Weed Research (2011) 51, 591-600

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M. Valerio, M.B. Tomecek, S. Lovelli and L.H. Ziska (2011)
Quantifying the effect of drought on carbon dioxide-induced changes in competition between a C3 crop (tomato) and a C4 weed (Amaranthus retroflexus)
Weed Research 51 (6), 591-600
Abstract: Recent and projected increases in atmospheric carbon dioxide concentration ([CO2]) and subsequent effects on climate are likely to alter competitive outcomes of weeds and crops. Rising [CO2] per se could increase the competitive ability of C3 crops relative to C4 weeds. However, such an outcome may depend on other climatic variables. In this study, tomato, a C3 crop species, was grown from emergence to anthesis using replacement series mixtures with Amaranthus retroflexus, a C4 weed species at three different [CO2], 400, 600 and 800 μmol mol−1, with and without water stress. Under well-watered conditions, leaf photosynthetic rates and plant height, leaf area and biomass all increased with elevated [CO2] for tomato relative to A. retroflexus, consistent with the kinetics of C3 photosynthesis. However, if water was limiting, a significant positive effect of [CO2] was noted for plant height and biomass of A. retroflexus with increased competition. This result may be related to a greater increase in leaf water potential with rising [CO2] for A. retroflexus relative to tomato under water stress. Overall, these are the first data to suggest that increases in atmospheric CO2 could still exacerbate crop losses from a C4 weed, even with a C3 crop, if drought occurs.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: English)
Link to article at publishers website
Database assignments for author(s): Stella Lovelli

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Amaranthus retroflexus (weed)