Combined Effects of Ozone and Water Stress on Alfalfa Growth and Yield

Abstract

A 2‐yr study (1984 and 1985) designed to determine the interactive effects of ozone (O3) and water stress on alfalfa (Medicago sativa L. cv. WL‐514) was conducted in Shafter, CA. The objectives of this study were to develop O3 dose‐yield response functions for alfalfa, to determine how water stress could alter these functions, and to describe the cumulative effects of multiple‐year exposures to O3 on this perennial crop. Field‐grown alfalfa, raised under normally irrigated (NI) or water‐stressed (WS) conditions in open‐top chambers, was exposed to five O3 treatments including charcoal‐filtered (CF), nonfiltered (NF), NF plus an additional 33, 67, or 100% of ambient O3 concentrations (NF × 1.3, NF × 1.7, and NF × 2.0, respectively). Ambient O3 concentrations averaged 0.049 µL L−1 in 1984 and 0.042 µL L−1 in 1985 for the seasonal 12‐h (0900–2100) means from April to October. Water stress reduced total seasonal yield about 10% in 1984 and 27% in 1985. Ozone significantly reduced yields in both years, and the interaction between O3 and water stress was statistically significant in 1985 and for combined 1984 and 1985 years. Seasonal yields for 1985 in NI plots were reduced 0, 14.9, 24.3, and 24.9% in NF, NF × 1.3, NH × 1.7, and NF × 2.0 treatments, respectively. Comparable seasonal yield reductions in WS plots were 5.9, 7.2, 13.5, and 18.1%. Ozone dose‐alfalfa yield loss functions were homogeneous between 1984 and 1985 and no evidence of a cumulative effect of multiple‐year exposure to O3 was found on top growth. However, crown (underground stem) weights were significantly reduced by O3, suggesting that continued exposure to O3 could shorten the productive life of alfalfa stands, in addition to its effect on yield.

California Statewide Assessment of the Effects of Ozone on Crop Productivity

“…10 -12 Most of the EPA NCLANsponsored data have been published in the peer reviewed literature. Crops using EPA NCLAN research equations for the loss assessment were alfalfa (normal irrigation, 1984), 21 barley, 17 dry beans, 12 ' 13 field corn, 15 cotton, 20 lettuce, 18 sorghum, 14 processing tomatoes, 12 -19 and wheat. 16 The equation for spinach was based on a research protocol very similar to that for NCLAN.…”

Diel trends in stomatal response to ozone and water deficit: a unique relationship of midday values to growth and allometry in Pima cotton?

“…), including antagonistic (protective) interactions (Temple , ; Temple et al . ,b; Silim et al . ) and synergistic (deleterious) interactions (Heggestad et al .…”

“…Stomatal closing responses to WD reduce O 3 influx (Temple , ; Temple et al . ,b; Grantz et al . ; Grunhage et al .…”

Demonstration of a diel trend in sensitivity of Gossypium to ozone: a step toward relating O3 injury to exposure or flux

“…It captures the potentially myriad diurnal, seasonal, and developmental changes that may occur in antioxidants, tortuosity of substomatal diffusion pathways, and even in the conformational sensitivity of specific ozone targets. Variability in susceptibility to [O 3 ] has been linked to stomatal responses (Brosche et al ., 2010), and this is the basis for protection against O 3 by drought (Temple et al ., 1985, 1988; Fuhrer, 2009). These conclusions are independent of diel patterns of stomatal regulation and of the diel patterns of ambient [O 3 ], since S is quantified in terms of F. S is an independent parameter that may be useful as a weighting factor in relating injury to F.…”