bluuebunny/crossref_metadata_2025 huggingface dataset:
Photosynthesis in marine macroalgae: evidence for carbon limitation
Authors: Holbrook Gabriel P. , Beer Sven , Spencer William E. , Reiskind Julia B. , Davis Joseph S. , Bowes George
Published: April 2011

During a shipboard expedition to Andros Island (Bahamas), photosynthetic measurements for the macroalgae Cladophoropsis membranacea (Chlorophyta), Dilophus guineensis, Turbinaria turbinata, and Lobophora variegata (Phaeophyta), and Laurencia papillosa (Rhodophyta), taken directly from their marine habitat, showed that only Cladophoropsis was saturated at seawater inorganic carbon levels (2.5 mM). The photosynthetic k0.5 values for inorganic carbon ranged from 1.1 to 3.2 mM. Decreasing the pH at 2.5 mM inorganic carbon, and thus enhancing the CO2 by 30-fold, only slightly increased photosynthesis, suggesting that bicarbonate was the major assimilated form of inorganic carbon. At 2.5 mM inorganic carbon, only Lobophora exhibited a Warburg effect on photosynthesis (49%), but at 0.5 mM, Turbinaria and Laurencia were also inhibited by O2. Ribulosebisphosphate carboxylase–oxygenase appeared to be the predominant carboxylation enzyme, but in Dilophus and Laurencia extracts, its activity was rivaled by phosphoenolpyruvate carboxylase and carboxykinase. Malate pools were detected in Turbinaria and Laurencia, and in the latter they were greater at night than during the day. However, this diel fluctuation was too small to implicate crassulacean acid metabolism. The data indicate that the bicarbonate concentration in seawater is insufficient to overcome O2 inhibition effects on photosynthesis, unless the macroalga has some form of CO2 concentrating system, based on bicarbonate uptake or C4 acid metabolism. In addition, the inorganic carbon in seawater may be a nutrient limiting the photosynthesis and productivity of certain macroalgae.
Dynamics of nitrogen (15N) in decomposing Scots pine (Pinus sylvestris) needle litter. Long-term decomposition in a Scots pine forest. VI
Authors: Berg Björn
Published: April 2011

Labelled (15N) Scots pine (Pinus sylvestris L.) needle litter was incubated in one laboratory and two field experiments and the nitrogen dynamics was followed during the decomposition process. Release of the litter's original nitrogen began immediately after the start of the decomposition process. Simultaneously an immobilization of nitrogen to the litter took place. Very little of the actual turnover of nitrogen in the litter, which was considerable, was reflected by the dynamics of total nitrogen. The dynamics of nitrogen in the lignin fraction (acid-insoluble substance) was partly different from that of whole litter. The dynamics of total nitrogen coincided so that a net loss of total nitrogen started simultaneously both in whole litter and in the acid-insoluble fraction. As the amount of acid-insoluble substance increased in the early stage, the amount of 15N associated to this fraction increased and when a net disappearance of acid-insoluble substance started, a net release of 15N from this fraction started simultaneously. This was interpreted to mean that some of the litter's own nitrogen was transformed into compounds that could be incorporated into humic and fulvic acids (e.g., NH3 or amino acids), which were analytically recorded as acid-insoluble substance.
The role of cell clusters and promeristemoids in determination and competence for caulogenesis by Pinus strobus cotyledons in vitro
Authors: Flinn Barry S. , Webb David T. , Newcomb William
Published: April 2011

Exposure of Pinus strobus cotyledons to a modified Schenk and Hildebrandt medium containing N6-benzyladenine revealed that caulogenic determination was present after 4 days and culminated by day 7. Delaying exposure to N6-benzyladenine by preculture on basal medium for 2 days caused a significant reduction in competence for caulogenesis. Competence declined steadily and explants were incompetent by day 14 of culture. Organized three- and four-celled clusters were present by day 4 in the presence or absence of N6-benzyladenine. The number of cell clusters was enhanced on N6-benzyladenine as a result of an increase of three- and four-celled clusters, plus the development of five- and six-celled clusters. The latter were similar to promeristemoids, and their appearance parallelled increasing levels of caulogenic determination. On growth regulator free basal medium, the number and organization of cell clusters did not change from day 4 to 7. Cell clusters were absent by day 14 on growth regulator free medium, when explants were incompetent to respond caulogenically.
Among-site differences in seedling size, growth, and survivorship in Solidago flexicaulis
Authors: Krannitz Pam G. , Carey C. Ken
Published: April 2011

Seedling and juvenile size, growth, and survivorship in Solidago flexicaulis L. were compared among three sites in southern Ontario in an attempt to evaluate environmental versus population effects on phenotype. In 1983, seedlings at the Eden Mills site were the largest in size, while survivorship was the lowest at the Guelph site ("Dairy Bush Hill"). When seedlings from Eden Mills were transplanted into the other two sites in 1984, among-site differences in growth and survivorship were predominantly due to environmental differences between sites rather than population differences between seedlings from Eden Mills and the seedlings resident at the site. However, at Dairy Bush Hill, seedlings transplanted within the site grew proportionally more than did the seedlings transplanted from Eden Mills, suggesting that the resident population was better adapted to the conditions. Mortality was again greatest at this site in 1984. Size-dependent mortality was not a factor at the Belfountain site, but was important at the other two sites. Herbivory was an important factor determining whether size-dependent mortality was exhibited at a site.
Multiplication of secondary sporidia of Tilletia indica on soil and wheat leaves and spikes and incidence of Karnal bunt
Authors: Dhaliwal Harcharan Singh
Published: April 2011

