Tropospheric Ozone and Interspecific Competition between Yellow Nutsedge and Pima Cotton
- D. A. Grantz *a and
- Anil Shresthab
- a Dep. of Botany and Plant Sci. and Air Pollution Research Center, Univ. of California, Riverside, CA, and Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier, CA 93648
b Statewide Integrated Pest Management Program, Univ. of California, Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier, CA 93648
Plant competition may be altered by ongoing climate change, including rising tropospheric O3 This may depend less on the O3 tolerance of isolated species than on O3 effects on the mechanisms of competition. To explore this possibility, we investigate the growth and gas exchange responses of a crop–weed system in partial additive competition in open-top chambers (OTCs). Yellow nutsedge (Cyperus esculentus L.) and Pima cotton (Gossypium barbadense L.) were grown in pots in ratios of 0:1, 1:1, 2:1, and 3:1, plus 1:0 to contrast with 0:1. O3 concentrations (12-h means) were 12.8 nL L−1 (low O3, LO3), 79.9 nL L−1 (medium O3, MO3), and 122.7 nL L−1 (high O3, HO3). Cotton was more sensitive than nutsedge to O3 (reduction at HO3: 75 vs. 20% in shoot growth, 33 vs. 20% in assimilation). Cotton was inhibited by O3 and by competition and the interaction was significant for leaf properties of cotton and tuber production in nutsedge. A coefficient of competition (slope of inverse cotton shoot biomass vs. nutsedge density) was significantly increased at HO3. The species were mutually inhibitory to similar extents. Root respiration declined with O3 in nutsedge but increased in cotton, though both species reduced allocation below-ground. Nutsedge tuber production increased inconsistently with O3 Rising tropospheric O3 may decrease the current C4 advantage of nutsedge in water use efficiency (WUE) and stomatal avoidance of O3, but appears likely to increase the competitiveness of nutsedge with respect to cotton.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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