Two sorghum lines, an erect leafed mutant sorghum and the wild type from which the mutant was generated, were field grown in rectilinear arrays at low (10 plants m-2) and high (23 plants m-2) population densities. Can...Two sorghum lines, an erect leafed mutant sorghum and the wild type from which the mutant was generated, were field grown in rectilinear arrays at low (10 plants m-2) and high (23 plants m-2) population densities. Canopy light interception, biomass accretion and yield were measured. Photosynthetically active radiation under the canopy at ground level and midway through the canopy were higher in the erect leafed line, as compared to the normal leafed line. Planting density had less effect on mean grain yield and biomass in the erect leaf line than in the wild type. Though not conclusive, when taken together, the results suggested that optimal planting densities are higher for the erect leaf line and that the erect leaf trait could be useful for incorporation into breeding programs.展开更多
An experiment was designed to test whether ambient levels of UV-B radiation affect stomatal development, decrease stomatal density, and lead to increased water-use efficiency (WUE). Soybean [Glycine max (L.) Merr.] is...An experiment was designed to test whether ambient levels of UV-B radiation affect stomatal development, decrease stomatal density, and lead to increased water-use efficiency (WUE). Soybean [Glycine max (L.) Merr.] isolines with different stomatal distribution and flavonol expression patterns were field grown under shelters that either transmitted or blocked solar UV-B. All isolines exposed to solar UV-B accumulated higher concentrations of UV-screening phenolic pigments but other responses were isoline dependent. Solar UV-B decreased stomatal density and conductance in isolines expressing a unique branched kaempferol triglycoside. Decreased stomatal density was associated with increased season-long WUE and decreased internal CO2 concentration of leaf (estimated by δ13C discrimination). We concluded that photomorphogenic responses to UV-B affected stomatal density and WUE in field grown soybean;but that the magnitude and direction of these response were associated with isogenic pleiotropic differences in stomatal distribution and pigment expression. UV-B radiation had no effect on biomass accumulation or yield in a cultivar expressing only trace levels of kaempferol suggesting that flavonol expression is not prerequisite to UV-B tolerance.展开更多
Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to meas...Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.展开更多
A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than ...A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process multiple samples simultaneously is advantageous and necessary for ecological or hydrological investigations. Presented here is a vacuum distillation apparatus, having six ports, that can process up to 30 samples per day. The distillation system coupled with the Los Gatos Research DLT-100 Liquid Water Isotope Analyzer is capable of analyzing all of the samples that are generated by vacuum distillation. These two systems allow larger sampling rates making investigations into water movement through an ecological system possible at higher temporal and spatial resolution.展开更多
Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work exists describing AEs and limited stem hydraulic conductivity under water stress, there is lim...Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work exists describing AEs and limited stem hydraulic conductivity under water stress, there is limited information about the effects of AEs on stomatal aperture and limitation on carbon assimilation. The objective of this work was to relate AEs to drought stress in cotton. Cotton was grown in mini-lysimeters in the greenhouse and instrumented with a portable photosynthesis system and ultrasonic transducers connected to a digital signal-processing unit. Whole plant transpiration, leaf level gas exchange and ultrasonic AEs were measured. Xylem cavitation events temporally associated with the onset of drought stress. The results are consistent with stomatal closure in response to reduced hydraulic conductance from xylem cavitation events. Clear direct empirical evidence of a reduction in carbon assimilation associated with xylem cavitation resulting from water stress is presented.展开更多
Bird damage is a problem in sorghum breeding and germplasm maintenance operations. Paper pollination bags are damaged by rain and provide only a minimal deterrent to birds. To overcome these limitations we fabricated ...Bird damage is a problem in sorghum breeding and germplasm maintenance operations. Paper pollination bags are damaged by rain and provide only a minimal deterrent to birds. To overcome these limitations we fabricated pollination bags from spun polyethylene fiber sheeting. No seed yield difference was found between plants bagged with either spun polyethylene or paper. Seed loss by bird damage was nearly eliminated under the polyethylene bags. In areas where bird damage is problematic bird resistant pollination bags can allow for a reduction in the plot size required for breeding and germplasm maintenance operations, increase the productivity of such operations as genetic diversity per unit land area, and make direct measurement of seed yield possible in agronomic field experiments.展开更多
文摘Two sorghum lines, an erect leafed mutant sorghum and the wild type from which the mutant was generated, were field grown in rectilinear arrays at low (10 plants m-2) and high (23 plants m-2) population densities. Canopy light interception, biomass accretion and yield were measured. Photosynthetically active radiation under the canopy at ground level and midway through the canopy were higher in the erect leafed line, as compared to the normal leafed line. Planting density had less effect on mean grain yield and biomass in the erect leaf line than in the wild type. Though not conclusive, when taken together, the results suggested that optimal planting densities are higher for the erect leaf line and that the erect leaf trait could be useful for incorporation into breeding programs.