Secondary allantoid sporidia of Tilletia indica released from mycelial colonies germinate and multiply on sterile soil. They also germinate on surface-sterile leaves and glumes of Karnal bunt-resistant triticale, durum wheat, and bread wheat, indicating that the mechanisms of resistance operate after the germination of sporidia. Inoculated spikes produce infective secondary sporidia in the field. Multiplication of sporidia on soil, leaves, and spikes suggests that the original inoculum from soilborne teliospores may play only a starting role in Karnal bunt epidemics.
Effect of plant growth regulators on growth and reproduction in the fungus Dipodascopsis uninucleata
Authors: Elwy Esmat Elwy Aly
Published: April 2011

Different concentrations of IAA, GA3, 4CPA, kinetin, and 2,4-D were used to study their effect on growth and reproduction in Dipodascopsis uninucleata. Most of the concentrations of IAA, kinetin, and 2,4-D tested promoted growth, whereas GA3 had no effect. All substances used stimulated lateral branch formation and 2,4-D had the greatest effect. Most concentrations of the growth regulators either inhibited or had no effect on ascus formation; only 10−8 M 4CPA, 10−6 M 2,4-D, and 10−6 M GA3 enhanced ascus formation. The percentage of hyphae with aborted gametangia increased in cultures treated with most concentrations of the tested substances except 10−8 M 4CPA, which decreased the percentage of failure. Also, growth regulators either delayed or had no effect on sporulation.
Nutritional requirements for growth of Cryptoporus volvatus
Authors: Pettey Thomas M.
Published: April 2011

Carbon and nitrogen sources were examined in a defined agar medium to determine the nutritional requirements of Cryptoporus volvatus, a Hymenomycete. Good growth was obtained with D-glucose, D-fructose, D-mannose, D-xylose, or dextrin as the carbon source. Good growth was obtained with ammonium sulfate, casein, peptone, glutamic acid, glycine, lysine, serine, or tyrosine as the nitrogen source. In a defined agar medium, C. volvatus exhibited a deficiency for thiamine, and a partial deficiency for biotin, inositol, and pyridoxine.
Flax rust from Linum marginale: variation in a natural host – pathogen interaction
Authors: Lawrence G. J. , Burdon J. J.
Published: April 2011

Melampsora lini, the causal agent of rust disease on flax and linseed (Linum usitatissimum), also occurs on the indigenous Australian species Linum marginale. Forty-five isolates of M. lini collected from L. marginale plants at 21 locations were tested for pathogenicity on 46 lines of L. marginale that originated from 22 sites spanning the same range (approximately 2000 km) covered by the rust isolate collection sites. The results reveal the existence of extensive variation in both host and pathogen. Rust isolates originating from different sites possessed unique virulence patterns in all cases. Among the host lines, 21 different phenotypes were identified. Lines from six sites were susceptible to all isolates, but no line was resistant to all isolates. The results, together with those of a companion study, provide evidence of virulence-gene adaptation of M. lini to different host species and of adaptation on a broad geographic scale within a host species. The rust reaction data suggest that the N gene for resistance in L. usitatissimum also occurs in L. marginale, but otherwise there is no evidence for commonality between the (presumptive) resistance genes in L. marginale and those in L. usitatissimum.
The marine algae of British Columbia, northern Washington, and southeast Alaska: division Rhodophyta (red algae), class Rhodophyceae, order Gelidiales
Authors: Renfrew Dawn E. , Gabrielson Paul W. , Scagel Robert F.
Published: April 2011

The red algal order Gelidiales is represented in the benthic marine algal flora of British Columbia, northern Washington, and southeast Alaska by two genera, Gelidium Lamouroux and Pterocladia J. Agardh. Three species of Gelidium are present, G. coulteri Harvey, G. purpurascens Gardner, and G. vagum Okamura, and one species of Pterocladia, P. caloglossoides (Howe) Dawson. For each species we provide a description of its habit and life history, vegetative and reproductive morphology, and habitat and seasonality. Distributions and representative specimens examined are given. Keys are provided to genera and species where appropriate. Habits, and salient vegetative and reproductive features useful in identifying each species, are illustrated. Gelidium vagum is reported for the first time in the northeast Pacific and appears to have been introduced to the flora from Japan in recent historical time. Its distribution is limited to two islands in the Strait of Georgia. Gelidium purpurascens and Pterocladia caloglossoides are distributed throughout British Columbia and northern Washington, and their ranges are extended north to southeast Alaska. Earlier reports of G. amansii (Lamouroux) Lamouroux, G. crinale (Turner) Lamouroux, G. pusillum (Stackhouse) Le Jolis, G. robustum (Gardner) Hollenberg et Abbott, and G. sinicola Gardner from British Columbia and northern Washington are shown to have been based upon misidentifications of other taxa, and these species are excluded from the flora.
The characterization of the heat-shock response in the arctic plant Saxifraga cernua
Authors: Mason-Apps Susan , Cummins W. R. , Filion W. Gary
Published: April 2011

