bluuebunny/crossref_metadata_2025 huggingface dataset:
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE IV. THE EFFECT OF MYCORRHIZAL INFECTION ON UPTAKE OF 15N FROM LABELLED SOIL BY VACCINIUM MACROCARPON AIT.
Authors: STRIBLEY D. P. , READ D. J.
Published: May 2006

Moorland soil was labelled with 15N by long incubation with glucose and [15N] ammonium sulphate. Excess ammonium was then removed by acid‐washing and the soil sterilized by gamma‐irradiation. The distribution of label between four N fractions of the soil was determined.

Shoots of mycorrhizal plants of the cultivated cranberry, Vaccinium macrocarpon Ait., grown on this soil for 6 months, were heavier, contained more nitrogen and a greater concentration of N on a dry‐weight basis than those of non‐mycorrhizal plants. Species of Trichoderma and Aspergillus, isolated from moorland soil, did not similarly stimulate growth of sterile plants.

The 15N‐excess (atom per cent) of shoots from mycorrhizal Vaccinium plants was lower than that of shoots of uninfected plants. The endophyte neither affected growth nor 15N enrichment of Festuca ovina L. nor caused net mineralization in infected soil. The hypothesis that mycorrhizal roots can absorb nitrogen compounds unavailable to non‐mycorrhizal plants is discussed.
NITRATE UTILIZATION BY SPECIES FROM ACIDIC AND CALCAREOUS SOILS
Authors: HAVILL D. C. , LEE J. A. , STEWART G. R.
Published: May 2006

Nitrate utilization by calcicole and calcifuge species has been measured using a field assay for nitrate reductase. Certain calcifuge species, notably members of the Ericaceae, showed no detectable enzyme activity in the field and very low values in the laboratory even after nitrate feeding. It is concluded that these species have a restricted ability to utilize nitrate. Other calcifuge species and all the species from calcareous soils had detectable nitrate reductase activities in the field and responded to nitrate addition by large increases in enzyme activities. Some of these species were used to compare nitrate utilization in a number of acidic and calcareous soils. Nitrate was utilized in all the soils, but utilization was minimal in ombrogenous peat. A comparison of closely adjacent acidic and calcareous soils showed that nitrate is an important source of inorganic combined nitrogen in at least some acidic soils.
THE USE OF NUMERICAL METHODS TO DESCRIBE POPULATION DIFFERENTIATION
Authors: JARDINE N. , EDMONDS J. M.
Published: May 2006

We discuss, with examples, the use of numerical methods to describe and compare patterns of differentiation between populations of organisms at low taxonomic levels. The role of such methods as adjuncts to the orthodox methods of experimental taxonomy is illustrated by an account of differentiation in Solarium L. Section Solatium (Maurella).
RIBOSOMAL RNA, FRACTION I PROTEIN SYNTHESIS, AND RIBULOSE DIPHOSPHATE CARBOXYLASE ACTIVITY IN DEVELOPING AND SENESCING LEAVES OF CUCUMBER
Authors: CALLOW J. A.
Published: May 2006

Summary

The synthesis of chloroplast ribosomes and Fraction I protein appear to be discrete events in the life of a leaf. Expanding cucumber leaves incorporated exogenous precursors of RNA and protein synthesis into chloroplastic rRNA and Fraction I respectively but, after full expansion, the synthesis of both of these components was greatly reduced while incorporation into cytoplasmic rRNA and other soluble proteins was still proceeding. It is suggested that the overall synthesis of whole molecules of Fraction I is controlled by the rate of synthesis, in the chloroplast of the large sub‐unit of Fraction I and that this in part is related to the availability of 70S ribosomes.

RuDPcarboxylase activity paralleled Fraction I protein content in developing leaves, but as the leaves senesced, the enzymatic activity declined at a faster rate than the loss of Fraction I protein.
THE BEHAVIOUR OF CHLOROPLASTS DURING CELL DIVISION OF ISOETES LACUSTRIS L.
Authors: WHATLEY JEAN M.
Published: May 2006

Summary

Cells in the meristematic tissue of Isoetes lacustris contain a single chloroplast which divides when the cells divide. Details of this process, as seen by electron microscopy, are described.
SOME OBSERVATIONS ON THE GROWTH OF LATERAL ROOTS OF VICIA FABA L. AND THEIR RESPONSE TO COLCHICINE TREATMENT
Authors: MACLEOD R. D.
Published: May 2006

Summary

The effect of colchicine treatment on the number of cells in prophase was investigated in the apical meristems of 2‐mm‐, 1‐cm‐and 4‐cm‐ long lateral roots of Vicia faba. Colchicine was most effective in causing an initial drop in prophase numbers in the 2‐mm‐long roots, while it had a less drastic effect on the 1‐cm laterals and no significant effect at all on the 4‐cm ones. Also, while a significant increase in the number of cells in prophase was found 24 h following the start of treatment in the 1‐cm‐long roots, no significant increase took place in the 2‐mm or 4‐cm laterals. Thus, elongating lateral roots at different developmental stages do not respond to colchicine in the same way.

