bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyphal growth promotion in vitro of the VA mycorrhizal fungus, Gigaspora margarita Becker & Hall, by the activity of structurally specific flavonoid compounds under CO2‐enriched conditions
Authors: CHABOT S. , BEL‐RHLID R. , CHÊNEVERT R. , PICHÉ Y. 
Published: April 2006

summaryPlant phenolic compounds are known to be inducers of virulence genes in plant‐pathogen interactions such as those involving Agrobacterium, and flavonoids are known to be inducers or inhibitors of Nod genes in Rhizobium‐legume symbiosis. More recent studies suggest that some of these compounds act as molecular signals in the development of vesicular‐arbuscular mycorrhizas (VAM). The present study has shown that hyphal growth of the VAM fungus, Gigaspora margarita Becker & Hall, is affected by both stimulatory and inhibitory flavonoids, when applied at 10 μ together with an optimal carbon dioxide enrichment. Stimulatory compounds were all flavonols (kaempferol, quercetin and morin) and possessed at least one hydroxyl group on the B ring. Conversely, two isoflavones (biochanin A, and genistein), a single flavanone (hesperetin) and two compounds without any hydroxyl group on the B ring, galangin (flavonol) and chrysin (flavone), were all inhibitors of hyphal growth.
The evolutionary significance of the legume genus Chamaecrista, as determined by nodule structure
Authors: NAISBITT T. , JAMES E. K. , SPRENT J. I. 
Published: April 2006

summaryNodulated plants of 14 species of Chamaecrista (Leguminosae, sub‐family Caesalpinioideae) were grown. The structure of cells from the active N2‐fixing region of nodules varied greatly with species. At one extreme bacteroids were confined solely by peribacteroid membranes, typical of advanced papilionoid legumes such as soybean. At the other extreme, bacteroids were retained within sheath‐bounded persistent infection threads, previously reported as typical of the Caesalpinioideae and also found in certain of the base genera of the Papilionoideae. Other species had an intermediate nodule structure. Nodules of the genus Chamaecrista thus appeared to be at an evolutionary crossroads between the primitive and more advanced forms.
Activity of ribulose bisphosphate carboxylase/oxygenase from potato cultivars with differential response to ozone stress
Authors: ENYEDI ALEXANDER J. , ECKARDT NANCY A. , PELL EVA J. 
Published: April 2006

summaryThe effect of ozone (O3) on the carboxylation activity of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) from the fifth youngest leaf of four cultivars of Solarium tuberosum L. (potato) was investigated. Ozone‐tolerant cultivars ‘Superior’ (SP) and ‘Norgold Russet’ (NR), and O3‐sensitive cultivars ‘Cherokee’ (CK) and ‘Norland’ (NL) were exposed to O3 for five consecutive days in controlled‐environment chambers. Leaf samples were obtained during the O3‐exposure period and at 1, 5, and 10 d post‐exposure. For both charcoal‐filtered air (control) and O3‐treated foliage, total activity of Rubisco declined with increasing leaf age. Ozone induced an accelerated decline in the carboxylation activity of Rubisco in leaves obtained from CK and NL by the third day of O3 exposure. In contrast, O3 had no impact on the Rubisco activity from leaves of SP and NR as compared to non‐treated foliage. Differential foliar conductance could not account for the response of the sensitive and tolerant cultivars.Rubisco was purified from cultivars SP and CK to determine whether protein sulphydryl content correlated with foliar O3 sensitivity. The number of SH groups did not differ between the two cultivars, either in chemically denatured or non‐denatured Rubisco. Consequently, neither number nor availability of SH groups appear to be factors controlling sensitivity of Rubisco to oxidative damage by O3.
The effects of the duration and timing of drought plus heat plus gibberellin A4/7 on apical meristem development and coning in Sitka spruce [Picea sitchensis (Bong.) Carr]
Authors: OWENS J. N. , PHILIPSON J. J. , HARRISON D. L. S. 
Published: April 2006

