bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DISTRIBUTION OF FRUCTANS IN ONIONS
Authors: DARBYSHIRE B. , HENRY R. J. 
Published: May 2006

SUMMARYThe non‐structural carbohydrate content of individual leaf bases of onion bulbs was determined, and confirmed the presence of glucose, fructose, sucrose and a series of fructans as the only components. The fructans decreased in concentration with increasing molecular weight and those with a DP (degree of polymerization) of up to 10 were estimated. Total fructan concentration decreased from the youngest to the oldest leaf bases of the bulb, while fructose levels increased and glucose and sucrose levels tended to remain constant.
VESICULAR‐ARBUSCULAR MYCORRHIZAS IN PLANTS COLONIZING BLACK WASTES FROM BITUMINOUS COAL MINING IN THE ILLAWARRA REGION OF NEW SOUTH WALES
Authors: KHAN A. G. 
Published: May 2006

SUMMARYThree commercial coal tips in the Illawarra region of New South Wales were investigated for the incidence of VA mycorrhizas in plants growing on them. All the plants examined except species of Personia and Banksia (Proteaceae) were infected by VA mycorrhizal fungi. Infection level ranged from 0 to 88%. Three main types of fungal endophytes, namely Glomus macrocarpus var. macrocarpus, Glom us mosseae, and Sclerocystis rubiformis, were identified. The possible role of VA mycorrhizas in plant colonization of coal spoil areas is discussed. The method of colorimetric quantification of VA infection was found a useful alternative to the slow and tedious method of clearing and staining. But the pigment‐extraction method is reliable only for measuring mycorrhizal infection in controlled short term experiments. This method, however, cannot be used to analyse infection in field‐grown, long established roots.
THE COLONIZATION OF A SLATE ROCK SURFACE BY A LICHEN
Authors: ARMSTRONG R. A. 
Published: May 2006

SUMMARYThalli of Parmelia glabratula ssp. fuliginosa on a vertical slate rock surface in South Gwynedd were significantly larger at the top of the face than at the bottom. The radial growth rates of the thalli measured over 1 year were not correlated with height on the face or with variation in thallus diameter down the face. These results suggest that the lichen thalli may be older at the top than at the bottom and are consistent with the hypothesis that the lichen colonized the top of the face first and then gradually spread downwards.
THE PARTITION COEFFICIENT OF 14C2H4 IN PLANT TISSUE AS A SCREENING TEST FOR METABOLISM OR COMPARTMENTATION OF ETHYLENE
Authors: JERIE P. H. , SHAARI A. R. , ZERONI M. , HALL M. A. 
Published: May 2006

SUMMARYA method is described for the direct measurement of 14C2H4 in toluene scintillator and for the measurement of toluene‐soluble 14C accumulated in tissue during 14C2H4 (0.7–1.0 μ1/l) treatment. Using these methods the partition coefficient for ethylene between air and plant tissues was estimated. Tissues from a substantial proportion of 36 species tested gave partition coefficients significantly higher than that for water (0.11) indicating either the sequestration of 14C2H4 or the accumulation of toluene‐soluble metabolites. Steam‐killed tissue gave partition coefficients similar to that of water.
THE CARBON FIXATION CHARACTERISTICS OF ISOLATED CODIUM FRAGILE CHLOROPLASTS. CHLOROPLAST INTACTNESS, THE EFFECT OF PHOTOSYNTHETIC CARBON REDUCTION CYCLE INTERMEDIATES AND THE REGULATION OF RuBP+ CARBOXYLASE IN VITRO
Authors: COBB A. H. , ROTT JACQUELINE 
Published: May 2006

