Growth and yield responses of potato to mixtures of carbon dioxide and ozone

Elevated carbon dioxide (CO2) concentrations in the atmosphere can stimulate plant growth and yield, whereas ground-level ozone (O-3) concentrations cause the opposite effect in many areas of the world. Recent experiments show that elevated CO2 can protect some plants from O-3 stress, but this has not been tested for most crop species. Our objective was to determine if elevated CO2 protects Irish potato (Solanum tuberosum L.) from foliar injury and suppression of growth and yield caused by O-3. An O-3-resistant cultivar (Superior) and an O-3-sensitive cultivar (Dark Red Norland) were exposed from within 10 d after emergence to maturity to mixtures of three CO2 and three O-3 treatments in open-top field chambers. The three CO2 treatments were ambient (370 muL L-1) and two treatments with CO2 added to ambient CO2 for 24 h d(-1) (540 and 715 muL L-1). The O-3 treatments were charcoal-filtered air (15 nL L-1), nonfiltered air (45 nL L-1), and nonfiltered air with 03 added for 12 h d(-1) (80 nL L-1). Elevated O-3 and CO2 caused extensive foliar injury of Dark Red Norland, but caused only slight injury of Superior. Elevated CO2 increased growth and tuber yield of both cultivars, whereas elevated O-3 generally suppressed growth and yield, mainly of Dark Red Norland. Elevated CO2 appeared to protect Dark Red Norland from O-3-induced suppression of shoot, root, and tuber weight as measured at midseason but did not protect either cultivar from O-3 stress at the final harvest. The results further illustrate the difficulty in predicting effects of O-3 + CO2 mixtures based on the effects of the individual gases.