Mitotic index and labelling index were also found to differ in control lateral roots of different lengths, as a result of fluctuations in the proportion of cells with a short cycle time during root elongation. These results, and the changes found in the response of lateral roots to colchicine as they lengthen, have been discussed with respect to growth hormone levels in developing roots.
ALTERNATIVES TO THE ASSESSMENT OF EARLYWOOD AND LATEWOOD IN DICOTYLEDONOUS TREES: A STUDY OF STRUCTURAL VARIATION IN GROWTH RINGS OF APPLE (MALUS PUMILA MILL.)
Authors: DOLEY D.
Published: May 2006

Summary

Several indices describing the variation in wood structure within growth rings of dicotyledon trees were examined in apple (Malus pumila Mill.) scions grafted on to four rootstocks of different vigour. The cross‐sectional dimensions of 9600 fibres and 7200 vessel elements were measured in each rootstock and scion combination. Indices incorporating lumen width and wall thickness of fibres varied more or less linearly across growth rings, so that assessment of latewood could be made only by selecting some arbitrary limit, which may not be suitable for all rootstocks. The patterns of variation in vessel lumen area within growth rings varied markedly between rootstocks, and gave no clear indication of the point in the ring at which latewood formation might begin. A less extensive study of the distribution of tissues in the xylem at five positions across a growth ring showed that there tended to be a prominent reduction in the proportion of vessels, and an increase in the proportion of fibres between 10 and 30% of the distance across the ring. It was concluded that the concept of earlywood and latewood is not helpful to fundamental studies of wood structure and formation, and that in industry, measurement of relevant properties, such as the density of wood or fibres, may be made as easily as the determination of proportions of earlywood and latewood, however these wood zones be defined.
CHANGING PATTERNS IN THE RESPONSE TO CYANIDE OF ARUM MITOCHONDRIA OXIDIZING MALATE AND OTHER SUBSTRATES
Authors: WEDDING RANDOLPH T. , McCREADY CHRISTOPHER C. , HARLEY JOHN L.
Published: May 2006

Over a flowering season of 7 weeks, mitochondria from the spadices of Arum maculatum showed a progressive increase in the rate at which added malate was oxidized from less than 20 nmoles min−1 mg protein−1 to more than 700 nmoles min−1 mg protein−1. In the oxidation of succinate, α‐ketoglutarate and other substrates, much smaller differences in rate were found.

Mitochondria oxidizing malate responded to the addition of high (3.8 HIM) concentrations of cyanide by stimulation when their initial rate of malate oxidation was low and by inhibition when it was high. Stimulation by KCN even with high concentrations did not increase the O2 uptake rate of young spadices to the level of mature ones.

Associated with this alteration in response to cyanide was a reverse response to ADP. The early, slowly respiring mitochondria which were stimulated by KCN were often inhibited by ADP while the mitochondria from later spadices which were inhibited by KCN were usually stimulated by ADP.

Similar variations in the relative rate of malate oxidation, response to cyanide and to ADP were observed in mitochondria prepared on the same day from spadices at different stages of development from the same location. In this case the change from young (β) to fully matured (ɛ) spadices approximately paralleled those from the early season to the end of the flowering period. The changes in malate metabolism of the spadix mitochondria were not solely related to stage of spadix development, however, since those from spadices at the same apparent developmental stage gathered over a 5‐week period also showed an increase in the rate of malate oxidation and a change in response to cyanide and ADP.

Several types of evidence—effects of additional washing of the mitochondria, response to additions of oxalacetate and pyruvate, response to inhibitors of cytochrome oxidase other than KCN, assay of oxalacetate concentration of mitochondria, and application of an inhibitor of cyanide‐resistant electron transport (mCLAM)—support the hypothesis that one of the factors in the mitochondria from young or early spadices which limits their ability to oxidize malate is oxalacetate within the mitochondria. As the spadix develops, mitochondrial oxalacetate is diminished or disappears. The stimulation of oxygen uptake in the early stages due to cyanide is thus thought to result from the reduction of the quantity of oxalacetate by cyanohydrin formation.

The inhibition by ADP is not clearly understood, but may result from the existence of other reactions which are subject to negative control by ADP and which have no relation to the role of ADP in oxidative phosphorylation or its coupling to electron transport.
NITROGEN FIXATION BY LICHENS ON GLACIAL DRIFT IN ICELAND
Authors: CRITTENDEN P. D.
Published: May 2006

Species of Peltigera Willd. and Stereocaulon Schreb. are among the most abundant macrolichens in the developing and older Rhacomitrium heaths on glacial drift at Sólheimajökull. The crustaceous Placopsisgelida (L.) Linds. is also a common pioneer lichen on rocks. These species contain a blue‐green alga either as the primary or secondary phycobiont. Five species of these genera were studied and showed appreciable rates of acetylene reduction. The total N content was greater in species with high nitrogenase activity. The biomass of Peltigera and Stereocaulon and surface area of Placopsis were determined at four sites of different ages and estimates of N2‐fixation m−2 day−1 are computed.
THE INABILITY OF BRACHYPODIUM SYLVATICUM AND OTHER SPECIES TO UTILIZE APATITE OR ORGANICALLY BOUND PHOSPHATE IN CALCAREOUS SOILS
Authors: ABEYAKOON K. F. , PIGOTT C. D.
Published: May 2006

Seedlings of Brachypodium sylvaticum (Huds.) Beauv., Festuca gigantea (L.) Vill., Lolium perenne L. and Urtica dioica L. were grown on freshly collected soil from the upper horizons of an uncultivated rendzina and a brown forest‐soil. All species responded to addition of a soluble phosphate on both soils but, while there was no response to the addition of apatite on the rendzina, there was as large a response to apatite as to soluble phosphate on the brown forest‐soil. Brachypodium sylvaticum and Urtica dioica were also grown in sand‐culture without phosphate, with a soluble phosphate, and with humus which is rich in organic phosphate. Both species responded to soluble phosphate but showed no response to the presence of humus. The experiments imply that even Brachypodium sylvaticum, which may occur naturally on calcareous soils containing only traces of soluble phosphate, cannot obtain phosphate from either apatite or humus when the pH is above 7.0.
ASPECTS OF TRANSLOCATION OF CARBON IN THE TULIP
Authors: HO L. C. , REES A. R.
Published: May 2006

Mature tulip plants were treated with 14CO2 in June after flower senescence, and the fate of 14C‐labelled products followed at irregular intervals by fractionation, chromatography and autoradiography until the senescence of the above‐ground parts and, later, following replanting, when reserves were mobilized for the growth of new shoots, new daughter bulbs and roots.

