bluuebunny/crossref_metadata_2025 huggingface dataset:
MYCELIAL STRANDS OF PINUS RADIATA D. DON: ULTRASTRUCTURE AND HISTOCHEMISTRY
Authors: FOSTER R. C.
Published: May 2006

Ultrastructural and cytochemical techniques showed that there was a marked difference in the structure and cytochemistry of the hyphae from old and young parts of mycelial strands produced by the mycorrhizas of Pinus radiata D. Don. The older strands were differentiated into an outer region of thick walled hyphae and inner region of thin walled hyphae of two types. Histochemical tests for carbohydrates were used to distinguish between gels produced by the micro‐organisms associated with the strands and those by the fungal hyphae themselves, and to distinguish between the polysaccharides of the mycelial gel and those of the layers in the cell walls of the hyphae. Carbohydrate distribution in and on the strands is discussed in relation to the breakdown of litter and to the stability of soil crumbs under pine forests.
THE UPTAKE OF COPPER BY PLANTS OF MIMULUS GUTTATUS DIFFERING IN GENOTYPE PRIMARILY AT A SINGLE MAJOR COPPER TOLERANCE LOCUS
Authors: MACNAIR M. R.
Published: May 2006

The pattern of uptake of copper by plants of Mimulus guttatus that are either homozygous tolerant, homozygous non‐tolerant, or heterozygous tolerant, was compared. Tolerant plants took up more copper, particularly into the roots, and root uptake by the homozygote tolerant was greater than the heterozygote. Plants of all three genotypes took up increasing quantities of copper to their roots until day 7, but no further increase was obtained by day 11. The physiological implication of these results is discussed.
THE EFFECT OF BIPYRIDYL HERBICIDES ON THE LOSS OF NUTRIENTS FROM FUNGI
Authors: SAHID ISMAIL B. , LYON A. J. E. , SMITH S. N.
Published: May 2006

Summary

Paraquat and diquat cause rapid loss of potassium and phosphate from Aspergillus niger, Penicillium frequentans, Mucor hiemalis and Zygorrhynchus heterogamus. The rate of loss is greater at higher concentrations of herbicide, particularly from Zygorrhynchus and Mucor. A brief incubation in paraquat or diquat is followed by sustained loss of potassium when colonies of the four species are transferred to water. Sodium azide also stimulates loss of potassium but thisceases when colonies are transferred to water. Paraquat enhances the level of malondialdehyde, a breakdown product of membrane fatty acids, in Zygorrhynchus and Mucor. These results are discussed with reference to the possible mode of action of bipyridyl herbicides in fungi.
VARIATIONS IN ENZYME ACTIVITY DURING PERIODIC FRUITING OF AGARICUS BISPORUS
Authors: HAMMOND J. B. W.
Published: May 2006

Summary

Glucose‐6‐phosphate dehydrogenase (G6PD), glucosephosphate isomerase (GPI) and mannitol dehydrogenase (MD) were assayed in sporophores harvested at stages 1 (pin) and 2 (button) of development throughout several fruiting cycles. Higher G6PD specific activity was consistently found in stage 1 and 2 sporophores harvested between periods of maximum stage 2 production (flushes). There was minimum G6PD activity during the flushes. At stage 1 the range of variation was greater and the timing of the peaks in the flush cycle more uniform than in stage 2 sporophores. GPI and MD activities also varied with flushing, but showed a less consistent pattern than G6PD. MD normally exhibited greatest activity in stage 1 and 2 sporophores between flushes. GPI activity was higher between flushes in stage 1 sporophores, and during flushes at stage 2.

Mannitol and trehalose were highest in stage 1 sporophores harvested between flushes. The results are discussed in relation to the mechanism of flushing.
INTRACLONAL VARIATION AND COMPETITION IN RANUNCULUS RE PENS
Authors: DOUST LESLEY LOVETT
Published: May 2006

Summary

Experiments were performed to study sources of variation between ramets of a clone, and differences in growth form between plants from two locally specialized populations of Ranunculus repens in a woodland and a grassland site. In one experiment, ramets were taken from different positions along each of five primary branches of clones. For both populations variability in growth parameters of ramets of each clone was attributed to the position of a ramet within a branch, and not to any differences between branches of a clone.

In clones which are made up of several interconnected ramets, these ramets may: (1) compete with each other for light and other resources; and (2) supply each other with resources. In clones where connections have been lost only (1) above, will pertain. In a second experiment clonal material selected from the two populations was grown in flats under conditions of high ramet densities. For each clone, in half of the replicates, stolon connections between ramets were severed; in the other half stolons were left intact. In clones originating from the grassland population, ramets of the same genotype accumulated significantly more total dry wt and had more above‐ground biomass when they were interconnected than if stolons had been cut. In clones from the woodland population, total dry wt was not significantly altered. In plants from both populations, after connections were cut, the distribution of dry matter to various plant organs was significantly altered (plants distributed more dry matter to inflorescences and ramet caudices, and less to stolons). The pattern of proportionate allocation of dry matter suggested that below‐ground competition was more intense when stolons had been severed.

