bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECTS OF ENVIRONMENT ON WOOD FORMATION AND CAMBIAL ACTIVITY IN ROBINIA PSEUDACACIA L.
Authors: WAISEL YOAV , FAHN A.
Published: May 2006

An investigation into the factors controlling cambial activity and wood production in Robinia pseudacacia is reported.

The effects of temperature on the activity of the cambium are of prime importance. At relatively high temperatures the cambium is active, while at low temperatures dormancy is induced.

Changes in photoperiod seem to affect the type of wood produced more than the activity of the cambium. Under long day conditions, xylem elements of the early wood type are formed, while under short day conditions the xylem produced is of the late wood type.

Photoperiod affects cambial activity and the type of its derivatives through its control of the buds. Under high temperature and short day conditions, axillary buds have been found to sprout occasionally. Below these buds the wood produced is of the early type.

Inhibitors produced by the leaves and retained in the stems seem to participate in the control of the cambial activity of R. pseudacacia.
DIFFERENTIAL RESPONSE OF THE EDAPHIC ECOTYPES IN CYNODON DACTYLON (L) PERS. TO SOIL CALCIUM
Authors: RAMAKRISHNAN P. S. , SINGH VIJAY K.
Published: May 2006

Summary

This paper describes the differential response to calcium of the three edaphic ecotypes of Cynodon dactylon (L) Pers. growing, respectively, on non‐calcareous, moderately calcareous, and highly calcareous soils. A close correlation was discernible for the three populations with the habitats they occupy in nature. The population from a highly calcareous soil showed a better yield in calcareous soils than in non‐calcareous soils, though in highly calcareous soils it tended to decrease. The reverse was found to be the case for the population from non‐calcareous soils; the population from moderately calcareous soil showed an intermediate behaviour. Significantly different responses were found between the three populations with regard to mineral uptake in both calcareous and non‐calcareous soils. Although calcium uptake was higher in the case of plants from non‐calcareous soils compared to those from calcareous soils in experiments using calcareous and non‐calcareous soils, in extremely calcareous soil the reverse was found to be the case. The ash content and the uptake of calcium, potassium and magnesium, in general, increased with increase in soil calcium level. However, the calcium uptake of the populations from moderately calcareous or non‐calcareous soils and the magnesium uptake of the latter decreased in highly calcareous soils. It is concluded from the present studies that there are at least three ‘edaphic ecotypes’ within this species, each markedly different from the other in its physiologic‐ecological attributes and that the basis for the differentiation is chiefly due to their response to soil calcium.
TWO QUATERNARY DEPOSITS IN THE LOWER TEES BASIN
Authors: BELLAMY D. J. , BRADSHAW M. E. , MILLINGTON G. R. , SIMMONS L G.
Published: May 2006

Summary

Two deposits from the Tees basin are investigated for their stratigraphical and pollen‐analytical content. A series of marls and lake muds from Romaldkirk includes material from zones I‐VIc of the Post‐glacial sequence and contained Bos bones. The deposit at Burtree Lane was revealed temporarily during motorway construction and covers zones IV‐VI. Its chief feature of interest is the thick layers of bryophyte peat which constitute the organic material, especially Paludella squarrosa which occurs in profusion. Other mosses include Acrocladium giganteum, A. cuspidatum, Camptothecium nitens, and the first British Post‐glacial record of Helodium blandowii. The possible developmental history of the deposits is discussed in the light of contemporary floating mat vegetation around some Polish lakes.
CYTOTAXONOMIC RELATIONSHIPS BETWEEN THE EUROPEAN AND NORTH AMERICAN ROSTRATE VIOLETS
Authors: HARVEY M. J.
Published: May 2006

Summary

Four European and three North American species of Viola belonging to subsection Rostratae were investigated cytotaxonomically to determine the likelihood of a past trans‐Atlantic migration of genomes. By analysis of meiotic pairing in hybrids it was concluded that two species, V. rupestris and V. adunca, were closely related, but from geographical evidence it seemed more likely that some ancestral species had migrated from Asia to North America via Beringia and not across the north Atlantic region.

In most hybrids there was considerable failure of chromosome pairing at meiosis and it was concluded that there are no close trans‐Atlantic relationships between the remaining species despite their interesting geographical distributions which had partly suggested the investigation in the first place.

The chromosome numbers and distributions of the plants investigated are reported.
PHYSIOLOGY AND ECOLOGY OF ORCHID MYCORRHIZAL FUNGI WITH REFERENCE TO SEEDLING NUTRITION
Authors: SMITH SARAH E.
Published: May 2006

Summary

Orchid mycorrhizal fungi have been assumed to supply carbohydrates to the orchid seedlings with which they are associated. To do this they must be able to utilize a regular source of carbohydrate in the soil, and also to translocate soluble compounds to the orchids. Mycorrhizal Rhizoctonia spp. were shown to decompose filter paper cellulose in pure culture. Secondly, R. repens and R. solani, isolated from Dactylorchis purpurella, were able to compete with other soil micro‐organisms in the exploitation of cellulose buried in unsterilized soil.