SUMMARYChloroplasts of the siphonaceous marine alga Codium fragile exhibit different carbon fixation characteristics in vitro from those of higher plants. A simple extraction medium, 0.8 M osmoticum and a saturating light intensity of 25 W.m−2 produced maximum rates of 40–60 μmoles CO2 fixed mg. chlorophyll−1 h−1 at 20°C, depending on the age and condition of the parent tissue. No marked lag phase was apparent and fixation proceeded at a linear rate for up to 60 min.Incubation with 10 mM PGA enhanced the fixation rate, as did 10 mM SBP, 10 mM FBP and 5 mM R5P to a lesser extent, whereas 6 PGlu, S7P, F6P, Ru5P and PEP produced no measureable effect. This lack of marked response to the addition of exogenous photosynthetic intermediates is correlated to a lack of induction by these chloroplasts.Using the retention of the soluble stromal enzyme RuBP carboxylase as a criterion of intactness, freshly isolated C. fragile chloroplasts were approximately 80% intact, and were still 40% intact after 96 h storage in the dark on ice.RuBP carboxylase was shown to resemble the higher plant carboxylase, existing in either an active or inactive form depending on the prevailing levels of RuBP and Mg2+, and to be metabolically regulated by PGA, 6PGlu, SBP, FBP and Pi. Maximum rates obtained with a chloroplast extract were 155 jumoles CO2 fixed mg chlorophyll−1 h−1, at 20°C.
ROOT EXUDATION IN RELATION TO SUPPLY OF PHOSPHORUS AND ITS POSSIBLE RELEVANCE TO MYCORRHIZAL FORMATION
Authors: RATNAYAKE M. , LEONARD R. T. , MENGE J. A. 
Published: May 2006

SUMMARYThe mechanism responsible for inhibition of the establishment of mycorrhizal associations inSorghum vulgarePers. (herbaceous monocot) andCitrus aurantiumL. (woody dicot) under high levels of soil phosphorus (P) was studied. Plants were grown on low fertility loamy sand (4.5 ppm P), receiving superphosphate [Ca (H2PO4)2H2O] at 0, 6, 28, 56, 228 and 556 ppm P along with all the other necessary nutrients. The percentage P content of root tissue was correlated with the amount of P added to the soil. Root exudation, measured in terms of the net leakage of soluble amino acids and reducing sugars from the roots within a 17–h period, was significantly higher under low P levels (0, 6 and 28 ppm P) than under high P levels (56, 228 and 556 ppm P). The amount of exudation was correlated with a P‐induced decrease in phospholipid levels and associated changes in permeability properties of root membranes, rather than with changes in the root content of sugars and amino nitrogen. The hypothesis is proposed that phosphorus inhibition of mycorrhizal symbiosis is associated with a membrane‐mediated decrease in root exudation.
NUTRITIONAL REQUIREMENTS OF ORCHID ENDOPHYTES
Authors: HADLEY G. , ONG S. H. 
Published: May 2006

SUMMARYFour geographically distinct isolates of Tulasnella calospora (Bourdier) Juel exhibited a similar nutritional pattern and utilized a wide range of carbon compounds including cellulose. None would grow on a mineral salts/glucose medium unless undefined materials were present. Growth occurred when a mixture of ten amino acids and ten vitamins was used, and all four isolates were heterotrophic for thiamine and p‐amino benzoic acid. They were also exacting for nitrogen. Growth on ammonium ions was very limited but asparagine, glycine and urea were good nitrogen sources while glutamine, arginine and alanine were less adequate.Isolates of Ceratobasidium cornigerum (Bourd.) Rogers and a Rhizoctonia sp. were self‐sufficient for vitamins and grew well on nitrate or other nitrogen sources tested. They were more efficient than Tulasnella calospora isolates in their nitrogen economy. T. calospora isolates may obtain vitamins and nitrogen compounds from their orchid hosts and may exhibit a limited phase of biotrophic nutrition.
POLYPHOSPHATE GRANULES IN THE FUNGI OF TWO LICHENS
Authors: CHILVERS G. A. , LING‐LEE M. , ASHFORD A. E. 
Published: May 2006

SUMMARYUsing Toluidine Blue‐stained sections, metachromatic granules have been detected in the fungi of two different lichens. These are histochemically identical with similar granules found in the fungal component of mycorrhizas and, like those, appear to consist largely of poly‐phosphate. Small numbers of polyphosphate granules have been previously reported from the algal component of a lichen, but not from the fungus. In the material examined here, the size and number of granules in the fungus greatly exceeded those in the algae. These granules merit further investigation to evaluate their significance in ion uptake and accumulation within this symbiotic system.
STUDIES ON THE GROWTH OF THE ENDOPHYTE OF OLALNUS GLUTINOSA (L.) VILL. IN NUTRIENT SOLUTIONS
Authors: QUISPEL A. , TAK T. 
Published: May 2006

