cytolysomes. As these changes also took place in control embryos maintained at 22° C, they were probably not directly concerned in the relief of dormancy by chilling. Certain deleterious changes are discussed in relation to the stress which may be experienced by the embryo during dormancy.
ULTRASTRUCTURAL OBSERVATIONS ON PINACEAE LEAF PHLOEM I. THE SPRING CONDITION
Authors: HARRIS WILLIAM M.
Published: May 2006

Summary

Pine and spruce leaves were fixed for electron microscopy during their period of rapid differentiation (April‐May 1970). The sieve cells are in radial rows and mature from the outside towards the inside of the leaf. The sieve cell initials have large nuclei and many organelles. As the sieve cells mature, the walls become thick and lamellar, the tonoplast breaks down, and most of the organelles disappear. The plastid stroma becomes fibrillar. The plastids then rupture, releasing fine fibrils into the mictoplasm. The plasmodesmata between phloem parenchyma cells and albuminous cells occur in expanded regions of the cell wall. The sieve areas have little callose in the spring.
INHIBITION AND STIMULATION OF THE RESPIRATION OF ARUM MITOCHONDRIA BY CYANIDE AND ITS RELATION TO THE COUPLING OF OXIDATION AND PHOSPHORYLATION
Authors: WEDDING R. T. , MCCREADY C. C. , HARLEY J. L.
Published: May 2006

Summary

Mitochondria prepared by standard methods from the sterile spadix of Arum maculatum show relatively poor coupling (ADP/O = 0.5–1.0, respiratory control ratio =1.5–2.8). This coupling is, however, crucial to the response elicited by the application of cyanide. Mitochondria oxidizing malate are inhibited by cyanide with an apparent Ki of 0.3 mM, but an infinitely high cyanide concentration would produce only 50–60% inhibition. With succinate, similar high concentrations of cyanide cause substantial (30–50%) stimulation of the rate of oxidation. When the mitochondria are completely uncoupled by the presence of dinitrophenol or by freezing and thawing, the application of cyanide causes a 12–40% stimulation of the rate of malate oxidation and an even greater increase in that of succinate oxidation. This stimulation by cyanide is not dependent on the nature of the cation supplied.

The inhibitor of cyanide‐resistant respiration, mCLAM,† shows an inhibition additive to that of cyanide with coupled mitochondria, with an apparent Ki of 12–40 μM and 2 maximal inhibition of 40–80%, but in the presence of DNP the addition of mCLAM completely eliminates the cyanide‐sensitive oxidation of succinate or malate.

These results indicate the presence of two pathways for electron transport in Arum mitochondria, of which one, the cyanide‐resistant pathway, is more readily available to the dehydrogenase of succinate than to that of malate and those of other substrates using DPN. The uncoupling of phosphorylation appears to permit electrons to flow more readily through the resistant pathway from either malate or succinate. The cyanide‐sensitive pathway appears to be inhibited readily by mCLAM, and the fact that the stimulation of oxidation by KCN is abolished by mCLAM indicates that the resistant pathway is responsible for the increased flow of electrons in the presence of cyanide.
MEASUREMENT OF NITRATE‐ AND NITRITE‐REDUCTASE ACTIVITIES IN WHOLE CELLS OF CHLORELLA
Authors: SYRETT P. J.
Published: May 2006

Summary

A method is described for the assay of nitrate‐reductase activity in frozen and thawed cells of Chlorella. The method depends on coupling nitrate reductase with malic dehydrogenase, both enzymes and the necessary coenzyme being retained within frozen/thawed cells. Other ways than destroying permeability by freezing are considered and a short treatment of fresh cells with 1.5 M glycerol is shown to be effective. The method has been used to follow the induction of nitrate‐reductase activity in Chlorella. Other enzyme activities that can be measured by similar methods, i.e. by enzymic coupling within damaged cells, are nitrite reductase and urea amidolyase.
IN VIVO MEASUREMENT OF CHLOROPHYLL CONTENT OF LEAVES
Authors: HARDWICK K. , BAKER N. R.
Published: May 2006

Summary

Details are given of the design and construction of an apparatus used in conjunction with a spectroradiometer for the measurement of the chlorophyll content of leaves in vivo.
UPTAKE OF PICLORAM BY EUCALYPT LEAF DISCS
Authors: SANDS R. , BACHELARD E. P.
Published: May 2006

Summary

Surfactants markedly increased the uptake of picloram by Eucalyptus viminalis and E. poly‐anthemos leaf discs. The effects of different surfactants and different surfactant concentrations on uptake depended largely on the degree of wetting by the applied solution on the leaf surface.