文摘An experiment was designed to test whether ambient levels of UV-B radiation affect stomatal development, decrease stomatal density, and lead to increased water-use efficiency (WUE). Soybean [Glycine max (L.) Merr.] isolines with different stomatal distribution and flavonol expression patterns were field grown under shelters that either transmitted or blocked solar UV-B. All isolines exposed to solar UV-B accumulated higher concentrations of UV-screening phenolic pigments but other responses were isoline dependent. Solar UV-B decreased stomatal density and conductance in isolines expressing a unique branched kaempferol triglycoside. Decreased stomatal density was associated with increased season-long WUE and decreased internal CO2 concentration of leaf (estimated by δ13C discrimination). We concluded that photomorphogenic responses to UV-B affected stomatal density and WUE in field grown soybean;but that the magnitude and direction of these response were associated with isogenic pleiotropic differences in stomatal distribution and pigment expression. UV-B radiation had no effect on biomass accumulation or yield in a cultivar expressing only trace levels of kaempferol suggesting that flavonol expression is not prerequisite to UV-B tolerance.
文摘Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.
文摘A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process multiple samples simultaneously is advantageous and necessary for ecological or hydrological investigations. Presented here is a vacuum distillation apparatus, having six ports, that can process up to 30 samples per day. The distillation system coupled with the Los Gatos Research DLT-100 Liquid Water Isotope Analyzer is capable of analyzing all of the samples that are generated by vacuum distillation. These two systems allow larger sampling rates making investigations into water movement through an ecological system possible at higher temporal and spatial resolution.
文摘Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work exists describing AEs and limited stem hydraulic conductivity under water stress, there is limited information about the effects of AEs on stomatal aperture and limitation on carbon assimilation. The objective of this work was to relate AEs to drought stress in cotton. Cotton was grown in mini-lysimeters in the greenhouse and instrumented with a portable photosynthesis system and ultrasonic transducers connected to a digital signal-processing unit. Whole plant transpiration, leaf level gas exchange and ultrasonic AEs were measured. Xylem cavitation events temporally associated with the onset of drought stress. The results are consistent with stomatal closure in response to reduced hydraulic conductance from xylem cavitation events. Clear direct empirical evidence of a reduction in carbon assimilation associated with xylem cavitation resulting from water stress is presented.
文摘Bird damage is a problem in sorghum breeding and germplasm maintenance operations. Paper pollination bags are damaged by rain and provide only a minimal deterrent to birds. To overcome these limitations we fabricated pollination bags from spun polyethylene fiber sheeting. No seed yield difference was found between plants bagged with either spun polyethylene or paper. Seed loss by bird damage was nearly eliminated under the polyethylene bags. In areas where bird damage is problematic bird resistant pollination bags can allow for a reduction in the plot size required for breeding and germplasm maintenance operations, increase the productivity of such operations as genetic diversity per unit land area, and make direct measurement of seed yield possible in agronomic field experiments.
