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CROP ECOLOGY, MANAGEMENT & QUALITY

Ozone Impacts on Competition between Tomato and Yellow Nutsedge

Above- and Below-Ground Effects

^a Statewide Integrated Pest Management Program, Univ. of California, Kearney Agric. Center, 9240 South Riverbend Ave., Parlier, CA 93648
^b Dep. of Botany and Plant Sciences, Univ. of California, Riverside, CA, and Kearney Agric. Center, 9240 South Riverbend Ave., Parlier, CA 93648

^* Corresponding author (david{at}uckac.edu)

Tomato (Lycopersicon esculentum L.) production in the San Joaquin Valley (SJV) of California is challenged by air pollution and weeds. Differential ozone (O₃) tolerance of tomato cultivars and weed species may alter crop–weed competition. A study was conducted in open top chambers (OTCs) at the Kearney Research and Extension Center, Parlier, CA, to assess O₃ impacts on competition between tomato and a C₄ weed, yellow nutsedge (Cyperus esculentus L.). Processing tomato (cv. HD 8892 and EMP 113) and nutsedge (locally collected biotypes) were grown in pots for 4 to 8 wk. Population ratios ranged from a tomato plant alone (0:1) to a nutsedge plant alone (1:0), and included 1:1, 2:1, and 3:1. Ozone exposures were to 12 h means of 19.8, 78.0, and 142.3 nL/L. Chlorophyll content of leaves of tomato and nutsedge was reduced with increasing O₃. Carbon assimilation was reduced in nutsedge but not in tomato. Root respiration was not affected in either species. Tomato main stem length, shoot, and root biomass declined at the highest O₃ concentration under all levels of nutsedge competition. Nutsedge was much less affected. In the absence of O₃ exposure, interspecific competition (all population ratios combined) reduced tomato and nutsedge shoot and root biomass. Tomato was more sensitive to O₃ than nutsedge, but nutsedge was more sensitive to competition than was tomato. Nutsedge allocated greater resources to reproductive structures (tubers) at the highest O₃ exposure. As nutsedge reduced tomato productivity under low and moderate O₃ concentrations, it may become even more difficult to control, exert greater competitiveness, and colonize fields more rapidly because of greater tuber production, in projected near-future environments. Under conditions of greatly increasing ambient O₃ concentrations, nutsedge may become less competitive because of its sensitivity to O₃.

Abbreviations: A_n, net carbon assimilation • CF, charcoal filtered air • g_s, stomatal conductance • gfwt, grams fresh weight • hm, mean of hourly mean O₃ concentrations over specified daylight period • HO3, high O₃ concentration • LAR, leaf area ratio (total leaf area/total shoot dry weight) • LO3, low O₃ concentration • LWR, leaf weight ratio (total leaf dry weight/total shoot dry weight) • MO3, medium O₃ concentration • OTC, open-top chamber • SLW, specific leaf weight (leaf area/total leaf dry weight)

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THIS ISSUE IN CROP SCIENCE

Crop Science 2005 45: vii. [Full Text]  

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