Following feeding with 14CO2, sucrose was identified as the main mobile sugar which was transported down the vascular bundles of the shoot to the daughter bulbs where it accounted for 74% of the total plant radioactivity after 7 days. In the daughter bulb conversion occurred progressively with time to starch and non‐starch ethanol‐insoluble material.

After replanting in mid‐September, both shoots and roots showed high radioactivity (10% and 14% respectively of total activity, 60 days after replanting). Vascular tissues were strongly labelled indicating their role in the redistribution of carbohydrates which were mainly sucrose and fructose polymers in the daughter bulbs and sucrose and glucose in the growing organs.
ADHERENCE OF SAND PARTICLES TO SOYBEAN ROOTS UNDER WATER STRESS
Authors: SPRENT JANET I.
Published: May 2006

The quantity of sand particles adhering to soybean roots is directly related to the degree of water stress imposed. Adherence is apparently by means of mucigel in the region of the root tip and is assisted by root hairs in older regions.
THE EVOLUTIONARY RELATIONSHIPS OF BRITISH SPECIES OF PAPAVER IN SECTION ORTHORHOEADES AS SHOWN BY OBSERVATIONS ON INTERSPECIFIC HYBRIDS
Authors: HUMPHREYS M. O.
Published: May 2006

The morphology and cytology of the three British species of poppy in Section Orthorhoeades, Papaver rhoeas L. (2n= 14), P. lecoqii Lam. (2n= 28) and P. dubium L. (2n= 42), and their hybrids were studied. The chromosome numbers of the three species suggest that they are of diploid, tetraploid and hexaploid origin respectively. Chromosome pairing during meiosis in the hybrids suggests that P. rhoeas is only distantly related to P. dubium and P. lecoqii but that the last two species are much more closely related.

The relationships between the three species and some variant, self‐fertile plants, originating from Henley‐in‐Arden, Warwickshire, were also studied. These plants have a chromosome number of 28 and the chromosome pairing behaviour in hybrids involving them is similar to that in hybrids involving P. lecoqii. However, hybrids between the Henley plants and the other three species were completely sterile. The stunted growth form of these hybrids suggests that genie differentiation has occurred in the Henley plants which upsets the physiological processes governing growth in the hybrids.

It is postulated that the polyploid species possess a mechanism which prevents homoeologous pairing. The mechanism appears to operate normally in hybrids between the polyploid species but appears to break down in hybrids involving the diploid species, P. rhoeas.

The significance of all the results obtained is discussed in terms of the origins and past evolution of poppies belonging to Section Orthorhoeades in Britain.
EFFECTS OF PHENYL‐MERCURIC ACETATE ON STOMATAL AND CUTICULAR RESISTANCE TO TRANSPIRATION
Authors: MORESHET S.
Published: May 2006

Phenyl mercuric acetate applied to both sides of the leaves of sunflower plants growing in both wet and dry soil caused a greater closure of the stomates on the upper than on the lower side of the leaves. By contrast, application of PMA increased cuticular resistance to gas diffusion only in the case of leaves of plants growing in dry soil, suggesting that soil moisture stress as well as PMA decreases the permeability of non‐stomatal epidermal cells.
ION TRANSPORT AND ENDODERMAL SUBERIZATION IN THE ROOTS OF ZEA MAYS
Authors: FERGUSON I. B. , CLARKSON D. T.
Published: May 2006

Progressive suberization and thickening of the endodermis along secondary seminal axes of Zea mays had little effect on the radial movement of phosphate into the vascular tissue. In all parts of the root, inhibitors of respiration, and low temperature, reduced uptake and xylem translocation of phosphate by more than 90%. With calcium, however, there appeared to be two components of the translocated fraction; one was sensitive to metabolic inhibition and was most prominent in young tissue near to the root tip, while the other was insensitive to metabolic inhibition. In older zones near the base of the root, where there was little calcium movement into the stele, only the second insensitive component of calcium transport was found.

A marked maximum in calcium translocation, but not in the translocation of phosphate, was found 12 cm from the root tip. This was not associated with a marked increase in total absorption but was due to a high proportion of the absorbed calcium which moved into the stele. This region is one where lateral roots are initiated in the pericycle and where the structure of the endodermis may change transiently.

At the extreme base of the roots the development of a suberized hypodermis appeared to restrict very severely the translocation of both phosphate and calcium.

Iron and manganese were also absorbed and translocated by all regions of the root examined; the proportion translocated was much greater for manganese than for iron.
HORMONAL CHANGES DURING AFTER‐RIPENING IN SEEDS OF STACHYS ALPINA L.
Authors: PINFIELD N. J. , MARTIN M. H. , STOBART A. K.
Published: May 2006

Unchilled seeds of Stachys alpina L. were dormant when harvested but germinated well if incubated in gibberellin. Chilling resulted only in limited increases in germination even after periods as long as 140 days. Endogenous gibberellins were not detectable in unchilled seeds, but extracts showed appreciable inhibitory activity. Chilling of the seeds resulted in increases in endogenous gibberellin‐like substances and decreases in endogenous inhibitors. Significant levels of gibberellins were first detected after 50 days and continued to increase thereafter, while inhibitory activity was considerably reduced after periods exceeding 26 days.

