bluuebunny/crossref_metadata_2025 huggingface dataset:
DISTRIBUTION OF NITRATE REDUCTASE ACTIVITY IN SIX LEGUMES: THE IMPORTANCE OF THE STEM
Authors: ANDREWS M. , SUTHERLAND J. M. , THOMAS R. J. , SPRENT J. I.
Published: May 2006

Summary

Nitrate reductase activity (NRA) was measured in leaves, stems and roots of six grain legumes supplied with different nitrate concentrations. The contribution of the stem relative to total plant activity was assessed.

In Lupinus angustifolius L., Pisum sativum L. and Viciafaba L., legumes of temperate origin, an increased proportion of total plant NRA occurred in the shoot as nitrate concentration was increased. In Cajanus cajan (L.) Wilisp., Glycine max (L.) Merr. and Phaseolus vulgaris L., legumes of tropical origin, the proportion of total plant NRA in root and shoot was relatively constant regardless of nitrate concentration.

More than 20% of total plant NRA can occur in the stem of G. max, L. angustifolius, Pisum sativum, Phaseolus vulgaris and V. faba. In C. cajan 10 to 15% of total plant NRA was found in the stem at all nitrate concentrations. It is concluded that stem tissues can contribute significantly to overall nitrate metabolism.
NEW NODULATING LEGUME TREES FROM SOUTH‐EAST BRAZIL
Authors: de FARIA S. M. , FRANCO A. A. , de JESUS R. M. , MENANDRO M. de S. , BAITELLO J. B. , MUCCI E. S. F. , DöBEREINER J. , SPRENT J. I.
Published: May 2006

Summary

An extensive search for active (acetylene reducing) nitrogen‐fixing root nodules was made amongst Brazilian forest legumes. Seven new nodulated species, including two new nodulating genera, were found in the Caesalpinioideae, 18 new species in the Mimosoideae and 30 new‐species, including four new genera, in the Papilionoideae. All have potential importance in reafforestation. Fifty‐eight new records of non‐nodulating species are included. The morphology of all nodules was studied and is discussed in relation to taxonomic position. Preliminary data on nodule structure are given.
ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZA IN THE ERICACEAE
Authors: BONFANTE‐FASOLO P. , GIANINAZZI‐PEARSON V. , MARTINENGO L.
Published: May 2006

Summary

The development of Pezizella ericae Read in living roots of host plants is typically limited to cells surrounding the central cylinder and the biotrophic phase of host‐fungus interactions is characterized by a highly compatible relationship between the symbionts at the cellular level. In non‐host plants, the ericoid endophyte extensively colonizes root tissues, including the central cylinder, without forming hyphal coils and a necrotrophic relationship occurs at the cellular level, the fungus provoking a rapid degeneration of the contents of plant cells. A fundamental difference between the interactions occurring in cells of host and non‐host roots is the constant presence of the plant plasmalemma surrounding P. ericae in the former and the complete lack of this membrane around hyphae in the latter. External hyphae of P. ericae develop an abundant fibrillar sheath in the presence of both host and non‐host roots. This disappears with hyphal development in living host cells but it persists around intracellular hyphae in non‐host tissues. These observations are discussed in relation to fungus‐plant recognition phenomena and the control of infection in ericoid mycorrhizas.
CHARACTERIZATION OF THE DIFFERENT FORMS OF PHOSPHORUS IN THE MYCELIUM OF THE ECTOMYCORRHIZAL FUNGUS, HEBELOMA CYLINDROSPORUM, CULTIVATED IN PURE CULTURE
Authors: ROLIN D. , LE TACON F. , LARHER F.
Published: May 2006

Summary

The ectomycorrhizal fungus, Hebeloma cylindrosporum, was grown in pure culture at different phosphorus concentrations, with or without shaking. Phosphorus fractions were separated by a modified Mudd, Yoshida & Koite (1958) method. Acid‐soluble and acid‐insoluble phosphorus precipitated with barium acetate were identified by thin layer chromatography.

In pure culture. Hebeloma cylindrosporum stores very little polyphosphate (4 to 9% of total P) and amounts are unrelated to the concentration of external phosphorus. Most of the phosphorus is stored as orthophosphate. Internal orthophosphate is well correlated with external orthophosphate and is readily utilized to form DNA and phospholipid. Internal soluble organic phosphorus can also be mobilized but to a lesser extent.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: JENNINGS D. H. , THORNTON J. D.
Published: May 2006

Summary

When mycelium of Dendryphiella salina Nicot & Pugh is exposed for 5 h to media containing various concentrations of the very slowly metabolized sugar, L‐sorbose, the total ethanol‐soluble carbohydrate content increases and there is also a stimulated synthesis of mannitol. Provided L‐sorbose is absorbed, the presence of glucose, fructose, mannitol or arabitol in the medium does not prevent these changes which are different from those brought about by the non‐metabolizable sugar, 3‐O‐methyl glucose. It is suggested that the apparent regulation of mycelial ethanol‐soluble carbohydrate concentration following uptake of the latter sugar cannot be controlled primarily by turgor.
KINETIC STUDIES ON THE TRANSPORT OF 2‐OXOGLUTARATE ANDL‐MALATE INTO ISOLATED PEA CHLOROPLASTS
Authors: PROUDLOVE M. O. , THURAMN D. A. , SALISBURY J.
Published: May 2006

