Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2003
Publication Date: 10/23/2003
Citation: Ratnayaka, H.H., Molin, W.T., Sterling, T.M. 2003. Physiological and antioxidant responses of cotton and spurred anoda under interference and mild drought. Journal of Experimental Botany. 54:2293-2305. Interpretive Summary: Crops experiencing competition from weeds generally have reduced vigor and yields. This paper seeks to explain the physiological basis for yield reduction through an examination of the effects of spurred anoda competition on cotton. Two cotton species were subjected to competition from like species, called intraspecific interference, or from spurred anoda, a weed commonly found in cotton. Spurred anoda had higher stomatal conductance and transpiration rates than cotton suggesting that this species had a different capacity to regulate its water status although its net photosynthesis rates were similar to cotton. Cotton in competition with spurred anoda had reduced photosynthesis and increased levels in physiological protective systems suggesting physiological stress resulted from competition. The impact of spurred anoda competition on cotton was mainly due to reduced carbon gain which can account for the yield losses resulting from weed competition.
Technical Abstract: Influence of plant interference and a mild drought on gas exchange and oxidative stress was investigated using potted plants of two cotton species (Gossypium hirsutum L. cv. Delta Pine 5415, and Gossypium barbadense L. cv. Pima S-7) and spurred anoda [Anoda cristata (L.) Schlecht.]) of Malvaceae. Without interference, cotton and spurred anoda had similar net photosynthesis (Pnet) but different pigment profiles. Stomatal conductance (gs) and transpiration rate (E) were greater in spurred anoda than cotton. Net photosynthesis and biomass in cotton were reduced more by spurred anoda interference than by intraspecific interference. With interference, de-epoxidation state (DPS) and alpha-tocopherol levels increased in cotton but remained unchanged in spurred anoda. Catalase, ascorbate peroxidase (APX) and glutathione reductase (GR) activities were not influenced by plant interference. Without interference, spurred anoda had lower APX, and similar catalase and GR activities compared to cotton. Mild drought increased APX activity more than 40% in cotton, and 26% in spurred anoda. During drought recovery, drought-induced APX activity was still higher in cotton, and GR activity was higher in previously drought-stressed cotton and spurred anoda plants compared to well-watered plants. Greater impact of spurred anoda interference on cotton biomass than intraspecific interference is due mainly to reduced carbon gain in cotton.