SUMMARYDuring incubation of nutrient solutions heavily inoculated with an axenic suspension of spore‐nodules of Alnus glutinosa (L.) Vill. we observed an increase in infective capacity. This effect was only obtained with nutrient solutions to which an extract with petrol ether‐soluble substances from roots had been added.The reproducibility of the experiments is definitely increased when the active lipid factor(s) is further purified by silicagel column chromatography. Aerobic conditions are essential. Microscopic examination of the infective nutrient solutions showed the presence of Actinomycete‐like hyphae. These hyphae were never observed in controls where the lipid extracts had been omitted. After several transfers to fresh media, cultures are still highly infective and microscopically characterized by growth of these hyphae.After inoculation with axenic suspensions of spore + nodules, neither an increase of infectivity nor growth of hyphae was observed.
SPORE FORMATION AND ENDOPHYTE DIVERSITY IN ROOT NODULES OF ALNUS GLUTINOSA (L.) VILL.
Authors: VAN DIJK C. 
Published: May 2006

SUMMARYAnalysis of root nodules of Alnus glutinosa sampled in a natural alder vegetation revealed two types, one containing clumps of endophytic spores and one without spores. The distribution pattern of both types, but especially the latter, showed considerable clustering. Both types of nodule sometimes occurred on the same tree, and some information on the dynamics of the distribution pattern was obtained from age analysis of nodules of both types. Since cross‐inoculation experiments showed a genetic basis for the presence or absence of spores in root nodules, the existence of two endophytic strains differing in their ability to produce spores seems likely. Different concentrations of ammonium and nitrate incorporated into the nutrient solution of nodulated test plants had only a slight influence on spore‐clump abundance in root nodules, and complete inversion of the spore type was not observed. Attempts to find additional strain differences led to the comparison of isomers of diamino‐pimelic acid (DAP) from the cell wall of both types of endophyte. DAP isomer analysis of genetically more distinct ‘Alnus‐type’ root nodules, i.e. those of Myrica gale and Hippophae rhamnoides, were used as reference. No additional taxonomic differences were found between the nodule types in Alnus glutinosa, but spore‐free nodules of Hippophae rhamnoides and Myrica gale differed with respect to the DAP isomer composition. Test plants of Alnus glutinosa provided artificially with either spore‐rich or spore‐free nodules did not differ significantly in acetylene reduction rate.
STUDIES ON MUCORALEAN MYCOPARASITES
Authors: EVANS G. H. , LEWIS D. H. , COOKE R. C. 
Published: May 2006

SUMMARYAt 15°C, axenically germinated spores of Mycotypha microspora gave rise to transient yeast‐phase growth before the establishment of hyphal development. At this temperature, germination in the presence of spores of Piptocephalis fimbriata resulted in the persistence of the yeast‐phase, few hyphae being formed. Where hyphae were produced these either reverted to the yeast‐phase, became severely attenuated, gave rise to dwarf sporophores or died. Such mycoparasite‐mediated effects did not occur at 20°C. When Mortierella vinacea was used as a host in similar experiments there was no yeast‐phase growth but severe stunting of hyphae occurred initially, followed by recovery and normal growth. Using Circinella mucoroides, there was again no yeast‐phase but there was massive death of host hyphae without any apparent disturbances to their morphology. These observations are discussed in relation to the physiological and ecological consequences of mycoparasitism.
THE HETEROCYSTS OF THE BLUE‐GREEN ALGA NOSTOCHOPSIS LOBATUS: EFFECTS OF CULTURAL CONDITIONS
Authors: TIWARI D. N. 
Published: May 2006

SUMMARYThe branched filaments of Nostochopsis lobatus form infrequent intercalary heterocysts in the main trichome while the short lateral branches (1–4 celled) characteristically produce only a terminal heterocyst when the alga is grown in a medium devoid of combined nitrogen. In the presence of ammonium nitrogen, intercalary heterocysts are not formed but the lateral heterocysts enlarge to assume a balloon‐like appearance; they undergo division in situ and liberate 3–5‐called germlings. These germlings grow and produce similar heterocysts and the cycle is repeated until growth ceases. Heterocysts are produced at the terminal ends of the long lateral branches during the later stages of growth in ammonium medium; they are not formed, in this position, in cultures grown in nitrogen‐free medium. The possible role of lateral heterocysts in controlling growth and development of long laterals is discussed.
REGENERATION OF CHLOROPLAST STRUCTURE IN TALBOTIA ELEGANS: A DESICCATION‐TOLERANT PLANT
Authors: HALLAM N. D. , GAFF D. F. 
Published: May 2006

