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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Experiments were carried out on Pinus radiata (D. Don) trees grown as cuttings from clonal parent stock. Some of these trees were about 0.4 m high while others were about 5 m high; all were grown in containers. The stem diameters at the tops and at the bottoms of the large trees, rates of photosynthesis, and needle water potentials were measured both when the trees were well watered and as they dehydrated after water was withheld. The water potentials of well-watered plants was highest in the small trees and lowest at the top of the large trees. When water was withheld, photosynthesis was in most cases unaffected by a small reduction in water potential, but the rate of photosynthesis fell as water potentials declined further. The stems of the large trees expanded at a constant rate when the trees were well watered and for part of the dehydration period, while subsequent stem shrinkage and the fall in photosynthesis both occurred at approximately the same time.Water potentials increased little in the 24 h after rewatering, and significant rates of photosynthesis were not measured until 2 or 3 d later while renewed stem expansion was not measured until 2 d after rewatering.Water deficits reduced the lumen diameter of newly matured stem tracheids, but increased the thickness of their walls. After 1 month of water potentials of about −2.4 MPa, tracheid lumen diameter and wall thickness were both much reduced, and this reduction continued in tracheids maturing shortly after rewatering.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Stomatal conductance and needle water potential of P. radiata clones were measured after 2, 5 and 8 months on plants grown in controlled environment rooms with markedly different water vapour saturation deficits (D). Conductance was significantly lower at high D, but water potential differences between treatments were not significant. When trees were moved between treatments most of the changes in conductances occurred within 2 h, with residual changes after 24 h. Water potentials were not different 24 h after the trees were moved. The effects were completely reversible.Transpiration rates of individual trees were highest in the high D treatment and lowest in the low D treatment. They were not linearly related to D because of decreasing conductance with increasing D.Height growth, diameter growth and foliage areas were not significantly different between treatments. Tracheid lumen diameters tended to be larger in trees grown at higher D although treatment differences were not significant.There were significant clonal differences in shoot conductance and tracheid dimensions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 38 (1982), S. 1249-1251 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ecdysterone has been identified in the schistosomiasis vectorBiomphalaria glabrata Say and inHelix aspersa Müller as well as inLymmaea stagnalis L. by chromatography, bioassay, radioimmunoassay, derivatization and by mass spectroscopy. Analysis of the food, faeces and hepatopancreas suggest that the sterol is derived from the diet. The probable function of ecdysterone in relation to calcification of the shell is discussed in this paper.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 75 (1983), S. 427-434 
    ISSN: 1573-5036
    Keywords: Absorption ; Availability ; Copper ; Extractable Cu ; Roots ; Soils ; Transport ; Trifolium repens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The absorption, distribution and concentration of Cu in white clover were examined in plants grown on 21 soils under controlled environment conditions, and the results compared with those from a previous study with perennial ryegrass. The clover absorbed more Cu and, in general, had higher concentrations in the shoots over six successive harvests than did the ryegrass. However, concentrations of Cu in the roots, and the proportion of the total plant Cu found in the roots were lower with the clover. The concentration of Cu in the shoots of the clover, and the total amount in shoots plus roots, respectively, were correlated with the concentration of Cu extracted from the soils by 0.05M EDTA (r=0.473 and 0.700), by 0.005M DTPA (r=0.610 and 0.638) and by 1.95 per cent HNO3 (r=0.627 and 0.699). Some of these correlations were improved slightly when the concentrations of extractable Cu were adjusted for soil pH. The exploration of the soils by root extension appeared to be less important in the acquisition of Cu by the clover than it was for the ryegrass.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 60 (1981), S. 275-286 
    ISSN: 1573-5036
    Keywords: Absorption ; Availability ; Copper ; Extractable-Cu ; Lolium perenne ; Nitrogen ; Roots ; Soils ; Transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The absorption and transport of Cu were studied in perennial ryegrass grwon on 21 soils under controlled environment conditions. Neither the concentration, nor the total amount, of Cu in the shoots was related to available Cu in the soils as assessed by extraction with 0.05M EDTA, 0.005M DTPA, or 1.95 per cent HNO3. The concentration in the roots and, more especially, absorption per unit weight of root (i.e. μg Cu g dry wt−1) were, however, highly correlated with available soil Cu. This suggests that, unless the extent of exploitation of the soil by roots is taken into account, measurements of available Cu will not be effective in predicting uptake by plants. On average, 63 per cent of the Cu absorbed by the roots was retained in the roots, and variation in the proportion retained was related to the transport of nitrogen from roots to shoots. On some soils the concentrations of N and Cu in the shoots were significantly correlated, and variation in N concentration accounted for a considerable proportion of the variance in the Cu concentration at later harvests. The relative importance of the measured soil (pH, organic matter) and plant (dry weight, N content) factors changed markedly over 6 successive harvests.