Summary

The transport of 2‐oxoglutarate and l‐malate into the sucrose impermeable space of pea chloroplasts has been studied by silicone oil centrifugal filtration. The inhibition of transport of these dicarboxylates has been shown to be markedly different in the presence of the alternative dicarboxylate. The suggestion is made that at least two carriers are involved in the transport of 2‐oxoglutarate with similar Km values of 0–20 mm for this substrate. l‐Malate inhibited 2‐oxoglutarate transport with a pseudo Ki value of 0–76 mm. l‐Malate uptake was found to have a Km value of 0–29 mM and its uptake appeared to be inhibited, mainly competitively, by 2‐xoglutarate with a Ki value of 0–2 mm.
SIZE AND ACTIVITY OF QUIESCENT CENTRES OF ROOTS
Authors: CLOWES F. A. L.
Published: May 2006

Summary

The quiescent centres of angiosperm roots of a wide range of size and architecture have been investigated by autoradiography and stathmokinetic measurements. The volume and number of constituent cells of the quiescent centre vary with the width of the root, but roots of the Gramineae and Cyperaceae have larger quiescent centres for their size than all other plants except Pistia. The difference is not correlated with the open or closed nature of the meristem nor whether the epidermis is derived from the cortex or cap, but is correlated with a thickened boundary between the cap and the rest of the apex or, in Pistia, ith a discrete epidermal meristem. The number of cells in the quiescent centre approaches zero in the non‐grass type of apex as the width of the root becomes smaller and nearer that of pteridophyte roots with tetrahedral apical cells. The ratio of rates of cell cycling in the quiescent centre to those in the surrounding meristem also varies with root width, but here all closed meristems show greater differences in rates than all open meristems. The ratio comes near to unity in the smallest open meristems. The data are discussed in relation to the reasons for quiescence, the differences between root and shoot meristems and our ability to perform certain surgical operations.
ANATOMICAL FEATURES OF THE SEED COAT OF ACACIA KEMPEANA (MUELLER) WHICH RELATE TO INCREASED GERMINATION RATE INDUCED BY HEAT TREATMENT
Authors: HANNA P. J.
Published: May 2006

Abstract

Entry of water and subsequent germination of hard seeds of Acacia kempeana occurs after the strophiole lifts and cracks. The ‘opening’ of a strophiole is induced by heat and is effected through the splitting of thin‐walled cells lying beneath short palisade cells within the strophiole. Estimated pressure increases of greater than 25 % within the vascular bundle, which passes directly under the thin‐walled cells, might influence strophiolar lifting. The vascular bundle between the hilum and the adjacent strophiole is virtually devoid of xylern vessels, thereby preventing water entry through the hilum. However, following the strophiole, the vascular bundle obtains a maximum number of about 35 xylern vessels and is itself enclosed in this region by a noticeable group of over 150 thin‐walled cells. Many of these thin‐walled cells appear crushed along the route of the vascular bundle through the mesophyll layer to the end opposite the hilum. At the non‐hilum end, the vascular bundle almost touches the internal side of the seed coat and thus entry of water would be facilitated through this zone to the internal endosperm and embryo.
THE QUANTITATIVE STUDY OF MYCORRHIZAL INFECTION
Authors: WALKER N.A. , SMITH S. E.
Published: May 2006

Summary

The processes of infection of roots of Trifolium subterr aneum by vesicular–arbuscular mycorrhizas are analysed using a modification of a model presented previously. The modified model uses as dependent variables the fraction of the root length infected and the linear density of infection units. It allows the evaluation of the rate of initiation of new infection units and of the rate of growth of hyphae within the root as functions of time.

The model is applied to data for T. subterraneum grown in a 20‐foid range of densities of randomly‐mixed propagules in soil; we show the rate of initiation of new infection units in both main and lateral roots was proportional to the propagule density over short periods (5 to 11 day). However, the rate of initiation of infection units in main roots during this period was approximately half that in lateral roots. The rate of growth of hyphae in the root did not depend on the propagule density.

As the main roots ceased to grow, both rates of infection and of mycelial growth fell: these rates did not fall for lateral roots during the 26 days of the experiment. The results raise the question of the dependence of mycelial growth‐rate on the age of the infection unit, which is discussed.

The model predicts that the fraction of the root length infected approaches asymptotically a value less than one, as has been repeatedly observed. Other models require arbitrary modification to accommodate such findings.
ANION ACCUMULATION BY LICHENS I. THE CHARACTERISTICS AND KINETICS OF ARSENATE UPTAKE BY UMBILICARIA MUHLENBERGII
Authors: RICHARDSON D. H. S. , NIEBGER E. , LAVOIE P. , PADOVAN D.
Published: May 2006

Summary

Arsenate was accumulated by discs of the lichen Umbilicaria muhlenbergii (Ach.) Tuck, to levels of 16/wnol As per gram oven‐dry weight during 1 h incubation in solutions containing 40μmol of arsenate at pH 4–6. Studies at lower external concentrations and at different pH values revealed that the more protonated species of arsenate were absorbed most readily. Light enhanced arsenate uptake only marginally, which supports the interpretation that the bulk of uptake was by the non‐photosynthetic fungal symbiont. Dinitrophenol caused a 30% reduction in uptake, while heat‐killing lichen samples resulted in negligible absorption, even from solutions of high arsenate concentration. The kinetics of arsenate uptake were studied using the Michaelis‐Menten treatment, and yielded an apparent value for Km of 360 ± 60 μ and a Vmax of 0.37 ± 0.03 μmol g−1 min−1 for H2AsO−4. Fürther analysis by means of the Hofstee and Lineweaver‐Burk plots suggested that two uptake systems may exist. The above results are discussed in relation to published data on free‐living fungi and algae and it is concluded that arsenate uptake provides a convenient means for investigating anion accumulation in lichens.
THE EFFECTS OF MAGNESIUM, NICKEL, CALCIUM AND MICRONUTRIENTS ON THE ROOT SURFACE PHOSPHATASE ACTIVITY OF A SERPENTINE AND NON‐S ERPENTINE C LONE OF FESTUCA RUBRA L.
Authors: JOHNSTON W. R. , PROCTOR J.
Published: May 2006