Growth form and the response to intraclonal competition are discussed in terms of local specialization in the woodland and grassland sites.
RESISTANCES TO CARBON DIOXIDE FIXATION IN FOUR SUBMERGED FRESHWATER MACROPHYTES
Authors: BLACK M. A. , MABERLY S. C. , SPENCE D. H. N.
Published: May 2006

Summary

Discs (0·6 cm diameter) from submerged leaves of Potamogeton lucens L., P. perfoliatus L., P. polygonifolius Pourr. and P. praelongus Wulff were allowed to photosynthesize in well stirred conditions at pH 4·3, 20 °C, and a saturating light intensity of 120 W m−2 (400 to 700 nm) in a range of free CO2 concentrations for 1 h, and the rates were calculated from 14CO2 uptake. Total resistance (1/k+ 1/P) was calculated from these data, using a modification of Fick's first law. 1/k+ 1/P was found to vary between 3·7 × 104 and 5·9 × 104 s cm−1 in the four species. The internal diffusive resistance (l/D) only made up 2·6 to 4·3 % of this total. Estimates were made of the proportions of 1/k (the chemical resistance), 1/P (the diffusive resistance) and δ/D (the boundary layer diffusive resistance) to the total resistance over a range of possible values for the concentration of CO2 at the site of carboxylation: 1/P was always greater than 1/k, and δ/D was always the single largest resistance. The average boundary layer thickness for the leaf discs was calculated as 340 μm; for whole leaves of these species, also well stirred, the boundary layer thickness was estimated to range between 440 and 1090 μm. The ecological significance of the boundary layer to freshwater macrophytes in standing waters is discussed.
VARIATION IN NITRATE REDUCTASE ACTIVITY BETWEEN AGROSTIS SPECIES AND ECOTYPES
Authors: OSBORNE B. A. , WHITTINGTON W. J.
Published: May 2006

Summary

It was shown that nitrate reductase activity varied between species of Agrostis. Lower values were found in A. setacea and A. stolonifera and higher but variable values occurred in A. tenuis and A. canina. The hypothesis that species or ecotypes within species might have nitrate reductase activities related to soil nitrate or applied fertilizers was examined, but no clear relationship was found. Consideration is given to the difficulties inherent in establishing such correlations. As in current published evidence the relationship between dry matter production and nitrate reductase was often found to be negative rather than positive as might have been expected.
PEROXIDASE ACTIVITY IN GRASS‐DWARF SELECTION LINES IN SPRING WHEAT (TRITICUM AESTIVUM L.)
Authors: MOORE K. , CUBITT I. R.
Published: May 2006

Summary

Grass‐dwarf and normal genotypes have similar peroxidase levels when grown at 26°C. Higher levels of peroxidase activity were found in grass‐dwarf lines induced to remain vegetative at low temperatures of 15°C than in the same lines grown at 26°C which is adequate for reproductive development. Peroxidase activity was greatest at 15°C in Type I grass‐dwarf genotypes and progressively lower in Type II, Type III and normal parental genotypes after 7 weeks’ growth. This promises a quantitative method for distinguishing different types of grass‐dwarf genotypes at an early stage of growth.

Heating the shoot apical meristem of grass‐dwarf genotypes to 26°C induced reproductive development and reduced peroxidase activity below that in unheated vegetative grass‐dwarf plants.
CELLULAR ORGANELLES AND CELL‐WALL FORMATION IN FIBRES FROM THE FLOWERING STEM OF LOLIUM TEMULENTUM L.
Authors: JUNIPER B. E. , LAWTON JUNE R. , HARRIS P. J.
Published: May 2006

Summary

The structure of the thick wall of lignified fibre cells from the flowering stem of Lolium temulentum L. is described. The formation of wall layers is related to the period of cell elongation and to the presence or absence and state of development of organelles which are possibly involved in the formation of the cell wall.

It is suggested that while the fibre cells are still elongating, rough endoplasmic reticulum (RER) and dictyosomes associated with small, electron transparent vesicles are involved in the formation of the cell wall, whereas in fibre cells which are nearing the end of elongation, and those which have stopped elongating, it is suggested that microtubules, lomasomes and dictyosomes associated with large electron transparent vesicles and small vesicles with electron dense cores are involved.

The nomenclature for labelling wall layers as primary or secondary is discussed.
THE ASSESSMENT OF NITROGEN FIXATION AND THROUGHPUT BY LICHENS
Authors: MILLBANK J. W. , OLSEN J. D.
Published: May 2006

Summary

An apparatus is described for simulating the natural environmental conditions relating to large thallose lichens, to enable their rates of nitrogen fixation to be estimated using 16N2 enriched nitrogen gas. Daylength, temperature, light intensity, thallus moisture and carbon dioxide concentration can be controlled and seasonal conditions can be reproduced. The rate of long term 15N2 incorporation can be compared with that of acetylene reduction measured over short periods and the relationship established. Details of materials and suppliers are given.
THE EFFECT OF SIMULATED ACID RAIN ON TWO POPULATIONS OF SENECIO VULGARIS L.
Authors: HODGKIN S. E. , BRIGGS D.
Published: May 2006

Summary

The effect of simulated acid rain on two populations of Senecio vulgaris was studied. Evidence suggests that the population from a relatively unpolluted area of the British Isles was more sensitive to applied dilute sulphuric acid than a population from east England, where a higher level of air pollution is likely. In making a cautious interpretation of our results, we point out that further studies are necessary before the hypothesis, that ecotypic differentiation occurs in response to acid rain, can be accepted.
EVOLUTION OF UNILATERAL INCOMPATIBILITY IN FLOWERING PLANTS: FURTHER EVIDENCE IN FAVOUR OF TWIN SPECIFICITIES CONTROLLING INTRA‐AND INTERSPECIFIC INCOMPATIBILITY
Authors: PANDEY K. K.
Published: May 2006

Summary

The breeding system in Nicotiana glauca is unique in that the species comprises mainly self‐compatible (S.C.) green‐flowered plants but also includes rare self‐incompatible (S.I.) red‐flowered races. The S.C. plants of Nicotiana glauca show unilateral interspecific incompatibility with other S.I. species of Nicotiana, a widely occurring characteristic normally associated with S.C. species with relatively long‐established self‐compatibility.

