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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 9 (1956), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 266 (1977), S. 282-282 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ACCORDING to Bowling's malate-switch hypothesis1 of stomatal action, the pH changes in the guard cell create a gradient of monovalent malate towards either guard cells or epidermal cells causing a diffusion of K+ (bound to monovalent malate) along with the gradient. His theory is based on (1) ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 376 (1995), S. 473-473 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FISHER ETAL. REPLY - The comments by Davidson et al. about the rainforests and the wooded communities of the cerrados are not relevant to our paper1, which was about the 35 million hectares (MHa) of treeless grasslands in Colombia and Venezuela and the 50 MHa (24%) of the cerrados of ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 22 (1969), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Leacthing the excised embryonic-axes from dormant groundunt (Arachis hypogaea) seeds resulted in their growth. However, their growth was stunted compared to that of after-ripened ones. It is attributed to (1) the lower amount of gibberellin-like substances in the dry, dormant embryonic-axes than in the after-ripened ones, and (2) the inability of the former to sythesise tbe tibberetllin as indicated by the lower content compared to the after-ripened ones kept in water. Exogenousty supplied GA3 (0.1 mg/1) increased both the endogenous gibberellin and growth of the dormant, leached embryonic-axes to the level of after-ripened ones.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Savannas occupy some 250 million hectares (Mha) of South America, mainly in Brazil (200 Mha), Colombia (20 Mha) and Venezuela (12 Mha). They are used for extensive cattle ranching on the native forage, although in Brazil cropping with maize and soybeans (now 12 Mha) and introduced ...
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5036
    Keywords: biomass partitioning ; nutrient uptake ; plant adaptation ; soil acidity ; somaclonal variation ; Stylosanthes guianensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Somaclonal variation offers the possibility to obtain changes in one or a few characters of an otherwise outstanding cultivar without altering the remaining, and often unique, part of the genotype. It has been shown to be heritable for some species. A check line of Stylosanthes guianensis (Aubl.) Sw., CIAT 2243 and 14 somaclones in the R4 generation, selected after three generations from the original 114 plants regenerated from callus cultures, were used in a glasshouse trial. The main objective of the study was to evaluate the physiological basis of the differences in agronomic performance of certain somaclones over the check genotype when grown in a sandy loam acid soil at low or high fertility level. Measurements at the time of harvest (170 days of plant age) included dry matter distribution between shoot and roots, leaf area production, nutrient levels in soil and plant parts, and uptake of nutrients from soil. Somaclones differed with the check genotype in terms of (i) partitioning of fixed carbon between the shoot and roots; (ii) root biomass production and (iii) uptake of nitrogen and phosphorus. Positive relationships were found between total nitrogen uptake and total biomass, and total phosphorus uptake and total biomass, and total phosphorus uptake and total nitrogen uptake. The results of this study provide an insight into the potential use of somaclonal variation for the improvement of plant adaptation to acid soil conditions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 31 (1969), S. 188-192 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Groundnut (TMV-2) seeds treated with ‘25 ppm boron’ solution germinated more quickly than the seeds supplied with deionized water. The borontreated seedlings also elongated rapidly in the initial phase of the growth even though all their different organs contained excess boron contents (with chlorosis in the leaves) than those of the control seedlings. However, the accentuation in the growth of treated seedlings was proceeded only upto a certain period (12 days after treatment); but further stimulation in the later phase of the growth was almost inhibited with ever increasing amounts of boron in the hypocotyl, plumule and leaves (which were severely chlorotic) and even brought about a deleterious effect on the total growth at the end of 21 days when compared to the controls.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5036
    Keywords: Brachiaria decumbens ; C3 legume ; C4 grass ; nitrogen mineralization ; Pueraria phaseoloides ; soil organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil carbon distribution with depth, stable carbon isotope ratios in soil organic matter and their changes as a consequence of the presence of legume were studied in three 12-year-old tropical pastures (grass alone —Brachiaria decumbens (C4), legume alone —Pueraria phaseoloides (C3) and grass + legume) on an Oxisol in Colombia. The objective of this study was to determine the changes that occurred in the13C isotope composition of soil from a grass + legume pasture that was established by cultivation of a native savanna dominated by C4 vegetation. The13C natural abundance technique was used to estimate the amount of soil organic carbon originating from the legume. Up to 29% of the organic carbon in soil of the grass + legume pasture was estimated to be derived from legume residues in the top 0–2-cm soil depth, which decreased to 7% at 8–10 cm depth. Improvements in soil fertility resulting from the soil organic carbon originated from legume residues were measured as increased potential rates of nitrogen mineralization and increased yields of rice in a subsequent crop after the grass + legume pasture compared with the grass-only pasture. We conclude that the13C natural abundance technique may help to predict the improvements in soil quality in terms of fertility resulting from the presence of a forage legume (C3) in a predominantly C4 grass pasture.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5036
    Keywords: litter decomposition ; Oxisols ; phosphorus fractionation ; root distribution ; root length ; savannas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil-plant processes which enhance P acquisition and cycling in low-P Oxisols were investigated in a crop rotations and ley pasture systems experiment on the Colombian eastern plains. Comparison of rooting patterns indicated that, despite low available P at depth, there are important differences in root size and distribution among native savanna, introduced forage and crop species which affect their ability to acquire P from these soils. Differences in crop/forage residue decomposition and P release rates suggest that managing the interaction of residue with soil may help slow P fixation reactions. Despite these differences, soil P fractionation measurements indicate that applied P moves preferentially into labile inorganic P pools, and then only slowly via biomass production and microbes into organic P pools under both pastures and crop rotations.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 229 (1991), S. 177-185 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study was designed to characterize the granulosa cell subpopulations derived from rats in which ovarian growth was induced by diethylstilbestrol (DES) or in which growth and differentiation was induced by pregnant mare's serum gonadotropin (PMSG). In the DES model, immature rats were given two separate injections of 2 mg DES/rat s.c. on 25 and 26 days of age and were killed 24 hr after the second injection. In the PMSG model, rats on day 28 were given 8 IU of PMSG s.c. and were killed 54 hr later. Granulosa cells were isolated from the ovaries, separated on a continuous Percoll density gradient, and divided into 12 fractions. The cells in each fraction were cultured in the presence of androstenedione with or without 20 ng/ml of follicle-stimulating hormone (FSH) and estradiol and progesterone in the incubation medium were measured. In DES-treated rats, granulosa cells in fractions 4 and 5 and fractions 9 and 10 contained about 30-40% of total cell yield and showed high steroidogenic potential. Granulosa cells from fractions 6, 7, and 8, which represent 55-60% of total cell yield, produced relatively low amounts of steroids on a per-million-cell basis. FSH was required for the stimulation of steroidogenesis. In granulosa cells from the PMSG treated rats, aromatase activity appeared maximally induced and incubation with FSH in vitro did not bring about any further increase. However, in vitro incubation with FSH was required for progesterone production. Furthermore, the granulosa cells from the PMSG treated rats also showed much more active estradiol and progesterone synthesis in fractions 9-12 as compared with lower density fractions. These studies suggest functional heterogeneity of granulosa cell populations in their response to FSH-induced steroidogenesis. In addition, it was observed that in both models, there are two major populations of granulosa cells as evidenced by light and electron microscopy. The functional role of small and large granulosa cells in steroidogenesis is unclear; further studies are in progress.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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