Rhizoctonia repens was found capable of translocating 32P and‘14C labelled compounds in an already established mycelium. Radioactivity could also be detected in infected seedlings if tracers were fed to the infecting hyphae some distance from the seedlings. This translocation from fungus to seedlings resulted in greater growth of the seedlings if cellulose was available to the infecting fungus than if no carbohydrates were supplied to either fungus or seedlings.
CHANGES WITH AGE IN THE PHOTOSYNTHETIC AND RESPIRATORY COMPONENTS OF THE NET ASSIMILATION RATES OF SUGAR BEET AND WHEAT
Authors: WATSON D. J. , WILSON J. H. , FORD MARGARET A. , FRENCH S. A. W.
Published: May 2006

Summary

The net assimilation rates (E) of sugar beet and wheat growing in a controlled environment, and their components, the rates of photosynthesis (P) and respiration (R) of the whole plant per unit leaf area, were determined at intervals by a method described previously that depends on measuring the decrease in E when photosynthesis is prevented on some days during an experimental period by keeping plants in darkness. An alternative method of changing the duration of photosynthesis, by shortening the daily photoperiod, gave estimates of P and R almost identical with those obtained by shading plants throughout some days.

In a period of 50 days from sowing for wheat and 90 days for sugar beet, E decreased by about a half. The value of P was always much greater than R; the smallest ratio of P to R was 5. Most of the decrease in E with age was caused by decrease in P, and the change in R with age was relatively small. At 30 days after sowing, E of sugar beet was twice that of wheat, wholly because of difference in P. These experiments confirm that, except perhaps in extreme conditions, change in E can safely be attributed to change in photosynthetic rate.
THE GROWTH OF TOMATO SEEDLINGS IN RELATION TO THE FORM OF THE NITROGEN SUPPLY
Authors: WOOLHOUSE H. W. , HARDWICK K.
Published: May 2006

Summary

Young tomato plants grown in nutrient solution cultures in which all of the nitrogen supply was in the form of nitrate had a higher relative growth rate than plants grown with ammonium nitrogen. Total phosphorus content expressed on a unit dry weight basis was not significantly different in the two treatments, but inorganic phosphorus content was high and organic phosphorus correspondingly low in ammonium‐grown as compared to nitrate‐grown plants. After 13 days this difference was found only in the shoots, but after 17 days the composition of the roots was similarly affected. Nitrate fed to ammonia‐grown plants resulted in a rapid increase in the dry matter and in organic phosphorus content in the young, incompletely expanded leaves. Total potassium content expressed on a dry weight basis did not differ in the two treatments for the first 10 days but thereafter the concentration in the ammonia‐grown plants fell whilst that in the nitrate grown plants remained approximately constant. The lowered potassium content in ammonia‐grown plants was first apparent in the leaves after 10 days, in the stems later and finally in the roots after 21 days. The causes of this reduced potassium content and its relationship to the lowered phosphate esterification and declining unit leaf rate are discussed.
THE EFFECTS OF FREQUENCY AND SEASON OF CLIPPING ON THE MORPHOLOGY, PRODUCTIVITY AND CHEMICAL COMPOSITION OF CALLUNA VULGARIS (L) HULL
Authors: GRANT SHEILA A. , HUNTER R. F.
Published: May 2006

Summary

An experiment is described in which heather plants growing in boxes were clipped either in summer or in winter at different yearly frequencies. The effects of the treatments on morphology, productivity and chemical composition are described.

The view is put forward that the vigour of growth is dependent on the physiological age of the plant and that this is determined by the distribution of the dry matter among the leaf and current seasons shoots, the older stems and wood, and roots.

It is suggested that a grazing intensity where approximately 60% of the current season's shoot length is removed should be the best form of moor management.
PHOSPHOHEXOISOMERASE IN BEECH MYCORRHIZA
Authors: HARLEY J. L. , LOUGHMAN B. C.
Published: May 2006

Summary

Phosphohexoisomerase is shown to be present in beech mycorrhizas and to be distributed between host and fungal tissues approximately in proportion to dry weight. These results show that the different destinations of glucose and fructose absorbed by mycorrhizas is not explicable in terms of the absence of this enzyme from mycorrhizas or from their fungal tissues.
THE MEASUREMENT OF SOIL WATER TENSION IN THE FIELD
Authors: WEBSTER R.
Published: May 2006

Summary

The water in soil under growing plants is not in equilibrium and knowledge of the soil water tension must be based on direct measurements from several tensiometers. A cheap, reliable and easily maintained tensiometer for field use is described. The instruments are constructed mainly from nylon, with mercury manometers, and have been assembled in sets of six with a single support and mercury reservoir for the manometers. The nature and extent of the variation of the water tension from point to point in the soil have been measured at a number of sites in the Oxford district. On arithmetic scales frequency distributions are very skew but may be normalized by logarithmic transformation (to pF). The degree of variation is in general moderate: coefficients of variation range from 4 % to 25 % depending on kind of soil and time of year. Since the cost of the tensiometers described is low there is no reason why comparative studies on soil water tension should not be carried out with adequate replication.
CAMBIAL ACTIVITY IN EUCALYPTUS CAMALDULENSIS DEHN.
Authors: WAISEL Y. , ILANA NOAH  , FAHN A.
Published: May 2006

Summary

The production of xylem and phloem elements by the cambium of Eucalyptus camaldudensis was investigated. Plants grown under various climatic treatments were exposed to 14CO2 for short periods. This treatment left a marker in the xylem and in the phloem cells derived from the cambium during the exposure. Thus, the newly formed cell layers could be counted. Results reveal that the ratio of the number of xylem layers produced to the number of phloem layers produced (4: 1) is practically independent of many environmental factors. The ratio was also found to he independent of the rate of cell production as well as of the width of the undifferentiated cambial zone.