Summary

Root surface phosphatases of a serpentine and non‐serpentine clone of Festuca rubra were assayed under a range of ionic concentrations based on those found in the soil solutions of the extremely toxic Meikle Kilrannoch serpentine. The phosphatases from the serpentine clone showed greatest activity in a solution similar to that in the soil and which had high concentrations of magnesium and nickel. The phosphatases from the non‐serpentine clone were partially inhibited in the same solution. Changes in calcium and concentrations of micronutrients produced no significantly different responses between the clones in phosphatase activity. The results contrast with those obtained by previous workers on a serpentine and imply subtle enzymic adaptations leading to a requirement for simultaneously high concentrations of the potentially toxic ions, for high phosphatase activity. The ecological significance of the adapted phosphatases is unclear.
SEEDS PER FRUIT AS A FUNCTION OF FRUITS PER PLANT IN ‘DEPAUPERATE’ ANNUALS AND BIENNIALS
Authors: KELLY D.
Published: May 2006

Summary

Reproduction was examined in one summer annual (Euphrasia pseudokerneri) and two biennials (Linum catharticum and Gentianella amarella) in chalk grassland, and three dune winter annuals (Erophila verna, Cerastium semidecandrum and Myosotis ramosissima). Gentianella was examined in 1979 to 1981 and all other species in 1980 and 1981, making a total of 13 separate datasets. Plants with one or two fruits had fewer seeds per fruit in all 13 cases. As plant size increased to six to ten fruits, seed number gradually increased. The relationship was similar in 1980 and 1981 for all six species. A ‘depauperate’ plant was therefore denned as one which produces significantly fewer seeds per fruit than large plants. Field populations of all species averaged less than nine fruits per plant, so that the relationship between seed number and fruit number was important in determining seeds produced per plant. Although this relationship has only been noted in three other species, I interpret five recent papers as suggesting the existence of a similar relationship between fruit number and seed number. I interpret the effect as analogous to the abortion of fruits in plants with many fruits.
SMALL‐SCALE DYNAMICS IN AN EARLY HOLOCENE WET SCLEROPHYLL FOREST IN TASMANIA
Authors: MACPHAIL M. K.
Published: May 2006

Summary

Pollen analysis of organic sediments in a small hollow at Tarraleah in central Southern Tasmania allows identification of some small‐scale patterns and processes withinEucalyptuswet sclerophyll forest during the early to middle Holocene. These events are related to a time scale of inferred ages (i.a.), based on three radiocarbon dates and stratigraphic constraints.

Although relatively few tree and tall shrub taxa are involved, changes in relative abundance show that at least five floristically distinctive communities of understorey mesophytes have surrounded the hollow. Prior to i.a, 9125 B.P., subalpineEucalyptusopen forest or woodland formed the local vegetation:

Pomaderris apetala– Compositae i.a. 8900 to 8325 B.P.

Atherosperma moschatum – Dicksonia antarcticai.a. 8175 to 7775b.p.

Phyllocladus aspleniifolius – (?)Nothofagus cunninghamiii.a. 7625 to 7350b.p.

Pomaderris apetala– sclerophyll shrubs i.a. 7200 to 6925b.p.

Dicksonia antarcticaafter i.a. 6925b.p.

In most general terms the forest and mire species have behaved consistently with their modern ecological preferences and established trends in Holocene climate. With more detailed resolution, the influence of climate is less apparent and the shifts in community composition more likely to be due to fire frequency and edaphic effects. The results confirm the modern observation that canopy eucalypts and understorey species are only weakly correlated in the presence of fire. Fire has resulted in the separation ofPomaderris apetalacommunities into two ecological entities but in the absence of fire ‐ and fire‐promoting climates ‐ during the early Holocene,P. apetalaand associated mesophytic small trees may have been able to exclude competitively the canopy eucalypts. Similarly the data indicate early Holocene rainforests may have been enriched withA. moschatum.

The marked increase in fire frequency at or after i.a. 6925b.p.is suggested to be due to migration into or increased utilization of the area by Aborigines.
PHOTOCONTROL OF SPORE GERMINATION IN POLYPODIUM VULGARE L.
Authors: AGNEW NORMA , McCABE ANNE , SMITH D. L.
Published: May 2006

Summary

Spore germination in the. fern Polypodium vulgare is induced by light at all wavelengths from blue to far‐red, although red light is most effective. The action spectrum for germination together with observations on the photoreversible effects of red and far‐red light provide evidence for the involvement of phytochrome, but the effects of blue light, particularly its interactions with red light, are incompatible with an interpretation in terms of phytochrome alone. It is suggested that two pigments are involved, phytochrome and a blue light absorbing pigment, but that not all spores contain effective levels of both pigments.
BIOLOGICAL EFFECTS OF SURFACTANTS VII GROWTH AND DEVELOPMENT OF BRASSOCATTLEYA (ORCHIDACEAE) SEEDLINGS
Authors: ERNST R. , ARDITTI J
Published: May 2006

Summary

Phytotoxicity of a homologous series of sulphoberaine surfactants, 3‐(alkyldimethyl‐ammonio)‐1‐propanesulphonates, on Brassocattleya orchids increased with increasing alkyl chain length from eight to 14 carbon atoms of the lipophile, levelled off and then declined with the 18 carbon derivative. Because of its high Krafft point the tatter had reduced solubility at the assay temperature. Interfacial tensions of the nutrient solutions, measured against a test lipid, declined m parallel with the observed phytotoxicity. This and previous findings strongly support the suggestion that disruption of cellular membranes by surface active agents plays a key role in their toxicity.
CHANGES IN THE PHOSPHORUS COMPOSITION OF SEEDS OFHAKEA SERICEA(PROTEACEAE) DURING GERMINATION UNDER LOW PHOSPHORUS CONDITIONS
Authors: MITCHELL D. T. , ALLSOPP N.
Published: May 2006

