SPAR—A Soil-Plant-Atmosphere Research System

Reflectance indices with precision and accuracy in predicting cotton leaf nitrogen concentration

“…Soil‐Plant‐Atmospheric‐Research (SPAR) units, the closed‐environment plant growth chambers used for this study were described in detail by Phene et al (1978), Acock et al (1985), and Reddy et al (1992) The SPAR units are located outside and provide control of temperature and CO 2 concentration at predetermined set points for plant growth studies in natural solar radiation regimens. Each SPAR unit consists of a steel soil bin (1 m tall by 2 m long by 0.5 m wide), a poly(methylmethacrylic) chamber (2.5 m tall by 2.0 m long by 1.5 m wide) to accommodate aerial plant parts, a heating and cooling system, and an environmental monitoring and control system.…”

Sunlit, controlled‐environment chambers are essential for comparing plant responses to various climates

“…In summary, SPAR > > FACE = TGG = OTC (Table 1). Characteristics of SPAR systems (items 5 to 10 in Table 1) are supported by several publications (e.g., Allen et al, 1991Allen et al, , 2003aBaker et al, 1990Baker et al, , 1997Gesch et al, 2003;Jones et al, 1984aJones et al, , 1984bJones et al, , 1985aJones et al, , 1985bPhene et al, 1978;Prasad et al, 2002Prasad et al, , 2003Prasad et al, , 2006Reddy et al, 2001;Tingey et al, 1996Tingey et al, , 2000Fleischer et al, 2010).…”

“…The SPAR chambers can be maintained at any daytime level from sub-ambient through supra-ambient CO 2 concentration ranging from < 100 ppm to > > 1000 ppm (Allen, Bisbal, Boote, & Jones, 1991;Phene et al, 1978). Night-time levels are not as easily controlled due to plant respiration in a contained environment, but it would be possible by injection of CO 2 -free air.…”

“…The SPAR systems can emulate CO 2 concentration that existed in any past climates and that may exist in the future. Emulations can include low values of 280-300 ppm (Cunniff et al, 2010;Sage, 1995) that existed during the Last Glacial Maximum (about 19,000-26,500 yr before present, Clark et al, 2009), pre-industrial revolution concentrations of about 287 ppm, current ambient concentrations of ∼410 ppm, and any projected concentrations into the future (Allen et al, 1991;Jones et al, 1984a;Phene et al, 1978;Reddy et al, 2001;Tingey et al, 1996;Fleisher et al, 2010aFleisher et al, , 2010b. The FACE systems are limited to a relatively small increase above ambient CO 2 concentration, which is a continuously increasing baseline.…”

“…The primary focus is to compare the SPAR system with the FACE system. The SPAR systems were developed originally by collaborators among USDA-ARS at Mississippi State University, USDA-ARS at Florence, SC, and Clemson University, SC (Parsons, Dunlap, McKinion, Phene, & Baker, 1980;Phene, Baker, Lambert, Parsons, & McKinion, 1978). These systems were adapted for crop research at USDA-ARS at Mississippi State University (McKinion & Baker, 1982); Clemson University (DeWitt, Wadron, & Lambert, 1983); University of Florida (Jones, Jones, Allen, & Mishoe, 1984b); USDA-ARS, Beltsville, MD (K. Reddy et al, 2001); and USEPA, Corvallis, OR (Tingey et al, 1996).…”