bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of phosphate supply on wheat seedlings infected with powdery mildew: carbohydrate metabolism of first leaves
Authors: ZULU J. N. , FARRAR J. F. , WHITBREAD R. 
Published: April 2006

summaryWheat (Triticum aestivum L. cv. Longbow) was grown hydroponically with either 0, 0.33 or 3.3 mol Pi m−3 and, after 12 d, was infected with powdery mildew (Erysiphe graminis D.C. ex Merat f.sp. tritici). Fructan content of infected first leaves was increased by mildew infection but infection increased starch content only at 0 Pi. Photosynthetic 14CO2 fixation was reduced by infection, especially at 0 Pi. Accumulation of 14C in fructan rose with reduced Pi supply but was unaffected by mildew; accumulation of 14C in starch was lower in infected leaves. Pi deficiency increased the content of sugars in the apoplast, as did mildew infection, the greatest content being in infected leaves of low Pi status. Acid invertase activity was increased by infection but was not affected by Pi status. Thus P‐deficiency alone does not mimic the effects of mildew but Pi status and mildew interact in their effect on leaf carbohydrate metabolism.
Biology and effectiveness of Uromyces heliotropii Sred., a potential biological control agent of Heliotropium europaeum L.
Authors: HASAN S. , ARACIL E. 
Published: April 2006

summaryThe rust fungus Uromyces hellotropii Sred. shows potential for the biological control in Australia of the common heliotrope (Heliotropium europaeum L.), an annual weed of European origin. Teliospores of the pathogen remained viable when stored for one year at temperatures between −8 and 20°C, and carried infection over from one summer growing season to the next under a Mediterranean‐like climate. Both in glasshouse and field inoculation experiments, the rust rapidly killed infected plants and reduced or prevented seed production. U. heliotropii appears capable of surviving in the Mediterranean‐like climatic areas of Australia where common heliotrope is a problem weed and is sufficiently virulent to cause significant field infection.
The influence of an inhibitor of phytochelatin synthesis on root growth and root meristematic activity in Festuca rubra L. in response to zinc
Authors: DAVIES K. L. , DAVIES M. S. , FRANCIS D. 
Published: April 2006

summarySix‐day‐old seedings of three cultivars of Festuca rubra L. (Merlin, Hawk and S59) were grown in aerated calcium nitrate solution at various concentrations of Zn in the presence or absence of buthionine sulfoximine (BSO), a potent inhibitor of phytochelatin synthesis.In the absence of BSO, increasing Zn concentrations reduced the root length of all three cultivars but the Zn‐sensitive cultivar (SS9) showed the greatest Zn‐induced reduction and the Zn‐tolerant cultivar (Merlin) the least. The presence of BSO in the medium, contrary to expectation, ameliorated the inhibitory effect of Zn on root growth in all three cultivars.Treatment with 0.2 μg Zn cm−3 reduced the length of the root apical meristem in Merlin and S59. The presence of BSO in the culture solution did not affect the length of the apical meristem in Zn‐treated roots in any cultivar but, in the absence of Zn, BSO increased the length of the apical meristem by an average of 14.0% compared with the controls (0 Zn minus BSO). The mean length of epidermal cells in the region between the proximal boundary of the root meristem and the first root hair was reduced by an average 43% in the three cultivars following treatment with 0.2 μ Zn cm−3. However, the presence of BSO in the rooting medium did not influence epidermal cell length in Zn‐treated or untreated roots in any cultivar.The presence of BSO resulted in an average 1.7–fold increase in the mitotic index in the root meristem of Zn‐treated roots; a comparable BSO‐induced stimulation of mitotic index has been found in roots grown without Zn. However, BSO did not affect the relative frequency of the four stages of mitosis. This preliminary evidence suggests that BSO stimulates cell division activity in roots of F. rubra.The unexpected effect of the phytochelatin‐inhibitor, BSO, in increasing the Zn‐tolerance of roots argues against a key role of phytochelatins in the Zn‐tolerance mechanism of roots of F. rubra
The micromorphological distribution of bound calcium in needles of Norway spruce [Picea abies (L.) Karst.]
Authors: FINK SIEGRIED 
Published: April 2006