Summary

Seeds ofHakea sericeaSchrad belonging to the subfamily Grevilleoideae of the Proteaceae greater P reserves than those belonging to the Proteoideae indigenous to South Africa. The main P‐containing compounds in seeds ofH. sericeaare phytic acid with smaller proportions consisting of lipid‐P, RNA, DNA, protein‐P, polyphosphate and orthophosphateHakea sericeagrew on sterile acid washed sand for up to 125 d after sowing before signs of mineral deficiency symptoms appeared. Proteoid roots were produced by seedlings grown in Clovelly sand from 60 d after sowing and their numbers appeared to be related to the accumulation of P in the seedling. It is concluded that the P reserves of seeds ofH. sericeamay provide a competitive advantage over those of the Proteoideae for establishment and growth in the acidic sandy soils of the south‐western Cape, South Africa.
ECOPHYSIOLOGICAL STUDIES OF THE LICHEN, PARMELIA PRAESIGNIS Nyl.
Authors: LINK S. O. , NASH T. H.
Published: May 2006

Summary

Losses in photosynthetic ability were observed in the lichen, Parmelia praesignis Nyl., over a 2‐week period under three out of four different combinations of temperature and hydration conditions during storage. At a constant daytime temperature of 16 °C, lichens which were wetted even, few days retained more photosynthetic ability than did lichens wetted everyday. Lichens which were maintained under a varying range of temperatures (12 to 26 °C) retained most of their photosynthetic ability, with the material wetted daily eventually losing 40% of its ability. The material wetted every few days did not lose a significant amount of photosynthetic ability. Lichen material maintained at a temperature of 33 °C and wetted everyday lost all photosynthetic ability after 3 d.

Photosynthetic ability was found to be normally distributed with a mean of 3.2 mg CO2 g−1 and a standard deviation of 0.65 mg CO2 g−1 h−1 when based on the experimental results from 25 randomly selected sets of thallus tips.
AMINES IN BARLEY LAVES INFECTED BY BROWN RUST AND THEIR POSSIBLE RELEVANCE TO FORMATION OF ‘GREEN ISLANDS’
Authors: GREENLAND A. J. , LEWIS D. H.
Published: May 2006

Summary

Free amines, present in healthy leaves of barley and in leaves infected by brown rust (Puccinia hordei Otth.), have been partially characterized. The concentrations of five amines present in both kinds of tissue rise following infection and at least three extra amines are detectable in rusted tissue. The concentration of the polyamine, spermidine, increases rapidly by 6 d after inoculation and, at sporulation, it is six to seven times that in comparable healthy tissues. The possible involvement of polyamines in the ‘green island’ syndrome is discussed.
DISTRIBUTION OF CLONES OF GALIUM BOREALE L. ON WIDDYBANK FELL, TEESDALE
Authors: DALE A. , ELKINGTON T. T.
Published: May 2006

Summary

Twenty‐one clones of Galium boreale L. have been provisionally identified in a grassland area 55 × 30 m on Widdybank Fell, Teesdale, Co. Durham, by comparison of plant samples collected in 25 cm quadrats and grown under cultivation. The species composition of each quadrat was also listed. Quadrat data were analysed by association analysis and a comparison of clonal distribution and major vegetational types made. The results are discussed in relation to the rate of recruitment of individuals and the ecology of G. boreale.
MALATE OXIDATION BY ARUM SPADIX MITOCHONDRIA: PARTICIPATION AND CHARACTERISTICS OF NAD MALIC ENZYME *
Authors: WEDDING R. T. , WHATLEY F. R.
Published: May 2006

Summary

When oxygen uptake by mitochondria from Arum spadix was determined at pH 6.5 and 7.7, striking differences were found in the response of malate oxidation to the addition of ADP, KCN, salicylhydroxamic acid (SHAM) and NAD. These responses are consistent with the hypothesis that at pH 6.5 malate was oxidized primarily through the NAD malic enzyme while at pH 7.7 the primary enzyme oxidizing malate was malate dehydrogenase.

Oxygen uptake rate plotted as a function of malate concentration up to a concentration of 120 mM produced curves which are best fitted by a model which assumes the presence of two enzymes with different affinities for malate. The change in the relative activities of the two enzymes at pH 6.5 and 7.7 is in agreement with the suggestion that malic enzyme was more active at the lower pH and malate dehydrogenase at the higher.

The NAD malic enzyme was purified from Arum spadix mitochondria and was found to utilize either Mg2+ or Mn2+ as the required divalent cation. Although the enzyme was capable of using NADP, it did so at a rate only 10% of that with NAD. The enzyme displayed hysteretic behaviour, with bursts of activity under some conditions and lags under others, perhaps indicating a shifting state of aggregation such as has been found with other plant malic enzymes. The Michaelis constants for the components of the reaction were similar to those found with other plant NAD malic enzymes.

Sulphate, fumarate, coenzyme A, AMP, ADP and ATP were activators of the enzyme, with activation constants similar to those found with malic enzyme from other plant sources. The relative effectiveness of ADP and ATP was strongly in favour of ADP, so that the enzyme may be under energy charge control in the cell.

