Xanthium Strumarium
Mostrando 13-24 de 38 artigos, teses e dissertações.
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13. Changes in the Levels of Abscisic Acid and Its Metabolites in Excised Leaf Blades of Xanthium strumarium during and after Water Stress 1
The time course of abscisic acid (ABA) accumulation during water stress and of degradation following rehydration was investigated by analyzing the levels of ABA and its metabolites phaseic acid (PA) and alkalihydrolyzable conjugated ABA in excised leaf blades of Xanthium strumarium. Initial purification was by reverse-phase, preparative, high performance liq
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14. Translocation Patterns in Xanthium in Relation to Long Day Inhibition of Flowering 1
The nature of long day inhibition of flowering in the short day plant Xanthium strumarium L. was studied by correlating the flowering response with the translocation of 14C-assimilates from induced leaves or parts thereof to the shoot tips.
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15. Abscisic Acid Content and Stomatal Sensitivity to CO2 in Leaves of Xanthium strumarium L. after Pretreatments in Warm and Cold Growth Chambers 1
The degree of stomatal sensitivity to CO2 was positively correlated with the content of abscisic acid of leaves of Xanthium strumarium grown in a greenhouse and then transferred for 24 hours or more to a cold (5/10 C, night/day) or a warm growth chamber (20/23 C). This correlation did not exist in plants kept in the greehouse continuously (high abscisic acid
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16. Temperature and Transpiration Resistances of Xanthium Leaves as Affected by Air Temperature, Humidity, and Wind Speed 1
Transpiration and temperatures of single, attached leaves of Xanthium strumarium L. were measured in high intensity white light (1.2 calories per square centimeter per minute on a surface normal to the radiation), with abundant water supply, at wind speeds of 90, 225, and 450 centimeters per second, and during exposure to moist and dry air. Partitioning of a
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17. Abscisic Acid Content, Transpiration, and Stomatal Conductance As Related to Leaf Age in Plants of Xanthium strumarium L. 1
Among the four uppermost leaves of greenhouse-grown plants of Xanthium strumarium L. the content of abscisic acid per unit fresh or dry weight was highest in the youngest leaf and decreased gradually with increasing age of the leaves. Expressed per leaf, the second youngest leaf was richest in ABA; the amount of ABA per leaf declined only slightly as the lea
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18. Effect of Light Quality on Stomatal Opening in Leaves of Xanthium strumarium L. 1
Flux response curves were determined at 16 wavelengths of light for the conductance for water vapor of the lower epidermis of detached leaves of Xanthium strumarium L. An action spectrum of stomatal opening resulted in which blue light (wavelengths between 430 and 460 nanometers) was nearly ten times more effective than red light (wavelengths between 630 and
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19. Prechilling of Xanthium strumarium L. Reduces Net Photosynthesis and, Independently, Stomatal Conductance, While Sensitizing the Stomata to CO21
Greenhouse-grown plants of Xanthium strumarium L. were exposed in a growth cabinet to 10 C during days and 5 C during nights for periods of up to 120 hours. Subsequently, CO2 exchange, transpiration, and leaf temperature were measured on attached leaves and in leaf sections at 25 or 30 C, 19 C dew point of the air, 61 milliwatts per square centimeter irradia
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20. Identification of the Flower-inducing Factor Isolated from Aphid Honeydew as being Salicylic Acid 1
Honeydew produced by the aphid Dactynotus ambrosiae when feeding on flowering or vegetative plants of the short day plant Xanthium strumarium contains an active substance capable of inducing flowering in the long day plant Lemna gibba G3. In the present study, this active material has been identified as salicylic acid through the use of gas-liquid chromatogr
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21. The Participation of Two Rhythms in the Leaf Movements of Xanthium Plants Given Various Light-Dark Cycles 1
We have shown Xanthium strumarium exhibit two distinct leaf movement rhythms with one occurring in continuous light and presumably related to an endogenous rhythm initiated by the “light-on” signal and the other occurring in continuous dark and presumably related to an endogenous rhythm initiated by the “light-off” signal. Characteristic of the light
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22. Aftereffects of Low and High Temperature Pretreatment on Leaf Resistance, Transpiration, and Leaf Temperature in Xanthium1
Leaf resistance for water vapor (total diffusion resistance minus boundary layer resistance), transpiration, and leaf temperature were measured in attached leaves of greenhouse-grown Xanthium strumarium L. plants that had been pretreated for 72 hours with high (40 C day, 35 C night), or low (10 C day, 5 C night) air temperatures. Measurements were made in a
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23. Isolation of Flower-inducing and Flower-inhibitory Factors from Aphid Honeydew 1
The aphid Dactynotus ambrosiae Thomas has been allowed to feed on vegetative or flowering plants of the short-day plant Xanthium strumarium L., and the honeydew which they produce is extracted and tested for an effect on flowering using the long-day plant Lemna gibba L., strain G3 for the bioassay. One zone of flower-inducing activity and at least two zones
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24. Abscisic Acid Biosynthesis in Leaves and Roots of Xanthium strumarium1
Research on the biosynthesis of abscisic acid (ABA) has focused primarily on two pathways: (a) the direct pathway from farnesyl pyrophosphate, and (b) the indirect pathway involving a carotenoid precursor. We have investigated which biosynthetic pathway is operating in turgid and stressed Xanthium leaves, and in stressed Xanthium roots using long-term incuba