bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHLOROPLAST DEVELOPMENT IN LIGHT‐ AND DARK‐GROWN SPOROPHYTES OF PHAEOCEROS LAEVIS (L.) PROSK. (ANTHOCEROTOPHYTA)
Authors: LIGRONE R. , FIORETTO A. 
Published: April 2006

SummaryChloroplast development in light and in darkness was investigated in the sporophyte of the anthocerote, Phaeoceros laevis (L.) Prosk. In both light‐and dark‐grown sporophytes, chloroplasts with an elaborate inner membrane system were found in chlorenchyma cells about 3 mm from the sporophyte base. Development in the dark resulted in a net increase of the average number of grana per unit of chloroplast area and of thylakoids per granum, and a parallel diminution in the chlorophyll a/b ratio. Substantial amounts of chlorophyll were synthesized in the dark. Small, paracrystalline arrays of membranes associated with extensive thylakoid stacks were found in immature plastids of dark‐grown sporophytes. These structures disappeared during early stages of subsequent chloroplast differentiation. These results are the first indication that the anthocerotes do not require light for the differentiation of their photosynthetic apparatus.
EFFECTS OF DROUGHT STRESS ON GROWTH RESPONSE IN CORN, SUDAN GRASS, AND BIG BLUESTEM TO GLOMUS ETUNICATUM*
Authors: HETRICK B. A. DANTELS , KITT D. GERSCHEFSKE , WIILSON G. THOMPSON 
Published: April 2006

SummaryThe responses of mycorrhizal corn (Zea mays L.), sudan grass [Sorghum vulgare (Piper) Hitch.], and big bluestem (Andropogon gerardii Vitman) under drought stress were compared. Although growth of each of the plant species benefited from the mycorrhizal fungus under adequately watered conditions, inoculation had no effect on the growth of corn or sudan grass when cyclic drought stress was imposed on these plants. In contrast, growth of mycorrhizal big bluestem was significantly greater than non‐mycorrhizal big bluestem, even under severe drought stress. Drought‐stressed mycorrhizal plants without phosphorus amendment were not larger than drought‐stressed, non‐inoculated, fertilized (15 mg kg 1p) plants, suggesting no increased drought tolerance.The ability of Glomus etunicatum Becker & Hall to benefit plant growth under drought stress was apparently plant‐mediated and possibly related to the dependency of the plant on this mycorrhizal fungus. Under adequately watered conditions, inoculated corn and sudan grass were respectively 1.23 and 1.13 times larger than non‐inoculated plants, while inoculated big bluestem was 6.56‐fold larger than non‐inoculated control plants.
WATER RELATIONS OF MYCORRHIZAL AND PHOSPHORUS‐FERTILIZED NON‐MYCORRHIZAL CITRUS UNDER DROUGHT STRESS*
Authors: GRAHAM J. H. , SYVERTSEN J. P. , SMITH M. L. 
Published: April 2006

SummaryRootstock seedlings of Carrizo citrange (Poncirus trifoliata (L.) Raf. x C. Sinensis (L.) Osbeck) and sour orange (Citrus aurontium L.) were grown in a sandy soil low in phosphorus (P) and either inoculated with Glomus intraradices Schenck & Smith (vesicular‐arbuscular mycorrhizal; VAM) or fertilized with soluble P (non‐mycorrhizal; NM). Five‐month‐old VAM and NM seedlings of each rootstock were comparable in size, P sufficiency, and relative growth rate whether they were kept well‐watered or subjected to two drought‐stress cycles of short duration. Under well‐watered conditions, whole plant transpiration, leaf water status, and root hydraulic conductivity were similar for VAM and NM plants of each rootstock. During drought‐stress and recovery periods, VAM plants also had very comparable whole‐plant transpiration rates and leaf water potentials to NM plants, but mycorrhiza reduced root hydraulic conductivity of Carrizo citrange and sour orange 66 and 49%, respectively. These data do not support the hypothesis that mycorrhiza significantly enhance water relations of citrus under the drought‐stress conditions studied.
THE PROCESSES OF ANTHER DEHISCENCE AND POLLEN DISPERSAL
Authors: KEIJZER C. J. 
Published: April 2006

