Gas Exchange Properties of Agronomic Crops: A Medley of Experimental Methodology and Results after 25 Years.
Gerard W. Wall, US Arid Land Agricultural Center, 21881 North Cardon Lane, Maricopa, AZ 85239 and Richard L. Garcia, LI-COR Inc., P.O. Box 4425, Lincoln, NE 68504.
Alterations in biotic (i.e., water, nitrogen) and abiotic (i.e., light, temperature, [CO2], [O3]) conditions can significantly affect gas exchange properties of agronomic crops. Our objective was to elucidate mechanistic-based ecophysiological response of a broad range of agronomic crops to global change. Pursuant to this aim we implemented a consistent experimental protocol across a multitude of species and functional types. Reported herein we have characterized and quantified the gas exchange properties (i.e., CO2, H2O) of agronomic crops over the past 25-years in open-field (OF), Soil-Plant-Atmosphere-Research (SPAR), Free-air CO2 enrichment (FACE), and open-top-chamber (OTC) technologies. Experimental results discussed include one on citrus (sour orange tree, Citrus aurantium 1987-05), three on fiber (cotton, Gossypium hirsutum L. 1989-91), eleven on grain (wheat, Triticum aestivum L. 1982-84, 1992-94, 1995-97; barley, Hordeum vulgare L. 1993-94; sorghum, Sorghum bicolor L. Moench 1998-99; corn, Zea maize 2002-04), and four on oil/meal (soybean, Glycine max 1983-85, 2002-04) crops. This medley of crops constitutes a broad range of species and functional types for the following comparative studies: monocot (corn, barley, wheat) vs. dicot (soybeans); cool- (temperate zone) (wheat, barley) vs. warm-season (tropical zone) (corn, sorghum) grasses; herbaceous annuals (barley, corn, sorghum, wheat, soybeans) vs. woody perennials (sour orange tree, cotton); photosynthetic pathways of C3 (barley, corn, sour orange tree, soybeans, wheat) vs. C4 (corn, sorghum). These studies have enhanced our understanding of the response of agronomic crops to global change.