SUMMARY Talbotia elegans (Velloziaceae) is a desiccation‐tolerant plant whose dry leaves contain chlorophyll. The plastids of dry viable leaves retain some semblance of thylakoid structure and organization but are in a loose array. This contrasts with desiccation‐tolerant plants that lose chlorophyll during dehydration and reduce the chloroplast to pro‐plastid like bodies containing vesicles and numerous plastoglobuli. During rehydration, the existing thylakoid stacks are rehabilitated by the production of a ‘chloroplast designate’ volume surrounding the mass of thylakoids. This region is delimited by a double membrane and the thylakoids stack to form grana and intergranal lamellae by 24 h of hydration. Few organelles other than the chloroplast initials are easily recognizable in dry leaves but mitochondria, reduced to membrane‐bound sacs in the dry state, reform cristae after full hydration has been achieved.
DEVELOPMENT OF THE SHOOT APEX IN ZEA MAYS
Authors: CLOWES F. A. L. 
Published: May 2006

SUMMARYIntact embryos of Zea mays have been studied by stathmokinesis and DNA labelling to find rates of cell proliferation in the regions of the developing shoot apex, and these have been compared with rates for seedlings, whose apices have to be partially uncovered for this purpose. In young embryo shoots, cells divide faster than they do in seedlings and rates at the summit do not differ greatly from those in the rest of the apex. The tunica, which contains about half the cells in the apex, contributes a decreasing fraction of the total cell production as the embryo ages. The results are discussed in relation to the maturation of the seed and the changes in the numbers of cells in the regions of the meristem.
TEMPERATURE AND THE COORDINATION OF CELL CYCLES WITHIN THE ROOT MERISTEM OF ALLIUM SATIVUM L.
Authors: TAYLOR A. T. , CLOWES F. A. L. 
Published: May 2006

SUMMARYCell cycling has been surveyed throughout the meristem over a range of temperature by stathmokinetic and DNA‐labelling methods.There is a quiescent centre of ninety cells either out of cycle or with prolonged cycles. The cap initials have the highest rate of cell production, but only over a short temperature range. Outside that range the distal stelar cells have higher rates. The numbers of cells in the cap and its initials fall off with increasing temperature and there is a twelve‐fold variation in the rate at which the initials can refurnish the cap with new cells. The reduction in cell production that occurs towards the proximal margin of the meristem is due solely to lowering the growth fraction and the meristem contracts at high temperatures.The phases of the cycle as fractions of the whole vary from region to region and with temperature in the same region. G1 is the most variable phase though it is never eliminated as it is in Zea and the shortening of the mean cycle of cycling cells in the stele from the tip to the proximal margin of its meristem is brought about largely by the reduction of G1 and, to a lesser extent, of G2 while both S and M lengthen. S and M decrease as the temperature increases from 20 to 30°C while G1 and G2 are minimal at 25°C. The coordination of cycle parameters in Allium is discussed in relation to the anatomical features of its meristem and contrasted with that in Zea.
HIGHER PLANT NUCLEOSOMES. A MICROMETHOD FOR ISOLATING AND DISPERSING CHROMATIN FIBRES
Authors: MORENO M. L , SOGO J. M. , DE LA TORRE C. 
Published: May 2006

SUMMARYA one‐step method to isolate and disperse chromatin fibres from unfixed plant tissues is described. Nucleosomes as units of chromatin organization in Allium cepa L. root meristems are demonstrated by this simple technique.
NOVEL TECHNIQUES OF GENE TRANSFER AND PLANT IMPROVEMENT: AN APPRAISAL OF TRANSFORMATION IN EUKARYOTES
Authors: PANDEY KAMLA KANT 
Published: May 2006