The exceptionally high concentration of NAD malic enzyme found supports the suggestion that this enzyme may be important in the metabolism of Arum spadix during floral development.
EFFECTS OF PRETREATMENT WITH PHOSPHATE IN NATURAL POPULATIONS OF AGROSTIS CAPILLARIS L.
Authors: McCAIN S. , DAVIES M. S.
Published: May 2006

Summary

Clones of six populations of Agrostis capillaris L., collected from contrasting soils, were grown in solution culture for a prolonged period at either 1 or 40 mg P dm−3. Large numbers of unrooted tillers were taken from these plants and grown for 8 weeks in similar solutions (low P‐ and high P‐pretreatrnents). Over the subsequent 10‐week period, the acid phosphatase (NPPase) activity of intact roots was measured in the presence of various concentrations of cationic Al.

Activity of NPPase was not dependent on membrane permeability, as measured by K+‐leakage into the assay medium, suggesting an extracellular enzyme location. The low P‐pretreatrnent resulted in, depending upon population, between four and six‐fold increases in root‐NPPase activity, with the highest activities being found in populations from the most acidic soils. The NPPase activity of the roots was not a linear function of plant P‐status and there was evidence that there was a genetic component in the regulation of enzyme activity in low P‐pretreated plants.

Increasing Al concentration had little effect on the NPPase activity of high P‐pretreated plants, but that of low P‐pretreated plants was inhibited to some extent (up to 30%) by the higher concentrations of Al (8 and 16 mg Al dm−3). Populations did not differ in the extent of this inhibition.

The low P‐pretreatment resulted in an increase in the K+‐leakage from intact roots, and populations differed in the degree of this increase. Populations from colliery spoils had a lower K+‐leakage than would be expected on the basis of the low concentrations of P in their shoots. There was some reduction in K+‐leakage with increasing concentration of Al in high P‐, but not in low P‐, pretreated plants.
RAY FLORET MORPHOLOGY AND THE ORIGIN OF VARIABILITY IN SENECIO CAMBRENSIS ROSSER, A RECENTLY ESTABLISHED ALLOPOLYPLOID SPECIES
Authors: INGRAM RUTH , NOLTIE H. J.
Published: May 2006

Summary

The genetic basis of polymorphism in the capitula of Senecio cambrensis has been shown to be the result of interaction between genes at two loci for ray floret length. This polymorphism is likely to be augmented by infrequent inter‐genomic pairing, despite the predominance of preferential homologous pairing. It is suggested that homoeologous pairing may be an important source of variability in the species.
THE COMPARATIVE ECOLOGY OF TWO SAND DUNE BIENNIALS: LACTUCA VIROSA L. AND CYNOGLOSSUM OFFICINALE L.
Authors: BOORMAN L. A. , FULLER R. M.
Published: May 2006

Summary

This paper compares two contrasting biennial plant species of the sand dunes of Holkham, North Norfolk. A survey of distribution, in relation to various habitat factors, showed that Lactuca virosa L. is characteristic of the tall, Ammophila‐dominated grassland on the younger dunes. It is favoured by gaps in the vegetation cover such as those produced by local wind erosion, but it is very sensitive to rabbit grazing. Cynoglossum officinale L. is a plant of older dune grassland and is not normally grazed by rabbits. It can exploit the bare ground around rabbit warrens, benefiting from the higher nitrogen levels resulting from rabbit excreta.

Studies on seed production and germination showed that Lactuca can produce large numbers (> 60000 per plant) of very small (c. 0–8 mg) wind‐dispersed seeds that germinate readily in the autumn. Cynoglossum, on the other hand, produces fewer (< 2500) seeds per plant that are larger (c. 30 mg) and animal‐dispersed. Cynoglossum seeds are inherently dormant; most germination is in the late winter and early spring, after a period of cold. Lactuca compensates for small seed size by having a higher growth rate than Cynoglossum as well as by its earlier germination. Despite all these differences, the two species survive at comparable densities.
THE INFLUENCE OF TEMPERATURE AND MOISTURE STATUS ON THE PHOTOINHIBITION OF SEED GERMINATION IN BROMUS STERILIS L. BY THE FAR‐RED ABSORBING FORM OF PHYTOCHROME
Authors: HILTON JANET R.
Published: May 2006

Summary

Germination of Bromus sterilis L. seeds is unusual in that it is inhibited when the photoreceptor phytochrome exists as Pfr, the degree of inhibition being dependent on the proportion of Pfr established. However, inhibition of germination is transitory and at 15 °C is evident only at l.5 d from sowing. Although germination is reduced at temperatures lower than 15 °C, Pfr is nevertheless inhibitory to germination; inhibition persisting far longer than at 15 °C C. Temperatures higher than 15°C C are also inhibitory to germination but at these temperatures there is no additional inhibitory effect mediated by Pfr. Under conditions of low moisture status the inhibitory effect of Pfr is also markedly increased. The results are discussed in relation to the role of light in the germination behaviour of B. sterilis seeds in the natural environment.
COMPARATIVE DEVELOPMENT OF INFECTION BY THREE VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: WILSON J. M.
Published: May 2006

Summary

The effect of inoculum density on the development of infection by Gigaspora decipiens Hall and Abbott, Glomus fasciculatum (Thaxter sensu Gerdemann) Gerdemann and Trappe and Glomus tenue Greenall (Hall) was investigated. From individual propagules, infection increased logarithmically for each fungus but, at higher inoculum levels, the infectivities differed. Of the three fungi, Gi. decipiens was the least, and Gl. fasciculatum the most infective. The fungi showed different strategies for infection spread. Glomus fasciculatum produced larger infection segments, and spread within the root more extensively than the other fungi. Gigaspora decipiens and GL tenue were more dependent on external spread by the formation of secondary entry points. The intensity of infections was affected by inoculum density, but not by the age of the infection.
THE EFFECT OF PHOSPHORUS ON THE FORMATION OF HYPHAE IN SOIL BY THEVESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS, GLOMUS FASCICULATUM
Authors: ABBOTT L. K. , ROBSON A. D. , DE BOER G.
Published: May 2006