A rapid increase in the incubation temperature of whole leaves of the arctic plant Saxifraga cernua, grown at 10 or 20 °C, resulted in the noncoordinate expression of 21 novel and (or) enhanced heat-shock polypeptides. Unlike other organisms, the expression of most of the normal polypeptides was not reduced. Incorporation of radioactivity during hyperthermic shifts was similar in both groups of plants at all temperatures investigated, with peak incorporation recorded at 33 °C. The temperature at which the expression of the heat-shock polypeptides was at a maximum level was also 33 °C. Protein synthesis was reduced after a heat shock at 35 °C and completely inhibited at 38 °C. These data suggest that the preshock growth temperature had no effect on the temperature of maximum expression of the heat-shock polypeptides nor the level of protein synthesis during heat shock. Recovery at 10 °C from a 33 °C heat shock was complete within 7–9 h. Extended time periods (up to 24 h) at the shock temperature of 33 °C demonstrated that the heat-shock response in this arctic plant was multiphasic, consisting of an early group and five sets of late heat-shock polypeptides
The paleoecology of a peatland complex in continental western Canada
Authors: Nicholson Barbara J. , Vitt Dale H.
Published: April 2011

The development of the present day vegetation, water chemistry, and landform features of a peatland complex in northeastern Alberta, Canada, was studied through analyses of macrofossils, peat stratigraphy, and inferred profiles. The Mariana Lakes peatland (55°54′N, 112°04′W) contains two geographical areas and four landform features (open lake basin, closed lake basin, water tracks, and forested Sphagnum islands). The surface vegetation was classified using TWINSPAN into four vegetation groups: (i) shrubby, open forest of Salix pedicellaris and Carex paupercula, (ii) closed Picea mariana forest, (iii) Sphagnum lawns of Sphagnum fallax, and (iv) Sphagnum carpets of Sphagnum subsecundum and Menyanthes trifoliata. Within the peatland complex, surface water chemistry ranges from a pH of 3.6 to 6.3, reduced conductivity of 0 to 232 μS, calcium content of 1.1–15.6 mg/L, and magnesium content of 0.6–2.8 mg/L. Peat macrofossils analyzed quantitatively were arranged (by TWINSPAN) into six macrofossil assemblages and were correlated to peat calcium content. Inferred pH profiles derived from linear regression transformations, and inferred-moisture profiles derived from a weighted moisture index, describe natural acidification and water levels. The mean initial inferred pH was at 5.6 ± 0.2, and mean initial inferred moisture indexed at 3.1 ± 0.2. Mean present day inferred pH is 4.9 ± 0.7, and mean moisture is 2.8 ± 0.6. Organic deposition at Mariana Lakes began about 8200 years BP in the closed lake basin. Filling-in of the lake basin produced a floating mat that upon enclosure developed into a poor fen. Paludification of the upper fen began about 6000 years BP, subsequent to terrestrialization in the lake basin, and progressed in a downslope direction. By 2960 years ago the entire drainage path was paludified.
Evolution in sedges (Carex, Cyperaceae)
Authors: Reznicek A. A.
Published: April 2011

Carex is the largest and most widespread genus of Cyperaceae, but evolutionary relationships within it are poorly understood. Subgenus Primocarex was generally thought to be artificial and derived from diverse multispicate species. Relationships of rachilla-bearing species of subgenus Primocarex, however, were disputed, with some authors suggesting derivation from other genera, and others believing them to be primitive. Subgenus Indocarex, with compounded inflorescence units, was thought to be primitive, with subgenera Carex and Vignea reduced and derived. However, occurrence of rachillas is not confined to a few unispicate species, as previously thought, but is widespread. The often suggested connection between Uncinia and unispicate Carex is shown, based on rachilla morphology, to be founded on incorrect interpretation of homology. Uncinia kingii, the alleged connecting link, is, in fact, a Carex. Unispicate Carex without close multispicate relatives probably originated from independent, ancient reductions of primitive, rachilla-bearing, multispicate Carex. The highly compounded inflorescences occurring in subgenus Vignea are hypothesized to represent a primitive state in Carex, and the more specialized inflorescences in subgenus Carex derived from inflorescences of this type. The relationships of subgenus Indocarex, with its unique perigynium-like inflorescence prophylls, remain unclear.
Interspecific and intraspecific variation in pollen morphology in four species of Salix
Authors: Kim K. H. , Zsuffa L. , Kenney A. , Mosseler A.
Published: April 2011

A study of inter- and intra-specific variation in pollen grain polar axis length, pollen equatorial diameter, colpus length, and colpus width in Salix discolor, S. eriocephala, S. lucida, and S. petiolaris demonstrated significant interspecific variation, unequal distances between the species, and various degrees of intraspecific variation. The taxonomic value of the pollen morphology parameters measured was found to vary according to species. A relationship between the pollen parameters measured to the ploidy level of the species is hypothesized. Key words: Salix, pollen, taxonomy.
A numerical taxonomic analysis of the Medicago littoralis – M. truncatula complex
Authors: Small Ernest , Brookes Brenda
Published: April 2011

