Elevated carbon dioxide and ozone effects on peanut: II. Seed yield and quality

Many adverse effects of tropospheric [O.sub.3] on [C.sub.3] crop plants are ameliorated by elevated concentrations of atmospheric C[O.sub.2], but the extent of the interaction can vary, depending on the species, gas concentrations, and other experimental conditions. A 2-yr open-top field chamber experiment was conducted to examine this interaction in peanut (Arachis hypogaea L.) by testing the effects of [O.sub.3] and C[O.sub.2] mixtures on yield and seed quality. Treatments were ambient C[O.sub.2] (375 [micro]mol [mol.sup.-1]) and C[O.sub.2] additions of approximately 173 and 355 [micro]mol [mol.sup.-1] in combination with charcoal-filtered (CF) air (22 nmol [O.sub.3] [mol.sup.-1]), nonfiltered (NF) air (46 nmol [O.sub.3] [mol.sup.-1]), and NF air plus [O.sub.3] (75 nmol [O.sub.3] [mol.sup.-1]). At ambient C[O.sub.2], pod number was suppressed 16% in NF air and 44% in elevated [O.sub.3]. Pod and seed mass were not significantly affected in NF air but were lowered 33 to 37% in elevated [O.sub.3]. Elevated C[O.sub.2] increased yield parameters 7 to 17% for plants grown in CF air and restored yield in NF air and elevated [O.sub.3] treatments to control or higher levels. Gas treatment effects on peanut market grade characteristics were small. No treatment effects were observed on the protein and oil contents of seeds, but there were changes in fatty acid composition. Overall results indicate that increasing concentrations of tropospheric [O.sub.3] will suppress yield of [O.sub.3]-sensitive peanut cultivars, while elevated C[O.sub.2] will moderate this response. Elevated [O.sub.3] and C[O.sub.2] are not expected to have major effects on peanut seed composition and quality.