Progress 07/01/06 to 06/30/09
Outputs
OUTPUTS: The program's primary objective is continued operation of the 37 station national network of UVB monitoring instruments to deliver high quality data, data products and services in support of agricultural research describing the geographic distribution of UVB solar irradiance, effects of increased or diminished UVB on crops, native and invasive plants and animals, and to facilitate the use of these measurements directly or as input to climate and crop models. Agriculture is entering a critical period with regard to climate change, crop stress and potential related impact to crop productivity. The UVMRP provides accurate UVB data available freely on the web. The program works with agricultural and forest researchers to evaluate the effects of UVB and other climate stressors on crops, livestock and forest and range resources sustainability. Decision makers need reliable and relevant crop yield and economic assessment tools. To meet this particular need UVMRP is completing development of an agricultural impact model that will couple satellite and in-situ observations of climate, solar radiation and a wide range of stressors with existing comprehensive crop growth models and economic analyses. Some research results of the program were presented in international scientific conferences and published in referred journals. Continued development, research and data dissemination are being provided for a program consisting of a regional status-and-trends network of 37 sites with spectral UVB and visible radiometers to provide data to determine climatology and trends and to support aerosol studies. Currently the emphasis is on instrument calibration; data management; QA/QC procedures and protocols; establishing comparability with other monitoring programs in the U.S. and around the world; supplying information to data users for agriculture, aquatic, atmospheric science research, risk assessment and mitigation, and policy development. Research is being conducted to determine the influence of clouds, aerosols and ozone on surface UVB irradiance. Enhanced UVB radiation generally has negative impacts on growth, yield and quality of some crop plants such as soybean, winter wheat, rice, sorghum, cotton and corn. A wide range of research problems regarding UV impact and other climate stress factors (moisture, temperature, soil nutrients, and CO2) on agriculture and ecosystems have been addressed by the program. The program facilitates research: 1) to quantify phenomenological, growth and physiological parameters of crop plants as affected by UV-B radiation in interaction with other environmental factors in growth chambers, green houses and fields, 2) to provide knowledge that will aid in identifying heat and UVB-sensitive parameters of crop plants that can be manipulated by plant breeders to develop cultivars better suited to high-temperature and higher UVB radiation environments, and 3) to provide quantitative functional algorithms needed to improve crop simulation models, which in turn can be used for climate change impact analysis across the nation to assist in crop management decisions for producers and economic and policy decisions for resource mangers. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
High quality data continues to be collected from the 37 climatological sites with average collection this fiscal year of 97.9% for the visible-wavelength instruments and 97.9% for the UV-wavelength instruments. Data collected by UVMRP is being used for agricultural response to UVB research performed at such places as Mississippi State University and the University of Illinois Urbana-Champaign. Data is also being used by health researchers at the University of California Davis and the University of Hawaii Manoa. Students routinely download data for science projects through our web site. Development of in-house calibration procedures for the UV shadowband instruments is underway to compensate for the closing of NOAA's Central UV Calibration Facility. Similar procedures for the other primary instruments will begin once the UV procedures are vetted and accepted by the scientific community. UVMRP's web site enhancements, in response to user requests, allow the user greater ability to define the download parameters without needing UVMRP staff to assist especially for requests that span the 16 years of data collected to date. Additional data products available are map-based presentations of the data and the ability to choose the type and level of calibration applied to the data. This web interface is the primary venue for disseminating UVMRP data and data products. The data is collected automatically every night, processed for quality control and made available on the web site, typically within one day of its collection. Most data is available back through 1997, with some additional data available back to 1993. The UVMRP staff traveled to present status and preliminary results of UVMRP's numerical modeling/simulation and radiation effects research using ultraviolet ground and space-based measurements at national/annual scientific meetings, the American Geophysical Union (AGU), American Meteorological Society (AMS), the American Society of Agronomy (ASA), and International Society for Optical Engineering (SPIE). The staff used these opportunities to communicate and collaborate with other federal agency researchers (USDA, NOAA, NASA, EPA, NSF, USFS, and Canadian-AES). A yearly trip to Washington, DC, was taken to meet with senior supervisory personnel at USDA CSREES. Dr. Wei Gao worked with Springer-Verlag and Tsinghua publication editors to finalize a manuscript for production of the "UV Radiation in Global Climate Change: Measurements, Modeling and Effects on Ecosystems" book. Dr. Gao is an editor and a contributing author for this book. There are 18 chapters including review chapters from renowned scientists in research fields of UV radiation, meteorology, environment and ecosystems. Springer-Verlag and Tsinghua University Press will jointly publish the book.