Changes in the ratio of xylem to phloem were not found in plants treated with naphthalene acetic acid, kinetin or triiodobenzoic acid, nor in plants which were defoliated or disbudded. However, a higher ratio was found for plants treated with gibberellic acid.
A RE‐APPRAISAL OF THE ELECTROMETRIC METHOD FOR THE DETERMINATION OF THE CONCENTRATION OF CARBON DIOXIDE IN SOIL ATMOSPHERES
Authors: LEE J. A. , WOOLHOUSE H. W.
Published: May 2006

Summary

The electrometric method for the measurement of Pco2 in soil atmospheres is considered from the pomt of view of accuracy and equilibration time. Departures from the expected relationship between the equilibrium pH of 0.01 M sodium bicarbonate solution and Pco2 emphasize the need for calibrations with each experimental procedure. A particular weakness of the method is the long equilibration time which is shown to be susceptible to both temperature and Pco2 gradient and to be particularly long in the range of the most frequently encountered CO2 concentrations in the soil.
ANALYTICAL STUDIES OF THE GROWTH OF THE ETIOLATED SEEDLING OF AVENA SATIVA
Authors: MER C. L. , CAUSTON D. R.
Published: May 2006

Summary

The increased final length of the mesocotyls of intact, etiolated oat seedlings which have been treated with carbon dioxide, sucrose or ethanol, results from the maintenance of cell division in the nodal meristem. Sucrose and ethanol initially retard the overall rate of mitosis but carbon dioxide, at the concentration used, does not. In contrast with these external effects on the growth of the mesocotyl, variation in cell length with treatment is negligible, hence the extra growth is due directly to the increased number of cells.

Illumination or high temperature each reduces mesocotyl length by means of two inhibitory effects, on mitosis and on cell elongation. The cells that respond are of a particular length when treated and they show maximum sensitivity when 0.12 mm long, at which length mitosis normally ceases.

The retardation of coleoptile growth by sucrose, or by ethanol, is associated with the presence of fewer cells; carbon dioxide appears not to modify the overall rate of cell division. A subsequent stimulation of mitosis, however, does not occur. The cells of the coleoptile, unlike those in the mesocotyl, increase in length after either illumination or heating. Since the same treatments applied to mesocotyl and coleoptile cells elicit different consequences, cell extension in the two organs is most probably controlled by different processes.
RACIAL DIVERSITY IN CALIFORNIAN PRUNELLA VULGARIS
Authors: NELSON ANDREW P.
Published: May 2006

Summary

Two sequential common garden studies of Californian Prunella ‐culgmis subsp. lanceolata have revealed the existence of a first‐year flowering low‐elevation race adapted to mild winters and a second‐year flowering montane race adapted to severe winters. Characteristics of habit and growth rate provide for the recognition of coastal and inland forms within the low‐elevation race and Cascade and Sierran forms within the montane race. The distribution of these four racial forms in California can be correlated with climatological features. Clinal variation correlated with latitude and elevation can be demonstrated within each form. A sequence by which the four forms might have evolved is postulated. Comparison of the results obtained with published accounts of variation in European P. vulgaris and other Californian species suggests that modes of infraspecific variation in California and Europe may be more comparable than previous studies would indicate.
ELECTROPHORETIC MOBILITIES OF FORMIC AND GLUTAMIC DEHYDROGENASES IN THE FABACEAE: A SYSTEMATIC SURVEY
Authors: THURMAN D. A. , BOULTER D. , DERBYSHIRE E. , TURNER B. L.
Published: May 2006

Summary

The albumins extracted from the seeds of a number of different species of the Fabaceae have been subjected to disc electrophoresis on acrylamide gel. Both formic and glutamic dehydrogenase activities were readily detectable on the gels for ninety of the 103 species examined and one or other of the dehydrogenases on gels of the remaining species.

The mobility values of the dehydrogenases varied among the different taxa examined. The more morphologically homogeneous the taxon the less variable were the enzymic data of the species within it, thus within the Vicieae, Trifolieae, Loteae and tribal groupings of Bentham's Phaseoleae species had more nearly similar formic dehydrogenase mobilities than did species of the Podalyrieae and Genisteae (sensu lato).

Before any taxonomic conclusions can be drawn a much more extensive survey is necessary; however, sufficient correlations were observed between formic dehydrogenase mobilities and the globulin data of the previous paper to indicate the potential usefulness of this method in systematic studies.
STOMATAL RESPONSES TO CHANGES IN CARBON DIOXIDE CONCENTRATION IN LEAVES TREATED WITH 3‐(4‐CHLOROPHENYL)‐1, 1‐DIMETHYLUREA
Authors: ALLAWAY W. G. , MANSFIELD T. A.
Published: May 2006

Summary

An inhibitor of photophosphorylation, 3‐(4‐chlorophenyl)‐1, 1‐dimethylurea, was supplied to detached leaves via their petioles. The stomata partly closed after the inhibitor had entered the lamina but opened again if the intercellular spaces were flushed with air free of carbon dioxide. It is suggested that the closing movement was a response to the accumulation of carbon dioxide in the intercellular spaces, following the inhibition of photosynthesis. The re‐opening after removal of carbon dioxide demonstrated that stomata could open while photophosphorylation was strongly inhibited. The conclusions from these experiments are discussed in relation to a recent hypothesis of the stomatal mechanism.
MORPHOLOGY OF THE NECTARY IN PROTEACEAE
Authors: RAO C. VENKATA
Published: May 2006