The comparatively slow changes in endogenous gibberellin levels are discussed in terms of the limited germination response of the seeds to prolonged chilling.
AN ULTRASTRUCTURAL STUDY OF THE AZOLLA, ANABAENA AZOLLAE RELATIONSHIP
Authors: DUCKETT J. G. , TOTH R. , SONI S. L.
Published: May 2006

Electron microscopy reveals that the multicellular hairs, in the Anabaena‐containing leaf cavities of Azolla, produce labyrinthine wall ingrowths, and have dense cytoplasm with numerous mitochondria and abundant endoplasmic reticulum. Development of transfer cell morphology, in this location, might be an adaptation facilitating interchange of metabolites between Azolla and its algal partner. Equally prominent wall ingrowths are also found in the absence of Anabaena. It is suggested that they may be either a constitutive feature of Azolla or may be induced as a response to the presence of combined nitrogen sources in the axenic culture medium. The occurrence of plasmalemmasomes, in the developing hair‐cells of Azolla, is compared with their presence in lichens, mycorrhiza and at host‐parasite interfaces.
GROWTH OF CROSS‐ AND SELF‐POLLEN TUBES IN THE STYLES OF BRASSICA OLERACEA
Authors: OCKENDON D. J. , GATES P. J.
Published: May 2006

Incompatible pollen tubes grew at approximately the same rate as compatible pollen tubes in the styles of Brassica oleracea. This is further evidence that in this species the chief barrier to the growth of incompatible pollen tubes is the stigmatic surface and that there is no positive inhibition of incompatible pollen tubes in the style. There were usually very many more pollen tubes at the top of the style than at its base, which indicated considerable variation in growth rate between the pollen tubes in a single style. The fastest pollen tubes in a style typically had a growth rate of 0.40–0.70 mm/h but the mean rate of growth was 0.14–0.34 mm/h.
STRATIGRAPHY AND POLLEN ANALYSIS OF BROMFIELD SWAMP, NORTH EASTERN QUEENSLAND, AUSTRALIA
Authors: KERSHAW A. P.
Published: May 2006

The sequence of vegetation changes evidenced in the Bromfield Swamp pollen diagram is similar to those derived from previous studies at Lake Euramoo and Quincan Crater. It is established that the initial presence of sclerophyll vegetation around the sites was a regional feature of the Atherton Tableland, determined by low precipitation. Throughout the succeeding rain forest phase, precipitation was higher at Bromfield Swamp than at the other sites suggesting that the rainfall gradient across the Tableland has remained constant. The contrast between the relatively simple stratigraphic sequence of deposits in the swamp and the present complex mosaic of vegetation types and depositional environments implies that there has been a great deal of recent interference with the swamp and the surrounding crater slopes.
HYBRIDS BETWEEN LOLIUM PERENNE AND FESTUCA PRATENSIS
Authors: GYMER P. T. , WHITTINGTON W. J.
Published: May 2006

Many cytogenetic abnormalities are described from Festuca‐Lolium hybrids. Some have not been reported before, notably extra spindles in meiotic interphase and second telophase, and the formation of secondary cells from syncytes. Many of the abnormalities prevent the formation of normal gametes and thus contribute to the sterility of the species. Previous work, however, has shown that this is largely due to genie imbalance in the hybrids.
POLYMORPHISM IN ARRHENATHERUM ELATIUS (L.) BEAUV. EX J. & C. PRESL
Authors: MAHMOUD A. , GRIME J. P. , FURNESS S. B.
Published: May 2006

In the vicinity of Sheffield, natural populations of Arrhenatherum elatius exhibit continuous variation in tiller and leaf number, leaf length and tiller angle. In the associated range of morphologies, the extremes are represented by erect and prostrate plants. Field and laboratory investigations suggest that this polymorphism is genetically controlled and may be attributed to the conflicting selection pressures imposed by competition for light in tall herbaceous vegetation and by continuous defoliation in pastures.
INTERFEROMETRIC CHANGES IN ONION NUCLEI AND NUCLEOLI DURING DEVELOPMENT
Authors: MONOSON H. L. , KULFINSKI F. B.
Published: May 2006

The inner epidermis of the outermost (1) through to the innermost (7) bulb scales of mature white onions were studied by means of quantitative interferometry. Scale 7 represented the oldest unemerged leaf, whereas scales 1 to 6 represented mature leaf bases whose blades had grown, emerged, and withered. A developmental sequence was observed from scale 7 through to scale 1. Nuclei increased in area from 2.9 × 10−6 cm2 in scale 7 to 9.9 × 10−6 cm2 in scale 1, with the greatest increases among the younger scales. Nucleoli increased in area from 3.7 × 10−8 cm2 in scale 7 to 13.9 × 10−8 cm2 in scale 2. Dry mass per unit area of the nuclei increased from 7.8 × 10−5 g/cm2 in scale 7 to 12.4 × 10−5 g/cm2 in scale 1, with a maximum of 13.7 × 10−5 g/cm2 in scale 3. Nucleoli increased in dry mass per unit area from 6.2 × 10−5 g/cm2 in scale 7 to 9.2 × 10−5 g/cm2 in scale 1, with a maximum of 11.6 × 10−5 g/cm2 in scale 3. Nuclear dry mass increased from 2.1 × 10−10 g in scale 7 to 12.1 × 10−10 g in scale 1. Nucleolar dry mass increased from 2.3 × 10−12 g in scale 7 to 12.9 × 10−12 g in scale 1. The data suggest that nuclei and nucleoli increase in size and mass with cell size, thereby providing a greater biosynthetic (control) capacity to enlarging cells.
THE INFLUENCE OF NIGHT LENGTH ON STOMATAL BEHAVIOUR IN TRADESCANTIA VIRGINIANA
Authors: MARTIN E. S. , MEIDNER H.
Published: May 2006

