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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Effects of the current (38 Pa) and an elevated (74 Pa) CO2 partial pressure on root and shoot areas, biomass accumulation and daily net CO2 exchange were determined for Opuntia ficus-indica (L.) Miller, a highly productive Crassulacean acid metabolism species cultivated worldwide. Plants were grown in environmentally controlled rooms for 18 weeks in pots of three soil volumes (2 600, 6 500 and 26 000 cm3), the smallest of which was intended to restrict root growth. For plants in the medium-sized soil volume, basal cladodes tended to be thicker and areas of main and lateral roots tended to be greater as the CO2 level was doubled. Daughter cladodes tended to be initiated sooner at the current compared with the elevated CO2 level but total areas were similar by 10 weeks. At 10 weeks, daily net CO2 uptake for the three soil volumes averaged 24% higher for plants growing under elevated compared with current CO2 levels, but at 18 weeks only 3% enhancement in uptake occurred. Dry weight gain was enhanced 24% by elevated CO2 during the first 10 weeks but only 8% over 18 weeks. Increasing the soil volume 10-fold led to a greater stimulation of daily net CO2 uptake and biomass production than did doubling the CO2 level. At 18 weeks, root biomass doubled and shoot biomass nearly doubled as the soil volume was increased 10-fold; the effects of soil volume tended to be greater for elevated CO2. The amount of cladode nitrogen per unit dry weight decreased as the CO2 level was raised and increased as soil volume increased, the latter suggesting that the effects of soil volume could be due to nitrogen limitations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 81 (1991), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nocturnal acid accumulation, water content, osmotic pressure (π), and nonstructural carbohydrates were determined in the chlorenchyma and the water-storage parenchyma of Opuntia ficus-indica (L.) Miller for well-watered plants and those subjected to drought for 15 weeks. During the 15-week drought, total cladode water content decreased by 57%, the water-storage parenchyma losing a greater fraction of water than the chlorenchyma, which most likely helped maintain nocturnal acid accumulation in the latter tissue. Despite the preferential water loss from the water-storage parenchyma, it had a lower π than the chlorenchyma over the 15 weeks of drought, suggesting a substantial decrease in osmotically active solutes in the water-storage parenchyma. Also, the measured π increases of both tissues were much less than those predicted based on the loss of water during drought and the initial content of osmotically active solutes under well-watered conditions. A decrease in the amount of soluble sugars (glucose. fructose and sucrose) occurred in plants subjected to drought. accounting for 46% and 81% of the difference between the measured and the predicted increases in π of the chlorenchyma and the water-storage parenchyma. respectively. The decrease in soluble sugars was associated with an equivalenl increase in polysaccharides, presumably starch, in the water-storage parenchyma. but not in the chlorenchyma.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 91 (1994), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth and daily net CO2 uptake were measured for fruit of Opuntia ficus-indica and for its cladodes with 0. 5, 10 and 15 fruit and for cladodes after fruit removal. Growth of individual fruit decreased but fruit dry weight per cladode increased as the number of fruit per cladode increased. Removal of fruit decreased the total daily net CO2 uptake of the bearing cladode by about 10%. From 15 to 45 days after flowering, nocturnal CO2 uptake per unit area of the fruit averaged 19% of that of cladodes and then declined, as did the chlorophyll content and the activity of the CO2-fixing enzymes. Fruit growth for O. ficus-indica was supported by the bearing cladode as well as other cladodes, especially for cladodes with more than 5 fruit.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Biomass accumulation and area expansion of newly initiated cladodes of Opuntia ficus-indica were studied to help understand the high productivity of this Crassulacean acid metabolism species. In a glasshouse, both dry weight and area increased more and more rapidly for about 30 days and then increased linearly with time up to 63 days. The relative growth rate averaged 0. 12 day-1, comparable to values for productive C3 and C4 plants. New cladodes initiated on basal cladodes with 2-fold higher initial dry weight grew twice as fast. Drought reduced biomass accumulation and area expansion of new cladodes by 62 and 52%, respectively. A 70% reduction in irradiation decreased biomass accumulation of new cladodes by 17% and their thickness by 11%. In a growth chamber containing 720 μmol Co2 (mol air)-1, biomass of newly initiated cladodes was 7% higher, area was 8% less, specific mass was 16% higher and less carbohydrate was translocated from basal cladodes than for 360 μmol Co2 mol-1. The large capacity for storage of carbohydrate and water in basal cladodes of O. ficus-indica apparently buffered environmental stresses, thereby reducing their effects on growth of daughter cladodes
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 78 (1990), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Net CO: uptake over 24-h periods was examined for 6 species of epiphytic cacti. which as a group number about 120 species that vary considerably in stem succulence. Nocturnal CO, uptake as a percentage of the total daily CO, uptake increased from 0% for Rhipsalis houlletiana to 14% for Epipliyl/urn pittieri to 21% for E. oxypetnluin to 51% for R. rhornbea to 87% for Schlumbergera truncata to 98% for Cryplocercus anthonyamis. For R. houlletiana and S. truncata, maximum net CO, uptake occurred at a photosynthetically active radiation of only 200 μmol m−2 s−1, as is typical for shade plants. Short-term drought of R. rhombea caused a shift favoring nocturnal CO, uptake. For the 6 species examined, increased reliance on nocturnal CO, uptake characteristic of Crassulacean acid metabolism (CAM) was closely correlated with increases in stem thickness, fresh weight per unit area, water mass per unit area, and to a somewhat lesser extent with another measure of succulence, water mass per unit mass of chlorophyll.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1939