Summary

Hyphae formed in soil by the vesicular‐arbuscular (VA) mycorrhizal fungus, Glomusfasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe were extracted using the membrane filter techniqe and their length was estimated by the grid intersection method. The effect of phosphorus on the formation of this external mycelium was assessed after sampling procedures had been investigated. Phosphorus supply was varied from amounts severely deficient to those adequate for the growth of subterranean clover. After 6 weeks, the alleviation of severe phosphorus deficiency increased both the length of infected root and the length of external hyphae per centimetre of infected root. Further additions of phosphorus decreased both of these measurements. However, the level of added phosphorus at which the most external hyphae was formed per centimetre of infected root was higher than the level of phosphorus which gave the greatest length of infected root. The increase in phosphorus supply which gave the greatest increase in the length of external hyphae per centimetre of infected root also decreased the formation of vesicles within infected roots. At phosphate levels adequate for growth of mycorrhizal plants, there was little development of either external hyphae in soil or vesicles within the mycorrhizal roots.
A COMPARISON OF THE ABILITY OF LEAF SURFACES OF THREE SPECIES TO NEUTRALIZE ACIDIC RAIN DROPS
Authors: ADAMS C. M. , HUTCHINSON T. C.
Published: May 2006

Summary

In order to compare the ability of leaf surfaces of different species to neutralize acidic rain, acidic droplets of identical size were placed on leaves of Artemisia tilesii, Spinacea oleracea and Phaseolus vulgaris. The pH values over time were measured using a micro‐pH electrode. The pH of rain droplets initially of pH 3.0, 3.5 and 5.6 increased after contact with leaves of these species. However, for droplets of pH 2.5 the pH of droplets actually decreased with time on leaves as the drops evaporated, despite the very large quantity of hydrogen ions neutralized by the leaf surface. Neutralization of acidic droplets was greatest in A. tilesii plants, which also showed the lowest sensitivity to foliar injury from simulated acid rain, Spinacea oleracea leaves were the least able to neutralize acid droplets and also were most sensitive to foliar damage. In each species the more acidic the rain, the greater the quantity of hydrogen ions neutralized by the leaf surface. This ability to neutralize acidic droplets on the leaf surface may be an effective means of reducing damage by acid rain, especially since rain events with a pH < 3.0 are very rare. Neutralization of acidic droplets may be brought about when cations are leached from exchangeable pools or by dissolution of salts deposited on the leaf surface through guttation. Large increases in Ca especially, but also in Mg and K in droplets collected from leaves of A. tilesii, suggest that these cations may play an important role in increasing the pH of acidic droplets.
VARIATION DUE TO ENVIRONMENT AND HEREDITY IN BIRCH TRANSPLANTED BETWEEN HEATH AND BOG
Authors: DAVY A. J. , GILL J. A.
Published: May 2006

Summary

Variation in growth and morphology within the Betula penduia/B. pubescens complex has been investigated by means of a reciprocal transplant experiment. Phenotypic responses to adjacent bog and heath environments have been contrasted and the heritability of morphometric characters has been investigated. The extent to which selection by the two environments had occurred was also examined.

Four tetraploid parent trees were selected: two from the bog resembled B. pubescens and two from the heath resembled B. pendula. Progeny were raised from seed and transplanted into the bog and heath field sites as established year‐old seedlings. Survival, growth, leaf and twig morphology, and the responses to fire and deer browsing were monitored for up to three years after planting.

Few of the transplanted individuals died, even after burning. Growth was determined largely by environment. Transplants grew much faster on the heath than on the bog; analysis of the annual radial growth increments in the boles of the parents and their neighbours revealed the same effect had occurred in the longer term. The slower growth of both parents and progeny on the bog was presumed to be due to the effects of soil anaerobiosis. After a fire on the heath, several main sterns regenerated from each burned stump, but the progeny of B. pendula‐like parents produced taller, more competitive growths than those of B. pnbescens parents. Deer were highly selective; they browsed only the progeny of B. pubescens‐like trees and only on the heath. Browsed trees became bushier and more branched.

Principal Components Analysis of eight continuously varying leaf variables showed consistent displacements between bog and heath plantings and between parent and progeny for all four half‐sib families. Regressions of progeny on parental values for the individual leaf variables suggested high heritabilities for all except base angle, even allowing for juvenile characters. Despite similar regression coefficients in the transplants to bog and heath, the relationships were displaced relative to one another between bog and heath by large differences of intercept for measurements of size; this reflected dwarfing of the leaves of bog transplants relative to heath transplants. Such displacements were much smaller for measurements of leaf shape, although apex angle was consistently more acute (i.e. more B. pendula‐like) in the transplants into the heath than in the transplants into the bog.

