bluuebunny/crossref_metadata_2025_split huggingface dataset:
The epidermal surface of the maize root tip
Authors: ABEYSEKERA R. M. , MCCULLY M. E. 
Published: April 2006

SUMMARYThe mutation Ageotropic (Agt) results in defective development of the surface pellicle which overlies the young epidermal cells of mesocotyl and nodal roots of maize. In roots of plants of the parent, cv. Kys, pellicle development is normal. This structure forms a coherent, smooth covering, up to ∼ 13/μm thick, over the epidermal cells distal to the elongation zone. This pellicle is external to the helicoidal outer wall of the epidermal cells and is composed of a thick inner layer with close‐packed, longitudinally oriented fibrils, and a thin outer layer with less regularly oriented fibrils. Both layers of the normal pellicle and the underlying epidermal wall are strongly stained by the periodic acid‐Schiff's (PAS) reaction. In Agt plants, the pellicle is irregular and diffuse, lacks definition of the two layers and is largely amorphous with occasional wisps of fibrils. Neither this mutant pellicle nor the underlying epidermal wall are PAS‐positive. Mesocotyl and nodal roots of Agt are sensitive to gravity but grow crookedly through soil. It is proposed that a normal pellicle maintains the smooth outer contour of young roots and provides stiffness in the region distal to the zone of elongation. When the pellicle is defective, the root tip is more compliant and bends result when the tip encounters small air spaces and barriers in the soil.
A pre‐Late Devensian pollen site from Camp Fauld, Buchan, north‐east Scotland
Authors: WHITTINGTON GRAEME , HALL ADRIAN M. , JARVIS JACK 
Published: April 2006

SUMMARYRecent investigations at Camp Fauld in Buchan, Scotland have yielded two peat deposits of pre‐Late Devensian age. Percentage pollen diagrams are presented. One peat is radiocarbon‐dated to 34–39 ka DP, which prompts correlation with the Hengelo‐Denekamp sequence of NW continental Europe, but the pollen evidence, revealing the presence of a birch‐pine woodland, suggests an earlier stage. The second peat deposit records an open shrub‐tundra in which Bruckenthalia spiculifolia is present. The peat yielded a radiocarbon date of 40–51 ka BP, but is suspected of having been contaminated by younger carbon. That suspicion and the presence of Bruckenthalia suggest that a correlation, based on the radiocarbon date, with the Glinde interstadial, identified in NW Germany, would be incorrect. Correlation with other Scottish pre‐Late Devensian sites has proved to be difficult.
Salt‐induced inhibition of phosphate uptake in plants of cotton (Gossypium hirsutum L.)
Authors: MARTINEZ V. , LÄUCHLI A. 
Published: April 2006

SUMMARYRadio‐labelled phosphate (32P) was used to study the effect of 150 mM NaCl on P1 uptake and P distribution in the roots of cotton plants (Gossypium hirsutum L. cv Alcala SJ‐2), Salinity inhibited P, uptake more severely at low P1 concentration (30μM) than at high P, concentration (1 niM). Data of 32P1 uptake at low P1 concentration μM range) in the nutrient solution showed a typical Michaelis‐Menten hyperbolic curve (uptake rate VSmax concentration). NaCl increased the apparent Km (from 2.23 to 4.73 μM and decreased the apparent Vmax (from 1.18 to 0.87 μmol g−1f. wt h−1). High NaCl inhibited P, uptake in the mature root zone. However, salinity enhanced P, uptake in the root tips. We speculate that salinity may induce alkalinization of the cytoplasm in root tips cells, increasing the transmembrane pH gradient and therefore P, uptake. Our results showed an inhibition of 32P transport within the roots and from the roots to the shoots m the salt treatment.
Growth responses of mutants of spring barley to fumigation with SO2 and NO2in combination
Authors: KASANA M. S. , LEA P. J. 
Published: April 2006