A species‐surfactant interaction was evident with some surfactants, and this was examined in terms of differences in leaf‐surface characteristics between the two species. The effects of surfactants on the leaf surfaces were also observed.

The inadequacy of surface tension as a measure of the ability of a solution to wet leaves, and to stimulate herbicide uptake, is discussed.
SOME GENERAL EFFECTS OF PHOSPHORUS DEFICIENCY ON GROWTH AND DEVELOPMENT
Authors: ATKINSON D.
Published: May 2006

Summary

A number of general effects of phosphorus deficiency on plant growth are described. The experiments employed a wide range of species from different ecological habitats. Most species followed a similar pattern regardless of ecological origin.

Seed size seemed to be the principal factor determining the severity of deficiency in short‐term experiments. Deficiency affected root/shoot ratio, hydration and leuco‐anthocyanin content. Even when plants were severely affected by deficiency they were sensitive to the physical environment.
A COMPARATIVE STUDY OF THE EFFECT OF SOIL‐ AND LEAF‐APPLIED PHOSPHORUS ON THE YIELD OF BARLEY (HORDEUM VULGARE L.)
Authors: AFRIDI M. M. R. K. , SAMIULLAH
Published: May 2006

Summary

Barley (Hordewn vulgare L.) variety N.P. 13 gave a higher yield of grain when an aqueous solution of phosphate was applied to the tops 70–80 days after sowing as compared with the controls sprayed with de‐ionized water only. The beneficial effect of spray was generally more pronounced when the plants had received a small dose of phosphatic fertilizer by basal dressing than when they were grown without soil‐applied phosphorus.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE BARBARA
Published: May 2006

Summary

The growth of mycorrhizal and non‐mycorrhizal plants was compared in several soils receiving increasing amounts of Ca(H2PO4)2. In some soils mycorrhizal plants grew better at all levels of applied phosphate. In other soils, where high phosphorus concentrations built up rapidly in the plants, those with mycorrhiza grew worse when more than 0.2 g Ca(H2PO4)2 was added per kg of soil. Because their roots take up more phosphate, mycorrhizal plants may reach supra‐optimal phosphorus concentrations with smaller amounts of added phosphate.

Mycorrhiza tended to die out when 1 g Ca(H2PO4)2 or more was given per kg soil. With added phosphate no arbuscules were formed, many attenuated hyphae ramified through the cortex and the host seemed to have lost control over fungal development. Eventually only certain, morphologically distinct cells in the sub‐epidermal layer were infected. With 6 g Ca(H2PO4)2 root infection disappeared completely, but some viable inoculum survived in the soil.
PHOTOSYNTHESIS BY ISOLATED CHLOROPLASTS: SOME FACTORS AFFECTING INDUCTION IN CO2‐DEPENDENT OXYGEN EVOLUTION
Authors: WALKER D. A. , KOSCIUKIEWICZ KRYSTYNA , CASE CHRISTINE
Published: May 2006

Oxygen production by chloroplasts isolated from spinach was measured. The lag in oxygen production following first illumination of the chloroplasts was independent of light intensity and chlorophyll concentration. The length of the lag period was unaffected by addition of DCMU to the reaction mixture but was increased by addition of orthophosphate or arsenate. It was also longer at lower temperatures. The data are consistent with the view that the lag results from the time necessary for the concentration of photosynthetic metabolites to increase to a level that allows maximal rate of photosynthesis. However, anomalies in behaviour occur and their significance is discussed.
THE CONVERSION OF GLYCERATE INTO PYRUVATE BY CHLORELLA EXTRACTS
Authors: LORD J. M. , MERRETT M. J.
Published: May 2006

Cell‐free extracts from autotrophically grown Chlorella convert glycerate to pyruvate by the reactions of glycolysis. It has already been demonstrated that exogenous glycollate is metabolized to glycerate by the reactions of the glycollate pathway in Chlorella. The activities of the constituent enzymes of glycolysis are great enough to account for the further metabolism of glycerate formed during the metabolism of exogenous glycollate by Chlorella.
[3H]THYMIDINE UTILIZATION IN THE PRIMARY ROOT OF VICIA FABA L.
Authors: MACLEOD R. D.
Published: May 2006

The size of the endogenous pool of TdR in roots of Vicia faba was found to influence the rate of [3H]TdR incorporation into DNA. Thus, increasing the size of this pool, as a result of treatment with TdR, resulted in a decrease in the amount of [3H]TdR incorporated into DNA, while decreasing the size of the endogenous TdR pool, resulted in increased incorporation of [3H]TdR into DNA. The size of the TdR pool could be decreased by excising the roots or by removing the cotyledons. TdR was found to be transported to the root apex from the cotyledons in young V. faba plants.

