Dr. Cheryl Irene Bawhey Profile

Dr. Cheryl Irene Bawhey

Post-Doc Research Assistant at Purdue Univ

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Proceedings Article | 13 September 2005 Paper

Short-term impacts of elevated UV-B radiation on soybeans

Kent Apostol, Richard Grant, Cheryl Bawhey, Wei Gao

Proceedings Volume 5886, 58860I (2005) https://doi.org/10.1117/12.613320

KEYWORDS: Ultraviolet radiation, Reflectivity, Lamps, Absorbance, Solids, Ozone, Proteins, Photosynthesis, Tolerancing, Nondestructive evaluation

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The impact of increased solar ultraviolet-B (UV-B) exposure due to stratospheric ozone depletion can negatively affect plant growth and physiology, decreasing crop productivity. While some effects of prolonged elevated UV-B exposure on plants is clear, relatively little is known about the short-term effects of UV-B exposure, although, there are evidence of short-term UV-B increases that likely occur during summer. Two greenhouse experiments were conducted to examine the short-term effects of UV-B exposure on stomatal conductance (gs), UV-B absorbing compounds and photosynthetic pigment concentrations of soybean cultivars Glycine max [L.] Merr. cvs. Essex and Williams 82. Results showed that changes in leaf reflectance at 552 and 714 nm with UV exposure appear to be linked to UV-B induced alterations in pigment concentrations and the changes in reflectance seemed to be more dependent on the period of exposure rather than the UV-B dosage received. The UV-B exposed Williams 82 exhibited lower gs compared to UV-B exposed Essex throughout the experiment. The concentrations of carotenoids, chlorophyll a and total chlorophyll in leaf extracts were unchanged in response to an 18-h UV-B treatment in Essex but they increased significantly in Williams 82. Anthocyanin did not change significantly in either cultivar after the 18-h exposure. The 18-h UV exposure did result in substantially higher of UV-B absorbing compounds in Essex compared to Williams 82. Results of a 6-h UV-B exposure caused an induction of Chlorophyll a/b binding protein (CAB) and Phenyl ammonia lyase (PAL) in the irradiated leaves of Williams 82 and Essex and an up regulation in Chalcone synthase (CHS) in Williams but not in Essex. Further work should assess whether these short-term responses are related to the long-term UV-B mechanisms of damage and protection in soybeans and examine how the induction of genes are related to sensitivity of soybeans to UV-B stress.

Proceedings Article | 4 November 2003 Paper

Effect of epicuticular wax on UV scattering of sorghum leaves and canopies

Cheryl Bawhey, Richard Grant

Proceedings Volume 5156, (2003) https://doi.org/10.1117/12.504903

KEYWORDS: Reflectivity, Scattering, Transmittance, Ultraviolet radiation, Magnesium, Data modeling, Radiometry, Calibration, Sensors, Atmospheric modeling

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Sorghum bicolor is grown in equatorial regions that have naturally high ultraviolet-B (UVB) exposures. To determine whether the increased wax production on the sorghum leaves and sheaths protects the plant by increased scattered radiation from the plant surface, the effects of wax amount on UVB reflectances were examined in greenhouse and field experiments involving three isolines of sorghum -- wild-type and two wax mutants. Reflectance of the wild-type sheath was found to be a result of the wax present while that on the mutant sheaths was not dependent on wax amount. Overhead UVB exposure corresponded with reduced sheath and increased leaf UVB reflectance for wild-type but negligible changes in both sheath and leaf reflectance for the two mutants. Although the sheath reflectances of wild-type were twice that of the two mutants, the negligible difference in leaf reflectance between isolines resulted in negligible differences in the canopy bi-directional reflectance, even at high view angles. The UVA canopy reflectance factors of the three sorghum isolines were measured at 0.03 at viewing angles near nadir on clear sky days. Predicted reflectance factors were calculated using the SAIL model then compared with the measured reflectance factors to evaluate the effect of sky diffuse fraction on the measured differences.

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