Ozone Impacts on Competition between Tomato and Yellow Nutsedge
- Anil Shresthaa and
- D. A. Grantz *b
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 O3Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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