Publications
- Lantz, K., P. Disterhoft, J. Slusser, W. Gao, J. Berndt, G. Bernhard, R. Booth, J. Ehramjian, L. Harrison, G. Janson, P. Johnston, P.Kiedron, R. McKenzie, M. Kimlin, P. Neale, M. O.Neill, V.V. Quang, G. Seckmeyer, T. Taylor, S. Wuttke, and J. Michalsky, 2008, The 2003 north American interagency intercomparison of ultraviolet spectroradiometers, part A: scanning and spectrograph instruments. Journal of Applied Remote Sensing, Vol. 2, 023547
- Singh, S.K., G. Surabhi, W. Gao, and K.R.Reddy, 2008, Assessing genotypic variability of cowpea (Vigna unguiculata [L.] Walp.) to current and projected ultraviolet-B radiation. Journal of Photochemistry and Photobiology B: Biology, Vol. 93, 71-81
- Barnes, P.W., S.D. Flint, J.R. Slusser, W. Gao, and R.J. Ryel, 2008, Diurnal changes in epidermal UV transmittance of plants in naturally high UV environments. Physiologia Plantarum, Vol.133-2, 363-372
- Bao, Y., W. Gao, Z. Gao, 2008, Estimation of winter wheat biomass based on remote sensing data at various spatial and spectral resolutions, Frontiers of Earth Science, 3(1): 118-128
- Smith, W. K., W. Gao, H. Steltzer, 2008, Current and future impacts of ultraviolet radiation on the terrestrial carbon balance, Frontiers of Earth Science, 3(1): 34-41
- Sarkissian A., J. Slusser 2009, Water vapor total column measurements using the Elodie Archive at Observatoire de Haute Provence from 1994 to 2004, Atmos. Meas. Tech. Discuss., 2, 1075-1097
- Hicke, Jeffrey A., J. Slusser, K. Lantz, F. G. Pascual, 2008, Trends and interannual variability in surface UVB radiation over 8 to 11 years observed across the United States. Journal of Geophysical Research, Vol. 113, D21302
- Wang, X.L., W. Gao, J.R. Slusser, J.Davis, B. Olson, S. Janssen, G. Janson, W. Durham, R. Tree, and R. Deike, 2008, USDA UV-B monitoring system: an application of centralized architecture. Computers and Electronics in Agriculture, doi:10.1016/j.compag.2008.04.006
- Warphea, Katherine M., J. Gibbons, A. Carol, J. Slusser, R. Tree, W. Durham, L.S. Kaufman, 2008, Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings, Plant, Cell and Environment, 31, 17561770, doi: 10.1111/j.1365-3040.2008.01878.
- Taylor, T.E., T.S. L'Ecuyer, J.R. Slusser, G.L. Stephens, and C.D. Goering 2008, An operational retrieval algorithm for determining aerosol optical properties in the ultraviolet, J. Geophys. Res., 113, D03201, doi:10.1029/2007JD008661.