The pattern of distribution of 3H‐compounds in the primary root of V. faba was found to change with increase in duration of the period of exposure to [3H]TdR. These changes were a consequence of the movement of 3H‐compounds from the base of the root to the apex and of the fact that DNA synthesis was greater in the root apex than in more basal segments.
THE EFFECTS OF PHOSPHORUS DEFICIENCY ON WATER CONTENT AND RESPONSE TO DROUGHT
Authors: ATKINSON D. , DAVISON A. W.
Published: May 2006

Acute phosphorus deficiency was induced in seedlings of a number of species over a period of 5 weeks. Deficiency affected dry weight, root/shoot ratio, leaf water content, leaf water deficits and the time taken for the plants to show visible stress after watering was stopped. Populations of two of the species from soils differing in phosphorus status showed consistent and major differences in the effects of phosphorus deficiency. The ecological implications of the results are discussed.
THE PRODUCTION OF TREHALOSE AND POLYOLS BY USTILAGO NUDA IN CULTURE AND THEIR UTILIZATION IN HEALTHY AND INFECTED WHEAT PLANTS
Authors: GAUNT R. E. , MANNERS J. G.
Published: May 2006

In liquid culture, Ustilago nuda hydrolyses exogenous sucrose and endogenously synthesizes trehalose, mannitol and erythritol. The two polyols are released into the medium. When injected into healthy host tissue, mannitol did not appear to be readily metabolized, but erythritol was converted into an unidentified compound, probably a glycoside derivative. It is suggested that a reciprocal flow of carbohydrate may occur from the fungus to the host. Spores produced in culture were shown to be pathogenic.
VESICLES IN THE PHYCOBIONT SHEATH AS POSSIBLE TRANSFER STRUCTURES BETWEEN THE SYMBIONTS IN THE LICHEN LICHINA PYGMAEA
Authors: PEVELING ELISABETH
Published: May 2006

In the lichen Lichina pygmaea, there are numerous vesicles in the fibrillar sheath of the phycobiont (a blue‐green alga of the genus Calothrix). The possible function of these vesicles is discussed in connection with the metabolic exchange between the symbionts.
CELL DIVISION AND WALL STRUCTURE IN MICROSPORA
Authors: PICKETT‐HEAPS IEREMY
Published: May 2006

Cell division and wall structure are described for Microspora. Persistent centrioles replicate at prophase and establish the poles of metaphase spindles. Microtubules penetrate the nucleus at prometaphase, and during metaphase and anaphase, the nuclear envelope although vesiculated, remains around the spindle. Kinetochores are present. The orientation of the metaphase spindle is highly variable; anaphase elongation of the skew spindle causes it to become bent and twisted. After telophase, daughter nuclei come together in the middle of the cell. The centrioles migrate around the nuclei to the plane of cytokinesis established by a typical phycoplast of microtubules. Both imagination of the outer membrane and a cell plate probably contribute to cross wall formation. These results establish an affinity of Microspora with certain Ulotrichalean algae (e.g. Ulothrix and Stigeoclonium), but not others (Klebsormidium).

The characteristic H‐shaped wall segments arise from two separate phases of wall secretion. During interphase, cell expansion is accommodated by the interlocking H‐shaped segments moving apart; concurrently, a new cylindrical wall is secreted inside these segments. Then during cytokinesis, the newly formed cross wall turns this cylinder into the typical wall segment. This pattern of wall secretion may be common in the Ulotrichales (and other algae) and it may have been derived by the acquisition of the filamentous habit from primitive unicellular ancestors. A scheme showing how this evolution could have occurred is proposed.
DO COLEOPTILE TIPS PRODUCE AUXIN?
Authors: SHELDRAKE A. R.
Published: May 2006