In continuous light the time course of stomatal opening in Tradescantia virginiana was substantially modified by the length of the preceding night, e.g. the time to maximum opening was decreased as the preceding night length increased. This response can be correlated with an underlying stomatal rhythm in darkness. The possibility that this rhythm is due to changes in osmotic relations between guard and epidermal cells is discussed.
A REGIONAL SUB‐DIVISION OF DINOFLAGELLATE CYSTS AROUND THE BRITISH ISLES
Authors: REID PHILIP C.
Published: May 2006

A cluster analysis of the dinoflagellate cyst assemblage of sixty‐eight intertidal sediment samples from the British Isles has been used to divide the coastline into eleven regions. The resulting pattern of regions is discussed in relation to hydrography and the distribution of dinoflagellates in the plankton. The subdivision of dinoflagellate regions shows a close relationship to the occurrence of chaetognath indicators of water masses around the British Isles. This suggests that cyst propagation is localized and that each water mass has its own characteristic dinoflagellate population.
THE ACTIVITY OF INVERTASE AND ITS RELEVANCE TO THE ACCUMULATION OF STORAGE POLYSACCHARIDES IN LEAVES INFECTED BY BIOTROPHIC FUNGI
Authors: LONG D. E. , FUNG A. K. , McGEE E. E. M. , COOKE R. C. , LEWIS D. H.
Published: May 2006

Infection of Senecio squalidus by Albugo tragopogonis and of Tussilago farfara and Poa pratensis by Puccinia poarum results in an increase in the activity of an acid invertase localized at the sites of infection. It is concluded that sucrose from the host is first hydrolysed and then absorbed by the parasite. Invertase also plays a key role in the provision of substrate for the typical accumulation of starch around pustules of biotrophic fungi on host species which store this polysaccharide. Compartmentation of invertase and the enzymes concerned with synthesis of sucrose and fructans permits these carbohydrates to be accumulated within pustules on host species which normally store fructans.
STIMULATION OF SEX ORGAN FORMATION IN PHYTOPHTHORA BY ANTAGONISTIC SPECIES OF TRICHODERMA
Authors: BRASIER C. M.
Published: May 2006

Evidence for the occurrence of the ‘Trichoderma effect’ in nature is reviewed. It is considered that the effect may be a specifically evolved defence mechanism, and that root inhabiting species of Phytophthora may be more ecologically specialized for response to Trichoderma than others. It is suggested that the ‘Trichoderma effect’ and similar phenomena could influence speciation in heterothallic Phytophthora species.
AN ALBINO MUTANT IN PLANTAGO INSULARIS REQUIRING THIAMINE PYROPHOSPHATE—EFFECTS OF TPP ON CHLOROPLAST ULTRASTRUCTURE
Authors: MICHAEL SANDRA D. , SPURR ARTHUR R.
Published: May 2006

The responses of normal (al+/al+) and albino mutant (aljal) seedlings of Plantago insularis to light and thiamine pyrophosphate (TPP) were studied by transmission electron microscopy.

Plastids in seedlings of normal and albino genotypes grown in darkness had the structure of etioplasts with a thylakoid plexus (prolamellar body) from which extend thylakoids. Some of the thylakoids were often associated into parallel or concentric sheets. In the mutant, the thylakoid sheets were generally shorter, and some were vesiculated. Exposure of normal plants to light resulted in the transformation of the etioplasts to chloroplasts, with the loss of the thylakoid plexus and the formation of typical grana and an intergranal thylakoid system, plus a few globules in the stroma. Exposure of the albino mutant to light caused the loss of the thylakoid plexus and the formation of highly ordered, concentrically associated thylakoid sheet systems, but no grana. After 24 h of illumination, the plastids of the albino mutant showed evidence of thylakoid degeneration and accumulation of globules and starch. These changes are interpreted as a consequence of very low TPP in the mutant and as evidence for the role of TPP in the degradation of glucose through the Krebs cycle in the normal genotype.

The application of TPP to the albino mutant resulted in the formation of essentially normal chloroplasts. The ultrastructural observations support the view that TPP deficiency does not handicap the mutant in protein synthesis until after exposure to light. TPP and light are essential for the formation of normal grana and TPP is in some way involved in the pathways for pigment and protein synthesis in chloroplasts.
CYLINDROCAPSA: CELL DIVISION AND PHYLOGENETIC AFFINITIES
Authors: PICKETT‐HEAPS IEREMY D. , McDONALD KENT L.
Published: May 2006

Each vegetative cell of Cylindrocapsa is enclosed by its own wall, and the filamentous form is maintained by a separate sheath of wall material derived from parental cells. Cell division differs from most other Ulotrichalean genera so far described. Cleavage is initiated even before prophase, usually first from that side of the cell where the interphase nucleus and centrioles lie near the wall. Centrioles replicate and the pairs then separate around the nucleus. The spindle is closed; the poles are broad and flattened with the centrioles coming to lie to one side of them. The nuclear envelope is highly perforated at each pole and spindle microtubules run into these small holes. As anaphase progresses, the ingrowing cleavage furrow impinges upon the interzonal spindle, often deforming it. No phycoplast is formed for cytokinesis. Instead, the spindle seems to collapse as the furrow pushes through it so that the daughter nuclei eventually lie on either side of it.