SummaryThe development of the locule of Gasteria verrucosa (Mill.) H. Duval and Lilium hybrida cv. Enchantment, especially the border between the sporophyte and the gametophyte, is investigated by means of light and electron microscopy, histochemistry and micromanipulation and related to pollen dispersal. The pecto‐cellulosic cell walls of both the middle layer and the tapetum and a part of the endothecium disappear, and the tapetum cells are covered with sporopollenin‐containing tapetal membranes and orbicules. The cell contents of the tapetum turn into the hydrophobic pollenkitt. In the locule, similar changes are observed as the pecto‐cellulosic and callose walls of the meiocytes disappear and the future pollen grains are covered with the sporopollenin‐containing exine. Due to their non‐wettability, these hydrophobic substances on both sides of the sporophyte–gametophyte surface are important in pollen dispersal.The transfer of pollenkitt from the tapetum to the locule appears to be due to capillary forces in the locule after the continuous expansion of the pollen, rather than to active flow or to direct attraction by the pollen grains.
THE EFFECT OF ABSCISIC ACID ON CALCIUM‐MEDIATED REGULATION OF HETEROCYST FREQUENCY AND NITROGENASE ACTIVITY IN NOSTOC 6720
Authors: SMITH R. J. , HOBSON S. , ELLIS I. R. 
Published: April 2006

SummaryAbscisic acid (ABA) promoted a significant increase of the heterocyst frequency in cultures of Nostoc 6720. A significant interaction between ABA and the concentration of Ca2+ in the growth medium was detected. Studies using 45Ca2+ confirmed that the intracellular Ca2+ content was raised by 20% in the presence of 10−6 M ABA. Verapamil, a Ca2+ channel antagonist, inhibited the ABA‐induced increase in heterocyst frequency. Trifluoroperazine, a known inhibitor of Ca2+/protein binding, also inhibited the response to ABA.The characteristics of the response to ABA were similar to those of the Ca2+ ionophore, A23187. Both promote an increase in the total nitrogenase activity of the culture, which, it is suggested, may result from a Ca2+‐dependent protective mechanism similar to that proposed for Gleocapsa. A Ca2+‐dependent repression of dinitrogen fixation is suggested to account for the increased nitrogenase activity in cultures induced to form heterocysts in the presence of lanthanum or when the concentration of Ca2+ in the growth medium is less than 10−4 M.
COMPARATIVE STUDIES OF PLANT GROWTH AND DISTRIBUTION IN RELATION TO WATERLOGGING
Authors: TALBOT RICHARD J. , ETHERINGTON JOHN R. 
Published: April 2006

SummaryRooted cuttings of Salix caprea and of S. cinerea ssp. oleifolia were supplied with 0 to 320 mg Fe2+ dm3 as sulphate dissolved in nutrient solution either at a constant concentration or supplied incrementally. Photosynthesis and respiration of the treated plants was monitored by infrared gas analysis for periods of 4 to 7 d.Control shoots, in air‐bubbled or nitrogen‐bubbled solutions, maintained constant rates of photosynthesis and dark respiration during the experimental period. S. cinerea was unaffected by a constant concentration of 160 mg Fe2+dm3 or incremental additions reaching 320 mg Fe2+ dm−3. S. caprea was unaffected by 10 mg Fe2+ dm3, but a constant concentration of 40 mg Fe2+ dm3 or incremental additions reaching 40 mg Fe2+ dm3 caused almost total inhibition of photosynthesis and considerable reduction of respiration.Repeating these experiments using cuttings with excised roots increased the sensitivity of both species so that, even in S. cinerea, 10 mg Fe2+ dm3 was inhibitory to photosynthesis.
GROWTH AND MAINTENANCE RESPIRATION OF PERENNIAL ROOT SYSTEMS IN A DRY GRASSLAND DOMINATED BY AGROPYRON DASYSTACHYUM (HOOK.) SCRIBN.
Authors: REEKIE E. G. , REDMANN R. E. 
Published: April 2006