Summary

A comprehensive study of the comparative morphology, anatomy and histology of the nectary in all genera of the Proteaceae was made and the trends in its evolution are discussed. The nectaries in some abnormal flowers of Hakea laurina and Buckinghamia celsissima are also described. The variations in shape of the nectary in the family (and sometimes within a genus); the diversity in its position, either on the thalamus, stipe or floral tube; its position always within the tepal‐stamen whorl; the anatomical and histological features and comparative morphology, all point to the nectary being an enation and not a modified or reduced corolla as previous investigators thought.
THE CROP RESPIRATION RATE OF TULIPS
Authors: REES A. R.
Published: May 2006

Summary

The shading methods developed by Watson and Hayashi (1965) for differentiating the photo‐synthetic and respiratory components of net assimilation rate were used on a field scale for estimating the respiratory losses in a tulip crop. By selecting a period in the plant's life which may be described by a linear regression, variation due to weather in growth rate under different sfiading treatments may be averaged.

The mean growth rates under each shading treatment may in turn be fitted by a regression line whose intercept with zero light estimates respiration rate, A value of 20% of gross crop growth rate was arrived at; this agrees closely with previous estimates of dry weight losses in bulb crops before emergence.
POLLEN ANALYSIS OF A PEAT FROM THE ISLAND OF CANNA (INNER HEBRIDES)
Authors: FLENLEY J. R. , PEARSON M. C.
Published: May 2006

Summary

Two complementary pollen diagrams from Canna show a forest history similar to that found elsewhere in north‐west Scotland, but the NAP values are unusually high. A late‐glacial may possibly be present.
ECOTYPE DIFFERENTIATION IN TEUCRIUM SCORODONIA WITH RESPECT TO SUSCEPTIBILITY TO LIME‐INDUCED CHLOROSIS AND TO SHADE FACTORS
Authors: HUTCHINSON T. C.
Published: May 2006

Summary

A study has been made of populations of Teucrium scorodonia from Britain and Europe. Edaphic ecotypes have been found to occur with respect to lime‐induced chlorosis. Chlorosis‐susceptible populations were found to be from acidic and non‐calcareous sites whilst chlorosis‐resistant populations were invariably from calcareous sites. The severity of the chlorosis and the retardation of growth in the laboratory suggests that in the field chlorosis‐susceptible populations would be at a great disadvantage compared with resistant ones, on many calcareous soils. In limited field‐experiments, however, seedling failure was found to be due to catastrophic effects such as drought, frost and animal depredation which eliminated both green and chlorotic seedlings. It was found, however, that seedlings of populations from shaded habitats had considerably larger cotyledons than had those from unshaded habitats. This was also true under controlled conditions, irrespective of the shade and nutritional regime given. The seedlings with large cotyledons formed their leaves more rapidly than did those with small cotyledons. Other morphological differences occurred which also appear to be of an adaptational nature. These differences were independent of the soil types from which the populations originated. A study of populations from within a very small area indicated that ecotypic differentiation can take place rapidly and precisely within such an area.
BRYOPHYTES AS INDICATORS OF AIR POLLUTION IN THE TYNE VALLEY
Authors: GILBERT O. L.
Published: May 2006

Summary

Detailed mapping and recording have shown that many of the commonest bryophytes in Northumberland are totally absent from a large part of the Lower Tyne Valley. The affected area is centred on the coalfield where scattered colliery towns, burning pit heaps and the huge conurbation of Newcastle upon Tyne lie. Emphasis is laid on sulphur dioxide pollution being responsible. Two anomalous situations where sensitive species are found growing well inside their normal limit were investigated. It appears that shelter has a greatly modifying effect in reducing SO2 (but not smoke) levels and that a high pH influences the degree of ionization and rate of oxidation of SO3= so as to favour survival. Protonemata appear to be more sensitive than mature gametophytes.

Most bryophytes cannot exist when the average winter concentration of SO2 exceeds 50 μg/ m3 or 0.01 ppm.
SOME ASPECTS OF THE RELATIONSHIP BETWEEN SHADE AND FUNGAL PATHOGENICITY IN AN EPIDEMIC DISEASE OF PINES
Authors: READ D. J.
Published: May 2006

Summary

Some of the environmental factors predisposing Corsican Pine to an epidemic disease known as dieback were studied. The disease is most prevalent on north‐facing slopes, while south‐facing slopes are normally unaffected. Trees on north‐facing slopes produce poor height growth and those showing the poorest growth eventually succumb to the disease. A characteristic feature of the diseased slopes is the absence of sunlight in winter. Disease symptoms appear in this period of sun shadow. The effect of shade on disease susceptibility was therefore investigated. Large increases of infection by Brunchorstia pinea were found after 2, 4, 8 and 12 weeks artifical shading.

Artificial shading caused reduction of the soluble carbohydrate content of the buds. Diseasesusceptible buds on north‐facing slopes had comparable low carbohydrate contents, while the levels in resistant buds on south aspects were significantly greater.

Soluble carbohydrate content at the end of the growing season was found to be similar in both aspects, but there was a steady decrease through the winter on the north‐facing slope until by January the content was considerably lower than that on the south aspect.

