bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SUMMARYThe 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

SUMMARYThe 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

SUMMARYThe 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

SUMMARYStudies 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

SUMMARYInsects 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

SUMMARYThe 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

SUMMARYSeedlings, 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

SUMMARYVesicular‐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

SUMMARYCarbon 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

SUMMARYCompetition 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

SUMMARYThe 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.
PHYSIOLOGICAL ASPECTS OF RAINFOREST REGENERATION
Authors: CHANDLER GRAEME 
Published: May 2006

SummaryPurified 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

SummaryA 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

SummaryA 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

SummaryAntifungal 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

SummaryIn 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

SummaryA 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

SummaryThe 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

SummaryWe 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

SummaryThe 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

SummaryBarley 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

SummaryFragments 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.