SUMMARYThis study was undertaken to evaluate the range of variation in growth responses of sodium azide‐induced M2mutants (stocks SI and S2) of spring barley, Hordeum vulgare. L. cv. Maris Mink, in relation to air pollution tolerance or sensitivity. The preliminary screening experiment with 150 nl l−1concentrations of SO2 and NO2 in combination for 10 d, yielded well‐defined sensitive and tolerant lines in both the stocks. However, the percentage frequency distribution of plants in different injury classes varied and stock S2 showed a better segregation of different lines. In a subsequent experiment, treatment with a mixture of each gas at 100 nl l−lconcentration for 22 d caused a variable degree of growth reduction. As a result of air pollution treatment, most of the growth parameters were significantly (P < 0.001) reduced in the sensitive lines of both the stocks, whereas the tolerant lines showed a marked resistance to the growth inhibitory effect of the pollutants. The magnitude of the difference between the sensitivities of different lines was usually double or more, and the effects were, more pronounced in stock S2 than in stock SI. Root dry weight was more adversely affected than shoot dry weight in sensitive lines of both the stocks. The results indicated that inter‐line differences in growth responses of these mutants were wide ranging, distinct and consistent. In conclusion, this study clearly demonstrates that artificial mutations may cause a markedly broad base of variation in air pollution sensitivity of crop plants which may be used in future plant breeding programmes of pollution tolerant cultivars.
Biology of the ectomycorrhizal genus, Rhizopogon
Authors: MASSICOTTE HUGUES B. , MOLINA RANDY , LUOMA DANIEL L. , SMITH JANE E. 
Published: April 2006

SUMMARYSeedlings of Abies grandis, Alnus rubra, Pinus ponderosa, Picea sitchensis, Pseudotsuga menziesii and Tsuga heterophylla were grown in monoculture and dual culture in the greenhouse and inoculated with spore slurries of 20 isolates representing 15 species of ectomycorrhizal hypogeous fungi (11 Rhizopogon species, Alpova diplophloeus, Truncocolumella citrina, Melanogaster euryspermus and Zelleromyces gilkeyae). The primary objectives were to assess and compare the pattern of host specificity between symbionts and to study the influence of neighbouring plants on ectomycorrhiza development. None of the fungal species had broad host range affinities. A variety of specificity responses were exhibited by the different fungal taxa, ranging from genus‐restricted to intermediate host range. In monoculture, nine species of Rhizopogon (R. arctostaphyli, R, ellenae, R, flavofibrillosus, R. occidentalism R. rubescens, R. smithii, R. subcaerulescens, R. truncatus and R. vulgaris) formed ectomycorrhizas on Pinus ponderosa whereas three Rhizopogon species (R. parksv, R. vimcolor and R. subcaerulescens) formed ectomycorrhizas on Pseudotsuga menziesii. Truncocolumella citrina associated with Pseudotsuga menziesii and Alpova diplophloeus with Alnus rubra. Melanogaster euryspermus and Z. gilkeyae did not form ectomycorrhizas with any hosts. None of the fungi tested developed ectomycorrhizas on Abies grandis, Tsuga heterophylla or Picea sitchensis in monoculture. In dual culture, the same nine Rhisopogun species that formed abundant ectomycorrhizas on Prints pcmderosa formed some ectomycorrhizas on secondary hosts such as Abies grandis, Tsuga heterophylla, Pseudotsuga meitsiesii and Picea sitchensis. Similarly, Truncocolumella citrina formed abundant ectomycorrhizas on Pseudotsuga menziesii and low levels on the secondary hosts Abies grandis, Tsuga heterophytla and Picea sitchensis. Rhizopogon parksii and R. vinicolor only formed ectomycorrhizas on Pseudotsuga menziesii, and Alpova diplophloeus only formed ectomycorrhizas on Alnus rubra. The specificity pattern obtained by using this dual‐culture approach is contrasted with previous pure‐culture synthesis data and is discussed in terms of potential interplant linkages and community dynamics.
Conduit diameter and drought‐induced embolism in Salvia mellifera Greene (Labiatae)
Authors: HARGRAVE K. R. , KOLB K. J. , EWERS F. W. , DAVIS S.D. 
Published: April 2006