An analysis of 152 populations of the Medicago littoralis Rhode – M. truncatula Gaertn. complex showed that the two putative species are separable, although all characters studied are overlapping. Some size differences previously used for discrimination did not appear under standard cultivation and are probably based on environmental modifications related to the different habitats of the species. Plants of M. littoralis of Israel, Greece, Italy, and Spain seemed to differ morphologically, the plants of each country being substantially discriminable from those of every other country. However, variation appeared continuous and overlapping and not conducive to formal infraspecific recognition. Plants of M. littoralis of the geographically closer combinations of these countries are more similar morphologically than are plants of the geographically more remote combinations.
Continuous variation within isolates of Typhula ishikariensis bio types B and C associated with habitat differences
Authors: Matsumoto Naoyuki , Tajimi Akitoshi
Published: April 2011

Isolates of the snow mold fungus, Typhula ishikariensis, were collected from seven localities in northern Japan where snow cover conditions differ. The isolates were identified as T. ishikariensis biotype B, which produces large sclerotia, biotype C with smaller sclerotia, and large sclerotial and intermediate forms. Mating experiments with tester monokaryons indicated that all populations were related. Populations from localities with deep, persistent snow cover produced larger sclerotia, which germinated more readily carpogenically (biotype B and the large sclerotial form) than those from localities where snow cover was shorter and intermittent (biotype C). The aggressiveness of the former was more variable, whereas the latter was without exception aggressive. There was no apparent correlation between growth rate at 0 °C and duration of snow cover. It was concluded that biotype C has been selected for localities with ephemeral snow cover, but that biotypes B and C and the related forms do not form distinct populations and should be regarded as a single taxon.
The structure of variation and correlations in Abies amabilis from southwestern British Columbia as assessed through a provenance test
Authors: Funck Philipp , Banerjee Satindranath , Maze Jack
Published: April 2011

Four provenances of Abies amabilis (Dougl.) Forbes from southwestern British Columbia planted in 1980 on southern Vancouver Island were compared using the following variables: leader growth in length over 3 different years, leader diameter, needle lengths on the leader and side branches, and internode length. These variables can all be related to specific developmental phenomena. The four provenances were poorly differentiated in all features, aside from internode length. The low among-provenance differentiation parallels the low among-population, half-sib, and full-sib family variation seen in other conifers. However, in spite of the low among-provenance differentiation, the provenances exhibited different correlations among the variables measured.
A method for measuring hyphal nutrient and water uptake in mycorrhizal plants
Authors: Faber Ben A. , Zasoski Robert J. , Munns Donald N. , Shackel Kenneth
Published: April 2011

A new system was designed that permits examination of long distance transport of water and nutrients through mycorrhizal hyphae without the architectural, nutritional, and physiological differences associated with comparing mycorrhizal and non-mycorrhizal plants. The "rhizobox" system consists of a rectangular box with a chamber where mycorrhizal plants are grown and an outer chamber where hyphae proliferate. The two chambers are separated by root-excluding screens and an air gap. Two slightly different experiments examined hyphal transport. The first experiment demonstrated the difficulties of comparing water use by mycorrhizal and nonmycorrhizal plants because of dissimilarities in plant architecture. The second experiment avoided the problem by comparing intact mycorrhizal plants with plants where hyphae passing to the outer chamber were severed. In the outer chamber, a 5 mM solution of RbCl was injected. Intact mycorrhizal plants transpired 35% more water than plants with severed hyphae in 16 h. The source of transpired water was the outer chamber, as suggested by lower soil moisture in the outer chamber and a higher Rb content in intact plants. This demonstrates an active role in water and nutrient transport by mycorrhizal hyphae, since plants were of a similar nature except for hyphal access to the outer chamber. Key words: water transport, mycorrhizal plants, rhizobox system, nutrient transport, hyphae.
Vegetative compatibility groupings in a local population of Fusarium oxysporum
Authors: Gordon T. R. , Okamoto D.
Published: April 2011

One hundred isolates of Fusarium oxysporum collected from soil in the San Joaquin Valley in 1988 were tested for their ability to form intra- and inter-isolate heterokaryons. Five thousand and fifty isolate combinations were tested for vegetative compatibility, using complementary nitrate nonutilizing mutants. Ninety-eight combinations (2%) produced weakly positive reactions, 248 (5%) produced strong reactions, and 4704 combinations (93%) were negative for heterokaryon formation. This result suggests that anastomosis occurs infrequently among isolates in this population. Isolates were assigned to vegetative compatibility groups based on strong reactions. By this procedure 100 isolates were placed in 29 vegetative compatibility groups. At least one isolate from each of the 29 vegetative compatibility groups was tested and found to be vegetatively incompatible with the muskmelon wilt pathogen, F. oxysporum f. sp. melonis, which occurs in the same field. Each of these isolates also was avirulent to muskmelon in greenhouse pathogenicity tests. Forty isolates of F. oxysporum were collected in 1989 and 32 (80%) were compatible with isolates collected in 1988. The remaining eight isolates represented eight different vegetative compatibility groups. Key words: anastomosis, fungi, heterokaryon.
Process morphology: structural dynamics in development and evolution
Authors: Sattler Rolf
Published: April 2011