summaryThe distribution of bound calcium in spruce needles is visualized by various microscopical techniques. Ca pectate occurs in the middle lamellae of cell walls and in a surprisingly great concentration in the thick cell walls of the sieve cells and transfusion parenchyma. The major fraction of the calcium, however, is bound in the form of insoluble Ca oxalate crystals, which occur extracellularly on the outside of the walls of mesophyll cells which face the intercellular spaces. Furthermore, numerous small crystals appear within the cell walls of the epidermal cells, especially in the cuticular layer. The development and distribution of these apoplastic crystals is described in detail. Some hypotheses are finally presented for possible interpretations of these unusual patterns of the crystallization of Ca oxalate outside the vacuole.
Physiological response of two soybean cultivars to simulated acid rain
Authors: SMITH C. R. , VASILAS B. L. , BANWART W. L. , WALKER W. M. 
Published: April 2006

summarySimulated acid rain has been reported to cause physiological changes in various plant species. Studies were conducted in 1983, 1984, and 1985 to determine the effect, of acid rain on physiological parameters in two soybean [Glycine max(L.) Merr.] cultivars. Simulated acid rain of pH 3.0, 4.2 and 5.6 was applied throughout the growing season to plots protected from ambient rain and grown on a Flanagan silt loam (fine, montmorillonitic, mesic Aaquic Argiudoll). Individual plants were evaluated for CO2fixation, leaf water potentials, and leaf chlorophyll content. Microplots were evaluated for flowering and podding patterns, and dry matter and N partitioning. Rain pH did not affect CO2fixation, water potentials, chlorophyll content, seed yield, shoot dry weight, or N accumulation. At pH 4.2 Amsoy 71 produced fewer flowers and pods than at pH 3.0 or 5.6. Abscised leaf dry weight of Amsoy 71 was greater at pH 3.0 and 4.2 than at pH 5.6 pH effects were detected for N partitioning, but these responses were dependent on year and cultivar. No physiological basis for reported soybean yield responses to acid rain of pH 3.0 was identified.
Influence of host (Alnus and Myrica) genotype on infectivity, N2 fixation, spore formation and hydrogenase activity in Frankia
Authors: HUSS‐DANELL KERSTIN 
Published: April 2006

summaryNine species of Alnus, two of them represented by several provenances, and Myrica gale were inoculated with a ‘local source’ of Frankia. The inoculum is an effective (N2‐fixing), spore‐Forming type of Frankia that lacks H, uptake (hydrogenase) activity in symbiosis with A. incana. Despite their wide geographical origin (Europe, China, North America) and their various taxonomie grouping within the genus, all Alnus species/provenances formed Infixing nodules. In all studied nodules Frankia had the phenotype Spore+. None of the studied symbioses had hydrogenase activity. The Frankia inoculum was infective also on M. gale, and gave effective nodules without hydrogenase activity. Unlike some other spore‐forming types of symbiotic Frankia, all studied symbiotic phenotypes of the ‘local source’ of Frankia were thus stable characters not influenced by the various host genotypes included in the study.
Respiration and photosynthesis in oats exhibiting different levels of partial resistance to Erysiphe graminis D.c. ex Merat f. sp. avenae Marchal
Authors: HAIGH G. R. , CARVER T. L. W. , GAY A. P. , Farrar J. F. 
Published: April 2006

summaryRates of photosynthesis and respiration were measured by two methods, oxygen electrode and infrared gas analysis (IRGA), in infected and control, seedling and adult leaves of oat genotypes exhibiting different levels of partial resistance. Measurements were carried out up to 9 d after inoculation, sporulation commencing on day 5. There was no decrease in the rate of photosynthesis, except in the second leaves of one genotype, and no decrease in any of the fifth leaves relative to controls. The two methods of measuring respiration gave different results, with no consistent differences being found. Measurements by oxygen electrode, up to 6 d after inoculation, revealed that disease treatment had a significant effect on respiration in only two cases; the susceptible first leaf of one genotype and the resistant fifth leaf of another. Measurements by IRGA, up to 9 d after inoculation, did not confirm these differences, but did reveal a significant increase in respiration in the diseased fifth leaf of another resistant genotype. SHAM inhibited respiration, indicating the presence of the alternative oxidase, but there was no significant difference in its activity between diseased and control plants. Thus changes in photosynthesis and respiration previously associated with powdery mildew infection are either delayed or compensated for in oats. Photosynthetic and respiratory responses do not appear to be involved in partial resistance of oats to powdery mildew.
Photosynthesis of tropical tree seedlings in relation to light and nutrient supply
Authors: RIDDOCH I. , LEHTO T. , GRACE J. 
Published: April 2006