Dieback is therefore believed to be caused by fungal attack following loss of respiratory substrate during a prolonged period of low light intensity. Factors such as low growing season temperature and high humidities play a subsidiary role by reducing host vigour and increasing the fungal population.
LICHEN PHYSIOLOGY
Authors: RICHARDSON D. H. S. , SMITH D. C.
Published: May 2006

Summary

The main carbohydrates which incorporate 14C during photosynthesis in Xanthoria aureola are ribitol, mannitol, arabitol and sucrose. Ribitol is the first product to accumulate 14C in substantial amounts, and it appears to be produced by the alga. Ribitol is also the main form in which carbohydrate moves from alga to fungus. Entry of [14C]ribitol into the fungus during photosynthesis could be prevented by addition of 1%12C‐pentitols to the medium. In short‐term photosynthesis experiments, incorporation of 14C into mannitol is relatively small, and none is detectable in arahitol. However, in long‐term experiments, more 14C eventually accumulates in mannitol than in other carbohydrates, and [14C]arabitol can also be detected; the delay before appreciable accumulation of 14C occurs into mannitol and arabitol is consistent with their being fungal products. Sucrose never incorporates much 14C, but its early appearance in photosynthesis suggests it is an algal product. The rate of movement of a pulse of 14C between the symbionts of X. aureola is much slower than in Peltigera polydactyla.
NUTRITIONAL REQUIREMENTS OF THE EDAPHIC ECOTYPES IN MELILOTUS ALBA MEDIC.
Authors: RAMAKRISHNAN P. S.
Published: May 2006

Summary

The present study deals with the nutritional requirements of the two edaphic ecotypes—(i) the ‘calcareous’, growing on a calcareous soil and (ii) the ‘acidic’, growing on an acidic soil. The germinability of the seeds was found to be inherently different for the two populations. The seeds of the ‘acidic’ population were found to do better in an acid medium and the reverse was found to be the case for the ‘calcareous’ population. Significant differences were noted with regard to the accumulation of calcium and other nutrients under different calcium levels and pH conditions. The ‘acidic’ population always showed a better accumulation of calcium, except at high calcium levels; it also showed a greater ability to accumulate other nutrients like potassium and phosphorus. The adaptive significance of such a behaviour is discussed. A differential response to phosphorus was noted between the two populations, the ‘acidic’ type showing an improved growth yield at higher phosphorus levels whilst that of the ‘calcareous’ type was insensitive. For the same level of phosphorus in the medium, phosphorus accumulation decreased for the ‘acidic’ type at pH 7 in a calcareous medium compared with accumulation in a non‐calcareous medium. For the ‘calcareous’ population, accumulation improved in an alkaline medium. Whilst the accumulation of phosphorus was little affected by change in phosphorus concentration in the medium for the ‘calcareous’ population, the ‘acidic’ type showed improved accumulation with increase in phosphorus level in the medium. The significance of these effects is discussed and it has been shown that besides the direct role of calcium itself, pH with the accompaniment of changes in the availability of phosphorus could be responsible for the restriction of these ecotypes to their respective habitats.
CHLOROPLAST MORPHOLOGY AND FINE STRUCTURE IN BRITISH FUCOIDS
Authors: EVANS L. V.
Published: May 2006

Summary

Chromatophores, principally from eggs, of representatives of the seven genera of the Fucales found in Britain were investigated with the electron microscope and the results are presented here.

The chromatophores are bounded by two pairs of membranes inside which lamellations consisting of three or four non‐cohering thylakoids are embedded in a stroma. The stroma of some genera is extended into a simple projecting, stalked pyrenoid and the inner pair of membranes (chromatophore envelope) loop back on themselves to form a covering also to the pyrenoid. The outer pair of membranes (chromatophore E.R.) take no part. Alternatively, two pyrenoids in close proximity, enclosed by a double looping of the chromatopbore envelope, may be found; they lie one above the other either facing in opposite ways or at right angles to each other. More rarely, two widely separated pyrenoids may be found.

Pyrenoids of this sort do not occur in association with the egg chromatophores in the Fucaceae (Fucus, Ascophyllum and Pelvetia), but they do occur in the eggs (but not in thallus cells) of members of the Cystoseiraceae (Bifurcaria and Cystoseira), with the exception of Halidrys, and in the Himanthaliaceae (Himanthalia). These pyrenoids are regarded as rudimentary, and as representing a stage close to total eclipse.

Pyrenoids in such a natural group are suggested to have phyletic value, their presence being thought to be indicative of greater antiquity than their absence. Hence members of the Fucaceae are thought to be more specialized than members of the Cystoseiraceae. This statement is discussed in relation to earlier results (Manton, 1964, etc.) where the Cystoseiraceae were found to have other kinds of primitive features, and the Fucaceae other kinds of advanced features.
THE MECHANISIM OF FRUCTOSAN METABOLISM IN HIGHER PLANTS AS EXEMPLIFIED IN HELIANTHUS TUBEROSUS
Authors: EDELMAN J. , JEEEORD T. G.
Published: May 2006

Summary

The physiological behaviour of the fructose polymers, which are the sole carbohydrate reserve in Jerusalem artichoke tubers, is briefly described. It is suggested that certain enzymes which have been isolated from this tissue can account for these changes, and a theory of their integrated action is put forward: this involves the trisaccharide IF‐fructosylsucrose, widely found in fructosan‐containing tissues, as a key intermediate, and the enzyme which produces it from sucrose as a controlling biochemical factor. Sucrose itself, both as a substrate and by its direct effect on the other enzymes, also acts as a major means of control. The hypothesis does not involve sugar phosphates or nucleotide sugars, and seems to be applicable to other plants which contain fructosans.
A THEORETICAL STUDY RELATING THE CONCENTRATION AND DIFFUSION OF OXYGEN TO THE BIOLOGY OF ORGANISMS IN SOIL
Authors: GRIFFIN D. M.
Published: May 2006

Summary

Some components necessary for the eventual construction of a general model relating the concentration and diffusion of oxygen to the ecology of soil organisms are elaborated from biochemical and physical data and concepts. From the analyses and discussions presented, tentative conclusions can be drawn concerning some of the factors involved in the relationship between oxygen and soil ecology.