The present study of S.I. and S.C. strains of Nicotiana glauca showed that the ♀ S.I. × S.C. ♂ type of unilateral incompatibility (U.I.) occurs within this species, and the U.I. is a function of the S alleles. Of the nine SI alleles studied seven, when present in the homozygous state in the style, made that style reject Sc (Nicotiana glauca) pollen whereas two alleles allowed styles to accept this pollen. Similar polymorphism at the Nicotiana glauca S locus was also found in relation to Sf pollen from the S.C. species Nicotiana langsdorffii. Sl alleles in Nicotiana glauca were classified differently for the polymorphisms in relation to Sc and Sf pollen.

The results show that the Sc allele is sporophytically determined causing allelic interaction in the pollen and style. Dominance, co‐dominance and competitive interaction were observed. In contrast the St allele of Nicotiana langsdorffii is gametophytically determined, stylar alleles always showing independent action.

Within the same species Nicotiana glauca, there is both gametophytic and sporophytic determination of 5 alleles. Whereas in species with sporophytic self‐incompatibility allelic interaction is predetermined in the pollen and style, in this case allelic interaction is not determined until after pollen/stigma contact and is complementary.

The occurrence within the same species of (1) the unilateral S.I. × S.C. type of incompatibility, (2) both gametophytic and sporophytic determination, (3) late determination of allelic interaction after pollen/stigma contact, and (4) competitive interaction of 5 alleles, is all explained on the basis of the author's theory of ‘twin specificities’ controlling intra‐and interspecific incompatibility in flowering plants.

Wider implications of the theory are discussed. Early evolution of specificity determination in prokaryotes provided a basis for cell to cell interaction that eventually led, on the one hand, to evolution of sex and genetic recombination systems and, on the other, to mechanisms for infection/disease protection, and graft‐incompatibility control. These phenomena are evident in both plant and animal kingdoms.
DIFFERENCES IN FRUCTAN CONTENT AND SYNTHESIS IN SOME ALLIUM SPECIES
Authors: DARBYSHIRE B. , HENRY R. J.
Published: May 2006

In Allium cepa (cv. Creamgold), A. cepa (cv. Bunching Onion), A. porrum (leek) and A. sativum (garlic), fructans were the only nonstructural carbohydrates detected apart from glucose, fructose and sucrose. No starch or members of the raffinose series of oligosaccharides were detected. Both cultivars of A. cepa, and A. porrum had fructan polymers of the same length. The maximum DP (degree of polymerization) detected was 12. However, maximum carbohydrate concentration occurred in DP5 for A. cepa (cv. Bunching Onion) and DP12 for A. porrum. A. sativum was different from the other species in that larger polymers were present, reaching a DP of 50. The trisaccharides, 1F‐fructosylsucrose and 6G‐fructosylsucrose were found in all species. A. cepa and A. sativum contained similar fructan: fructan frutosyltransferases. Enzymes from both plants transferred fructosyl residues from trisaccharide to form tetrasaccharide and sucrose as the major products. This self‐transfer predominated even in the presence of higher molecular weight acceptor molecules.
INFLUENCE OF WATER AND SALT STRESS ON WATER RELATIONSHIPS AND CARBON DIOXIDE EXCHANGE OF TOP AND ROOTS IN BEANS
Authors: JENSEN C. R.
Published: May 2006

When low‐salt plants, grown in nutrient solution, were exposed to osmotic potentials in the root medium (πs)* of minus 2.7 and minus 4.7 bar due to the addition of KNO3, osmotic adjustment occurred. The leaf osmotic potential (π1,) decreased, leaf turgor potential (Ψp) and leaf water content (W) were maintained, no wilting took place, stomatal conductance (g) was partially regained and net photosynthesis was only moderately depressed.

When low‐salt plants were exposed to πs of minus 2.7 and minus 4.7 bar due to the addition of PEG 1500, no adjustment to water stress was observed. Ψp decreased, the leaves became dehydrated and a high percentage wilted. Stomatal conductance, net photosynthesis, top dark respiration and root respiration were depressed. NO3‐uptake ceased completely at minus 4.7 bar.

When low‐salt plants were exposed to πs of minus 4.7 bar, due to both PEG (minus 2 bar) and KNO3 (minus 2 bar), osmotic adjustment took place; π1 decreased, Ψp, W, g, net photosynthesis, top dark respiration and root respiration recovered to some extent, but the proportion of wilted leaves was high.

When medium‐ and high‐salt plants, osmotically adjusted to πs of minus 2.7 and minus 4.7 bar due to KNO3 were exposed to water stress due to PEG (minus 2 and minus 4 bar), (Ψp and W were maintained, none or few leaves wilted and g was depressed less than in low‐salt plants. These responses are attributed to influence of pre‐osmotic adjustment on turgor maintenance and hydration of the plant.

It is concluded that osmotic adjustment by inorganic solute uptake, before or during exposure to water and salt stress, can reduce the severe effects of low water potentials in the root medium.
PHYSIOLOGICAL ASPECTS OF RAINFOREST REGENERATION
Authors: CHANDLER GRAEME
Published: May 2006

Syzygium floribundum, a rainforest climax species and Solarium mauritianum, a rainforest pioneer, were raised in sand cultures containing NO3− or NH4+ under various shade regimes. Optimum growth of Syzygium occurred with NH4+ and of Solatium with NO3−. Ammonium appeared toxic for Solatium at low light intensity.

Shoot‐root ratios of Syzygium were remarkably constant irrespective of light intensity but ammonium promoted greater leaf production. Conversely, Solatium shoot‐root ratios were not affected by nutrients but increased dramatically at low light intensity.