The significance of soil conditions, heath fires and deer browsing in interacting with heredity to mould the observed phenotypes of birch is discussed.
AGE‐SPECIFIC SEX RATIO IN A MONOECIOUS SPECIES CROTON BONPLANDIANUM BAILL
Authors: UMA SHAANKER R. , GANESHAIAH K. N.
Published: May 2006

Summary

The ratio of male to female flowers (sex ratio) in the monoecious Croton bonplandianum Baill decreased as plants aged in three habitats. Two major forces, male and female gametic success and intra‐sexual selection, have been invoked to explain the decrease in sex ratio. While increasing female gametic success at successive stages of growth might be responsible for the enhanced allocation of resource to the females and hence for the absolute increase in number of female flowers at a later age, increasing male gametic success does not change the absolute number of male flowers but merely causes an increase in the number of pollen grains deposited on the stigma. Differences in the sex ratio between habitats was influenced by the differential fitness gained by the two sexes in the various habitats.
VARIATION IN SIZE AND DEVELOPMENT OF SPIKELETS WITHIN THE EAR OF BARLEY
Authors: COTTRELL JOAN E. , DALE J. E.
Published: May 2006

Summary

Carpel size at anthesis is known to vary with position along the ear in barley (Hordeum vulgare L.) and the aim of this work was to determine when differences in the size of spikelets at given developmental stages are established. The width of spikelet primordia at the double ridge stage was progressively less from the base to the tip of the developing ear and the difference in spikelet or floret size was maintained until the stage of stamen initiation. With the exception of the two lowest fertile spikelets measured, there was a good correlation between width of the spikelet at the double ridge stage and the final weight of the grain produced. The possible reasons for the differences in spikelet size are discussed.
OBSERVATIONS ON ZOOSPORIC FUNGI OF CERATIUM SPP. IN LAKES OF THE ENGLISH LAKE DISTRICT; IMPORTANCE FOR PHYTOPLANKTON POPULATION DYNAMICS
Authors: CANTER HILDA M. , HEANEY S. I.
Published: May 2006

Summary

Three fungi and a monad‐like protozoan have been found living in the vegetative cells of Ceratium hirundinella (O. F. Müll.) Bergh. and C. furcoides (Levander) Langhans in Windermere, Esthwaite Water and Blelham Tarn, lakes in the English Lake District. The life‐histories of two, hitherto unknown, biflagellate fungi are described and one is named as a new species, Aphanomycopsis cryptica. Based on the long‐term examination of phytoplankton samples, the occurrence of these fungi as well as Amphicypellus elegans Ingold is presented for 26 years. The effects of some fungal epidemics on populations of Ceratium are discussed.
STUDIES ON BUD INDUCTION IN THE MOSS TREMA TODON BREVICALYX DIXON
Authors: CHOPRA R. N. , DHINGRA‐BABBAR SADHANA
Published: May 2006

Summary

Protonema of Trematodon brevicalyx remains bud‐free on basal medium (Knop's Major and Nitsch's Minor salts). Indoleacetic acid (IAA), gibberellic acid, abscisic acid, chelates, salicylic acid and altered temperature, pH, agar, sucrose levels, light levels and photoperiod do not induce buds but affect gemma initiation and growth rates of protonema. Buds are induced only by cytokinins, the largest number being produced with kinetin, followed by benzylaminopurine, bryokinin (2iP) and zeatin. When varying concentrations of IAA (10−4 to 10−8M) were added together with the optimum concentration of kinetin (10−5 M), normal shoot buds were formed but their number was considerably reduced.
THE ROLE OF THE EPIDERMAL CELLS IN THE CARBON DIOXIDE RESPONSE OF STOMATA OF VICIA FABA L.
Authors: SPENCE R. D. , SHARPE P. J. H. , POWELL R. D.
Published: May 2006

Summary

The role of the epidermal cell has rarely been adequately investigated in studies of stomatal movements. In this study of Vicia faba, the changes in aperture in isolated epidermal strips and in intact leaf sections in response to a variety of CO2 concentrations and temperatures in both light and darkness have been observed for guard cells that were in contact with live epidermal cells. The results indicate that the response of the stomatal system to CO2 is largely dependent upon the degree to which the guard cell is functionally connected to the rest of the leaf. Stomata of guard cells in contact with live epidermal cells from leaf sections showed a significant decrease in aperture with increased CO2. Stomata of guard cells in contact with live epidermal cells on isolated epidermal strips, however, showed an increase in aperture with increased CO2 which also appears to be related to temperature. Results can be interpreted as supporting the chemiosmotic hypothesis of stomatal movements. The data also indicate that there are two opposing responses in the stomatal system to CO2: an opening response located in the epidermis and an overriding closing response controlled by the mesophyll.
ALTERATION OF 13C‐ASSIMILATE PARTITIONING IN PLANTS OF PHASEOLUS VULGARIS EXPOSED TO OZONE
Authors: OKANO K. , ITO O. , TAKEBA G. , SHIMIZU A. , TOTSUKA T.
Published: May 2006

Summary

A quantitative tracer experiment was conducted to elucidate the effects of continuous exposure to ozone (O3) at 0.2 μl 1−1 on the translocation and the distribution of 13C‐labelled photosynthetic assimilates from the individual source leaves in 14‐d‐old plants of Phasealus vulgaris.

The amount of labelled assimilates exported from the primary leaf, which acted as a main source of photosynthates for growth of the roots, decreased remarkably in the presence of O3 as a result of both a considerable reduction of 13CO2 fixation (62%) and the inhibition of translocation. On the other hand, that from the first trifoliate leaf, which mainly nourished the immature growing leaves, was not decreased in the same way by O3 because a smaller reduction of 13CO2 fixation (24%) was almost compensated by an acceleration of translocation. The pattern of assimilate distribution was altered by O3, so that a greater proportion of assimilates was partitioned to the growing leaves at the expense of the root and the stem. Consequently, the amount of labelled assimilates translocated to the non‐photosynthetic organs (stem and root) decreased by 53 %, while that to the photosynthetic organs (leaves) was reduced by only 28%. These results suggest that the plants might have adapted themselves to an environment containing O3 so that the reduction of growth efficiency caused by O3 could be minimized.
MICROPROCESSOR‐CONTROLLED SYSTEM FOR EXPOSING PLANTS TO FLUCTUATING CONCENTRATIONS OF SULPHUR DIOXIDE
Authors: MUELLER P. W. , GARSED S. G.
Published: May 2006