summaryThe photosynthetic performances of two tropical tree species, a pioneerNauclea diderrichii(De Wilde.) Merrill, and a climax speciesEntandrophragma angolense(Welw.) C. DC., both from West Africa, were compared. Young plants were grown in controlled environments where photon flux density and nutrient supply were varied.A/C1curves of the two species were very similar, both showing an increased initial slope and maximal rate of photosynthesis when the leaves had been grown at high photon flux density. Nutrient supply had a similar, but smaller, influence. However, the pioneerNaucleashowed a greater increase in initial slope in relation to both light and nutrient supply. It also showed greater anatomical response to light, developing a second layer of palisade mesophyll when grown at high photon flux density. Light response curves of photosynthesis were also determined. The apparent quantum efficiency was insensitive to growing conditions, but the carboxylation rate, dark respiration and tight‐saturated photosynthetic rate were sensitive to the light climate of growth. The pioneerNaucleadisplayed an increase in assimilation rate as the photosynthetic photon flux density was increased beyond 300 μmol m−2s−1, butEntandrophragmadid not, and often showed a decline.
Conservation of the British National Begonia Collection by micropropagation
Authors: BOWES B. G. , CURTIS E. W. 
Published: April 2006

summaryRegeneration was investigated in non‐sterile leaf explants taken from 87 Begonia lines after culturing for up to 10 weeks in vitro on Knop's mineral salts agar medium with no exogenous growth substances present. For many lines, only very limited supplies of leaf samples were available; nevertheless, in 66 lines de novo regeneration of roots and buds occurred and potted plants were recovered from 49 lines. Additionally in 13 Begonia lines, buds were excised from stock plants and cultured under non‐sterile conditions on Knap's agar. In seven of these the buds rooted and gave rise to potted plants. In six lines organogenic cultures (derived from sterile leaf explants) have been established in long‐term culture on Murashige & Skoog medium supplemented with growth substances and potted plants have been recovered. Sterile explants from a further 12 lines showed regeneration and have been sub‐cultured. The establishment of such sterile cultures, with continued regenerative capacity, is a significant step in the development of a programme for the conservation of rare and endangered begonias.
Apoplastic and symplastic pathways in the leaf of the grey mangrove Avicennia marina (Forsk.) Vierh.
Authors: FITZGERALD MELISSA A. , ALLAWAY WILLIAM G. 
Published: April 2006

summaryPathways for water and salts were traced from the vein endings to their sites of exit in leaves of Avicennia marina (Forsk.) Vierh. Investigations were conducted to determine whether the water and solutes separate at any point in the transpiration stream, and to identify their subsequent pathways. Leaves were placed with their cut petioles in solution containing one of two fluorochromes chosen to trace the transpiration stream. The apoplastic tracer was B‐hydroxypyrene‐1, 3, 6‐trisulphonic acid (PTS), and the symplastic tracer was riboflavin buffered to pH 6.8. Leaf pieces were freeze‐substituted with special care to keep the specimens dry to prevent redistribution of the water‐soluble fluorochromes. Stages of the technique were sensitive to atmospheric moisture, so sections were cut in a room dried to 30% relative humidity, and they were stored in a sealed box containing desiccant. Riboflavin was never seen in the apoplast, and was inside the abaxtal (lower) glands within 30 min indicating a low resistance pathway through the symplast to the gland. The veins terminate in heavily pitted xylem vessels, and at the ends of these pits, the junction between the vein ending and the apoplast of the surrounding mesophyll, were high concentrations of PTS indicating regions of separation of the fluorochrome from water – places where the water crosses from the apoplast to the symplast. PTS diffused slowly in cell walls (measured diffusivity: 4.7 × 10−10 cm2 s−1 reaching the abaxial epidermis after 8 h, which was sufficient time for four complete changes of leaf water. It was concluded that the transpiration stream, probably containing the salt destined for secretion, moved symplastically from the xylem vein endings.
The influence of substrate pH on carbon translocation in ectomycorrhizal and non‐mycorrhizal pine seedlings
Authors: ERLAND SUSANNE , FINLAY ROGER , SÖDERSTRÖM BENGT 
Published: April 2006