Since structure is not completely static, but more or less changing, it appears appropriate to see it dynamically as process. More specifically, each particular structure can be conceived of as a combination of morphogenetic processes. These process combinations may change during development and evolution, during ontogeny and phylogeny. Evolutionary processes, or more specifically modes of morphological transformation, can be seen more dynamically when conceptualized as changes in process combinations. These evolutionary dynamics are illustrated by examples of the evolutionary processes of several schemes such as Zimmermann's scheme (heterochrony, heterotopy, heteromorphy), Takhtajan's scheme (prolongation, abbreviation, deviation) and other processes such as homeosis. Process morphology, which deals with the diversity of plant form in terms of process combinations (instead of structural categories such as root, stem, and leaf), provides a dynamic integration of development and evolution in terms of process combinations and their changes. In other words, the (developmental) dynamics of process combinations representing structures is seen undergoing further (evolutionary) dynamics. Hence, there are (evolutionary) dynamics of the (developmental) dynamics. Key words: plant morphogenesis, evolutionary processes, homology, heterochrony, neoteny, homeosis.
Embryogenèse somatique du cocotier (Cocos nucifera L.) à partir d'explants foliaires: étude histologique
Authors: Buffard-Morel J. , Verdeil J. L. , Pannetier C.
Published: April 2011

Histological studies were carried out at different stages of somatic embryogenesis of coconut (Cocos nucifera L.) from leaf explants. The primary formations resulted from mitotic divisions of perivascular cells. Differentiation of a cambium-like layer insured the growth of nodular calluses. The root origin of some formations was observed. Embryogenic structures appeared on some nodular calluses maintained in culture; initially they were highly meristematic and often developed an epidermis and divided. Then embryo-like formations could be obtained after fragmentation of the cambium-like layer producing meristematic areas. However, modifications of this scheme could be observed: (i) Embryos rapidly developed from a primary callus, and from these embryos, a secondary embryogenesis was induced leading, at the root pole, to a clump of somatic embryos. One of the latter developed a shoot and roots; the regenerated plant was then transferred to the field. (ii) Secondary granulous calluses producing larger quantities of embryogenic structures were formed. This material should prove useful for mastering the technique of developing embryogenic structures. Key words: Cocos nucifera L., histology, somatic embryogenesis, foliar explants.
Release of intracellular glycerol and pore formation in Dunaliella tertiolecta exposed to hypotonic stress
Authors: Fujii Shuhei , Hellebust Johan A.
Published: April 2011

When Dunaliella tertiolecta cells, previously cultured in a 0.5 M NaCl medium, were resuspended in a 0.25 NaCl medium, about 50% of the intracellular glycerol was lost within 2 min. A corresponding amount of glycerol appeared in the medium, while other organic solutes, such as amino acids and sugars, were not detected. These results indicate that intracellular glycerol is rapidly released without significant concomitant cell damage. Rubidum, in the case of rubidium-loaded cells, was also rapidly released to the medium in response to hypotonic shock. Gramicidin, dimers of which form stable membrane pores, caused rapid release of intracellular glycerol, while the ionophore, valinomycin, had no effect. When 0.5 M NaCl-grown cells were resuspended in 0.25 M NaCl medium, intracellular trapping of 14C-glycerol occurred but not of 14C-glucose, 14C-sucrose, or 14C-glycine. However, when 0.5 M NaCl-grown cells were resuspended in 0.05 M NaCl medium, intracellular trapping of small amounts of, 14C-glucose, 14C-sucrose, or 14C-glycine, in addition to considerable amounts of 14C-glycerol, occurred. These results indicate that abrupt hypotonic shocks cause transient formation of small nonspecific pores in the plasma membrane of D. tertiolecta cells and that intracellular glycerol is released to the medium through such nonspecific transient pores. Key words: Dunaliella, hypotonic shock, glycerol release, rubidum, pore formation.
Évolution ontogénique de la tolérance au NaCl chez le soja: comparaison des réponses au sel à deux stades de développement et chez les cals correspondants
Authors: Bourgeais-Chaillou P. , Perez-Alfocea F. , Guerrier G.
Published: April 2011

The ontogenic evolution of tolerance to NaCl was demonstrated for soya: plantlet biomass, 6 days after germination, was already reduced in the presence of 25 mM NaCl, whereas adult plants (after 28 days of culture) were barely affected in the presence of 100 mM NaCl. Calluses from embryos showed the same level of sensitivity as plantlets; in contrast, calluses from roots showed a higher sensitivity than those obtained from stems or leaves. The soja response to salt (at the plantlet stage, at the adult plant stage and in undifferentiated callus cells) is not dependent on the concentrations of Cl, Na, or on the osmolarity due to (in)organic solutions; it is the expression of cellular mechanisms (the degradation of soluble proteins, as well as peroxydase and invertase potentials, are indicative of salt sensitivity) and of the requirement of tissue organization. This organization promotes the regulation of some enzymes (nitrate reductase, glutamine synthetase, and glutamate synthase, among others) and the evolution of nonenzymatic functions: the phosphoenolpyruvic carboxylase seems to be more related to the control of amino acid synthesis in adult plants and to the heterotrophic use of carbon by plantlets as well as by calluses. Therefore, amino acids and sugars play a major role in the adaptative mechanisms at these ontogenetic stages. Key words: osmotic adjustment, tissue culture, regulation, salinity, soya. [Journal translation]
Drosera rotundifolia growth and nutrition in a natural population with special reference to the significance of insectivory
Authors: Stewart Jr. C. Neal , Nilsen Erik T.
Published: April 2011