SUMMARYThe relationship between conduit (vessel and tracheid) diameter and water‐stress‐induced air embolism was examined using a double staining technique. Comparisons were made between irrigated control plants at water potentials of −13 MPa and water stressed plants at about −8 MPa. Water stress was induced either by natural drought conditions or by laboratory drying of shoots from previously irrigated shrubs. Stem segments were perfused with 0.1 % basic fuchsin to mark the initially conductive conduits, and, following high pressure perfusion of 10 DIM citric acid to remove embolisms, with 0.1% alcian blue to mark the initially embolized conduits. Hydraulic conductance per pressure gradient (kh) was measured before and after embolisms were removed. Diameters of non‐embolized and embolized conduits were then measured microscopically in transverse stem sections. In irrigated controls there was little embolism and mean diameters were not significantly different for embolized SM. non‐emboltzed conduits. For both artificially dehydrated and naturally droughted plants there was a 91% drop in kh due to embolism, and the mean diameter of embolized conduits was about 30 μm vs. 21 μm vs for non‐embolized conduits. With increasing conduit diameter there was an increased probability of embolism. Wider conduits may have larger pores in their pit membranes, thus increasing their vulnerability to water‐stress‐induced embolism. Alternatively, wider conduits may merely have more pits, thus increasing their statistical chances of having a particularly large pore in an air‐exposed pit membrane. Narrow vessels and tracheids provide an interwoven auxiliary transport system that appears to be of importance to transport when many of the wider, more efficient conduits become embolized.
Effects of low temperature on nitrate uptake, and xylem and phloem flows of nitrogen, inSecale cerealeL. andBrassica napusL.
Authors: LAINE P. , BIGOT J. , OURRY A. , BOUCAUD J. 
Published: April 2006

SUMMARYThe effect of low temperature on nitrate uptake and subsequent N translocation and cycling was investigated inSecale cerealeL. andBrassica napusL. transferred to 7 °C for 9 d or kept at a warm temperature (20 °C). Some plants were grown with a split root system and15NO3−, labelled to measure NO3−uptake, root‐to‐shoot and shoot‐to‐root translocation of N from NO3−, taken up. Other plants with single‐root system were subjected to15N pulse‐chase labelling to quantify endogenous N remobilization.Lowering growth temperature from 20 to 7 °C reduced nitrate uptake more strongly in rye (−59%) than in winter rape (−28%). A very large proportion of the nitrate taken up was further translocated to shoots in both species. However, lowering the temperature decreased, xylem N translocation by about 60 and 30% inS. cerealeandB. napus, respectively. Most root N in the latter species came directly from root absorption, while in rye roots the proportions ascribe able to direct root allocation and phloem flow were well balanced. Cold treatment did not significantly modify the imbalance between the two origins. Mobilization of endogenous N from roots to shoot, estimated by pulse‐chase labelling, was limited inB. napusand significant inS. cerealedespite a depressive effect of low temperature. In general, low temperature led to an increase in root N concentration in both species. It is Suggested that low temperature may directly affect the nitrate uptake system, and also that N accumulation in the roots (resulting from greater inhibition of N xylem flow than of NO3−uptake) might increase the inhibition of uptake by higher cellular NO3, and/or amino acid content. The usefulness (for spring growth) of root N accumulation triggered by low temperature is discussed.
Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders associated with subterranean clover produces non‐infective hyphae during sporulation
Authors: PEARSON J. N. , SCHWEIGER P. 
Published: April 2006

SUMMARYSubterranean clover (Trifolium subterraneum L.) inoculated with either Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders or Glomus sp. (WUM 10(1)) was grown in 3 kg of Lancelin sand surrounding a fine mesh bag (< 38 μm) filled with 400 g of steamed sand. The mesh size was chosen to allow hyphae to penetrate but to exclude plant roots. Every week, from 3 wk after planting the original plants, subterranean clover seeds were sown into the sand inside the mesh bags. The last sowing date was 8 wk from sowing of the original plants. The seedlings, with their roots growing inside the mesh bags, were allowed to grow for 3 wk. At that stage the seedlings and the original plants were harvested and their roots assessed for mycorrhizal colonization.The percentage of root length of the original plants colonized by S. calospora decreased from the first harvest onwards, while colonization by Glomus sp. maintained a similar level at all harvests. Seedlings growing in pots whose original plants were colonized by S. calospora had a her percentage of root length colonized at the first two harvests but levels of Colonization decreased substantially thereafter. Seedlings in the Glomus sp. treatment on the other hand, had similar levels of colonization at all but the last harvest. The length of hyphae g−1 soil in the mesh hues increased throughout the experiment for both fungi. However, the length of hyphae in the S. calospora treatment increased at a faster rate. Spore production by S. calospora commenced 7 wk after sowing the original plants.These results indicate that the hyphae produced by S. colospora after internal colonization had stopped increasing were largely non‐infective, and that these hyphae are primarily involved in the production of spores.
Early processes involved in host recognition by arbuscular mycorrhizal fungi
Authors: GIOVANNETTI MANUELA , SBRANA CRISTIANA , LOGI CABLE 
Published: April 2006