Leaves of Syzygium exhibited high levels of glutamate dehydrogenase (GDH) activity which decreased with increasing light intensity. Roots of Syzygium exhibited low GDH activity. This, together with high glutamine synthetase (GS) activity in the roots, suggests that GS is the main ammonium assimilating enzyme in the roots of Syzygium. GDH and GS are both active in the leaves of this species. High GDH and low GS activity in both leaves and roots of Solatium suggests that GDH is the main NH4+ assimilating enzyme in this species.
EFFECT OF DESICCATION ON DNA SYNTHESIS AND THE CELL CYCLE OF THE MOSS POLYTRICHUM FORMOSUM
Authors: Mansour K. S. , Hallet J. N.
Published: May 2006

The effects of a 24‐h dehydration period on the mitotic and DNA‐synthetic activities have been studied in the meristematic cells of the leafy gametophyte of the moss Polytrichum formosum. During the first 2 h of water stress the mitotic index decreased dramatically, and after 6 h none of the cells was observed in division. It is concluded that the stress provokes not only cessation, but also completion of the mitotic phase, so that all the cells of the desiccated plants become interphasic. On rehydration, a period of 24 h was necessary for the first cell to enter division. After 4 h of recovery from water stress, DNA synthesis resumed in the nuclei of a few cells indicating that replication processes were not injured to any marked extent by the desiccation treatment. However, a clear increase in the number of nuclei entering the S phase was only observed 24 h after the start of rehydration. It is suggested that the effect of the dehydration period is to prevent the cells which are situated in G1 or G2 phases to enter respectively the phases of S and M of the cell cycle immediately upon rehydration. In any case the result is to delay, for about 24 h from the beginning of rehydration, the return of proliferative activity. These data are compared with those previously obtained on the metabolism of water‐stressed mosses.
INFLUENCE OF PLANT INTERACTIONS ON VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTIONS.
Authors: OCAMPO J. A. , HAYMAN D. S.
Published: May 2006

The effects of crop rotation on mycorrhizal development were examined in pot experiments, using sterilized soil inoculated with Glomus fasciculatus‘E3’ or Gigaspora margarita or unsterile soil containing mainly a type of Glomus macrocarpus var. geosporus. In four crop pairs tested, the amount of VA mycorrhizal infection in a host plant was not depressed in soil previously cropped with a ‘non‐host’ plant, even where roots of the preceding ‘non‐host’ plant were retained intact in the soil. Indeed the early establishment of VA infection in barley, lettuce and maize inoculated in sterilized soil was stimulated by the ‘non‐hosts’ oilseed rape, cabbage and sugar beet, respectively. VA hyphae were sometimes observed growing in moribund ‘non‐host’ roots. Effects of crop rotation in unsterile soil were similar but less marked. G. margarita in sterilized soil infected lettuce considerably less than other crops.
EVALUATION OF THE COMMERCIAL POTENTIAL OF THE VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS, GLOMUS EPIGAEUS
Authors: DANIELS B. A. , MENGE J. A.
Published: May 2006

The potential of Glomus epigaeus for commercial use was evaluated with respect to epigeous spore production, host growth stimulation, and methods of spore storage. Significantly more sporocarps were produced on sudan grass watered manually than on tomato, soybean, or asparagus plants which were watered manually, misted, or enclosed in plastic to increase surface humidity. Sporocarps produced on sudan grass varied in size from 3 to 7 mm to 8 to 12 mm in diameter, depending on age, and each contained approximately 1 × 105 to 7.5 × 106 spores. An average of 4.5 sporocarps were produced per pot monthly. Significant (P = 0.05) growth responses occurred on tomato, soybean, citrus, maize, sudan, asparagus and cotton but not in olive. Growth responses to G. mosseae occurred on tomato, citrus and cotton; to G. fasciculatus on citrus only; to G. epigaeus on tomato, citrus, maize, sudan grass and asparagus; and to G. constrictus on maize only. Germinability of nondisinfested and surface disinfested (10 % chlorox or chloramine T‐streptomycin) G. epigaeus spores was tested following storage for 3 months using 13 methods. No surface disinfested spores germinated except those stored in wet loamy sand. Nondisinfested spores stored in moist loamy sand, dry loamy sand, sterilized bentonite, sterilized H2O, streptomycin gentamycin solution, and as whole sporocarps germinated 1, 33, 80, 37, 13 and 83% respectively. The spore producing capacity, efficiency on a wide range of host plants, and ease of storage make G. epigaeus a vesicular‐arbuscular mycorrhizal fungus with considerable commercial potential.
COMPONENTS OF VA MYCORRHIZAL INOCULUM AND THEIR EFFECTS ON GROWTH OF ONION
Authors: MANJUNATH A. , BAGYARAJ D. J.
Published: May 2006

Studies were conducted to assess the effect of different components of VA mycorrhizal inoculum on growth of onion. The associated micro‐organisms and sterilized root segments, did not significantly influence the growth and phosphorus nutrition of onion. Application of mycorrhizal inoculum containing extramatrical chlamydospores and infected root segments containing mycelium, vesicles and arbuscules had a significant effect on shoot and root weight, and phosphorus content of the plant. Further fractionation of inoculum indicated that chlamydospores are the important component, since plants inoculated with chlamydospores produced more dry matter and contained more phosphorus.
INSECTS AND THEIR POLLEN LOADS AT A HYBRID HERACLEUM SITE
Authors: GRACE J. , NELSON M.
Published: May 2006