- Bao, Y. W. Gao, Z. Gao, 2008, Estimating winter wheat biomass based on LANDSAT TM and MODIS data. Remote Sensing and Modeling of Ecosystems for Sustainability V, Vol. 7083, 70831L, doi: 10.1117/12.806210
- Gao, W., H. Wang, 2008, Remote Sensing and Modeling of Ecosystems for Sustainability, Proceedings of SPIE, Vol. 7083, 0277-786X
- Xie, X., W. Gao, Z. Gao, 2008, A Method for Estimating the Incident PAR on Inclined Surfaces. Remote Sensing and Modeling of Ecosystems for Sustainability V, Vol. 7083, 70831L, doi: 10.1117/12.806210
- Xie, X., W. Gao, Z. Gao, 2008, Estimation of Land Photosynthetically Active Radiation in Clear Sky Using MODIS Atmosphere and Land Products. Remote Sensing and Modeling of Ecosystems for Sustainability V, Vol. 7083, 70830O-1, doi: 10.1117/12.806210
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Progress 07/01/07 to 06/30/08
Outputs
OUTPUTS: An in-house experiment was conducted at the CSU greenhouse complex to assess the effects of various levels of UV-B plus various levels of moisture on the decomposition of aspen leaf litter collected from a high-altitude forest floor in southwestern Colorado. This experiment was conducted and concluded by Bill Smith, one of the graduate degree students working with UVMRP who successfully completed the requirements for a master's degree. Senior research scientists from UVMRP were part of the review committee for this student, and UVMRP staff assisted with the preparations and set-up of the experiment. The report of this study and its findings is currently being written for submission to a peer-reviewed scientific journal. UVMRP was invited to submit a proposal to AmericaView, National Consortium for Remote Sensing Education, Research and Applications to help establish a Colorado consortium.In February 2008 America View formally confirmed the acceptance of ColoradoView to affiliate membership in the AmericaView national consortium, under the leadership of researchers from UVMRP and its parent department, the Natural Resource Ecology Lab (NREL) at CSU.Dr. Wei Gao presented a talk about his research into modeling of cotton yields at the SPIE/COS Photonics Asia 2007 Conference, at the Jiuhua Grand Convention and Exhibition Center in Beijing, China.He was a contributor to the United Nations Environment Programme's (UNEP) recently published tome "Global Environment Outlook (GEO-4) Environment for Development", which provides a comprehensive, reliable and scientifically credible, policy-relevant, up-to-date assessment of, and outlook for, the state of the global environment. Dr. Jim Slusser presented a talk entitled "Solar UV-B Radiation: Measurements, Models and Effects" to the Department of Physics at Western Michigan University. He was co-chair of the SPIE Remote Sensing of Clouds and the Atmosphere Conference in Florence, Italy. He presented a poster about the UVMRP's ten years of UV data to the Solar UV Radiation Research Conference in Davos, Switzerland. William Durham, senior site technician, represented UVMRP at the 50th anniversary celebration of Hawaii's Mauna Loa Observatory (MLO), which included a commemoration of their 50 years of carbon dioxide measurements and NOAA's 200th anniversary. He installed two additional UV shadowband sensors to our array at MLO, which will enhance our ability to monitor the calibration and stability of these aging instruments. A write-up about the UVMRP is included in the commemorative book about the MLO facility's 50 year history. UVMRP's web site is currently being updated to comply with new graphics standards from CSU that are intended to provide a common appearance for any web sites hosted by CSU. Concurrently, additional performance enhancements are being incorporated in response to user requests.High quality data continues to be collected from the 36 climatological sites, with average collection rates during this fiscal year of 98.26% for the visible-wavelength instruments, and 98.46% for the UV-wavelength instruments.This web interface is the primary venue for disseminating UVMRP data and data products. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
For the CSU greenhouse study listed above, it was observed that varying levels (zero, ambient, elevated) of UV-B exposure did not consistently increase litter decomposition across simulated precipitation intervals of 4, 12 or 24 days. Both ambient and elevated UV-B decreased litter decomposition rates under the 4-day precipitation frequency by 14% and 10%, respectively, but increased litter decomposition under the 24-day frequency by 50% and 62%, respectively. Under the 12-day precipitation frequency UV-B did not affect decomposition rates, possibly due to offsetting effects of UV-B upon decomposition. These results indicate the abiotic effects of UV-B on decomposition may be strongly dependent on precipitation patterns, and demonstrate the importance of abiotic photodegradation as a driver of decomposition when precipitation is infrequent. A joint experiment between UVMRP and Mississippi State University was conducted in their outdoor controlled-environment chambers to evaluate the sensitivity of six cowpea genotypes (representing diverse locations) to four levels of UV-B radiation imposed from eight days after emergence to maturity. In general, most of the vegetative parameters showed a positive response to UV-B, whereas the reproductive parameters exhibited a negative response, showing that reproductive characteristics need to be considered in determining tolerance of cultivars to UV-B. It is possible that any selection for UV-B tolerance based only on vegetative traits may not confer simultaneous tolerance to reproductive traits. These differences imply there are options for selecting or developing genotypes with tolerance to niche environments. Results of the 2003 North American Intercomparison of Ultraviolet Monitoring Spectroradiometers were recently published in the Journal of Applied Remote Sensing. This was a blind intercomparison for spectral solar irradiance and the comparison between instruments agreed very well, i.e. DOY 172 at 17:00 UTC (solar zenith angle of 30.6 degrees) has a 1-sigma standard deviation of +/- 1.8% to +/- 4.3% for 300 to 360 nanometers. Instrument agreement across a range of solar zenith angles improved when compared to previous years. A study of trends and interannual variability of UV-B radiation across the USA, using data from UVMRP's network of well-characterized UVB-1 instruments, was recently published in the Journal of Geophysical Research. Annual values of UV-B irradiance changed between -5% per decade to +2% per decade, with relatively wide confidence intervals that include zero and that reflect the small magnitude of trend values and short time period of measurements. Interannual variability of annual irradiance was 2-5% of the mean annual values. Monthly and decadal increases were both positive and negative, with magnitudes often >10% per decade. The largest absolute changes typically occurred in May-September.This study's observed irradiance increases were not always consistent with reported increases in Northern Hemisphere total ozone during 1995-2004, indicating other geophysical mechanisms (including cloud, aerosol and snow conditions) are more likely affecting this variability of UV radiation.