For roots, bacteria and fungi, most oxygen is taken up through the cytochrome system. Little error is introduced by neglecting the rate of uptake by other terminal oxidases. The rate of diffusion to cells is thus a direct consequence of uptake by the cytochrome system. Oxygen uptake by individual cells will not be affected until the concentration at the sites of the terminal oxidases is of the order of 1 × 10−6to 1 × 10−7M.

In many species, the rate of respiration of single fungal hyphae or single bacterial cells will be limited at low external oxygen concentrations by the rate of diffusion of oxygen to the respiratory sites through membranes, walls and sheaths external to those sites. An increase in concentration of oxidase at limiting oxygen concentrations may be ecologically significant in micro‐organisms. The rate at which oxygen diffuses radially through roots with a high respiration rate will often restrict the total rate of oxygen uptake. The centres of such roots will tend to be anaerobic under some field conditions and the situation is likely to be aggravated by root infection and by the presence of some organisms in the rhizosphere. Most roots will be adversely affected at oxygen concentrations higher than those required to adversely affect micro‐organisms on the root surface. The oxygen status of roots will be greatly modified if longitudinal diffusion of oxygen through intercellular spaces that are gas‐filled is considerable.

The evaluation of the critical oxygen characteristics in field studies is fraught with difliculties largely associated with specifying the diffusion path of oxygen through the soil to the organ and with obtaining accurate measurements of either oxygen concentration or oxygen flux at the surface of the organ. Use of the platinum micro‐electrode to measure flux can probably give only empirical results but appears to be of practical use where a statistical approach can be used.

In some organisms, the major effect of reduced oxygen concentration may well be on the synthesis, or absorption, of some metabolite and not be linked directly to the cytochrome system. Such an organism may be adversely affected by a relatively small reduction in the oxygen concentration and would thus be an exception to the general arguments presented in the article.
EFFECTS OF SEED TREATMENTS WITH GIBBERELLIC ACID ON SUBSEQUENT GROWTH OF SOME EUCALYPT SEEDLINGS
Authors: BACHELARD E. P.
Published: May 2006

Summary

Germination of seeds of Eucalyptus regnans and E. pauciflora in 50 mg/1 gibberellic acid markedly affected seedling growth. These effects included: stimulation of leaf production and shoot extension growth; slight reduction of root growth; alteration of the root/shoot ratio, and leaf shape; reduction in total dry weight and leaf thickness. Gibberellic acid affected leaf growth through reduced cell division.

Stimulation of growth of E. camaldulensis hypocotyl by seed treatment with gibberellic acid could also be attributed to changes in cell division. No evidence of interaction between gibberellic acid and auxin was obtained.

These results are discussed in relation to effects of gibberellic acid on other plants and tissues, and it is suggested the responses are explicable in terms of mobilization of food reserves.
NUTRITIONAL REQUIREMENTS OF THE EDAPHIC ECOTYPES IN MELILOTUS ALBA MEDIC.
Authors: RAMAKRISHNAN P. S.
Published: May 2006

Summary

The differential tolerance of the calcareous and acidic populations of Melilotus alba Medic, to toxic levels of aluminium and manganese was studied since the availability of these micro‐nutrients is very much dependent upon the pH of the soil. The reduction in the growth yield at toxic levels of aluminium was more pronounced in the case of the calcareous population and at such high levels the acidic type had a significantly higher yield. Only the calcareous population showed symptoms of toxicity due to excess aluminium and it consisted of chlorotic spots on the leaves, particularly the lower ones. The growth yield of the calcareous population was markedly affected by toxic manganese levels in the nutrient solution; the plants were stunted in growth with highly chlorotic leaves, the leaf blades were cupped and the margins of the leaves were crinkled. On the other hand, though the growth yield of the acidic type was also reduced to a lesser degree, the plants did not show any visual toxicity symptoms. At toxic levels of manganese and aluminium, the uptake of other nutrients such as calcium, potassium and phosphorus was more adversely affected in the case of the calcareous than the acidic types.

It was concluded that the greater tolerance to aluminium and manganese toxicity of the acidic population is partly responsible for its occurrence in acid soils and the absence of the calcareous population from acidic habitats.
EARLY PLEISTOCENE DINOFLAGELLATES FROM THE ROYAL SOCIETY BOREHOLE AT LUDHAM, NORFOLK
Authors: WALL DAVID , DALE BARRIE
Published: May 2006

Summary

A more complete account is presented of the ‘hystrichospheres’, both indigenous and recycled, originally found by West (1961) during his palynological investigation of Early Pleistocene marine sediments penetrated by the Royal Society Borehole at Ludhatii, in Norfolk, England. The commonly encountered ‘hystrichosphere’ types of West are identified as x=Operculodinium israelianum (R.)W., y=Tectatodinium pellitum W. and z = Leptodinium mulliplexum sp. nov., while it is probable that a collection of Hystricliospliaera species comprise West's category ‘hooked‐Hystrix’. The majority of these organisms are fossilized gonyaulacid and protoceratioid dinofiagellate resting cysts (spores). These dinoflagellates form five facies‐associations in this sequence. The palaeoecological significance of their distribution is discussed with special concern to palaeoclimates and the future use of dinofiagellates in Quaternary stratigraphy.
A LOWESTOFTIAN LATE‐GLACIAL FLORA FROM THE PLEISTOCENE DEPOSITS AT HOXNE, SUFFOLK
Authors: TURNER C.
Published: May 2006