Insects were caught at a site where Heracleum sphondylium and Heracleum mantegazzianum occur together, along with a few hybrid individuals. Fifty‐nine species of insect were caught on flowers of H. sphondylium and 48 from H. mantegazzianum. Only 23 species of insect were common to both. Pollen grains taken from individual insects were identified on the basis of size. Insects caught on H. sphondylium carried H. sphondylium pollen almost exclusively and those from H. mantegazzianum carried mainly H. mantegazzianum pollen. Very few individual insects carried both types of pollen. It is concluded that the selective foraging behaviour of insects is a main barrier to gene flow between the two species of Heracleum in Britain.
ULTRASTRUCTURAL CHANGES OF PLASTIDS IN FLAX EMBRYOS CULTIVATED IN VITRO
Authors: Člamporová MILADA , PRE?ová ANNA
Published: May 2006

The ultrastructure of plastids in the cells of flax cotyledons was investigated at three stages during embryogenesis and germination: (1) immature 14‐day old green embryos excised from seeds, (2) 24‐day old embryos which yellowed following a 10‐day cultivation in vitro and (3) 34‐day old embryos which grew for 20 days on the medium and after a temporary loss of pigment regreened and germinated. For comparison, the ultrastructure of chloroplasts from the mature leaves was also investigated.

The chloroplasts of 14‐day old embryos are characterized by a well‐developed system of both the grana and the intergranal lamellae and stroma which contains starch grains and phytoferritin. During cultivation in vitro the dimensions of plastids decrease and the internal structure of the chloroplasts undergoes disintegration. In the stroma of plastids of the 24‐day old embryos, lamellae of different length, vesicles and electron‐dense, membrane‐bound bodies and numerous plastoglobulin can be identified and amoeboid plastids occur in the cells. During continued cultivation the dimensions of plastids again increase and in them again differentiation of the system of grana and intergranal lamellae can be observed. The structure of plastids in the 34‐day old embryos is in good agreement with the structure of those in the mature, assimilating leaves of flax. The results indicate that the basic developmental pathway takes place in the same plastids of the flax embryos once during the embryogenesis and once during germination.
DETERMINISM OF THE MYCORRHIZOGENIC ROOT FORMATION IN PINUS PINASTER SOL.
Authors: FAYE M. , RANCILLAC M. , DAVID A.
Published: May 2006

Seedlings, axillary buds and apical root meristems of Pine (Pinus pinaster Sol.) were used in different controlled environments. A kinetic study of root morphogenesis was performed, supported by light and electron microscopic analysis.

Without any symbiotic or parasitic fungus, short roots (histologically similar to the ectomycorrhizae except for the absence of the fungus), able to produce dichotomous branches, were observed on all the kinds of explant and in all the environmental conditions used. Hence the formation of these mycorrhizogenic short roots is ‘genome dependent’.

In clones of young plant lets (produced by vegetative propagation by means of axillary budding in vitro), the root systems exhibit a similar intensity, strong or weak, to dichotomize; this emphasizes the relationships between the formation of mycorrhizogenic short roots and the pinus genome.

This study seems to be the first attempt to demonstrate, under controlled conditions, a direct relationship between plant genome and root branching in a woody species.
PRESENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZAE IN EUCALYPTUS SPP. AND ACACIA SP., AND THEIR ABSENCE IN BANKSIA SP. AFTER INOCULATION WITH GLOMUS FASCICULATUS
Authors: MALAJCZUK NICHOLAS , LINDERMAN ROBERT G. , KOUGH JOHN , TRAPPE JAMES M.
Published: May 2006

Vesicular‐arbuscular (VA) mycorrhizae occurred in seedlings of Eucalyptus marginata, E. diversicolor and Acacia pulchella grown in soil inoculated with Glomus fasciculatus. Infection levels were 30 to 35 % of the root length of the eucalypts and 50 to 70 % of the Acacia. When A. pulchella was grown in the same pots with the two eucalypts, its infection was not increased. Banksia grandis did not form VA mycorrhizae when grown alone or in association with A. pulchella. These results are discussed in relation to the evolution of plants in Australia and the ecological significance of VA mycorrhizae in the eucalypt forest ecosystem.
CARBON DIOXIDE EXCHANGE IN LICHENS.
Authors: GREEN T. G. A. , SNELGAR W. P. , BROWN D. H.
Published: May 2006

Carbon dioxide (CO2) exchange of Sticta latifrons Rich, was studied using an infrared gas analyzer. Slight differences in the relationship between net photosynthetic rate (NPR) and water content were found when thalli were dried by using air directed solely onto the upper or lower surfaces. Further studies using a simple split chamber which allowed separate analysis of the CO2 exchange of upper and lower thallus surfaces demonstrated that the vast majority of CO2 exchanged through the lower surface. The results provide strong circumstantial evidence for the suggestion that cyphellae act as air pores and the possible importance of such pores in the water relations of the species is discussed.
ECOTYPIC DIFFERENTIATION IN POA ANNUA: INTERPOPULATION DIFFERENCES IN RESPONSE TO COMPETITION AND CUTTING
Authors: McNEILLY T.
Published: May 2006

Competition between seed‐derived populations of Poa annua from three open and three closed habitats, and Lolium perenne cv. S23 was examined in a glasshouse experiment. Pure stands of P. annua and L. perenne, and 50: 50 mixtures of the two species were compared after 13 weeks growth when uncut, and when cut at 5, 7, 9, 11 and 13 weeks, to a height of 15 cm. Yields of both the P. annua populations and L. perenne were reduced by both competition and cutting; cutting causing the greatest yield reduction. Mean yield of the three populations from open habitats and of the three populations from closed habitats were regressed on overall mean yields of the four treatment combinations ‐ pure stand uncut, mixed stand uncut, pure stand cut, mixed stand cut. Results indicated that populations from closed habitats performed better in the less favourable conditions imposed by cutting or competition or both these conditions than those from open habitats, whereas this situation was reversed in their absence. Under the cutting and competition treatment the P. annua populations from closed habitats significantly outyielded their Lolium associate. No comparable difference was found for the P. annua populations from open habitats.