Publications
- Barnes, P.W., S.D. Flint, J.R. Slusser, W. Gao, and R.J. Ryel, 2008, Diurnal changes in epidermal UV transmittance of plants in naturally high UV environments. Physiologia Plantarum, Vol.133-2, 363-372
- Liu, S.Y., X.Z. Liang, W. Gao, and H. Zhang, 2008, Application of climate-weather research and forecasting model (CWRF) in China: domain optimization. Journal of Atmospheric Sciences, Vol.32, No.3, 457-468
- Singh, S.K., G. Surabhi, W. Gao, and K.R.Reddy, 2008, Assessing genotypic variability of cowpea (Vigna unguiculata [L.]Walp.) to current and projected ultraviolet-B radiation. Journal of Photochemistry and Photobiology B: Biology, Vol. 93, 71-81
- Wang, X.L., W. Gao, J.R. Slusser, J.Davis, B. Olson, S. Janssen, G. Janson, W. Durham, R. Tree, and R. Deike, 2008, USDA UV-B monitoring system: an application of centralized architecture. Computers and Electronics in Agriculture, doi:10.1016/j.compag.2008.04.006
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Progress 07/01/06 to 06/30/07
Outputs
High quality data had been continuously collected during this fiscal year with the average collection rates of 98.28% and 98.52%, respectively, for visible and ultraviolet instruments. Various categories of collected data and derived products were routinely provided. Special requests were processed. A new webpage was launched to include enhanced synthetic spectra data, a new data gaps category, and improve its performance. The lamp calibrated UV-MFRSR data have been significantly improved through the application of out-of-band corrections due to the red light leakage of silicon photodiodes. Algorithms were developed to make radiometric calibration for short wavelengths and retrievals of ozone and aerosol using RSS104 measurements. The measurements of erythemally weighted UV radiation were processed and analyzed to assess the data quality and quantify the dependence of the radiation on latitudes and altitudes, which is useful to predict the radiation at places where no
observation is made. A fully coupled cotton growth module (GOSSYM) within the framework of the CWRF regional climate model was developed and validated using the data derived from county survey maps, reports of state cooperative extensions, satellite measurements, and global irrigation estimates. The North American Re-analysis products at each grid were used as the observed climatic parameters. Agreement between simulated yields and those derived from the USDA statistics in the whole US cotton belt from 1979 to 2005 is better than 85% at most of the grids. The components of UV-B effects on cotton growth, photosynthesis, and leaf area expansion were integrated into the GOSSYM model and were validated using independent experimental data. For the first time, we simulated the effects of enhanced UV-B radiation on cotton productivity in the US cotton belt using this fully coupled regional climate model and crop growth module. The preliminary results show that the reduction in cotton yield
could be more than 30% when biologically active UV-B radiation reaches the level of 16 KJ/m2/day, which is predicted with 30% depletion of stratospheric ozone. Experiments in open fields, green houses, and growth chambers were continued to examine the effects of enhanced UV-B radiation on the productivity, growth, photosynthesis, and biochemical processes of crops and plants as well as the consequences in ecosystem development. Soybeans, red clovers, and cowpea cultivars were tested. The gene which controls the response of soybeans to UV-B radiation was examined using experimental data and statistical analysis techniques. For cowpeas, enhanced UV-B radiation, higher temperature, as well as their combinations all caused reductions in vegetative growth and physiological parameters, such as photosynthesis and chlorophyll fluorescence. Elevated CO2 alleviated the damaging effects of UV-B radiation and high temperature on photosynthesis and vegetative growth, but it did not improve the
reductions in productivity, retention, and size of flowers. The combination of enhanced UV-B and high temperature caused the failure to retain flowers.