The impact of nutrient addition on growth and nutrient accumulation in Drosera rotundifolia was studied in a field population. Experiments were performed by exclosing insects and (or) adding phosphorus and (or) nitrogen to soil. Drosera rotundifolia did not significantly benefit from insect capture nutritionally or energetically in native or nutritionally enhanced soils. Added nutrients to the soil or supplemental foliar insect feeding decreased phosphorus retention in hibernacula by 50%. Nutrient additions reduced D. rotundifolia vegetative growth in both N and P addition treatments. In addition, allocation to reproduction (inflorescences) decreased by 98% when N was added to the soil. Phosphorus retention in hibernacula was especially high in plots in which no nutrients were added via the soil or by insect applications. Although not statistically significant, flower stalk density and floral biomass were greater where insects were available to plants. The data from this study indicate that insectivory has little impact on growth of field grown D. rotundifolia. This species is adapted to low nutrient availability and nutrient enhancement reduces growth. Indices of nutrient retention suggest that phosphorus is conserved more than nitrogen and therefore may be an important limiting nutrient. Key words: insectivory, nitrogen, phosphorus, sundew.
The apoplastic permeability of root apices
Authors: Enstone Daryl E. , Peterson Carol A.
Published: April 2011

The apoplastic permeability of regions near the root tips of two nonexodermal species (Vicia faba L. and Pisum sativum L.) and three exodermal species (Zea mays L., Allium cepa L., and Helianthus annuus L.) was investigated with a berberine – thiocyanate tracer procedure. In regions of nonexodermal roots where the endodermis was mature, the walls of the epidermis and cortex were permeable; inward diffusion of the tracers was arrested at the endodermis. In regions of exodermal roots where the exodermis was mature, the apoplast was permeable only up to the anticlinal walls of the exodermis; in regions where the exodermis was immature but the endodermis was mature, the cortex was permeable up to the Casparian band of the endodermis. In root tips of both exodermal and nonexodermal species, berberine penetration into the meristem was greatly restricted. In some species there were additional areas adjacent to the meristem into which berberine movement was similarly restricted. It is concluded that even though root apices lack suberized structures, these zones are nevertheless partially apoplastically isolated from the external environment. Key words: apoplastic transport, berberine, fluorescent tracer, root tips.
Genetic structure after forest fragmentation: a landscape ecology perspective on Acer saccharum
Authors: Foré Stephanie A. , Hickey R. James , Vankat John L. , Guttman Sheldon I. , Schaefer Robert L.
Published: April 2011

Fragmentation of large expanses of forests into small stands has isolated local populations of organisms. Sugar maple (Acer saccharum) was used to determine if the degree of forest fragment isolation affects genetic diversity and structure of local populations. Genetic data were collected from canopy (prefragmentation) and juvenile (postfragmentation) individuals in 15 woodlots. Genotypes were inferred from phenotypic enzyme patterns of seven enzymes representing eight loci extracted from cambium and resolved with starch gel electrophoresis. Analyses of allelic data indicated that genetic diversity was not significantly different between juvenile or canopy subdivisions, or between woodlots with low and high degrees of isolation. Genetic differentiation among woodlots was significantly greater for the canopy than for the juvenile subdivision. Estimates of gene flow indicate that postfragmentation gene flow rates are higher than prefragmentation rates. Apparently, sugar maple's high potential for long-distance gene flow is enhanced by altered wind flux across a fragmented landscape. The results also show that forest fragmentation does not always result in greater isolation of local populations. Key words: sugar maple, gene flow, conservation, isolation, allozymes.
Ultrastructural studies of ascospores of some Remispora species
Authors: Manimohan P. , Jones E. B. G. , Moss S. T.
Published: April 2011

Ascospore appendage ultrastructure is described for Remispora crispa, Remispora quadriremis, and Remispora stellata. The polar appendages are exuded through pores in the polar episporium and become extensions of the episporium. This form of appendage is compared with that reported for other species of Remispora and with other members of the Halosphaeriales. Key words: ascospore appendage, marine ascomycetes, taxonomy, ultrastructure
Studies of mature seeds of eleven Pinus species differing in seed weight. I. Element concentrations in embryos and female gametophytes
Authors: West M. M. , Lott J. N. A.
Published: April 2011