summaryThe effects of changed substrate pH on translocation and partitioning of14C‐labeled plant assimilates were examined in laboratory microcosms containing mycorrhizal (unidentified fungal isolate ‘Pink FMT 87:2’) and non‐mycorrhizal seedlings ofPinus sylvestrisL. andPinus contortaDougl. ex Loud. The mycorrhizal plants had intact mycelial systems at different developmental stages, and microcosms contained non‐sterile peat (pH 3.8) or peat adjusted to different pH values with CaO. In systems with mycorrhizal mycelium which had just started to colonize the peat no significant differences in14C assimilation were found, either with respect to substrate pH or mycorrhizal status of the plant. Loss of activity from the mycorrhizal plants was more rapid, however, probably mainly as a result of increased respiration from the infected root systems. After 8 wk growth in peat at pH 3.8 and 5.2 shoot weights of all seedlings were the same, whereas non‐mycorrhizal plants had root systems twice the size of the mycorrhizal ones. In plants with well developed extramatrical mycelia translocation of labeled carbon to the mycelium growing at pH 3.8 was faster than that to mycelium growing at pH 5.2. After 4 d incubation, however, the percentage of the originally supplied carbon present in the mycelium was 5% regardless of substrate pH. Activity found in the peat surrounding non‐mycorrhizal plants rarely exceeded 0.3%.
Effects of ozone and ammonium sulphate on carbon partitioning to mycorrhizal roots of juvenile Douglas fir
Authors: GORISSEN A. , JOOSTEN N. N. , JANSEN A. E. 
Published: April 2006

summaryIn this study the impact of two components of air pollution, i.e., ozone and ammonium sulphate, on carbon transport to mycorrhizal roots of Douglas fir was investigated. Juvenile Douglas fir (Pseudulsuga menziesii [Mirb.] Franco) were inoculated with Rhizopogon vinicolor A. H. Smith and Lactarius rufus (Scop.: Fr.) Fr., and allowed to grow outdoors for a period of four months. Subsequently, they were transferred to a phytotron and treated with 0 or 200μg m−3 ozone for 28 days. During these treatments, they were watered with a solution of ammonium sulphate of concentrations corresponding to 5, SO and 200 kg N ha−1 yr−1, During the last three days, the trees were pulse‐labelled with 14CO2. Ozone increased the amounts of 14C recovered in the new needle fraction, whereas the amounts recovered in the roots and root/soil respiration tended to decrease. Mycorrhizal frequency tended to increase during ozone treatment. Ammonium sulphate did not affect the distribution pattern of 14C over the trees, but seemed to stimulate the activity of the root system and mycorrhizal frequency at the intermediate nitrogen level.
Seasonal changes in the pigments of Norway spruce, Picea abies (L.) Karst, and the influence of summer ozone exposures
Authors: ROBINSON DEBORAH C. , WELLBURN ALAN R. 
Published: April 2006

summaryThere are always significant pigment changes in Norway spruce [Picea abies (L.) Karst.] needles with time in different year classes, even through the winter, but no significant changes in current year needles occur either during summer exposure due to ozone (70 nl i−1) or in the winter following. Effects of summer ozone fumigation on pigment levels, however, are very evident in 1‐ (and 2‐)yr‐old needles. These include significant decreases of total amounts of chlorophyll a and b, violaxanthin, antheraxanthin, and lutein. The only increase in pigment of 1‐yr‐old needles in the summer caused by ozone is that of 5, 6‐epoxy‐lutein; consequently, the 5, 6‐epoxy‐lutein/lutein ratio rises. Although traces of 5, 6‐epoxy‐lutein also occur in the winter afterwards, they are not significant but significant decreases in levels of chlorophylls, vioiaxanthin, antheraxanthin, lutein and β‐carotene persist. The fall in chlorophyll a levels are greater than those of chlorophyll b so a significant fall in the chlorophyll a/b ratio also occurs. Similarly, the declines in amount of β‐carotene are not as great as those of chlorophyll a and therefore significant increases in the ratio of β‐carotene to chlorophyll a are observed. No time x treatment interactions occur after ozone fumigation of 1‐yr‐old needles has been stopped but time x ozone interactions are observed during fumigation in both chlorophyll a/b and violaxanthin/antheraxanthin ratios. Most pigment changes in 2‐yr‐old needles due to summer ozone exposure are complementary to those which occurred in 1‐yr‐old needles in response to ozone the summer before.
Responses of three arid zone grass species to varying Na/Ca ratios in saline sand culture
Authors: ASHRAF M. , NAQVI M. I. 
Published: April 2006