Impacts
Measurements of UV-B radiation are essential in the research of its effects on plants, ecosystems, and human health. The program continued to provide high quality UV-B data to the users from universities, research institutions, government agencies, and the public who use these data in their research, environment assessment, and health concerns. With the development of a new web page and enhanced algorithms, more useful products are provided and the service has been improved. The quantitative relationship between UV-B radiation and latitude and altitude permits the prediction at locations where no measurements are made, which is essential to develop UV-B climatology. The experimental results, which show different responses of crop growth and productivity to enhanced UV-B levels, indicate a promising direction in which UV-B tolerant species might be chosen or bred to grow in higher UV-B environments. These results also provide the basis to assess the UV-B risks in
agriculture and ecosystems and serve as a good reference for related research in genetic engineering. Experience was gained from the development of a fully coupled cotton growth module within the CWRF regional climate model framework to further develop an integrated crop risk assessment system as proposed. A better understanding of UV-B and its cross effects with other abiotic factors on cotton yield is useful in agricultural practice and management for cotton growth in the changing climatic conditions.
Publications
- Kiedron, P., J. Schlemmer, J. Slusser, P. Disterhoft. 2006. Validation of ozone and aerosol retrieval methods with UV rotating shadowband spectroradiometer (RSS), Remote Sensing of Clouds and the Atmosphere XI. Edited by Slusser, James R.; Schafer, Klaus; Cameron, Adolfo. Proceedings of the SPIE, Volume 6362.
- Caldwell, Charles R. and Steven J. Britz. 2006. Effect of supplemental ultraviolet radiation on the carotenoid and chlorophyll composition of green house-grown leaf lettuce (Lactuca sativa L.) cultivars. J. Food Comp. Anal. 19: 637-644.
- Mostovoi, G. V., R. L. King, K. R. Reddy, V. G. Kakani and M. F. Filippova. 2006. Regression estimate of daily maximum and minimum air temperatures from MODIS LST data over state of Mississippi: Variations with season, spatial resolution and satellite platform. GIScience and Remote Sensing. 43: 78-110.
- Read, J.J., K.R. Reddy and J.N. Jenkins. 2006. Yield and fiber quality of cotton as influenced by nitrogen and potassium nutrition. European Journal of Agronomy. 24: 282-290.
- Wang, X., Gao, W., Slusser, J. R., Gao, Z., Reddy, K. R. and Xu, M. 2006. Preliminary results of UV-B effect incorporated GOSSYM model. In: Remote Sensing and Modeling of Ecosystems for Sustainability III (Ed. W. Gao and S. L. Ustin), Proc. of SPIE, vol. 6298, 1-10.
- Wang, X.L., W. Gao, J. Slusser, J. Davis, G. Scott, B. Olson, N. Krotkov, M. Xu, and X-Z. Liang. 2006. Spectral distribution of UV-B irradiance derived by synthetic model compared with simulation results of TUV and ground measurements. In Remote Sensing and Modeling of Ecosystems for Sustainability III, 62980L-1-62980L-9, Published by SPIE, Bellingham, WA, USA
- Kakani, V.G., K.R Reddy and D Zhao. 2006. Deriving a simple spectral ratio R1689/R1657 for spatial and temporal determination of cotton leaf water potential. Journal of New Seeds. 8: 11-27.
- Reddy, K. R. and H. F. Hodges. 2006. Exploring the limitations for cotton growth and yield. Journal of New Seeds. 8: 1-22.
- Xu, M., X.-Z. Liang, W. Gao, J. Slusser, and K. Kunkel. 2006. Validation of the TUV module in CWRF using USDA-UVB network observations. In Remote Sensing and Modeling of Ecosystems for Sustainability II. W. Gao and D. Shaw (Eds.), 9 pp.