SummaryRespiration coefficients were determined for laboratory‐grown root systems of Agropyron dasystachyum (Hook.) Scribn. (northern wheatgrass). The growth respiration coefficient (0˙85 g g−1) was similar to published rates for species from mesic sites. The maintenance coefficient (0˙037 g g−1 d−1) was relatively low, suggesting that plants growing in semi‐arid habitats have inherently low maintenance costs per unit of biomass. The proportion of total root biomass requiring maintenance (degradable fraction) was determined by measuring the non‐structural root biomass. The degradable fraction (0˙13) was substantially lower than published measurements of functional (or ‘live’) biomass, because the latter include structural biomass, which has no maintenance requirement. Respiration parameters, root growth, degradable root fraction, soil temperature and soil moisture were used to construct a model of root respiration in field‐grown roots. The maintenance coefficient was adjusted downward during periods of water stress and low temperature when roots probably were dormant. Parameters in the model, particularly the degradable biomass fraction, explained much of the discrepancy between respiration rates of laboratory‐grown and field‐grown root systems. Maintenance respiration represents a substantial outlay in the carbon budgets of dry grasslands but is lower than expected considering the large root biomass in these systems.
RESPIRATORY METABOLISM IN ISOLATED ORCHID PETAL CELLS
Authors: HEW C. S. , YIP K. C. 
Published: April 2006

SummaryA respiratory drift has been demonstrated in cells isolated from petals of Aranda flowers at different stages of development. Tight buds had a respiratory quotient of 0˙5; this increased to 0˙7 in the first flower and reached 1˙0 in the mature flower. There appeared to be a non‐glycolytic pathway contribution in addition to the EMP pathway in tight bud and newly opened flower stages. Carbohydrate metabolism in the mature flower proceeds predominantly via the EMP pathway. Cyanide‐insensitive respiration was demonstrated in the tight bud. There was a shift towards cyanide‐sensitive respiration as the flower developed.
THE DIURNAL PATTERN OF DINITROGEN FIXATION BY CYANOBACTERIA IN SITU
Authors: GRIFFITHS MARK S. H. , GALLON JOHN R. , CHAPLIN ALAN E. 
Published: April 2006

SummaryThe diurnal patterns of cyanobacterial acetylene reduction (nitrogen fixation) and seasonal variations in these patterns were investigated in situ on a salt marsh and in a limestone cave. In the field, the non‐heterocystous species fixed N2 mainly at night, while heterocystous species fixed N2 mainly during the day. These basic patterns could be influenced by environmental conditions such as O2 availability and temperature. No acetylene reduction was observed in December, January or February.
NITROGEN ASSIMILATION AND ZINC TOXICITY TO ZINC‐TOLERANT AND NON‐TOLERANT CLONES OF DESCHAMPSIA CESPITOSA (L.) BEAUV.
Authors: SMIRNOFF N. , STEWART G. R. 
Published: April 2006

SummaryThe effect of nitrate and ammonium nutrition on the toxicity of zinc to zinc‐tolerant and non‐tolerant clones of Deschampsia cespitosa (L.) Beauv, was investigated. Zinc and nitrogen source interacted in their effect on root growth and zinc tended to be less toxic if ammonium was the nitrogen source. Root growth of the non‐tolerant clone was inhibited by ammonium. Zinc caused chlorosis in nitrate‐grown tolerant plants but not in ammonium‐grown plants. Zinc caused a decrease in the concentrations of reduced nitrogen compounds in leaves and decreased nitrate translocation to them. The zinc concentration in roots was slightly decreased in ammonium‐grown plants. In vivo nitrate reductase activity was stimulated by high zinc concentrations in the tolerant clone. Asparagine and proline accumulated in response to zinc treatment in the non‐tolerant clone. Ammonium nutrition also induced asparagine accumulation and such accumulation was much greater in the non‐tolerant clone.The small decrease in zinc toxicity when ammonium is the nitrogen source could be only partly accounted for by lower zinc uptake. It is suggested that asparagine which accumulates in ammonium‐grown plants, forms an intracellular complex with zinc and thereby decreases its toxicity.
ROOT HAIRS AND PLANT GROWTH ATLOW NITROGEN AVAILABILITIES
Authors: ROBINSON DAVID , RORISON I. H. 
Published: April 2006