Recent work has shown this type of cell division to occur in several other Ulotrichalean algae. A recent redefinition of the order Ulvales based on this type of cell division includes several algae formerly in the Ulotrichales. We support this redefinition and the inclusion of Cylindrocapsa in the Ulvales as the only genus in the family Cylindrocapsaceae.
MITOTIC SYNCHRONY INDUCED IN MERISTEMS OF VICIA FABA BY 5‐AMINOURACIL: RESPONSE OF SYNCHRONIZED CELLS TO DEOXYNUCLEOSIDES
Authors: RUDOLPH J. M. , DAVIDSON D.
Published: May 2006

Root systems of Vicia faba L. were treated with 3.93x10‐3 solutions of 5‐aminouracil (5‐AU). Cells are blocked, apparently at the S‐G2 transition point, and subsequently a wave of synchronized mitoses are seen. The time and the degree of synchronization differed in different meristems. Cells of primordia are blocked by 5‐AU to the same extent as cells of lateral or primary roots but their cells recover more rapidly than those of fully developed roots. Treatment with a solution of deoxyrinucleosides (10‐6 or 10‐7M) immediately after 5‐AU appears to reverse the block at the S‐G2 transition and results, in a number of cases, in an increase in the degree of mitotic synchrony. The evidence presented shows that 5‐AU and deoxynucleosides reach primordia and fully emerged meristems in effective concentrations; no evidence was found for differential permeability to these compounds. It is suggested that differences in the rate of recovery from the inhibition imposed by 5‐AU reflects some physiological differences between cells of different meristems.
THE GIANT LOBELIAS: PACHYCAULY, BIOGEOGRAPHY, ORNITHOPHILY AND CONTINENTAL DRIFT
Authors: MABBERLEY D. J.
Published: May 2006

Recent revisions of the Asian, Jamaican and African species of pachycaul lobelias raise a number of evolutionary and biogeographical problems. Discussion of the apparent forest pachycaul ancestry of the African species is applied to problems of biogeography, pollination and Continental Drift. The available facts are accommodated in an hypothesis, wherein the African species are considered to have had an American ancestry. Herbaceous habit, dry fruit, wingless seeds, enhanced alpine pachycauly and entomophily are considered advanced characters. Further investigations, particularly with regard to the American species, are suggested to test the hypothesis.
BACTERIA AND NUCLEI IN PELOMYXA PALUSTRIS: COMMENTS ON THE THEORY OF SERIAL ENDOSYMBIOSIS
Authors: WHATLEY JEAN M.
Published: May 2006

The primitive giant amoeba, Pelomyxa palustris, contains a population of endosymbiotic bacteria. The distinctive ultrastructure of one of the species of bacteria is described in detail. A particularly close relationship exists between these bacteria and the nuclei of Pelomyxa. The significance of some aspects of this relationship is discussed with reference to the endosymbiotic theory of the origin of mitochondria from bacterial precursors.
VARIATION WITHIN COMMON GROUNDSEL, SENECIL VULGARIS L. II. LOCAL DIFFERENCES WITHIN CLIFF POPULATIONS ON PUFFIN ISLAND
Authors: ABBOTT RICHARD J.
Published: May 2006

Differences of height between plants from subjectively determined exposed and sheltered sites were examined in two cliff populations of Senecio vulgaris L. from Puffin Island, Anglesey, N. Wales. Under glass the relative dwarf habit of exposed plants from a N. cliff site was retained in their progeny throughout development, but for S. cliff material there was no difference in height between progenies of exposed and sheltered plants at maturity. It was inferred that within the N. cliff site, genetic variability seems to parallel variation in exposure. But in the S. cliff site response to different levels of exposure is mainly facilitated by a wide measure of developmental flexibility for height. It is suggested that the apparent difference of adaptive strategy between the two cliff populations some 500 m apart may be explained in terms of disparate wind speeds in the respective sites. The N. cliffs are particularly exposed to strong winds and under these conditions it is possible that genetic adaptations to the separate micro‐environments enhances survival.

The reported predominant self‐pollination within S. vulgaris (Trow, 1912; Hull, 1974) is considered in discussion to be of value to an ephemeral as a means of adapting it to the local micro‐habitats in a heterogeneous environment, so perpetuating the between plant variability. There are indications that the observed pattern of localised genetic variation on Puffin Island, both between and within populations, has evolved over the last 20 years.
GLUCOSE METABOLISM IN HYDRODICTYON AFRICANUM IN RELATION TO CELL ENERGETICS
Authors: RAVEN J. A.
Published: May 2006

When ATP is supplied by oxidative phosphorylation alone, cyclic photophosphorylation alone or from both photosynthetic and oxidative phosphorylations, exogenous glucose is metabolized to a similar range of non‐volatile products of which a major one is starch. When only fermentative ATP supply can occur, much less starch is produced. Cyclic photophosphorylation alone supports a rather lower rate of starch synthesis from exogenous glucose than does oxidative phosphorylation alone. This is apparently due to rate‐limitation by glucose influx, since cyclic ATP production supports a faster rate of starch synthesis than does oxidative ATP production when endogenous substrate is used.

Production of CO2 from specifically labelled glucose is consistent with the operation of the EMP, PPP and TCAC in both light and darkness in the presence of oxygen. Fermentation of exogenous glucose is inhibited by light absorbed by photosystem one, probably via cyclic photophosphorylation. Respiratory CO2 production is also inhibited to a small extent by photo‐system one, although most of the light inhibition needs photosystem two. This DCMU‐reversed inhibition of CO2 production in the light is due to a direct inhibition of decarboxylation reactions as well as to reassimilation of respired CO2.