summaryThe effects on three grass species, Cenchrus pennisetiformis Hochst. & Steud., Leptnchloa fusca (L.) Kunth. and Panicum turgidum Forssk., of decreasing Ca2+ concentration in a saline growth medium were assessed after 7 weeks growth in sand culture. The different Na/Ca ratios of the salt treatment were 24, 49, 99, and 199, at a constant concentration of 200 mol m−3. Leptuchloa fusca produced the highest fresh and dry biomass, and was able to maintain Na+ and Cl− Concentrations in the shoots and roots almost constant at varying external Na/Ca ratios, except that the shoot Na+ concentration increased significantly at the highest Na/Ca ratio. In C, pennisetiformis the shoot Na+ decreased, whereas the shoot Cl− concentration increased at the highest external Na/Ca ratio. But the root Na+ and Cl− concentrations in this species remained unchanged at varying Na/Ca ratios. C. pennisetiformis and L. fusca maintained almost constant K+ and Ca2+ concentrations in both shoots and roots at varying Na/Ca ratios. In P. turgidum the shoot K+ and shoot and root Ca2+ remained almost unchanged at all Na/Ca ratios, whereas the root K+ concentration decreased significantly but uniformly at the three, higher Na/Ca ratios. No consistent pattern of increase or decrease was observed in the shoot and root Na/K and Na/Ca ratios of all the species. The shoot selectivity (Sk + na) increased consistently in C pennisetiformis with the increase in Na/Ca ratios and it decreased in L. fusca only at the highest Na/Ca ratio in the growth mediumIt was established that L. fusca was tolerant, C. penni‐setiformis intermediate and P. turgidum relatively sensitive to low Ca2+ concentrations of the saline growth medium.
Biotransformation of nicotine to nornicotine by cell suspensions of Nicotiana tabacum L. cv. Wisconsin‐38
Authors: HOBBS MICHAEL C. , YEOMAN MICHAEL M. 
Published: April 2006

summaryPlant cell suspension cultures of Nicotiana tabacum cv. Wisconsin‐38 accumulate nornicotine as the major alkaloid, unlike the parent plant where nicotine predominates. Nicotine was added to cultures of this cultivar, grown with differing degrees of dependence on photosynthesis for the provision of organic constituents, and also to cultures grown on medium that was optimised for alkaloid accumulation. Under optimal conditions nicotine was converted to nornicotine at an efficiency close to 100% over 10 d. Conversion appeared to he intracellular, with nicotine being taken up from the medium, demethylated to nornicotine and the product released. Illumination of cultures caused a slight decrease in conversion but, when cultures were partially photosynthetic, both growth and the degree of biotransformation were decreased by approximately 40%. As well as the four main tobacco alkaloids several minor alkaloids were detected in cultures after incubation with added nicotine.
Fructan exohydrolase activity in leaves of Lolium temulentum L.
Authors: SIMPSON R. J. , WALKER R. P. , POLLOCK C. J. 
Published: April 2006

summaryCrude extracts from leaves of Lolium temulentum L. exhibited invertase activity and activity capable of releasing fructost from fructans (fructan exohydrolase; FEH), The optimum pH for FEH activity was between pH 4.8 and 5.5. When shoots of 10‐d‐old seedlings were induced to accumulate fructans by cooling their roots to 5 °C and exposing them to continuous light, FEH activity declined by at least 50 %, FEH activity increased when the shoots were induced to mobilize the fructans by warming the roots to the ambient temperature (20°C) and darkening the plants. Declining activity coincided with loss of one of at least two FEH isoforms observed after starch gel electrophoresis. Partially purified FEH from leaves of L. temulentum was inhibited when assayed in the presence of 10 HIM sucrose.