SummaryFour grass species, Holcus lanatus L., Deschampsia ftexuosa (L.) Trin., Poa annua L. and Lolium perenne L. cv. S.23 and cv. ‘Norlea’ were grown for 28 d in continuous flow nutrient solution containing nitrogen (N) at one of three concentrations (0.02, 0.21 or 4.0 mol m−3) as nitrate or ammonium. Growth, N uptake and root hair production were measured.Root hair growth in D. flexuosa and P. annua was the most responsive to low N availability. These responses were generally greater to ammonium than nitrate.The possible effects of the absence of root hairs on growth were tested via empirical relationships between relative growth rates and N inflow rates to estimate the contributions made to growth by root hairs. Only in D. flexuosa at the lowest N concentration were significant contributions found. Nitrate and ammonium had no differential effect in this respect.
NH4+ UPTAKE BY THE UNICELLULAR ALGA CYANIDIUM CALDARIUM
Authors: RIGANO VITTORIA DI MARTINO , VONA VINCENZA , MANZO LUIGI , RIGANO CARMELO 
Published: April 2006

SummaryMeasurements of NH4+ uptake by Cyanidium caldarium (Tilden) Geitler, an acidophilic thermophilic non‐vacuolate unicellular red alga, were made with cells grown either in batch culture with excess ammonium or in continuous culture with nitrogen limitation.Batch‐grown cells absorbed NH4+ at a lower rate than chemostat‐grown cells, and uptake was greatly inhibited in darkness (83 %) and by CO2 deprivation (74%). In chemostat‐grown cells, in contrast, darkness inhibited uptake by only 20 to 30%. In chemostat‐grown cells subjected, after the addition of ammonium, to alternate light/dark cycles over 7 h of incubation, the rate of NH4+ uptake in the successive dark periods progressively decreased and fell to only 15% of the initial rate after 5 h incubation. In the successive light periods, in contrast, there was a 15% decrease in rate from one light period to the next, and after 7 h the rate of uptake was still 50% of the initial value. At this time, transfer of the cells from light to darkness resulted in 85% inhibition of uptake. It is suggested that in C. caldarium the overall process of ammonium assimilation is controlled, at the level of ammonium entry into the cell, either through the involvement of two independently controlled uptake systems or through multiple interconvertible forms of a single system, sharing different regulatory properties.
HYDROXYLAMINE METABOLISM IN MONORAPHIDIUM BRAUNII
Authors: BALANDIN TERESA , APARICIO PEDRO J. 
Published: April 2006

SummaryCells of Monoraphidium braunii L‐egnerova metabolized hydroxylamine, reducing it stoichio‐metrically to ammonium in darkness. In light, the rate of hydroxylamine disappearance was slightly higher than that of the ammonium release to the medium. This may indicate photo‐oxidation of hydroxylamine. Hydroxylamine much impaired ammonium assimilation. Therefore its reduction always resulted in the release of the generated ammonium.Light‐dependent nitrite utilization by the cells was also severely impaired by hydroxylamine, whereas the hydrogen‐dependent nitrite reduction carried out by anaerobic dark‐adapted cells was unaffected. Hence, hydroxylamine does not appear to inhibit nitrite reductase. There was a close correlation between the kinetics of nitrite utilization and those of oxygen evolution.Hydroxylamine prevented photosynthetic cell growth, but when the cells had removed hydroxylamine from the medium growth resumed.
DYNAMIC EXPERIMENTAL EVIDENCE FOR THE PLASMA MEMBRANE ATPase DOMAIN HYPOTHESIS OF HAUSTORIAL TRANSPORT AND FOR IONIC COUPLING OF THE HAUSTORIUM OF ERYSIPHE GRAMINIS TO THE HOST CELL (HORDEUM VULGARE)
Authors: GAY JOHN L. , SALZBERG A. , WOODS A. M. 
Published: April 2006