With competition, uncut P. annua populations from open habitats significantly outyielded Lolium whilst two of the populations from closed habitats, one adjacent to one of the open populations, were significantly outyielded by Lolium. The results suggest that population differentiation in Poa annua has occurred over short distances in response to competition or grazing or mowing and that competitive ability is not a fixed characteristic of a species.
ANT‐HILL VEGETATION IN ACIDIC GRASSLANDS IN THE GOWER PENINSULA, SOUTH WALES
Authors: KING T. J.
Published: May 2006

The vegetation of ant‐hill and adjacent pasture was compared in five acidic grasslands in the Gower peninsula, South Wales. The acrocarpous mosses Dicranum scoparium Hedw., Polytrichum juniperinum Hedw. and P. piliferum Hedw. were almost confined to the mounds but several perennials, including Anthoxanthum odoratum L., Luzula campestris (L.) DC, Potentilla erecta (L.) Rausch and Sieglingia decumbens (L.) Bernh., were much less abundant on ant‐hills than in the surrounding vegetation. The factors which influence the distributions of the plant species are discussed briefly. In considering the responses of plants to ant‐hills soil chemical and physical factors are probably less important than a plant's dispersal ability and capacity to withstand burial.
THE CONTROL OF FOOD MOBILIZATION IN SEEDS OF DICOTYLEDONOUS PLANTS
Authors: DAVIES H.V. , SLACK P. T.
Published: May 2006

Two alternative hypotheses can be used to explain how the embryo or embryonic axis controls food mobilization in seeds of many dicotyledonous plants. The first involves the production of a hormonal stimulus by the axis which initiates the development of optimal rates of hydrolytic enzyme activity in the storage organs. The second involves the continual operation of a source‐sink relationship between the storage organs (source) and axis (sink) during germination and early seedling development. The evidence for the operation of these modes of control is discussed.
DIURNAL ACETYLENE REDUCTION BY MATS OF BLUE‐GREEN ALGAE IN SUB‐TROPICAL GRASSLAND: USE OF SHORT‐TERM AND LONG‐TERM IN SITU ASSAYS
Authors: JONES KEITH
Published: May 2006

Mats of blue‐green algae in sub‐tropical grassland in Florida show the same pattern of diurnal acetylene reduction as algal mats from similar habitats in South Africa. In situ short‐term‐cumulative assays (2 h) gave higher amounts of acetylene reduction during daylight than long‐term assays (dawn to dusk), even when temperatures were not inhibitory. However, the rates of acetylene reduction at night were the same whether obtained using long‐term or short‐term‐cumulative assays. Therefore, when measuring the daily rate of acetylene reduction by algal mats, day‐time assays should be short and cumulative whereas night‐time assays should be long‐term.
THE PHYSIOLOGICAL ASSOCIATION BETWEEN APHIS CRACCIVORA KOCH AND VIGNA SESQUIPEDALIS FRUW.
Authors: WU ALICE , THROWER L. B.
Published: May 2006

In a greenhouse experiment, adult apterae of Aphis craccivora were either confined to the second trifoliate leaf of 19‐day‐old plants of Vigna sesquipedalis or allowed to move freely after infestation. When the aphids were confined the dry wt of the plant after 14 days infestation was 62% of the controls; when they were free to move, it was 29·5% of controls. When the second trifoliate leaf was infested, the rate of photosynthesis per unit leaf area decreased to 3·6% of its initial rate on day 10, when it was moribund. Over 10 days, the total photosynthesis of the infested leaf was 56% of the control but this was reduced to 32% if the longer life of the control (more than 20 days) was taken into account. Photosynthesis was not stimulated at any time. Respiration of the infested second trifoliate was little influenced by infestation until it became prematurely moribund. Infestation of the young third trifoliate was accompanied by a slower expansion of the second trifoliate and by increased photosynthesis by that leaf during the first 6 days: the photosynthetic rate per unit area of the second trifoliate was 1·18 and 1·34 times that of the control on days 3 and 6 respectively, but declined to 0·85 on day 10. Infestation reduced the quantity of photosynthate available for movement from the second trifoliate to normal sinks from over 80% to less than 1% of the amount produced. When the third trifoliate was infested and the second was given 14CO2, the aphids were able to divert over 20% of translocated assimilate from its normal destination. The inhibition of vegetative growth is discussed in relation to these physiological changes.
LIFE CYCLE OF STICHOSIPHON INDICA IN CULTURES*
Authors: SARMA T. A.
Published: May 2006

The life cycle of Stichosiphon indica Rao was studied in pure cultures. Baeocytes, from clonal populations, germinated in Chu‐10 medium giving rise to two‐celled germlings. These later developed into large sporangia which, upon dehiscence, released baeocytes in two rows. The differentiation of biconcave or disc cells characteristic of the Oscillatoriaceae was observed. The young baeocytes were smooth, cylindrical or cuboid, the mature ones being spherical, wrinkled and enclosed in a thin wall. The alga, upon serial subculturing did not form sporangia but the baeocytes increased in numbers multiplying like a unicellular organism. The significance of these features is discussed.
THE ROLE OF BRANCH LENGTH AND ANGLE IN BRANCHING PATTERN OF FOREST SHRUBS ALONG A SUCCESSIONAL GRADIENT
Authors: KEMPF JEFFREY S. , PICKETT S. T. A.
Published: May 2006