Summary

A Late Lowcstoftian macroflora is described from a new stratum at Hoxne, Suffolk, underlying the Pleistocene lacustrine beds investigated by West (1956). The flora is very similir in aspect to other ‘full‐glacial’ floras described from Gipping and Weichselian deposits in Southern Britain.
ELECTROCHEMICAL POTENTIAL GRADIENTS OF IONS IN AN AQUATIC ANGIOSPERM, POTAMOGETON SCHWEINFURTHII (BENN.)
Authors: DENNY P. , WEEKS D. C.
Published: May 2006

Summary

The concentrations of the major ions present in mature leaves of Potamogeton schweinfurthii and its natural pond waters were measured, together with membrane potential differences between the interior of leaf cells and the pond waters. Simple electrochemical interpretation of the data suggests active import of chloride, phosphate and sulphate, and active export of potassium and sodium ions. Calcium and magnesium ions may enter very slowly passively but may also be actively exported.
THE RESPONSE TO PHOSPHORUS OF SOME ECOLOGICALLY DISTINCT PLANT SPECIES
Authors: RORISON I. H.
Published: May 2006

Summary

Seedlings of four ecologically distinct species were grown in solution cultures containing a range of phosphorus concentrations. Evidence for relationships between their relative growth rates and phosphorus absorption was then considered. Descliampsia flexuosa and Scabiosa columbaria, the two species from edaphically extreme habitats, had slow relative growth rates, but differed in their response to phosphorus. Deschampsia flexuosa grew continuously in concentrations as low as 10−7 M and respontled only slightly to concentrations as high as 10−3 M. Scabiosa columbaria whose response was poor at 10−7 m responded more markedly to 10−3 M at which concentration there was a significant increase of phosphorus in the roots. Rumex acetosa and Urtica dioica, the two ruderal species, had high relative growth rates and differed in their response to phosphorus; Rumex acetoso survived over the whole range; Urtica dioica thrived only at 10−5 M or above. These results, particularly the increase of phosphorus in roots of Scabiosa columbaria, were considered to be of ecological importance.
THE EFFECTS OF FUNGI ON MORPHOGENESIS OF GAMETOPHYTES OF POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M.
Published: May 2006

Summary

Growth and development of gametophytes of Polypodium vulgare L. in culture were affected by several fungi. Of those tested the fungus having the greatest effect was Fusarium oxysporum Schlecht ex Fr. When added just before spore germination this fungus delayed the transition from one‐ to two‐dimensional growth of the gametophytes and when added after the transition had occurred it caused a reversion to one‐dimensional growth. Analysis of culture filtrates showed that the detectable volatile substances present in greatest concentration were ethanol and acetaldehyde. Changes in gametophjrte morphology were correlated with changes in the level of ethanol present in the medium and the main effects of the fungus were reproduced by treating gametophytes in uncontaminated cultures with ethanol.
ROOT GROWTH AND DARK FIXATION OF CARBON DIOXIDE IN CALCICOLES AND CALCIFUGES
Authors: LEE J. A. , WOOLHOUSE H. W.
Published: May 2006

Summary

The inhibition of root growth by bicarbonate ions has been further investigated by an examination of the process of dark fixation of carbon dioxide by Arrhenatherum elatius and Deschampsia flexuosa. Excised roots incorporated [14C]bicarbonate mostly into malate in 4 hours. Intact plants grown on solutions containing 10 m‐equiv./1 bicarbonate for 24 hours showed large increases in the total acid content of the roots. Malate was increased in both species and citrate also in Arrhenatherum elatius. The increases in total acidity were similar and could be explained solely by the dark fixation of bicarbonate. Seedlings grown on solutions of sodium hydrogen malate showed similar inhibitions to those observed on sodium bicarbonate solutions. Root growth of Deschampsia flexuosa was inhibited throughout a range of malate concentrations (1–20 m‐equiv./l) whereas Arrhenatherum elatius was stimulated at low malate concentrations and only slightly inhibited at 20 m‐equiv/1. The inhibiting action of bicarbonate on the root growth of Deschampsia flexuosa is associated with the increase in malate in the roots by dark fixation. The results are discussed in terms of the organic acid content and metabolism of calcicole and calcifuge species.
ASEXUAL SPORE MORPHOLOGY IN SPECIES OF PIPTOCEPHALIS
Authors: YOUNG T. W. K.
Published: May 2006

Summary

Electron microscopic observation of surface replicas of the asexual spores of four species of Piptocephalis, reveals that three dry‐spored forms, P. unispora, P. henjaniinii and P. virginiana bear patterns of warts and ridges whilst those of the slime‐spored form P. freseniana, are relatively smooth. The transverse walls of spores of P. virginiana and P. freseniana are rough. Spore scars on the head cell of P. unispora apparently possess a central area which may represent a plug.
A CRITICAL EXAMINATION OF THE USE OF DETACHED EPIDERMIS IN STUDIES OF STOMATAL PHYSIOLOGY
Authors: WILLMER C. M. , MANSFIELD T. A.
Published: May 2006

Summary

Although several workers have published accounts of stomatal studies with detached epidermis, there has not been general agreement as to whether the stomata continue to respond to environmental factors as they do in the intact plant. This paper reports a critical examination of the value of the technique, experiments having been carried out on material from Vida faba and two species of Commelina.