- R. McKenzie, G. Bodeker, G. Scott, J. Slusser, K. Lantz. 2006. Geographical Differences in Erythemally-weighted UV measured at mid-latitude USDA Sites, Photochem. Photobiol. Sci.Vol. 5 (3). 343-352.
- K. Lantz, P. Disterhoft, C. Wilson, G. Janson, B. Durham, J. Slusser. 2006. Remote Sensing of Clouds and the Atmosphere, XI, Long Term Evaluation of the Calibration of YES UVB-1 Broadband Radiometers of the Central UV Calibration Facility and the suite of UV radiometers in the USDA UV Monitoring Network. Proceedings of SPIE, Vol. 6362, 63620X.
- Kiedron, P., M. Beauharnois, J. Berndt, P. Disterhoft, L. Harrison, J. Michalsky, G. Scott, J. Schlemmer, J. Slusser. August 2007. Calibration, data processing, and maintenance of the United States Department of Agriculture high-resolution ultraviolet spectroradiometers. Optical Engineering. 46. 8. 086201.
- Michalsky, J. and P. Kiedron. September 2007. Comparison of UV-RSS Spectral Measurements and TUV Model Runs During the May 2003 ARM Aerosol Intensive Observation Period. One century of UV Radiation Research. Davos, Switzerland. page 151, 18-20.
- Lantz, K., P. Disterhoft, P. Kiedron, J. Slusser. September 2007. Direct-to-diffuse UV solar irradiance ratio for a UV rotating shadowband spectroradiometer (UV-RSS) and a UV multi-filter rotating shadowband radiometer (UV-MFRSR). One century of UV Radiation Research. Davos, Switzerland. Page 43. 18-20.
- Koti, S., K.R. Reddy, V.G.Kakani, D. Zhao and W. Gao. 2007. Effects of carbon dioxide, temperature and ultraviolet-B radiation and their interactions soybean (Glycine max L.) growth and development. Environmental and Experimental Botany. 60: 1-10.
- Reddy, K. R. and V. G. Kakani. 2007. Screening pepper genotypes for high temperatures by in vitro pollen germination and pollen tube length. Scientia Horticulrae. 112: 130-135.
- Koti, S., K. R. Reddy, G. W. Lawrence, V. R. Reddy, V. G. Kakani, D. Zhao and W. Gao. 2007. Effect of enhanced UV-B radiation on reniform nematode (Rotylenchus reniformis Linford and Oliveira) populations in cotton (Gossypium hirsutum L.). Plant Pathology Journal. 6: 51-59.
- Singh, R. P., P. V. V. Prasad, K. Sunita, S. N. Giri and K. R. Reddy. 2007. Influence of high temperature and breeding for heat tolerance in cotton: a review (Ed. D. L. Sparks). Advances in Agronomy. 93: 315-385.
- Caldwell MM, Bornman JF, Ballare CL, Flint SD, Kulandaivelu G. 2007. Terrestrial ecosystems, increased solar ultraviolet radiation, and interactions with other climate change factors. Photochemical & Photobiological Sciences. 6:252-266.
- Zhao, D., K. R. Reddy, V. G. Kakani, J. J. Read and S. Koti. 2007. Canopy reflectance in cotton for growth assessment and prediction of lint yield. European Journal of Agronomy. 26: 335-344.
- Koti, S., K. R. Reddy, V. G. Kakani, D. Zhao and W. Gao. 2007. Effects of carbon dioxide, temperature and ultraviolet-B radiation and their interactions on soybean (Glycine max L.) growth and development. Environmental and Experimental Botany. 60: 1-10.
- Salem, M. A., V. G. Kakani, S. Koti and K. R. Reddy. 2007. Screening soybean genotypes for high temperatures by in vitro pollen germination and pollen tube length. Crop Science. 47: 219-231.
- Salem, M. A., V. G. Kakani, S. Koti and K. R. Reddy. 2007. Screening soybean genotypes for high temperatures by in vitro pollen germination and pollen tube length. Crop Science. 47: 219-231.
- Salem, M. A., V. G. Kakani, S. Koti and K. R. Reddy. 2007. Limited variability in USA soybean varieties to high temperature tolerance delays development of climate-ready crops. CSA News February. V52: 4-5.
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