SummaryBarley coleoptile epidermes, prepared in special mounts for microscopic examination, were infected with Erysiphe graminis D.C. ex Merat (powdery mildew) and, after 2 d, used for experiments in which reagents were introduced to the exposed underside. Fluorescein, introduced by means of fluorescein diacetate, fluoresced for periods of over 45 min in the epidermal cytoplasm and for longer in the Haustoria which had developed. Cytoplasmic streaming in the epidermal cells continued for over 24 h. The duration of fluorescence was reduced by FCCP, but fusicoccin increased both the duration and intensity.In similar experiments in which the upper surfaces of infected leaves were detached so that the epidermal cells were disrupted and the extrahaustorial membranes were in direct contact with the experimental solutions, the duration of haustorial fluorescence was shorter than as described above in controls and with FCCP. Fusicoccin had no effect.The fluorescence, interpreted as an indicator of intracellular pH, confirms the ATPase domain hypothesis of haustorial transport and indicates that each haustorium is ionically coupled to the cytoplasm of its host cell.
GENOME HETEROGENEITY AND CLASSIFICATION OF THE POACEAE
Authors: KING G. J. , INGROUILLE M. J. 
Published: April 2006

SummaryIntragenomic base composition heterogeneity was investigated in 35 species of the grass family Poaceae, using high‐resolution thermal denaturation of DNA to produce base composition distributions. These show a pattern of peaks and shoulders which represent overlapping components of discrete base composition and provide a ‘fingerprint’ of the genome of a species. Quantitative comparison of distribution by distance matrix and cluster analysis supported traditional groupings within the Poaceae and allowed clarification of previous artificial relationships between taxa. The technique was most successful in distinguishing between taxa within subfamily, from tribal to generic level. Use of an absolute measure of all sequences present in a genome avoids problems inherent in commonly used DNA/DNA hybridization methods for determining homology. The non‐random distribution of DNA base composition components conserved among related genomes is discussed in relation to chromosome architecture and to exploitation of the gene pool of the Poaceae.
SECONDARY EMBRYOGENESIS IN LONG‐TERM CULTURES OF WINTER OILSEED RAPE, BRASSICA NAPUS SSP. OLEIFERA
Authors: SHU W. , LOH C. S. 
Published: April 2006

SummarySecondary embryogenic potential of winter oilseed rape, Brassica napus ssp. oleifera (Metzg.) Sinsk. cv. Primor, was maintained for over six years without diminution. Cytological analysis of 22 randomly selected secondary embryoids showed that they were all haploid. Many factors affect secondary embryogenesis in culture. The frequency of secondary embryogenesis was enhanced by the incorporation of 15 g l−1 sucrose into the medium; sucrose at 60 to 120 g l−1 inhibited secondary embryogenesis. Incubation in continuous darkness or continuous light led to a marked suppression of secondary embryogenesis. The best light regime for secondary embryogenesis was 16 h light/8 h dark. Incorporation of activated charcoal into the culture medium and the application of gamma radiation suppressed secondary embryogenesis. Further secondary embryogenesis was significantly reduced when only part of the secondary embryoid was cultured. The results discussed are based on the possibility that endogenous growth regulators may be involved in the initiation of secondary embryoids.
PLASTID DIMORPHISM IN LEAVES OF THE TERRESTRIAL ORCHID, OPHRYS SPHEGODES MILLER
Authors: LUX A. , HUDÁK J. 
Published: April 2006