The nature of the incubating medium was found to exert a considerable influence on the behaviour of the stomata. In Commelina, the presence of monovalent cations (K+, Na+) stimulated opening, but divalent cations (Ca2+, Mg2+) had an antagonistic effect suppressing opening or even preventing it altogether. In Vicia faba cations exerted less noticeable effects. pH changes affected aperture, but in Commelina the changes were of much smaller magnitude than those induced by the different cations.

Factorial experiments were performed to determine the effect of detaching epidermis on the stomatal responses to environmental factors. In Vicia faba the light effect was very apparent on attached epidermis, but on detached epidermis the effect was largely obscured by stomatal opening that occurred in darkness; effects of CO2 concentration were detectable on epidermal strips, particularly in darkness, but were of smaller magnitude than those on attached epidermis. On the other hand, in Commelina, effects of both light and CO2 were of considerable magnitude when strips were immersed in media containing the cations that stimulated opening.

The theory that the opening stimulated by monovalent cations is the outcome of their being actively taken up into the guard cells is discussed, and it is concluded that while this might apply to epidermal strips in media, there is inadequate evidence that such a mechanism is responsible for opening in the intact plant; there was no stimulation of opening on attached epidermis when pieces of leaf were immersed in media containing monovalent cations. Attempts are made to explain the difference in behaviour between Vicia faba and Commelina on the basis of the course of ion uptake into the cells of the epidermis; evidence of a possible difference in uptake was obtained from studies of the penetration by neutral red.

It is concluded that epidermal strips from both species of Commelina are suitable for studies of stomatal responses to Hght and CO2 so long as they are incubated in a suitable medium. Epidermal strips from V. faba are unsuitable for studies of the light responses, and less satisfactory than Commelina for the responses to CO2.
RANDOMNESS IN THE GENESIS OF PHYLLOTAXIS
Authors: RIJVEN A. H. G. C.
Published: May 2006

Summary

This paper attempts to localize the ‘random factor’ at the inception of a spiral phyllotactic pattern, and to discover which other factors may influence leaf initiation at this point.

The study shows that the third leaf of Trigonella foenum‐graecum L. can occupy an alternative site, left (L) or right (R) of the first leaf and thereby introduces L‐R asymmetry. The mean divergency angle with the second leaf is about 125°. The positions occupied were, within statistical expectations, equal, but in about 4% of seedlings both the L and R site were occupied resulting in ‘symmetries’. L‐R asymmetry was established independently of the sense of dorsiventrality.

In the seed only the first leaf was present and the site of the third leaf not yet determined. Removal of one cotyledon when performed during germination (Day 2 and 3 but not on Day 4), resulted in bias away from the remaining cotyledon. Removal of the distal half of a cotyledon did not affect the L‐R frequency distribution.

In immature embryos removal of one cotyledon often resulted in a change of the siting of the second leaf, but toward the remaining cotyledon.

In intact seedlings the occupancy of the L or R site was not correlated with differences in weight between the left and right cotyledon, but a rather weak effect of gravity was observed.

The effects of applying some phytohormones to a petiole stump in decotylized embryos were investigated. Morphological variants of primordial development were recorded.

It is concluded that the ‘random factor’ is of internal origin, close to the apex. Auxins which stimulate primordial development, and other inhibitory substances may play a role in leaf siting.
STOMATAL MOVEMENTS AND RATES OF GASEOUS EXCHANGE IN EXCISED LEAVES OF VICIA FABA
Authors: BALASUBRAMANIAM S. , WILLIS A. J.
Published: May 2006

Summary

Simultaneous measurements of leaf resistance to gaseous flow, rate of transpiration and rate of carbon dioxide exchange were made with the main object of investigating the effects of severing the petiole on stomatal movements and gaseous exchange of leaves of Vicia faba of differing initial water content.

Extensive stomatal changes occurred on cutting the petioles of illuminated leaves in air. The magnitude and direction of the stomatal movements were strongly influenced by the water relations of the leaf at the time of excision. When the water deficit was small there was a substantial temporary stomiatal opening and corresponding temporary increases in rates of transpiration and photosynthesis. In leaves of moderate water deficit the stomatal opening on leaf excision was much less pronounced and, in leaves under severe water stress at he time of cutting, there was little evidence of any immediate stomatal response. Preliminary stomatal opening and a temporary increase in transpiration rate were also observed in leaves excised in air from plants kept in darkness. In experiments in which the illuminated leaves were severed under water, however, a temporary increase of leaf resistance to gaseous flow was found on leaf excision, and associated declines in rates of transpiration and of photosynthesis.

The changes in transpiration rate resulting from leaf severance are clearly associated with stomatal behaviour, and there is evidence of close stomatal control, under these conditions, of rates of transpiration and of photosynthesis. The phenomena involved in leaf excision both in air and under water are discussed and stomatal behaviour shown to depend to a considerable extent on the water relations of the leaf; stomatal movements are interpreted largely in terms of differential turgor changes in the guard cells and neighbouring epidermal cells.
MORPHOLOGY AND TAXONOMY OF THE OOMYCETES, WITH SPECIAL REFERENCE TO SAPROLEGNIACEAE, LEPTOMITACEAE AND PYTHIACEAE
Authors: DICK M. W.
Published: May 2006

Summary

The morphology of sexual reproduction is reviewed and the importance of developmental stages is considered. Particular attention is drawn to the taxonomie significance of the size, wall structure and protoplasmic organization of the oospore.