ARS | Publication request: Gas exchange and water relations responses of spring wheat to full-season infrared warming

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2010
Publication Date: June 1, 2011
Citation: Wall, G.W., Kimball, B.A., White, J.W., Ottman, M.J., 2011. Gas exchange and water relations responses of spring wheat to full-season infrared warming. Global Change Biology. 17:2113-2133.

Interpretive Summary: The Earth is warming globally, which may affect the growth and water use characteristics of wheat – the world’s foremost food and feed crop. Therefore, scientists utilized an ecosystem warming apparatus to induce full-season warming of a spring wheat crop by 1.5 and 3.0°C during the day and night periods, respectively. Measurements of growth and water use were made over a broad range of leaf temperatures throughout the growing season of the crop. Warming of the wheat crop accelerated its growth and created mild drought conditions, which affected water usage. Understanding the effects of global warming on a wheat crop will enable growers and end-users to make more efficient use of water resources in wheat producing regions of the world under conditions of global climate change.

Technical Abstract: Gas exchange and water relations responses to full-season in situ infrared (IR) warming were evaluated for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semi-arid desert region of the Southwest USA. A Temperature Free-Air Controlled Enhancement (T-FACE) apparatus was employed to increase the wheat canopy temperature in Heated plots above the corresponding temperature in Reference plots with dummy heaters by set-point differences of 1.5 and 3.0 oC during daytime and nighttime, respectively. In addition, there were Control plots with no apparatus. The three warming treatments (i.e., Control, Heated, Reference) in three replicates were configured in a Latin Square (3x3) experimental designs on six planting dates during three months (Mar., Sept., Dec.). One natural temperature variation treatment (i.e., Control) in three replicates was configured in a Randomized Complete Block experimental design on nine planting dates during seven months (Jan., Feb., Apr., June, July, Aug., Oct.). On average the increases in the wheat canopy temperature of the Heated plots above those of the Reference plots were 1.3 and 2.5 oC for daytime and nighttime, respectively. Soil temperature (TS) and volumetric soil-water content ('S) were 1.3 oC warmer and 14% lower in the IR-warmed compared with non-warmed plots, respectively. Other than a 1% shading effect, no experimental artifacts on gas exchange or water relations responses appeared to be associated with the IR warming apparatus itself. Seasonal oscillations in IR warming effects on gas exchange and water responses were observed – this lack of discernable response may have been attributed to the well-watered condition of the wheat crop. The most significant effect of IR warming was its thermal protection during tipping point threshold cardinal temperature frost/freeze events. Infrared warming is an effective way to investigate the impact of global climate change on agronomic cropping systems to a wide range of natural and artificially imposed air temperatures.