We investigated the branching structure of shrubs to quantify architectural changes along a successional gradient and to compare these findings with the behaviour of trees. Although shrubs did not differ in bifurcation ratio, it was discovered that branch length, interbranch distance and branching angle are all important display characters. Later successional shrubs had longer whole branches or interbranch lengths than early successional shrubs. In addition, there is a tradeoff between interbranch length versus whole branch length and angle size as part of the overall strategy for minimizing leaf overlap in the later successional shrubs. Early successional shrubs allocate less to long branches as a component of multilayer display of numerous, small leaves. We conclude the existence of great flexibility in the shrub form which utilizes horizontal areas rather cheaply and exploits different successional positions by manipulating the same small‐scale branching features that differ within single tree crowns.
PHYSIOLOGICAL ASPECTS OF RAINFOREST REGENERATION
Authors: CHANDLER GRAEME
Published: May 2006

Summary

Purified glutamine synthetase (GS) from the leaves of a rainforest tree, Bauerella simplicifolia exhibited Mg2+‐dependent activity which was completely inhibited by 5 mM MnSO4. No shift in the pH optimum for the Mg2+‐dependent enzyme was observed with Mn2+. AMP, ADP, NO3− and NO2− also inhibited GS activity, although at low concentrations NO3− and NO2− stimulated GS. Using the Mg2+‐dependent assay, the Km for NH4+ was about 25 × 10−4 M. The Km for glutamate was 3 mM whilst the Km for ATP was lower at 0·5 mM.

With the exception of Bauerella simplicifolia and Argyrodendron trifoliolatum, GS activity in leaves of a variety of rainforest plants was very low or essentially zero.
A NEW METHOD FOR PRODUCING PURE VESICULAR‐ARBUSCULAR MYCORRHIZA‐HOST CULTURES WITHOUT SPECIALIZED MEDIA
Authors: JOHN T. V. ST. , HAYS R. I. , REID C. P. P.
Published: May 2006

Summary

A method is reported for synthesizing pure two‐membered vesicular‐arbuscular mycorrhiza infections without complex media. The method should make possible several kinds of experiments not feasible with previously published methods. Plant growth rate was comparable to that in non‐sterile systems.
ROUTINE PRODUCTION OF AXENIC VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: MACDONALD R. M.
Published: May 2006

Summary

A compact autoclavable hydroponic culture system is described for the production of axenic vesicular‐arbuscular mycorrhizas formed between Trifolium parviflorum and Glomus caledonius. Liquid is circulated by means of a low pressure air supply and sterility is maintained by glass fibre air‐filters. Provision is made for sampling of the nutrient solution for analysis and sterility tests.
ANTIFUNGAL ACTIVITY IN CARROT ROOTS IN RELATION TO STORAGE INFECTION BY MYCOCENTROSPORA ACERINA (HARTIG) DEIGHTON
Authors: DAVIES W. P. , LEWIS B. G.
Published: May 2006

Summary

Antifungal activity in diffusate and tissues of stored carrot roots was studied. Three main compounds inhibitory to Mycocentrospora acerina were separated. Of these, 6‐methoxymellein and p‐hydroxybenzoic acid were identified with the aid of chromogenic agents, u. v. spectroscopy and low resolution mass spectrometry. A third inhibitor, which has subsequently been identified as falcarindiol, was also found. ED50 values for inhibition of chlamydospore germination were 79 μg ml−1 for 6‐methoxymellein and 292 μg ml−1 for p‐hydroxybenzoic acid. 6‐Methoxymellein accumulated to levels above the ED50 in diffusate from roots and in the locality of restricted lesions. The possible role of these compounds in carrot root resistance to Mycocentrospora acerina is discussed.
CHLOROPLAST DEVELOPMENT IN AZOLLA ROOTS
Authors: WHATLEY JEAN M. , GUNNING B. E. S.
Published: May 2006

Summary

In the water fern, Azollapinnata, all the cells of the root are ultimately derived from a single apical cell. The programme of sequential cell divisions which take place as the root develops can be identified with precision. A median longitudinal thin section of this small root provides an ultrastructural transect in which successive stages of cell development are displayed. From a series of sections of roots of different ages it was established that the state of plastid development and the size of the chloroplast population within a cell depend on (1) the age of the root (2) the type of cell and (3) the distance of that cell from the single apical cell.
POLAROGRAPHIC MEASUREMENT OF PHOTOSYNTHETIC OXYGEN EVOLUTION BY LEAF DISCS
Authors: DELIEU T. , WALKER D. A.
Published: May 2006

Summary

A simple polarographic device is described which permits the measurement, in the gas‐phase, of O2 evolved by leaf discs during photosynthesis and O2 consumed in respiration. A method of calibration is described and results are included which illustrate the performance of the apparatus in typical experiments.
BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)
Authors: ABO‐HAMED S. , COLLIN H. A. , HARDWICK K.
Published: May 2006

Summary

The dormant phase of the flush cycle of leaf growth in cocoa is known to be correlated with high abscisic acid (ABA) levels in the mature leaves of the new flush (NF) and previous flush (PF) leaves. Defoliation of either the NF leaves or PF leaves of cocoa seedlings reduced the length of the dormant phase of the flush cycle, thus showing that the mature leaves were a source of growth inhibitors which could affect shoot apical activity. The application of ABA to the NF and PF leaves led to an extension of the dormant phase, whereas application of zeatin or gibberellic acid decreased it. The distribution of [14C]ABA following its application to NF and PF leaves at different stages throughout the growth cycle showed that [14C] ABA was accumulated by the bud in relatively larger amounts during the final stages of bud dormancy (I‐1 and I‐2) than in the earlier stage (F‐2). The results suggest that internal competition for nutrients may be responsible for the inhibition of growth at the F‐2 stage but that ABA translocated from the mature leaves causes the buds to remain dormant during the subsequent stages of I‐1 and I‐2.
A QUANTITATIVE STUDY OF MYCORRHIZAL INFECTION IN TRIFOLIUM: SEPARATE DETERMINATION OF THE RATES OF INFECTION AND OF MYCELIAL GROWTH
Authors: SMITH S. E. , WALKER N. A.
Published: May 2006

Summary

We present a simple mathematical model of the infection of roots of Trifolium subterraneum by vesicular‐arbuscular mycorrhizal fungi. The model permits separate calculation of the following.