summaryConing was induced on container‐grown grafts of Picea sitchensis (Bong.) Carr. by stem injection of 2 mg per month or part of a month of gibberellin A4/7 in combination with drought and high temperatures. The treatments were applied in a polyethylene‐covered greenhouse at five different times or durations during spring and summer. Coning response was determined the following spring. Shoots were sampled every fortnight from early May until late August and buds were dissected and fixed for anatomical study of apical development. The best coning resulted from the May to June, and June treatments with lesser coning occurring in the May, July, and May (2 wk only) treatments (all received heat + drought + gibberellin A4/7). Both pollen cones and seed cones were induced. Apices from control trees began to initiate bud scales in early May and leaf primordia about mid‐July. Apices from May‐treated trees began to differentiate into vegetative, pollen‐cone or seed‐cone buds in mid‐June. Apices from the June‐treated trees showed the earliest stages of vegetative, seed‐cone and pollen‐cone bud differentiation in mid‐July, about 2 wk after treatment stopped. Apices from the May to June, and the July‐treated trees began to differentiate into vegetative, pollen‐cone and seed‐cone buds in mid‐June and mid‐July respectively. The 2 wk May treatment induced too few cones to warrant anatomical study. The long period (May‐July), during which apices can be induced to differentiate into cone buds, may be explained partly by variation in the stage of bud development and partly because treatments alter the time of differentiation and synchronize apical development. Thus the earliest treatment (May) produced earlier differentiation and promoted more buds to develop in a uniform and vigorous manner to the stage where differentiation occurs. Other treatments (May‐June, and June) which preceded the natural time of bud differentiation also promoted early and uniform bud development and the longer treatment stimulated many apices, which would otherwise have slowed or stopped their development, to continue developing. Later treatment, in July, delayed apical differentiation and allowed lagging and retarded apices to catch up and thus be susceptible to the inductive treatment.
An electron microscope study of resin production and secretion by the glands of seedlings of Betula pendula Roth
Authors: RAATIKAINEN O. J. , TAIPALE H. T. , PELTTARI A. , LAPINJOKI S. P. 
Published: April 2006

summaryTransmission and scanning electron microscopy were used to study the ultrastructure and secretory processes of resin glands on shoot stems of Betula pendula seedlings during seasonal growth. The multicellular peltate glands possess a cortex of columnar cells surrounding a parenchymal medulla differing from the stem parenchyma below. Myelin‐like deposits comprising concentric layers of membranes and osmiophilic substances accumulate mainly in the cortical cells, while only the medullar cells have chloroplasts. Both of these deposits appear to be synthesized, initially, in the endoplasmic reticulum. The myelin‐like material is believed to consist of steroidal triterpenoids in cytoplasmic membranes, and the osmiophilic deposits to represent phenolics. Studies of glands of different ages suggest that the electron‐transparent resin ultimately exported is formed by combining the two initial products. In the cortical cells the secretion first accumulates in vesicles that fuse with larger ones and the periplasmatic space. From the latter the secretion diffuses through the cell wall and the resin is finally deposited in the subcuticular space. Secretion vesicles, but no periplasmatic deposits were seen in the medullar cells. At the end of seasonal growth the cortical cells are markedly vacuolate and appear to have lost their organelles. Some of the cells accumulate an electron‐opaque material not seen earlier. The medullar cells of the glands are suberized before winter dormancy, but usually later than in the surrounding stem bark.
Ribosomal DNA variation and population differentiation in Salicornia L.
Authors: NOBLE S. M. , DAVY A. J. , OLIVER R. P. 
Published: April 2006