SummaryThe leaves of the terrestrial orchid Ophrys sphegodes Miller possess two entirely different types of plastid. Mesophyll cells contain chloroplasts with well‐developed grana and scattered plastoglobuli. By contrast, vascular parenchyma cells have plastids which lack thylakoids. Their shape varies from spherical to irregularly cup‐shaped.
THE EFFECTS OF LIGHT AND TEMPERATURE ON THE GROWTH OF AND BALANCES OF CARBON, NITROGEN AND POTASSIUM BETWEEN VICIA FABA L. AND APHIS FABAE SCOP.
Authors: GARSED S. G. , DAVEY H. , GALLEY D. J. 
Published: April 2006

SummaryThe effects of light, temperature and infestation by Aphis fabae Scop, on Vicia faba L. were examined in a factorial experiment. Light was 1116 or 40 μmiol m‐2 s‐1 PPFD and temperature 15/10 °C or 25/20 °C (16 h day/8 h night). Plants and aphids were harvested after 9 d at 25/ 20 °C and 13 d at 15/10 °C. High light and high temperature increased the relative growth rate (RGR) of aphid colonies, but without interaction. Under high light, alatae produced more nymphs which grew larger. High temperature did not affect nymph production, but mature apterae weighed less. More honeydew was produced at high light. High temperature increased honeydew at high light, but decreased it at low. Reduction in dry weight (d.w.) of infested plants was similar to the calculated dry matter (d.m.) ingested by the aphids except at high light/low temperature, where it was much less. Calculated NAR was increased by high light, but reduced by high temperature. In infested plants, ‘true’ NAR (calculated from plant d.w. + ingested d.m.) was compared with ‘apparent’ NAR (calculated from plant d.w. alone). Infestation decreased ‘apparent’ NAR, but the effect was small at high light/low temperature because ‘true’ NAR increased. Infested plants at low light/high temperature had negative ‘apparent’ NARs. High light and high temperature generally decreased leaf diffusive resistance, except that uninfested plants at high light/low temperature had large values. Stem, leaf and root d.w. were all increased by high light and decreased by infestation. Leaf carbohydrate showed similar responses. Chlorophylls were reduced at high light, particularly at low temperature in uninfested plants. These plants showed positive relationships between chlorophyll and (1) the starch: sucrose ratio and (2) leaf total nitrogen, but a negative relationship with leaf diffusive resistance. Leaf potassium (K) and amino nitrogen showed only small responses to light and temperature. Aphids retained > 80 % of N ingested and < 20 % of K. Ingested material contained more K than N, but the ratio of both to carbohydrate was much greater under low light, particularly at high temperature. Aphids under these conditions appeared starved of carbohydrate. Low light increased the proportions of proline, amides and ammonia in both leaf extracts and aphid honeydew.
DEVELOPMENT OF TOTAL AND VIABLE EXTRARADICAL MYCELIUM IN THE VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS CLARUM NICOL. & SCHENCK
Authors: SCHUBERT A. , MARZACHÍ C. , MAZZITELLI M. , CRAVERO M. C. , BONFANTE‐FASOLO P. 
Published: April 2006

SummaryClover (Trifolium repens L.) plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus clarum Nicol. & Schenck in three experiments performed in similar environmental conditions. Extra radical mycelium was separated from soil by the membrane filter technique and its total length was measured; viable amounts were assessed after staining with the fluorescent dye fluorescein diacetate (FDA). Total mycelium increased steadily, and reached its maximum length 8 weeks after inoculation, unlike viability rate which decreased, from an initial value of about 100% to less than 15% after a period of 5 to 8 weeks. Consequently, the length of viable mycelium decreased after the first weeks following inoculation. The viability of extra radical mycelium may be an important factor influencing nutrient uptake and translocation by the VAM fungus.