Neutron activation analysis and spectrophotometric phosphorus analysis gave quantitative determinations of elements in female gametophytes and embryos from mature seeds of 11 Pinus species. High concentrations of P, K, Mg, and S and significant concentrations of Cl, Ca, Mn, Zn, and Fe were detected in both tissues. Within each species of Pinus, the total mineral nutrient concentrations in haploid female gametophyte samples were similar to total mineral nutrient concentrations within diploid embryo samples. Seed size and weight varied greatly among the 11 species of Pinus investigated. P and Mg concentrations in female gametophytes and (or) embryos were not correlated with seed weight. Interspecific seed weight was negatively correlated with female gametophyte concentrations of S, Ca, Zn, and Fe, and also negatively correlated with embryo concentrations of Mn, Zn, and Fe. Interspecific seed weight was positively correlated with embryo concentrations of K and Cl. On a per tissue basis, larger seeded species contained higher total amounts of all the measured elements than small-seeded species. Key words: Pinus, seed weight, female gametophyte, neutron activation analysis, phosphorus analysis, mineral nutrient stores.
The influence of surfactants on transpiration of strawberry leaves
Authors: Kubik Marek , Michalczuk Lech
Published: April 2011

Surfactants introduced into strawberry (Fragaria grandiflora Duch. cv. Redgauntlet) leaves in doses of 5.5 × 10−4 – 5.5 × 10−2 μmol per leaf blade decreased the transpiration rate of treated leaves regardless of the electrical charge brought to the membranes. A 5.5 × 10−2 μmol dose of surfactants applied during constant illumination caused almost the same decrease in transpiration as a dose of 7.5 × 10−4 μmol of abscisic acid. Surfactants also accelerated the decrease in transpiration in plants grown in the dark, and there was a consistent rate of solute efflux from guard cells. Fusicoccin applied to plants under the influence of surfactants or abscisic acid caused a sustained increase in the transpiration rate. Mannitol and sucrose caused a temporary increase in transpiration rate. KCl increased transpiration when applied after abscisic acid but decreased transpiration when applied after surfactants. These observations suggest that surfactants and abscisic acid influence the guard cell membrane in different ways and that the electrical charge introduced on the plasmalemma surface is not essential in the regulation of stomatal aperture. Key words: abscisic acid, strawberry, surfactants, transpiration.
Molecular approaches to the manipulation of carbon allocation in plants
Authors: Blakeley S. D. , Dennis D. T.
Published: April 2011

In plants, sucrose is the end product of photosynthesis and is converted to a wide variety of storage compounds in tissues such as seeds and tubers. The allocation of carbon from sucrose to the various metabolic pathways leading to these products will determine the quantity of each synthesized in the respective storage organs. If the level of the enzymes involved in the allocation of carbon could be changed by genetic manipulation, it is probable that the relative yields of the various storage products can also be altered. The initial breakdown of sucrose occurs in the cytosol of the cell. Many biosynthetic pathways, however, including those involved in the synthesis of storage products such as fatty acids, starch, and amino acids, occur in the plastid. The distribution of carbon substrates for these processes will be determined, to a large extent, by the flux of carbon through the glycolytic pathways found in both the cytosolic and plastid compartments. This article will discuss the importance and consequences of compartmentation, review the extent of our understanding of glycolysis and other enzymes and pathways regulating carbon allocation, and will speculate on the potential for the genetic manipulation of these pathways. Key words: genetic manipulation, carbon allocation, metabolism, glycolysis.
Control of pressure-chamber and rehydration-time effects on pressure–volume determination of water-relation parameters
Authors: Abidine Abdenbi Zine El , Bernier-Cardou Michèle , Bernier Pierre Y. , Plamondon André P.
Published: April 2011

In a study of the seasonal variation of water-relation parameters in four black spruce (Picea mariana (Mill) BSP) populations, the weekly derivation of 32 pressure–volume curves with the sap-expression method between May and October required the simultaneous use of four pressure chambers and variable sample rehydration periods. Pressure chamber had a significant effect on three of the five characteristics studied: symplastic water fraction, maximum modulus of elasticity, and osmotic potential at full turgor. These effects were constant over the growing season. On average, rehydration-time effects were significant for all water-relation parameters except osmotic potential at turgor loss point, but they were not constant over sampling dates. Variations in water-relation parameters due to chambers and rehydration times were controlled and estimated through an experimental design based on the Latin square, which allowed precise comparisons among populations despite the increase in variability due to these two factors. The efficiency of the design varied between 110 and 142% relative to a completely randomized design in which neither chambers nor rehydration times would have been controlled for. Key words: black spruce, populations, experimental design.
An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). I. Tetrad to early binucleate microspore stage
Authors: Polowick P. L. , Sawhney V. K.
Published: April 2011

Microspores undergo considerable ultrastructural changes between the tetrad and early binucleate microspore stages of microsporogenesis in tomato (Lycopersicon esculentum). Pollen wall deposition began late in the tetrad stage, and by the early microspore stage a lamellar foot layer and tectum were deposited. Sculpturing of the tectum was evident by the early binucleate microspore stage. Dictyosomes and vesicles were abundant during the period of pollen wall formation. Plastids were associated with the endoplasmic reticulum (ER) to form plastid–ER complexes, from the late tetrad to the vacuolate microspore stage. At the vacuolate microspore stage, endoplasmic reticulum independent of plastids was also observed, and at the early binucleate microspore stage ER was not associated with plastids. Free ribosomes were evenly distributed throughout the cytoplasm until the vacuolate microspore stage when they were organized into polysomes. Mitochondria were spherical to ellipsoid, with an electron-dense matrix and swollen cristae, until the early binucleate microspore stage when they were highly elongate and became convoluted. Key words: Lycopersicon esculentum, microsporogenesis, pollen development, tetrads, tomato, ultrastructure.
Pollination in alpine Norway: flowering phenology, insect visitors, and visitation rates in two plant communities
Authors: Totland Ørjan
Published: April 2011