summaryAnalysis of nuclear rDNA variation within and between populations of Salicornia from the salt marsh at Stiffkey, Norfolk has detected new patterns of genetic differentiation. Individual plants may have alternative 10.5 and 12 kb repeat units. A strong association between the frequency of particular genetic variants and the environmental gradient of tidal inundation was evident. Salicornia dolichostachya Moss from sandy flats on the lowest parts of the marsh, near to the seaward edge, and S. fragilis Ball & Tutin from deep creeks were both monomorphic for the 12 kb variant; in contrast, S. pusilla J. Woods, characteristic of the highest parts of the tidal range, was monomorphic for the 10–5 kb variant. The more phenotypically variable S. europaea L. and S. ramosissima J. Woods populations that are found in large areas of lower and upper marsh, respectively, were heterogeneous for rDNA variant type. Nevertheless, the frequency of the 12 kb variant was significantly higher in plants from the lower marsh than in those from upper marsh, and in plants from low‐lying pans than in those from raised interfluves; the 10.5 kb variant had the converse distribution. Variation in rDNA was not obviously associated with variation in morphology, or with variations in isozyme frequency established previously.Comparison of these results with those for populations from an extensive study, ranging from Anglesey (N. Wales) to S.W. Spain and the Gulf coast of Saudi Arabia, suggested that the rDNA variation and its association with environmental variation are complex and site‐dependent. Plants from Anglesey had 10.5 and 11.5 kb variants, whereas only a 10–75 kb variant was detected in material from Spain and Saudi Arabia.rDNA variants were used as genetic markers in order to test the hypothesis that Salicornia is predominantly an inbreeder; conventional breeding experiments have been hampered by its highly specialized morphology and this represents the first direct, sensitive test of an idea that has been suggested mainly on morphological and phenological grounds. Analysis of rDNA in 38 maternal plants from Stiffkey and 2112 of their progeny provided no evidence for out‐crossing.
Evidence that abaxial leaf glands are the sites of salt secretion in leaves of the mangrove Avicennia marina (Forsk.) Vierh
Authors: FITZGERALD MELISSA A. , ORLOVICH DAVID A. , ALLAWAY WILLIAM G. 
Published: April 2006

summaryPieces of leaf from the halophyte Avicennia marina (Forsk,) Vierh. were freeze‐substituted and sectioned with special precautions to keep specimens always dry. Spot energy dispersive X‐ray microanalysis and X‐ray mapping showed that vacuoles of water parenchyma and palisade mesophyll cells had much more sodium and chlorine than the cytoplasm of the same cells. Potassium and phosphorus were also found in the vacuoles of the palisade mesophyll cells but in the water parenchyma cell vacuoles, sodium and chlorine generated most of the X‐ray counts. This is consistent with a function for the water parenchyma cells of vacuolar salt storage. No sodium and chlorine were detected in the peltate cells of the abaxial epidermal hairs, and there was very little sodium in the vacuoles of their basal cells, potassium apparently being the major cation. Salt crystals were not detected in substomatal cavities. Abaxial epidermal glands contained sodium and chlorine in the collecting cell, stalk cell, secretory cells and the subcuticular cavity. Material just outside the glands gave extremely high X‐ray counts for sodium and chlorine. We conclude that the material was salt that had been secreted, and that the glands are the secretory apparatus on the abaxial surface of the leaves.
Drought‐induced changes in hydraulic conductivity and structure in roots of Ferocactus acanthodes and Opuntia ficus‐indica
Authors: NORTH GRETCHEN B. , NOBEL PARK S. 
Published: April 2006

summaryDrought‐induced changes in hydraulic conductivity (Lp) and anatomy were investigated for 1‐, 3‐ and 12‐month‐old roots of Ferocactus acanthodes (Lem.) Britton & Rose and Opuntia ficus‐indica (L.) Miller. Responses were similar for the two species but varied for the three root ages. Drying in soil for 30 d caused little change in Lp or internal structure for 1‐month‐old roots, primarily due to the formation of soil sheaths in the root hair zone. For 3‐month‐old roots, Lp declined three‐ to five‐told after 30 d of drying, partly because of lacunae caused by rupture of cortical cells. For 12‐month‐old roots after 30 d of drying, the dehydration of suberized peridermal layers led to a two‐ to three‐fold decline in Lp. Measurements of axial hydraulic conductance per unit pressure gradient (Kh) before and after pressurization indicated that air embolism, caused by 30 d of drying, decreased Khby 53, 97, and 98% for 1‐ 3‐ and 12‐month‐old roots, respectively. Rewetting after 30 d of drying restored Kh to initial values within 7 d for all three root ages. Lpafter rewetting attained 100 % of its initial value for 1‐month‐old roots arid about 60% for 3‐ and 12‐month‐old roots. The formation of soil sheaths around young roots, the reduction in radial conductivity for older roots by cortical lacunae and peridermal dehydration, and the reduction in Kh by embolism thus caused a moderate, partly reversible decline in Lp that can help limit water loss from roots to the soil during drought.
The response of native, herbaceous species to ozone: growth and fluorescence screening
Authors: REILING K. , DAVISON A. W. 
Published: April 2006