A re‐examination of the evidence for auxin production by coleoptile tips reveals that it is not conclusive and that several important problems remain unresolved. The possibility that auxin and auxin precursors move acropetally in the xylem was tested by analysing guttation fluid from intact coleoptiles, decapitated coleoptiles and primary leaves of Avena sativa. In all cases two zones of auxin activity were detected on chromatograms of the acidic ether‐soluble fraction, one of which corresponded to the RF of indol‐3‐yl acetic acid (IAA). Similar auxin activity was found in guttation fluid from seedlings of Zea mays, Triticum aestivum and Hordeum vulgare. Evidence that guttation fluid also contains alkali‐labile auxin complexes was obtained. Experiments on the movement of dyes and radioactive IAA introduced into the xylem of transpiring or guttating coleoptiles showed that these substances accumulate at the tip of the coleoptile, or at the apical region of decapitated coleoptiles. The hypothesis that IAA and‘inactive auxins move acropetally in the xylem from the seed to the coleoptile tip where they accumulate and where the ‘inactive auxins’ can be converted to IAA is shown to be consistent with the classical work on coleoptiles; it can also explain the autonomous curvature of coleoptiles and the influence of the roots on the auxin content of coleoptile tips. An analogous accumulation of auxin probably occurs at the tips of primary leaves. The anomalous auxin economy of coleoptile tips is discussed.
RNA METABOLISM IN DEVELOPING COTYLEDONS OF PHASEOLUS VULGARIS*
Authors: WALBOT VIRGINIA
Published: May 2006

RNA metabolism in the cotyledons of Phaseolus vulgaris L., cv. Taylor's Horticultural, has been examined as well as the composition of the RNA synthesized during embryogeny and germination. The cotyledons cease RNA synthesis during maturation at the onset of dehydration. During germination RNA synthesis resumes; however, organellar rRNA is the major class of RNA synthesized. The total RNA content of the cotyledons doubles during the first 3 days of germination and then declines as the cotyledons senesce. RNA synthesis is restricted to periods of near normal water content.
THE GROWTH OF BARLEY MUTANTS AT THE XAN‐B AND XAN‐C LOCI IN THE PRESENCE OF SUCROSE OR l‐LEUCINE IN THE GROWTH MEDIUM
Authors: LAND J. B. , NORTON G.
Published: May 2006

The effects of additions of leucine or sucrose to the medium on which chlorotic barley mutant seedlings developed were examined and compared with those of corresponding green segregants. These additions often raised their fresh weight to that of the green segregants grown on basal medium; their protein content was also higher. Although the chlorophyll content of the mutants Xan‐b15,18 and Xan‐c23 was increased, it remained substantially below that of the green segregants; that of the mutants Xan‐b22 and Xan‐b54 did not increase.

In addition to these abnormal growth characteristics, the soluble amino acid pools of the mutants grown on all media and of green segregants grown on leucine medium showed characteristics of chlorotic growth with high levels of aspartic acid and asparagine; these levels were less marked in the mutants which responded to sucrose supplementation.

Levels of ribulose‐1,5‐diphosphate carboxylase remained substantially below those of the green segregants irrespective of the medium supplementation. It was concluded that while these Xantha mutants of barley responded to leucine and sucrose supplementation, this response was different from the pattern associated with strictly auxotrophic growth.
ASYMBIOTIC GERMINATION OF ORCHID SEEDS ON CARBOHYDRAES OF FUNGAL ORIGIN
Authors: SMITH S. E.
Published: May 2006

Asymbiotic germination of two orchid species on sugars found in orchid mycorrhizal fungi was studied. Trehalose and glucose both provided a satisfactory carbon source for growth of non‐photosynthetic orchid protocorms while mannitol did not.
UPTAKE OF SUGARS BY EPICHLOE TYPHINA (PERS. EX FR.) TUL. IN CULTURE AND FROM ITS HOST, AGROSTIS STOLONIFERA L.
Authors: THROWER L. B. , LEWIS D. H.
Published: May 2006

Epichloe typhina forms an intercellular systemic mycelium within its host, Agrostis stolonifera, and a stroma (upon which conidia and perithecia are produced) at the junction of the lamina and sheath of the flag leaf where association between the stroma and vascular tissue of the host is close. There is movement of labelled photosynthate to the stroma from other parts of the shoot. Movement through the systemic mycelium appears to be slight and most probably occurs through the host vascular tissue with subsequent uptake of photosynthate by the stroma.

The principal carbohydrate acquired from the host is sucrose, and there is concomitant transformation to mannitol and trehalose by the fungus.
MULTIPERFORATE SEPTA IN LICHENS
Authors: WETMORE CLIFFORD M.
Published: May 2006

Ascomycetes usually have only one pore in the hyphal septum. This paper reports the first observation of multiperforate septa in lichen fungi using the electron microscope. Multi‐perforate septa are reported in Peltigera, Peltula and Hydrothyria. The extra pores probably facilitate intercellular transport of nutrients and water within the thallus. Previous reports of multiperforate septa in other lichen genera using the light microscope need to be verified by electron microscope studies.
THE CONSTRUCTION AND OPERATION OF A DEW‐SIMULATION CHAMBER
Authors: CLIFFORD BRIAN C.
Published: May 2006