The relatively small randomization of C1 and C6 labelled glucose during assimilation into starch suggests that conversion to triose phosphate may not be essential for transport of hexose across the outer chloroplast membranes.
THE RATE OF CYCLIC AND NON‐CYCLIC PHOTOPHOSPHORYLATION AND OXIDATIVE PHOSPHORYLATION, AND REGULATION OF THE RATE OF ATP CONSUMPTION IN HYDRODICTYON AFRICANUM
Authors: RAVEN J. A.
Published: May 2006

Work previously published by the author shows that either cyclic photophosphorylation or oxidative phosphorylation can supply ATP to a variety of ATP‐requiring processes in Hydrodictyon africanum. The rate at which the process occurs with ATP supplied from cyclic photophosphorylation is in some cases faster than that when ATP is supplied by oxidative phosphorylation; for other processes the reverse is true. The reasons for this variability in the rate at which the two ATP sources can support different ATP‐requiring processes is discussed and it is suggested that regulation of the rate of ATP‐requiring processes involves changes in the activity of the ATP‐consuming reactions as well as in the ATP concentration (or energy charge). It is concluded that the in vivo capacity for cyclic photophosphorylation is at least as great as that for oxidative phosphorylation. Based on the capacity for respiratory electron flow in vivo, it is suggested that cyclic and oxidative phosphorylation each have capacities of some 20 μMoles (mg chl)−1 h−l. Based on the capacity for non‐cyclic electron flow in vivo, it is suggested that the capacity for non‐cyclic phosphorylation in vivo is 150 μMoles (mg chl)−1 h−1. Cyclic photophosphorylation saturates at an irradiance of about 1 J m−2 s−1, while non‐cyclic photophosphorylation saturates at about 10 J m−2 s−1. These low figures for this shade‐Actapted alga contrast with about ten‐ to twenty‐fold higher values for capacity and light requirement for the various phosphorylation processes in sun‐Actapted microalgae.
CHANGES IN THE ACTIVITY OF FERREDOXIN NADP REDUCTASE DURING THE GREENING OF BEAN LEAVES
Authors: HASLETT BARRY G. , CAMMACK RICHARD
Published: May 2006

During continuous illumination of etiolated leaves of Phaseolus vulgaris L. ferredoxin–NADP reductase activity increased exponentially after an initial lag period of 10–15 h while the chlorophyll/reductase molar ratio increased to a constant value of 750±50 after approximately 15 h illumination. The same ratio was obtained when greening occurred at low light intensity.

The synthesis of ferredoxin–NADP reductase was influenced by phytochrome activity as indicated by its response to red/far‐red light treatments. The effects of D‐threo chloramphenicol and lincomycin indicated that synthesis of this enzyme did not involve translation on chloroplast ribosomes. The data are discussed in relation to the development of ferredoxin and plastocyanin in greening bean leaves.
SEED PROTEINS OF PHASEOLUS AND VIGNA
Authors: DERBYSHIRE E. , YARWOOD J. N. , NEAT E. , BOULTER D.
Published: May 2006

Protein band patterns of globulins extracted from the seeds of a number of different species of Phaseolus and Vigna, have been obtained by disc electrophoresis and the sub‐units of the major seed proteins have been separated on gels by use of continuous SDS electrophoresis. The agglutinin potential of seed extracts with respect to human Group O red blood cells has also been determined. The globulin extracted from Phaseolus lunatus was different from that from P. acutifolius, P. coccineus, P. dumosus and P. vulgar is, and these globulins were different from the major globulins extracted from other species which differed among themselves. The globulin patterns for P. atropurpureus and P. lathyroides were not the same as those of the other species examined and saline extracts from the two species Iysed red blood cells. Agglutinin activity was detected only in extracts from P. acutifolius, P. coccineus, P. dumosus and P. vulgaris. Glyco‐protein II, the major seed protein of P. vulgaris, was tentatively identified as the major globulin in extracts from P. acutifolius, P. coccineus and P. dumosus, and was not detected in the other species, with the exception possibly of P. atropurpureus and P. lathyroides. We discuss our data in relation to recent re‐classifications of species of Phaseolus and Vigna.
DISTRIBUTION OF THE C4 DICARBOXYLIC ACID PATHWAY OF PHOTOSYNTHESIS IN LOCAL MONOCOTYLEDONOUS PLANTS AND ITS TAXONOMIC SIGNIFICANCE
Authors: RAGHAVENDRA A. S. , DAS V. S. R.
Published: May 2006

The photosynthetic characteristics of fifty‐six monocotyledonous plants belonging to seventeen families were examined. As many as twenty‐three plants, hitherto unreported, showed C4 pathway characteristics. C4 species were recorded in ten new genera. The C4 plants were confined to the families, Cyperaceae and Gramineae. The findings confirm the highly evolved nature of the tribes Andropogoneae and Paniceae in contrast to the primitive features of Agrosteae and Festuceae. On the basis of photosynthetic characteristics, it is suggested that Aristida should be included in a separate tribe, Aristideae, whereas Eragrostis resembles more panicoid grasses rather than the members of Festuceae. The importance of the C4 syndrome in relation to the evolution of grasses is stressed.
ULTRASTRUCTURE OF WHEAT RHIZOSPHERE
Authors: FOSTER R. C. , ROVIRA A. D.
Published: May 2006

Ultrathin sections of rhizospheres of wheat roots showed sparse colonization of the root surface by microorganisms in young roots. Older roots at the flowering stage showed considerable development of microorganisms both in the rhizosphere and in the outer cortical cells and cell walls. The invasion of cortical cells was preceded by lysis of the host cell wall, the stages of lysis are illustrated. The spatial relationships between clay aggregates, microorganisms, mucilaginous materials and the root surface are described.
A MICROSCOPICAL STUDY OF THE DEVELOPMENT OF A SPORE‐LIKE STAGE IN THE LIFE CYCLE OF THE ROOT‐NODULE ENDOPHYTE OF ALNUS GLUTINOSA (L.) GAERTN.
Authors: van DIJK C. , MERKUS E.
Published: May 2006

A light‐ and electron‐microscopical study of the root‐nodule endophyte of Alnus gluttinosa (L.) Gaertn. was carried out to investigate the development of a spore‐like stage, here called the granule, in the life cycle of the endophyte. Comparison of granule‐rich and granule‐free root nodules showed that granule formation takes place via local transverse growth of thick endo‐phytic hyphae, giving rise to multicellular‘granulated bodies’differing in shape and size. Subsequently, the cells of these granulated bodies are transformed into granules by cell separation and ultrastructural changes, the most striking of which are cell‐wall thickening, reduction of the number of mesosomes, and increased density of the cytoplasm. Granule development takes place both intracellularly and intercellularly. Intracellularly produced granules are eventually liberated by the death of the host cell. Mature granules show a strong resemblance to spores of free‐living actinomycetes in their ultrastructure and behaviour.