summaryOzone concentrations in many parts of Europe exceed the proposed UN‐ECE Critical Levels for the protection of ecosystems but there is so little known about the effects on native, herbaceous species, that it is presently impossible to judge what effect, if any, these concentrations are having on this group of plants. This paper reports the results of an initial screening of 32 taxa that was used to select a small number of species for further work. All were exposed to 70 nl 1−1O3 given for 7 h d−1for two weeks and the response measured in terms of mean relative growth rate (R̄), the allometric root/shoot coefficient (K), and changes in induced chlorophyll fluorescence (FR).Only six species showed visible symptoms but 14 showed a significant reduction in R̄. There was no relationship between the extent of visible symptoms and growth reduction, confirming that visible symptoms are often of little value in determining growth sensitivity to O3 stress. There were marked differences within genera and within species; a population of Plantago major collected in Athens showed no effects, while a Derbyshire population, with a 24% reduction in R̄, was the most sensitive of taxa tested, including Bel‐W3 tobacco which has been specifically bred for O3 sensitivity.There was a significant regression of R% change on the R̄ of controls (R̄%= 12.4−10.4 ×R̄, P= 0.0007, r=−0.56), implying that > 30% of the variation in response between taxa was related to the inherent R̄; faster growing taxa tending to show a greater reduction in R̄ on exposure to O3. It is tentatively suggested that this may be related to differences in stomatal conductance.Ozone caused a significant shift in K in 14 taxa, with many of the biggest changes being in grasses. Although O3 reduced K in some taxa, contrary to several published accounts, it increased it in others, and in some there was an effect on K with no effect on R̄. Possible reasons for this are discussed.Chlorophyll fluorescence was examined as a tool for detecting O3 stress. The maximum rate of rise of induced fluorescence, FR, was very sensitive to O3 but showed a complex pattern of response dependent on species and time. Most taxa showed a significant change in FR, even when there was no effect of the O3 on R̄ or K. Whilst the sensitivity of FR makes it a useful method for in vivo detection of O3 stress, the complexity of the response makes it very difficult to quantify and use for comparisons between species.
The effect of long‐term ozone exposure on injury in seedlings of red spruce (Picea rubensSarg.)
Authors: FINCHER JEAN , ALSCHER RUTH G. 
Published: April 2006

summaryThe death of many mature red spruce (Picea rubensSarg.) trees in the northeastern United States has sparked controversy over the roles natural factors and air pollutants play. The goal of this work was to investigate the effects of long‐term ozone exposures on development of injury and, in particular, the expression of winter injury in red spruce. Red spruce seedlings were exposed to elevated levels of ozone during two growing seasons, starting just after budbreak, and continuing into the period of early frosts. Trees spent both winter periods under ambient conditions of light and temperature. No visible lesions on foliage that could be attributed to ozone developed during the growing seasons. Yellow and brown needles appeared each winter, with much more injury in the second year. However, in the spring after two seasons of ozone exposure, there was no significant effect of ozone on the overall appearance of the entire population of seedlings. Samples were taken for histology and ultrastructure approximately monthly. Ozone treatments increased mesophyll cell disruption after frosts in early winter in the first year, but not in the second. There was no correlation between histological injury in the autumn and visible symptoms in the spring, indicating that there may be different aspects of the winter injury syndrome. In the second summer from 20 to 40%, of all mesophyll cells were damaged. This damage was not related to ozone treatment, and probably resulted from high summer temperatures.
Differences in the spectral characteristics of white clover exposed to gaseous pollutants and acid mist
Authors: WILLIAMS J. H. , ASHENDEN T. W. 
Published: April 2006

summaryWhite clover plants (Trifolium repensL. cv ‘Grasslands Huia’) were exposed to combinations of gaseous pollutants and acid mists similar to those found in many parts of upland Britain. The gaseous pollutant treatments were (a) charcoal‐filtered air (control), (b) SO2+ NO2(c) O3and (d) O3+ SO2+ NO2. The acid mist treatments were 6 mm per week of solutions at pHs of 2.5, 3.5, 4.5 and 5.6. After 12 weeks, canopy reflectance was measured at green, red, near infrared and middle infrared wavelengths using a portable radiometer. Distinct changes in the characteristic spectral reflectance of the clover canopies were noted. The effect of the gaseous pollutants was significant when examined by analysis of variance. The two treatments containing ozone showed particularly marked changes and were statistically separable from the control in a pairwise comparison; the sulphur and nitrogen dioxide treatment was not statistically separable from the control. The acid mists had no significant effect on canopy reflectance. Simple and 4‐waveband vegetation indices showed positive linear relationships with shoot dry weight. The O3+SO2+NO2, in particular, and O3treatments produced marked decreases in shoot dry weight and vegetation index. The green and near infrared wavebands were the best discriminators of change in canopy reflectance.
Structural responses of needles of conifer seedlings to acid rain treatment
Authors: BÄCK JAANA , HUTTUNEN SATU 
Published: April 2006