A variable dew‐point chamber which simulates dew fall on plant parts within a temperature range of 1–35° C is described, with technical data on construction and performance. Although designed to obtain uniform infections of cereal leaves following their inoculation with rust uredospores in a settling tower, possible wider uses of the apparatus in biological research are discussed.
THE ROLE OF TAXIMETRICS IN ANGIOSPERM TAXONOMY I. EMPIRICAL COMPARISONS OF METHODS USING CROTALARIA L.
Authors: BISBY F. A.
Published: May 2006

Two hundred and seventy‐three African species of Crotalaria L. (Leguminosae) were subjected to three taximetric procedures: single‐link clustering, with subgraph representation; principal co‐ordinate analysis; and median clustering. The classifications suggested by these methods were compared with each other, compared with a contemporary orthodox classification by Polhill and checked against the original plant material to see if the groupings were recognizable notwithstanding any similarity with Polhill's classification. Above the species level Crotalaria presents classification problems in size and complexity not uncommon for the angiopersms.

The results of single‐link clustering suggest a classification close to Polhill's. In one case, where selected characters had been used, much of the correspondence is exact and of the few discrepancies some reveal possible improvements to the classification and others were caused by external factors. The principal co‐ordinate analysis results are difficult to interpret, suggest some unrecognizable groupings and only vaguely resemble Polhill's arrangement. The median clustering results suggest a tidy‐looking classification which, on investigation, proves largely spurious.

The single‐link and principal co‐ordinate analysis were used to process two different sets of data. One set consisted of data for characters chosen mainly from the other set, selected for high intercorrelations using the information contribution measure. For both methods data for the selected character set gave more useful results.

These findings favour the use of single‐link clustering for classifying angiosperms above the species level. They are a variance with the conclusions of some earlier empirical comparisons using angiosperms, but lend support to a number of theoretical arguments for preferring the single‐link procedure.
MYCORRHIZAS OF THE LILIIFLORAE I. MORPHOGENESIS OF ENDYMION NON‐SCRIPTUS (L.) GARCKE AND ITS MYCORRHIZAS IN NATURE
Authors: DAFT M. J. , CHILVERS M. T. , NICOLSON T. H.
Published: May 2006

Bluebell [Endymion non‐scriptus (L.) Garcke] annually produces a new root system that becomes mycorrhizal very quickly after the roots emerge from the bulb. Morphogenesis of the mycorrhizas is rapid during the autumn and cold winter periods whilst the host is subterranean. Infection is restricted to roots free in the soil and never extends to the root tissues enclosed within the bulb. Environmental conditions alter the rates of host and mycorrhizal development. On the basis of spore and mycelial characters, five species of endophytes were identified. The importance of mycorrhizas to the bluebell and other members of the Liliiflorae is discussed.
THE GENECOLOGY OF LAWN WEEDS. IV. ADAPTIVE SIGNIFICANCE OF VARIATION IN BELLIS PERENNIS L. AS REVEALED IN A TRANSPLANT EXPERIMENT
Authors: WARWICK S. I. , BRIGGS D.
Published: May 2006

In order to study the adaptive significance of variation in Bellis perennis L., an experiment was carried out in which plants from 19 populations – drawn from four habitat groups (I, lawns; II, grazed areas; III, seasonally mown and/or grazed areas; and IV, areas not seasonally reduced in height by grazing and/or mowing) ‐ were transplanted into a lawn subjected to regular mowing. Vegetative growth (as revealed by increment of plant width, dry wt and number of rosettes) and reproduction (as estimated by the number of capitula which survived mowing and produced fruit) were investigated over a 17 month period. As most plants in the experiment grew successfully and approximately 60 % of the 95 individuals (including plants from all four habitat groups) produced fruiting capitula, there was no evidence of distinct ‘races’ of B. perennis in the regularly defoliated habitats of lawn and pasture studied. However, the more successful plants, in terms of numbers of fruiting capitula, were found in samples collected from lawns and Port Meadow: pasture. Four individuals (three from lawns and one from Port Meadow) yielded approximately 50% of all the capitula which fruited. Within ‘successful’ populations there were plants which produced few or no fruiting capitula. Various hypotheses are presented to account for population variation.

Estimates of coefficients of selection, comparing different features of growth and reproduction, may yield different values. For example, even though different individuals are apparently equally successful in vegetative growth under experimental conditions, i.e. with coefficients of selection of 0, a comparison of reproductive success for the same plants may give a value of 10.