    Keywords: Extracellular ice ; Freezing tolerance ; Opuntia humifusa ; Osmotic pressure ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thickness, relative water content (RWC), osmotic pressure, water potential isotherms, and mucopolysaccharide content were measured for the photosynthetic chlorenchyma and the water-storage parenchyma of the winter hardy cactus, Opuntia humifusa, after shifting from day/night air temperatures of 25° C/15° C to 5° C/−5° C. After 14 d at 5° C/−5° C, the average fraction of water contained in the symplast decreased from 0.92 to 0.78, the water potential of saturated (fully hydrated) tissue was essentially unchanged, but the osmotic pressure of saturated tissue decreased (by 0.15 MPa for the chlorenchyma and 0.12 MPa for the water-storage parenchyma). After 7 weeks at 5° C/−5° C, tissue thickness was reduced by 61% for the chlorenchyma and 65% for the water-storage parenchyma, and the RWC decreased by 42% and 68%, respectively; these changes contributed to an osmotic pressure increase of 0.55 MPa for the chlorenchyma and 0.34 MPa for the water-storage parenchyma. During the 7 week acclimation to low temperature, mucopolysaccharide increased by 114% for the chlorenchyma and by 89% for the water-storage parenchyma. The water potential of the extracted mucopolysaccharide was relatively constant for an RWC between 1.00 and 0.30, decreasing abruptly below 0.30. Changes in water relations parameters and in mucopolysaccharide content during low-temperature acclimation may reduce water efflux from the cells, and thus reduce damage due to rapid dehydration during extracellular freezing.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1939
    Keywords: Agave ; Cactus ; Root morphology ; Sonoran Desert ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At a site in the Sonoran Desert, subterranean rocks and exposed boulders affected soil water potential as well as root morphology and distribution. For Agave deserti, the number of lateral roots per unit length of main root was 11 times higher under rocks and six times higher alongside rocks than in rock-free regions. Total root length per unit soil volume for Echinocereus engelmannii averaged 3-fold higher within 1 cm of boulders than 5 cm away, where the soil was drier. The total length of lateral roots per unit length of main root for Ferocactus acanthodes was 4.2 m m−1 under rocks but only 0.8 m m−1 in rock-free regions. The number of lateral roots per unit length of main root for Opuntia acanthocarpa was 7-fold higher alongside rocks than in rock-free regions and even higher under rocks. For transplanted and watered A. deserti, the number of new main roots produced per 1–2 month interval averaged 13 for five plants on the north side of boulders, 8 on the south side, 11 for five plants with half of their roots under rocks, 2 for those with half of their roots over rocks, and 3 for the control plants without rocks. Laboratory experiments showed that the soil water potential under rocks for 10 and 30 mm waterings stayed above −0.5 MPa for 13 and 19 d longer, respectively, than for regions away from rocks. The shortwave absorptance of granitic rocks from the field site was 0.82, the thermal conductivity coefficient was 1.50 W m−1 °C−1, and the volumetric heat capacity was 1.75 MJ m−3 °C−1. Field measurements indicated that 5-cm-thick buried rocks decreased the diel variation in soil temperatures on their undersurface by only 0.4° C compared with soil. Thus, the primary influence of rocks at the field site on root proliferation and branching for the four species was apparently caused by influences on soil water content.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5036
    Keywords: Agave deserti ; hydraulic conductivity ; root shrinkage ; soil ; water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water movement between a root and the soil depends on the hydraulic conductances of the soil, the root, and the intervening root-soil air gap (Lgap) created as roots shrink during soil drying. To measure Lgap, segments of young cylindrical roots of Agave deserti about 3 mm in diameter were placed concentrically or eccentrically within tubes of moistened filter paper at a known water potential. As the width of the air gap between the filter paper and a concentrically located root was made smaller, measured Lgap increased less than did predicted Lgap based on isothermal conditions. For gaps of the size expected in the soil during water loss from roots (e.g., 10% of the root radius), the underprediction was about 70% and was primarily caused by a lowering of the root surface temperature accompanying water evaporation. As a root segment was eccentrically moved toward the filter paper, the measured Lgap increased. For the most eccentric case of touching the filter paper, the measured Lgap was 2.4-fold greater than for the concentric case, compared with an infinite Lgap predicted if the water potential were constant around the root surface. When a root touched soil with a water potential of -1.0MPa, Lgap estimated using a graphical method increased about 2.3-fold and the overall conductance of the root-soil system increased by 31% compared with the concentric case. For markedly eccentric locations of roots in air gaps, Lgap, which can be the principal conductance initially limiting water loss from roots to a drying soil, can be about 60% of the value predicted for the concentric isothermal case.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5079
    Keywords: Crassulacean acid metabolism ; CO2 enrichment ; Opuntia ficus-indica ; PEPCase ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Responses of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPCase) to an elevated atmospheric CO2 concentration were determined along with net CO2 uptake rates for the Crassulacean acid metabolism species Opuntia ficus-indica growing in open-top chambers. During the spring 13 months after planting, total daily net CO2 uptake of basal and first-order daughter cladodes was 28% higher at 720 than at 360 μl CO2 l-1. The enhancement, caused mainly by higher CO2 assimilation during the early part of the night, was also observed during late summer (5 months after planting) and the following winter. The activities of Rubisco and PEPCase measured in vitro were both lower at the elevated CO2 concentration, particularly under the more favorable growth conditions in the spring and late summer. Enzyme activity in second-order daughter cladodes increased with cladode age, becoming maximal at 6 to 10 days. The effect ofelevated CO2 on Rubisco and PEPCase activity declined with decreasing irradiance, especially for Rubisco. Throughout the 13-month observation period, O. ficus-indica thus showed increased CO2 uptake when the atmospheric CO2 concentration was doubled despite lower activities of both carboxylating enzymes.
    Type of Medium: Electronic Resource
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