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  • 6
    Publication Date: 1984-12-01
    Description: The relationships between foliage area and sapwood area between trees and within the crowns of 20 Piceasitchensis (Bong.) Carr., provenance Queen Charlotte Island, British Columbia (10 in a control plot and 10 in a plot fertilized with potassium and phosphorus 8 years before harvest) and 10 Pinuscontorta Dougl., provenance Ladysmith trees were examined using a physiological analysis based on Darcy's law. Foliage area index on the fertilized P. sitchensis plot was higher than on the control. The variation of foliage area density with depth in the canopies followed a normal distribution. Relationships between foliage area and sapwood basal area were linear but the slopes were different for the two species. There was no significant difference between the control and fertilized P. sitchensis trees. The relationship between foliage area and the product of sapwood area and permeability was linear and data from the three plots fell on the same line. Sapwood area, permeability, and their product decreased with depth through the crowns of the trees. Within the crowns, relationships between cumulative foliage area and sapwood area, and between cumulative foliage area and the product of sapwood area × permeability were different with species and treatment. A single linear relationship resulted when the product of cumulative foliage area above an internode × the internode length was plotted against sapwood area × permeability for the internode. This suggests that it is the drop in potential across a node and internode rather than the gradient of potential across the internode that is related to the flux of water through tree crowns. The data support the hypothesis that the relationship between foliage area and sapwood area depends on permeability of the sapwood and the local climate through its influence on transpiration rate, particularly via average water vapour pressure deficit of the air and stomatal conductance.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 1984-10-01
    Description: Stomatal conductance was measured with porometers in two plots of Pinussylvestris L. with markedly different tree spacings (plot 1, 608 stems ha−1; plot 2, 3281 stems ha−1), and hourly rates of transpiration were calculated using the Penman–Monteith equation at intervals throughout one growing season. Stomatal conductance varied little in relation to height or age of foliage. There was a linear decrease in canopy conductance with increasing water vapour pressure deficit of the air. Transpiration rates on both plots increased during the summer (maximum 0.3 mm h−1); rates on plot 1 were always lower (ca. 0.7 times) than on plot 2. Needle water potentials were similar throughout the season and only slightly lower on plot 1 than on plot 2. The mean hydraulic resistance of the trees on plot 1 was 2.4 times that on plot 2. The results support a hypothesis that considers the changes in transpiration rate, conducting cross-sectional area, canopy leaf area, water potential, and hydraulic resistance following thinning as a set of homeostatic relationships.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 1982-10-01
    Print ISSN: 0014-4754
    Topics: Biology , Medicine
    Published by Springer
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  • 9
    Publication Date: 1980-12-01
    Description: The Penman–Monteith equation was used with measured values of stomatal conductance and leaf area, in conjunction with weather station measurements of net radiation, vapor pressure deficit, and wind speed to calculate the transpiration rates of two Scots pine (Pinussylvestris L.) stands of widely different densities. Transpiration was compared with water uptake estimated from 32P radioisotope movement through trees of known conducting area and water content. Uptake consistently lagged behind transpiration throughout the day. From dawn to dawn, however, uptake and transpiration were in close agreement as a result of recharge during the night.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
    Publication Date: 1981-06-01
    Print ISSN: 0032-079X
    Electronic ISSN: 1573-5036
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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