It is concluded that, in view of the terminology currently used in the description of members of the Actinomycetales, the term granule should be replaced by spore and thus the term granulated body by sporogenous body.
ECOLOGICAL PHYSIOLOGY OF THE LICHEN HYPOGYMNIA PHYSODES
Authors: FARRAR J. F.
Published: May 2006

The effect of constant saturation with water upon Hypogymnia physodes for periods of up to 7 days was investigated in either light or dark, at either 20°C (representative of most laboratory experiments on lichen physiology) or 5°C (more representative of field conditions). In all cases the capacity for photosynthesis, phosphate uptake, and total polyol content declined over 7 days; the decline was greater at 20°C than 5°C, and usually greater in the dark than in the light. In general, both alga and fungus reacted similarly to the treatments.

Previously fixed 14C mostly remained in the polyol pool during the treatments, with relatively little entering the insoluble fraction. The substantial loss of previously fixed 14C during 7 days saturation was almost entirely from the methanol soluble fraction. Within the insoluble fraction, there was also no loss of 14C during the 7‐day period if protein had been previously labelled with 14C‐leucine.

Two other lichens, Xanthoria aureola and Peltigera horizontalis, also showed broadly similar declines to Hypogymnia physodes in various physiological characteristics.
ORIGIN OF INTERNODAL AIR SPACES IN HIPPURIS VULGARIS L.
Authors: KORN ROBERT W.
Published: May 2006

Air spaces in the internodal regions of Hippuris vulgaris L. are separated from each other by a single file of cells, a feature which permits a geometric description of their arrangement according to the number of adjacent air spaces. This number ranges from four to eight with an average of 6.04 ± 0.29. Vertices between three adjacent air spaces are composed of either an hexagonal central cell from which three cells radiate outward, is called a cell vertex (CV) and has a frequency of 0.453, or by three pentagonal cells with a common wall point, is called a wall vertex (WV) and has a frequency of 0.547. Air spaces arise from certain three‐rayed vertices by wall separation and a subsequent series of unequal cell divisions in which the ends of cell plates only attach to walls bordering air spaces.

A paper‐pencil model was devised in order to identify the critical steps of this ontogenetic sequence. One important ordering process in generating this pattern of air space arrangement is an alternating selection of vertices around cell and cell groupings which will become air spaces. A second ordering feature is the positioning of cell plates in order that they attach only to facets bordering air spaces. This model produces the features of spaces separated by a single row of cells and the ratio of the two types of vertices cited above but only approximates the number of cells around a space. It has been demonstrated here that walls of a cell can influence each other through some type of inhibition, and as a morphogenetic mechanism in general, it may play an important role in other cases of tissue development.
BREEDING SYSTEM AND POPULATION STRUCTURE OF ARMERIA MARITIMA (MILL.) WILLD. ON A ZINC‐LEAD MINE
Authors: LEFÈBVRE C.
Published: May 2006

Using marker genes the breeding system (mating type gene) and the structure (hairy stalk gene) of a zinc–lead mine population of Armeria maritima, an insect‐pollinated plant, was studied in situ. Strict allogamy occurs in the population in nature although this population shows self‐fertility in experimental garden plots. The population is divided into sub‐populations differing in the frequency of hairy stalked individuals. Gene flow between these sub‐populations is very low (if any) so that the differences, which are likely to have originated by chance, remain constant through generations.
WOUND REPAIR IN YAM TUBERS: PHYSIOLOGICAL PROCESSES DURING REPAIR
Authors: PASSAM H. C. , READ S. J. , RICKARD J. E.
Published: May 2006

When bisected or deeply cut by knife, yam tubers (Dioscorea rotundata Poir.) undergo a process of wound repair which comprises: (a) an immediate migration of starch to the cut surface (within 5–10 h of injury); (b) after 2–3 days, the formation of a suberized layer beneath the cut surface; (c) after approx. 5 days, the production of periderm (cork). Concurrent with these structural changes are a rapid increase in the rate of respiration, a hydrolysis of starch to sugar and an increase in invertase activity. Metabolic activity remains high until healing is complete. When tubers are wounded by surface abrasion or severe bruising these wound‐healing processes do not occur. Weight loss and respiratory activity of bruised tubers remain high until decay. Abrasions or superficial cuts are not sealed off by a layer of periderm, and in consequence a prolonged loss of moisture content and an increased susceptibility to pathogen attack result.
THE ESTIMATION OF PLANT ORGANIC ACIDS BY GAS‐LIQUID CHROMATOGRAPHY
Authors: PHILLIPS R. D. , JENNINGS D. H.
Published: May 2006

A gas‐liquid chromatographic technique for the rapid separation of organic acids as silyl derivatives is described. The procedure involves two successive analyses using different stationary phases, one of which separates citric and isocitric acids directly as silyl derivatives. This avoids the tedious conversion of isocitric acid to the lactone. The chromatographic analysis of the major acids in a plant with Crassulacean acid metabolism can be completed in under 20 min.