SUMMARYCertain recent theoretical and technological advances make possible the development of new techniques for combining genes from diverse sources without normal sexual hybridization. These include: (1) DNA‐ and phage‐induced transformation; (2) protoplast fusion and organelle transfer; (3) gametic transformation; and (4) graft hybridization. The essential feature of these novel techniques is ‘transformation’, broadly defined here as a phenomenon in which a part of the genetic information of one organism is combined with the entire genome of another. The present article reviews these topics briefly with reference to their potential value in plant improvement, and their contribution to a better understanding of induced transformation in flowering plants.A critical consideration of differences between prokaryotic and eukaryotic DNA leads to a better appreciation of possible natural constraints operating against gene transfer across this major evolutionary line. Since transformation is essentially a natural mechanism in prokaryotes, and occurs in place of true sexuality and recombination, the occurrence of artificial transformation in eukaryotes may be considered to indicate an inherent capacity for recombination by transformation which has been superceded by the evolutionary development of the sexual mechanisms, meiosis and syngamy, but which may still be expressed if appropriate conditions can be generated. Future major developments may lie in discovering factors and techniques which would make eukaryotic organisms ‘competent’ as donors and recipients in transformation. It is suggested that the egg, zygote, and early embryonic cells may be better targets for transformation than differentiated somatic cells. The rapid successive divisions following fertilization of a eukaryotic egg cell presumably place heavy demands on DNA metabolism, and this may allow exogenous fragments to compete more favourably for integration into new DNA strands.It is pointed out that in nature, as far as is known, none of the beneficial, healthy symbiotic or associative systems between eukaryotic and prokaryotic organisms involve gene transfers. The only case where gene transfer is known to occur is that of crown‐gall tumour disease–an unhealthy development.It is concluded that although simple genes comprising short nucleotide sequences, or certain major genes for which genetic homology may exist between the two partners, may be transferred and expressed across the prokaryotic‐eukaryotic boundary, major advances may be achieved by altering the structure or expression of genes within their respective boundary limits. It is suggested that the most promising form of genetic engineering involving prokaryotic and eukaryotic genomes may be the fostering of a new, or improved, symbiosis or association of two genetically engineered partners, without actual transfers of genes between them.
THE GENECOLOGY OF LAWN WEEDS
Authors: WARWICK S. I. , BRIGGS D. 
Published: May 2006

SUMMARYIn order to investigate the hypothesis that disruptive selection is acting on Poa annua L. populations within a mosaic environment of bowling greens and flower beds, two experimental approaches were employed.(1) Studies of samples of seedlings, raised from the seed present in soil and surface debris from the two bowling greens and one flower bed, established that in each site the seed population was more variable than the adult. This result is compatible with the notion of disruptive selection.(2) An experiment was set up to examine the response of the two growth forms to clipping and to estimate the effectiveness of clipping as a selective force in the bowling green environment. In the control (unclipped treatment), the erect and prostrate variants differed both in total production and in their relative energy allocation to both vegetative and floral reproduction. These differences have been discussed in relation to r and K selection strategies.Differential response to clipping was observed; the groups in descending order of relative fitness consisted of prostrate individuals from the two bowling green populations > prostrate individuals from the flowerbed populations > erect individuals from flower bed populations. Clipping appears to have two effects on the erect forms resulting in: (1) a greater percentage decrease in total dry matter production in the erect compared with the prostrate forms, and (2) a greater percentage of the dry weight produced being removed by the cut in the erect forms compared with the prostrate forms.Coefficients of selection acting against erect plants under a regime of clipping ranged from 0.53 to 0.68. A selection coefficient of 0.77 was obtained for prostrate plants in the absence of clipping. In the light of the management of the lawns and flower beds, evidence for selection and gene flow is discussed.
THE GERMINATION AND VIABILITY OF FESTUCA VIVIPARA (L.) SM. PLANTLETS
Authors: HARMER R. , LEE J. A. 
Published: May 2006

SUMMARY Festuca vivipara plantlets were collected from a site in the English Lake District at several dates during the summer and autumn 1976. Various germination tests showed that plantlets from the early harvests were non‐viable. Viability increased towards the end of the growing season and, at the last harvest, approximately 90% of the plantlets were capable of germinating. Plantlets showed no innate dormancy. However, the majority of plantlets were not dehisced from the panicle and establishment was largely through the collapse of the culm. Seeds of the closely related species, F. ovina, dehisced in July and exhibited a low primary dormancy. This could be broken by stratification and was lost after 2‐3 months dry storage. Plantlets retained a greater capacity than seed to germinate at low temperature (3°C) and field observations show that F. vivipara plantlets establish after culm collapse in the autumn whereas F. ovina seeds may not germinate until the following spring. However, plantlets were capable of surviving for at least 25 weeks in conditions of high relative humidity and low temperature in the laboratory, suggesting that they have the capacity to survive the winter if they do not reach a suitable substrate for establishment.