SUMMARYPlant species that are hosts of non‐arbuscular mycorrhizas were utilized to investigate the early processes involved in host recognition by arbuscular mycorrhizal fungi. The roots of plant hosts of ecto‐, arbutoid and ericoid mycorrhizas, as well as those of non‐mycorrhizal species, did not elicit the differential morphogenesis that occurred in the hyphae ofGlomus mosseae(Nicol. & Gerd.) Gerd. & Trappe when challenged with the roots of its hosts. In the absence of this morphogenetic response, infection structures were not formed, any further step in the recognition process was hindered, and defence reactions did not occur. The ability of arbuscular mycorrhizal fungi to discriminate their specific hosts from alt other plant species through a recognition process is probably determined by chemical signals.
Sinuous ordinary epidermal cells: behind several patterns of waviness, a common morphogenetic mechanism
Authors: PANTERIS E. , APOSTOLAKOS P. , GALATIS B. 
Published: April 2006

SUMMARYMorphogenesis of sinuous epidermal cells in leaves of the fern Asplenium nidus and the monocotyledonous Cyperus papyrus, petals of the dicotyledonous Begonia lucerna. and in‐vitro‐grown leaves of the fern Adantum capillus‐veneris is controlled by the local differentiation of their walls. In all these cases wall pads, including radial cellulose microfibrils, arc deposited at the junctions of the external periclinal wall with the anticlinal ones. Moreover, in Asplenium nidus, similar wall pads form at the junctions of the internal periclinal wall with the anticlinal ones. The wall pads are connected to anticlinal cellulose microfibril bundles running the whole depth of the anticlinal walls nr part of it. This wall differentiation imposes a highly controlled cell wall expansion, a consequence of which is the waviness of the epidermal cell anticlinal, walls. The pattern of wall reinforcement varies among different species, resulting in differences in the pattern of waviness. Cortical microtubule arrays mirror the orientated deposition of cellulose microfibrils in the epidermal Cells.These findings, derived from plants from different major groups, show a common epidermal cell morphogenetic mechanism depending on radial cellulose microfibrils and cellulose microfibril bundles. The facts that (a) epidermal cell morphogenesis in Adiantum copillus‐veneris leaves grown in vitro differs considerably from that of typical leaves and (b) petal epidermal cells in Begonia lucerna are sinuous, while leaf epidermal cells are not, suggest that this mechanism may he affected by epigenetic factors.
First evidence of myrmecochory in fleshy‐fruited shrubs of the Mediterranean region
Authors: ARONNE G. , WILCOCK C. C. 
Published: April 2006

SUMMARYIn the mediterranean ecosystems of South Africa and Australia, the role of ants in the dispersal of seeds is well known and antagonistic interactions as well as myrmecochory occur. The high prevalence of seed dispersal by ants, relative so that by vertebrates, is viewed as evidence of adaptation to the nutrient poor soils typical of these environments. Ant dispersal has been considered unimportant in the Mediterranean region and, until now, no systematic study of ant‐seed interaction has been undertaken.In the Mediterranean shrubland of Southern Italy the seed content of functioning nests of the antMessor minor(André) has been quantitatively analyzed. The existence in the nest of seeds from shrub species, as well as those of the Fabaceae and Poaceae, suggest that ant dispersal may be much more widespread in the Mediterranean environments than has been realized. A large proportion of the seeds came from fleshy‐fruited shrub species previously reported to be bird dispersed, e.g.Rhamnus alaternusL.,Myrtus communisL.,Smilax asperaL.,Pistacia lentiscusL. andPhillyrea latifoliaL. Analysis of nest mounds showed that, although many seeds bad been partially predated by the ants, a very large number had been collected, transported to the nest and subsequently removed to the mound without damage.Examination of the structure of the fruits and seeds ofR. alaternusandM. communis, and summer fruiting phenology ofR. alaternus, provided further evidence of specific adaptation to ant dispersal. The presence of an elaiosome on the seed is reported for the first time in both specific. Feeding trials showed that ants selectively remove specific diaspores, preferentially collecting the seeds with the elaiosome.
Predicting leaf gas exchange and δ13C responses to the past 30000 years of global environmental change
Authors: BEERLING D. J. 
Published: April 2006