(1) The frequency of infection in unit length of root in unit time from mycorrhizal propagules distributed uniformly and randomly in soil. A value of 40·8 m−1 day−1 was found for the soil used in the experiments.

(2) The rate of fungal growth along the root cortex from a single entry point, which was found to be 12·2 × 10−4 m day−1 for infections derived from propagules in the same soil.

An alternative method of estimating the frequency of infection close to the root tip (from measurements of the rate of root growth and distance between the apex and the most apical entry‐point) is presented. Comparison of values obtained suggests that the root tip is nearly 10 times more infectible than the average for the whole root system.

Some of the assumptions implicit in the model have been investigated experimentally and the results are reported here.

The model should be useful in distinguishing between environmental effects on the phases of colonization occurring in the soil, and at the root surface and within the root.
ULTRASTRUCTURE OF PSEUDOPERONOSPORA HUMULI MYCELIUM
Authors: PARES R. D. , GREENWOOD A. D.
Published: May 2006

Summary

The hyphae of Pseudoperonospora humuli were examined at 3, 4, 5 and 6 days after inoculation of hop leaves. The structure and occurrence of lomasomes, centrioles, Golgi bodies, mastigonemes, crystalline inclusion bodies and invaginated mitochondria are discussed.
PERFORMANCE OF PURE AND MIXED STANDS OF FORAGE GRASSES AT THE ESTABLISHMENT PHASE
Authors: BEBAWI F. F. , NAYLOR ROBERT E. L.
Published: May 2006

In two species mixtures over all nutrient levels and harvests, mixtures of cocksfoot and timothy invariably gave relative yield total (RYT) values well above 10 thus implying a synergistic relationship, while mixtures of cocksfoot and perennial rye grass (PRO) consistently gave RYT values well below 1‐0 thus indicating a mutually antagonistic relationship. However, mixtures of PRO and timothy generally gave RYT values approaching 10. Similarly mixtures of cocksfoot and timothy overyielded their respective highest yielding pure stands and mixtures of cocksfoot and PRG underyielded their respective lowest yielding pure stands. PRG and timothy generally gave intermediate yields between those of their highest and lowest pure stands.

Relative yield values over all nutrient levels and harvests revealed that PRG is more aggressive than cocksfoot, which in turn is more aggressive than timothy. In a three species mixture this trend in order of aggressiveness was also maintained. The yields of the three species mixtures invariably exceeded those of their highest yielding pure stand.

In both experiments pure stands of cocksfoot gave the highest yields and timothy the lowest. Nitrogen fertilization significantly affected herbage yield maximizing it at high nutrient level. There were also significant differences in yield between harvests over all nutrient levels. However, the particular combination of species in a mixture affected the mixture behaviour and yield, though generally the behaviour of a component in a mixture was not predictable from a knowledge of its behaviour in pure stands. The present findings also suggest that the hypothesis that mixtures yield more than pure stands is untenable as a general statement about all mixtures.
INFLUENCE OF FOUR VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI ON NUTRIENT UPTAKE AND GROWTH IN BARLEY (HORDEUM VULGARE)
Authors: JENSEN ANNI
Published: May 2006

Summary

Barley was inoculated with Glomus constrictus, G. fasciculatus isolate no. 185, G. fasciculatus isolate no. 0–1 and Gigaspora margarita in sterilized soil in pots. Plants inoculated with G. constrictus and with G. fasciculatus isolates showed an increased total uptake of P, Cu and Zn, an increased yield of grain and an increased yield of straw. Plants inoculated with G. margarita did not differ from control plants in growth or P, Cu and Zn uptake. Increase of growth was not correlated with intensity of infection.
COMPETITION BETWEEN THREE SAXICOLOUS SPECIES OF PARMELIA (LICHENS)
Authors: ARMSTRONG R. A.
Published: May 2006

Summary

Fragments of three foliose, saxicolous lichens were glued in 5 × 5 cm plots on pieces of slate in the field, either in monoculture or paired in 1:1 mixtures with each of the other two species. A preliminary experiment suggested that glueing did not influence the radial growth of the lichen fragments. No species eliminated another after 3 years but the growth (total area in mm2) of Parmelia saxatilis and P. glabratula ssp. fuliginosa was reduced significantly in the mixtures with P. conspersa; the growth of P. glabratula ssp. fuliginosa was reduced significantly in the mixture with P. saxatilis compared with their growth in monoculture. The results suggest that the three lichens show interference by competition for space and light in the following order of competitive ability: P. conspersa > P. saxatilis > P. glabratula ssp. fuliginosa. A high radial growth rate and the ability to overgrow a thallus may be important competitive attributes in foliose lichens and the results also suggest that competition can reduce the abundance of a lichen and lead to distribution patterns in the field.
METAL UPTAKE IN TERRICOLOUS LICHENS
Authors: GOYAL R. , SEAWARD M. R. D.
Published: May 2006

Summary

The observed modifications of the morphology and histology of Peltigera canina and Peltigera rufescens in metal‐polluted environments are: reduction in thallial size and rhizinal length, and dense rhizinal growth, profusely‐branched veins and hypertrophy of the medulla. The value of terricolous lichens as bioindicators of metal‐enriched substrata is related to the biologically‐available metal concentrations in the associated soils and the nature of the substratum.