Effects of elevated carbon dioxide and ozone on the growth and yield of potatoes (Solanum tuberosum) grown in open-top chambers

Potato (Solanum tuberosum cv. Bintje) was grown in open-top chambers under three carbon dioxide (ambient and seasonal mean concentrations of 550 and 6 80 mu mol mol(-1) CO2) and two ozone concentrations (ambient and an 8 h day (-1) seasonal mean of 50 nmol mol(-1) O-3) between emergence and final harv est. Periodic non-destructive measurements were made and destructive harves ts were carried out at three key developmental stages (24, 49 and 101 days after emergence) to establish effects on growth and tuber yield. Season-lon g exposure to elevated O-3 reduced above-ground dry weight at final harvest by 8.4% (P < 0.05), but did not affect tuber yields. There was no signific ant interaction between CO2 and O-3 for any of the growth and yield variabl es examined. Non-destructive analyses revealed no significant effect of ele vated CO2 on plant height, leaf number or green leaf area ratio. However, d estructive harvests at tuber initiation and 500<degrees>Cd after emergence showed that above-ground dry weight (8 and 7% respectively) and tuber yield (88 and 44%) were significantly increased (P < 0.05) in the 550 <mu>mol mo l(-1) CO2 treatment. Responses to 550 and 680 mu mol mol(-1) CO2 were not s ignificantly different for most parameters examined, suggesting the existen ce of an upper limit to the beneficial influence of CO2 enrichment. Signifi cant effects on above-ground dry weight and tuber yield were no longer appa rent at final harvest, although tuber numbers were increased (P < 0.05) und er elevated CO2, particularly in the smaller size categories. The results s how that the O-3 treatment imposed was insufficient to reduce tuber yields and that, although elevated CO2 enhanced crop growth during the early stage s of the season, this beneficial effect was not sustained to maturity. (C) 2000 Elsevier Science Ltd. All rights reserved.