Summary

A system is described which uses a combination of solenoid valves under the control of a microprocessor unit and flow‐controllers to provide fumigation chambers with accurately controlled fluctuating concentrations of SO2 for long periods. The system is versatile, both within the specific experimental requirements for which it was built and for other applications.
THE INTERACTION BETWEEN AUXIN AND BORON IN ADVENTITIOUS ROOT DEVELOPMENT
Authors: JARVIS B. C. , YASMIN S. , ALI A. H. N. , HUNT R.
Published: May 2006

Summary

An interaction between auxin and boron in the rooting response of stern cuttings of Phaseolus aureus Roxb. is described. The optimum response to one variable is dependent upon the value of the other and vice versa. Whereas the number of roots per cutting which develop is diminished when high concentrations of boron are supplied immediately after treatment of cuttings with auxin, subsequent root growth is enhanced by such treatment. These results are discussed with respect to the possible role of boron in controlling endogenous auxin concentration via an effect on IAA oxidase.
THE ULTRASTRUCTURE OF PLASTIDS IN THE PETALS OF CALTHA PALUSTRIS L.
Authors: WHATLEY JEAN M.
Published: May 2006

Summary

The petals of Caltha palustris are unusual in that they contain chromoplasts belonging to two different ultrastructural classes. Other forms of plastid are also present and one of these provides the petal with a reflective starch layer. These different types of plastid and several distinctive features of petal morphology all point to a type of petal which is particularly well‐adapted to encourage pollination of the flower by insects.
THE LEVEL AND DISTRIBUTION OF PHENOLIC PLANT GROWTH INHIBITORS IN YAM TUBERS DURING DORMANCY
Authors: IRELAND C. R. , PASSAM H. C.
Published: May 2006

Summary

In this study a possible role for batatasin‐type phenolic growth inhibitors in the control of dormancy and, therefore, the storage life of tubers of Dioscorea alata and D. esculenta, two economically important food yams, was investigated. After extraction, the level of endogenous growth inhibitory phenolics was estimated by a wheat coleoptile growth test and batatasins specifically determined by fluorescence spectroscopy and gas‐liquid chromatography. There was a gradual decrease in growth inhibitory phenolics in tubers of both species during dormancy and in D. alata this closely paralleled a decrease in batatasin content. It was found that batatasin‐type growth inhibitory phenolics accumulated rapidly in developing tubers just prior to the onset of dormancy and were assyrnetrically distributed, being concentrated in the proximal (head) region and in the peripheral zone just beneath the periderm. Gibberellin A3 treatment produced a promotion of the dormant period and a correlative rise in the growth inhibitory phenolic level. Effects of maleic hydrazide and ethylene chlorohydrin are also reported. The results are discussed in terms of the mechanism of dormancy control in these tubers and it is concluded that endogenous batatasin‐type phenolics are involved in this.
UPTAKE AND ASSIMILATION OF NITRATE AND AMMONIUM BY AN EVERGREEN FYNBOS SHRUB SPECIESPROTEA REPENSL. (PROTEACEAE)
Authors: STOCK W. D. , LEWIS O. A. M.
Published: May 2006

Summary

The uptake and assimilation of15N supplied either as NO3−or NH4+has been studied over a 9‐d period inProtea repens, a member of the Fynbos (South African Mediterranean‐type vegetation) to establish the preferred N source for plant growth and development. Low uptake and assimilation rates were found for both NO3−and NH4+feeding (4.8 and 5.9/μg15N g−1fresh mass d−1, respectively) and total15N absorbed over 9 d was greater in the NH4+‐fed plants than in NO3+‐fed ones. The form of N supplied did not cause significant changes in the total N content of the plants over the feeding period and no alteration in total N distribution patterns was evident, the shoot to root nitrogen ratio being 7:3.

Distribution of15N between the soluble N fraction and the bound fraction within root and shoot was similar for both NO3+and NH4+‐fed plants. In both treatments approximately 70 % of the15N was found in the root, mainly in the bound fraction.

Protea repensappears to have adapted to the conditions prevalent in the later stages of Fynbos succession, not by showing an absolute requirement for a particular inorganic N form, but by an ability to absorb and assimilate small quantities of both NO3−and NH4+, which satisfy the low N demand of this slow growing, evergreen species.
NITROGEN SOURCES AND ‘A’ VALUES FOR VESICULAR–ARBUSCULAR AND NON‐MYCORRHIZAL SORGHUM GROWN AT THREE RATES OF 15N‐AMMONIUM SULPHATE*†
Authors: AMES R. N. , PORTER LYNN K. , ST. JOHN T. V. , REID C. P. PATRICK
Published: May 2006

Summary

Mycorrhizal and non‐mycorrhizal sorghum [Sorghum bicolor (L.) Moench] plants were grown in soil treated with one of three rates of (15NH4)2SO4, fertilizer. Mycorrhizal plants did not significantly differ from non‐mycorrhizal plants in total plant dry weight, total plant N, or percent utilization of the applied N by the whole plant at any fertilizer rate. However, the atom percent 15N excess in shoots, roots and the whole plant, and percent N derived from fertilizer were significantly higher for non‐mycorrhizal plants at the intermediate level of fertilizer N. The percent N derived from native soil sources, and ‘A’ values were significantly higher for mycorrhizal plants, compared to non‐mycorrhizal plants, at the intermediate but not low or high fertilizer rates. The results suggest that, at the intermediate fertilizer rate, where plants produced the most growth, mycorrhizal sorghum plants derived N from a source that was less available to non‐mycorrhizal plants.