Pollination studies in European alpine communities are few. The objective of this study was to describe the pollination ecology in two alpine plant communities at Finse, southwestern Norway. Because of late snowmelt and early winter at Finse, the time available for flowering and seed maturation is restricted. Flowering was concentrated at the beginning of the season in both communities, and large overlaps in flowering time were found for most species. In one of the communities, flowering peaks were significantly clumped, whereas in the other they were randomly distributed through the season. However, in this community, five insect-pollinated species flowered simultaneously early in the season. Diptera almost exclusively dominated the visitor assemblage. Most plant species pairs had high overlaps in flower visitor species. Species flowering simultaneously attracted the same visitor species. In one community, eight species pairs flowered sequentially and shared visitors. Visitation rates were highest at the lowest elevated site. The results are compared with those obtained in other alpine areas. It is argued that selection for an early flowering is probably stronger than selection pressures resulting from interspecific interactions. Key words: alpine, Diptera, flowering phenology, flower visitors, season length, visitation rate.
Ectomycorrhizal fungi associated with aspen on three sites in the north-central Rocky Mountains
Authors: Cripps Cathy , Miller Jr. O. K.
Published: April 2011

Sporocarps of ectomycorrhizal fungi were collected over three field seasons in aspen (Populus tremuloides) stands in the Rocky Mountains, 1800–2000 m above sea level. The two sites in southwestern Montana and one site in southeastern Idaho vary in size, age of trees, type of soil, drainage patterns, and to a certain extent, climatic conditions. In all, 43 species of ectomycorrhizal fungi were found associated with aspen. The Cortinariaceae were a dominant component of the mycoflora, including at least seven species of Inocybe. Fourteen species of ectomycorrhizal fungi, including Leccinum aurantiacum, occurred on all three sites in association with aspen, and the dominant or characteristic mycorrhizal species varied among sites. The early colonizers Inocybe lacera and Laccaria laccata, which were previously reported on acidic soil, were characteristic of the smelter-acidified, nutrient-poor soil of the site near Butte, Montana. Late stage fungi such as Amanita muscaria and Lactarius controversus were more prevalent in the older, undisturbed aspen stands. Key words: aspen, ectomycorrhizal fungi, mycorrhizal fungi, Populus tremuloides.
A preliminary account of endolithic algae of limestone cliffs of the Niagara Escarpment
Authors: Gerrath J. F. , Gerrath J. A. , Larson D. W.
Published: April 2011

This paper reports the discovery of endolithic algae from vertical limestone cliffs associated with the Niagara Escarpment, southern Ontario, Canada. The endolithic habitat forms a distinctive dark green layer 1–3 mm below the surface of the porous dolomitic limestone. Samples of the algal layer were isolated from freshly cleaved rock samples using sterile probes and grown on a solid (agarized) standard algal mineral medium supplemented with soil extract. A diverse assemblage of organisms grew on the agar plates, including bacteria, fungi, blue-green algae (cyanobacteria), green algae, yellow-green algae, and occasionally the protonemata of mosses. Isolated algae belong to unicellular, colonial, and filamentous morphological types. Algal genera that have been identified include seven blue-green algae (Cyanophyta or Cyanobacteria), six green algae (Chlorophyta), and one yellow-green alga (Xanthophyceae). Six of the algal genera found in Ontario rocks also occur inside rocks of the Colorado plateau in northern Arizona, and one genus also occurs inside Antarctic rocks. Key words: terrestrial algae, endolithic organisms, limestone cliffs, Niagara Escarpment, southern Ontario.
Effects of detritus accumulation on the growth of Scirpus maritimus under greenhouse conditions
Authors: Clevering Olga A. , Van der Putten Wim H.
Published: April 2011

The effects of accumulation of dead belowground plant parts (detritus) of the emergent macrophyte Scirpus maritimus on the growth of this species were studied under greenhouse conditions. In the first experiment, the growth of S. maritimus seedlings decreased when the thickness of the detritus mat, covered by a layer of sediment, was increased. The position of a 5 cm thick detritus mat in a 15-cm column filled up with sediment had only a minor effect on the growth of this species. In the second experiment, fragmentation of detritus turned out to increase the growth-reducing effects found in the first experiment. Unfertilized seedlings with the lowest dry mass proportionally allocated most dry matter to their roots. The supply of nutrients either did not or only partly compensated for differences in plant growth among substrate types. In all instances the supply of nutrients strongly reduced the proportional dry matter allocation to roots, whereas differences in nutrient concentrations in plants diminished. In most instances the soil redox potential indicated a reduction of iron, but iron concentrations in the shoots never reached toxic levels. The most likely explanations for the poor growth of S. maritimus in its own detritus are the release of toxic compounds into the substrate and deficiency of oxygen to the roots due to reduced substrate conditions. Key words: freshwater lakes, emergent macrophytes, organic matter, degeneration.