summaryTheoretical developments in our understanding of leaf gas exchange processes and carbon isotope composition (δ13C) mean that it should now be possible to model their responses to global environmental change. Such a model would be of use for process‐based interpretations of historical changes in leaf δ13C and for understanding the global stable carbon isotope balance. This paper describes the development and validation of a model towards this aim. The resulting model is used to simulate changes in leaf photosynthesis, stomatal conductance and δ13C of limber pine (Pinus flexilis) in response to the past 30000 y of global environmental change. The predictions of needle δ13C are in line with reported measurements of δ13C from fossilized Pinus flexilis needles preserved in packrat middens in western USA. Leaf gas exchange predictions show that the increased water use efficiency (WUE) of these trees growing in present‐day environments, relative to the past, was brought about through an increase in photosynthetic rates and a decrease in stomatal conductance. This contrasts with the explanation of the recent (past 200 y) increase in the WUE of temperate and Mediterranean ecosystems inferred from δ13C measurements which are predicted by the model to have arisen largely by a decrease in stomatal conductance in response to increases in the concentration of atmospheric CO2 since the pre‐industrial era.The model as described offers the potential to contribute to our understanding of vegetation effects on the global carbon isotope balance during the glacial periods, and therefore to provide a further constraint on the carbon cycle models used to explain the low concentrations of atmospheric CO2 at these times.
Effect of nitrogen supply on frost hardiness in Calluna vulgaris (L.) Hull.
Authors: CAPORN S. J. M. , RISAGER M. , LEE J. A. 
Published: April 2006

summaryFrost hardiness in Calluna vulgaris (L.) Hull, which had received ammonium nitrate applications in the field for 30 months, was assessed using scores of visible injury and measurements of the rate of total electrolyte leakage from excised shoots following controlled freezing treatments in the laboratory. There was good overall correlation between the two methods (Spearman correlation coefficient 0.77), but leakage measurements were more sensitive than injury scores to the effects of nitrogen. Visible injury was not significantly altered by nitrogen supply (Kruskal‐Wallis non‐parametric test). Ion leakage was analyzed in different ways, using either calculations of the first‐order rate coefficients or expressions of relative conductivity. These analyses produced similar results with respect to the effect of frost and nitrogen. Shoots of nitrogen‐fertilized (40, 80 and 120 kg ha−1 yr−1) C. vulgaris sampled in October 1991 showed significantly (P < 0.05) less leakage after overnight frosts of −15 and −20 °C than did the water‐treated controls. In October the temperature which killed 50% of the shoots (LT50), derived from the leakage data, was raised by at least 4 °C by the highest nitrogen treatments compared with the control plants. Frost treatments to pot‐grown C. vulgaris in November produced similar visible injury to attached and excised shoots from the same plants, both being significantly less damaged by a −18 °C frost after a 7‐month exposure to an NaNO3 mist solution (1.0 mM, pH 4.5) than were water‐misted controls. Ammonium‐mist treatments also marginally reduced frost injury, but the effects were not statistically significant. These results demonstrate that frost hardiness of C. vulgaris in the field can be assessed rapidly and accurately in the laboratory by analysis of electrolyte leakage from excised shoots.
Resistance to an ineffective Frankia strain type in Alnus glutinosa (L.) Gaertn.
Authors: VAN DIJK CORNELIS , SLUIMER ARIA 
Published: April 2006

summaryCharacteristics of natural resistance to the ineffective Frankia strain type AgI‐WD1 were investigated in different progenies of the host species Alnus glutinosa (L.) Gaertn. with the aid of nodulation experiments. This strain type of Frankia was abundant in the soil of an A. glutinosa stand at Voorne, The Netherlands. Soil suspensions from this site produced high numbers of ineffective root nodules on some of the A. glutinosa seedlings used in biotests, but ii significant number of the seedlings did not produce ineffective nodules. Resistance (R) or susceptibility (S) of the seedlings to Frankia strain type AgI‐WD1, as expressed by absence or presence of ineffective root nodules, proved to be persistent in cloned plants of each phenotype. Both R and S‐seedlings were susceptible to effective Frankia strains in the soil suspensions.Variation in nodulation time was examined among cloned plants of S‐seedlings selected for this trait. Average nodulation times of three selected clones were 11, 26 and 39 d, respectively. Relative growth rates of cloned plants showed no relationship with nodulation time.Both R and S phenotypes were present in all seed‐lots of A. glutinosa under study, but the frequency of R phenotypes of seed‐lots from different locations ranged from 24 to 100%. R‐frequencies of seed‐lots of nine trees from a small population of A. glutinosa segregated into two distinct frequency classes which suggested genotypic differentiation of the R‐trait among these trees. A significant correlation was found between R‐frequencies of seedlots from the same trees over successive years.