summaryThe mesophyll ultrastructure of needles of Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) seedlings was examined in the course of experimental acid rain treatment lasting three years. The pH 3‐treated needle mesophyll cells exhibited thicker granal packing in their chloroplasts than the dry control needles after one season's irrigation. Starch occurrence had decreased due to pH treatment when the whole hardening and rest period was considered. Chloroplast shapes were seen to vary from ellipsoid to irregular, especially in the pH 4 and pH 3‐treated needles, due to divisions during hardening. The mean area of mesophyll chloroplasts in the hardened state after three seasons, irrigation was largest (10.3 μm2) in the pH 3‐treated needles, which also contained the smallest number of dark‐stained plastoglobuli. Starch occurrence in the hardened mesophyll cells in October reflected disturbances in the hardening processes in the pH 3‐treated needles.
Stomatal response of mycorrhizal cowpea and soybean to short‐term osmotic stress*
Authors: AUGÉ R. M. , STODOLA A. J. W. , BROWN M. S. , BETHLENFALVAY G. J. 
Published: April 2006

summaryCowpea [Vigna unguiculata (L.) Walp.] and soybean [Glycine max (L.) Merr.] plants were grown in pots and either inoculated with the vesicular‐arbuscular (VA) mycorrhizal fungi, Glomus intraradices Schenck and Smith (cowpea) and G. mosseae (Nicol & Gerd.) Gerd. and Trappe (soybean), or provided with regular P fertilization (non‐VA mycorrhizal plants). When plants were six to ten weeks old, roots were exposed to osmotic stress and stomatal behaviour monitored for several hours. Leaves of VA mycorrhizal cowpea had higher stomatal conductance (gS) than those of non‐mycorrhizal cowpea before and after lowering soil water potential (Ψ) to −0.7 MPa with either sorbitol or macronutrient solutions. Pre‐stress gs and the initial decline in gs after exposure to − 0.5 MPa sorbitol were similar in mycorrhizal and non‐mycorrhizal soybean leaves. Stomatal conductance was higher in the latter after 2 h but higher in the former after 21 h. CO2 exchange rates and leaf water relations were similar in VA mycorrhizal and non‐mycorrhizal soybean before and after soil Ψ was lowered. Higher gs at equal soil Ψ suggests that mycorrhizal root systems either scavenged water of low activity more effectively or influenced nonhydraulic root‐to‐shoot communication differently from that in non‐infected root systems.
The growth of the extramatrical mycelium of ectomycorrhizal fungi and the growth response of Pinus sylvestris L.
Authors: COLPAERT JAN V. , VAN ASSCHE JOZEF A. , LUIJTENS KRISTEL 
Published: April 2006

summaryNine ectomycorrhizal fungi have been studied for their effect on the growth of Pinus sylvestris L. seedlings. The plants were kept growing for six months in root chambers with a changeable volume. All seedlings were cultivated under conditions of low substrate nutrient concentrations and they became strongly infected within a short time. We demonstrated the existence of an important negative correlation between the extent of the fungal development and the growth of the host plants. In most studies this reduced growth is attributed to an energy drain by the fungus. Fungi producing large amounts of fungal tissue are more energy consuming than species which only develop a sparse mycelium. However we suggest that also nitrogen acquisition by the plants might be altered by the fungus. Certain fungi probably retain a considerable amount of nitrogen for their own growth, thus reducing the amount transported to the host plant. A decreased N transport finally results in a slower growth. In this study the extramatrical mycelium in the rooting substrate was determined by wet oxidation and by nitrogen determination. This component of the fungal biomass showed the biggest variation among the different mycobiont species. The results are discussed in relation to the culture technique employed.