Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2006
Publication Date: 8/1/2006
Citation: Bettmann, G.T., Ratnayaka, H.H., Molin, W.T., Sterling, T.M. 2006. Physiological and antioxidant responses of cotton and spurred anoda (anoda cristata)under nitrogen deficiency. Weed Science 54:641-650. Interpretive Summary: Physiological responses of two species of cotton and two accessions of the weed, spurred anoda, were investigated under nitrogen (N) deficiency in the greenhouse. This research was performed at New Mexico State University in Las Cruces, NM, as part of a USDA/CSREES National Research Initiative competitive grant to Drs. Sterling and Molin. The results show that one species of cotton had the most photo-reactive pigments (chlorophyll, lutein). Both cotton species had greater anthocyanain, vitamin e, and oxidative stress alleviating compounds compared to spurred anoda. These physiological characteristics of cotton may contribute to cotton’s ability to compete with this weed species when grown in close association with cotton.
Technical Abstract: Physiological and antioxidant responses of two species of cotton (Gossypium barbadense L. cv. ‘Pima S-7’, and Gossypium hirsutum L., cv. ‘Delta Pine 5415’) and two accessions of spurred anoda [(Anoda cristata L. Schlecht, New Mexico (NM) and Mississippi (MS)] were investigated under nitrogen (N) deficiency in the greenhouse. Pima had the highest N content of all the plants regardless of treatment. Biomass decreased in all species when N was withheld, with Pima exhibiting the least reduction and MS the greatest. Plant height decreased in all plant types except for MS, which increased in height under N stress. Height:node ratio increased 2% in spurred anoda accessions, but decreased as much as 8% in cotton when deprived of N. Withholding N reduced photosynthesis 45% regardless of species. Comparable decreases were found in stomatal conductance and transpiration, suggesting strong stomatal regulation of gas exchange under N stress. The quantum efficiency of photosystem II (dark-adapted Fv/Fm) decreased as much as 4% in N deficient treatments. Alpha-carotene decreased for all species when N was withheld, except for the NM accession, in which the levels increased. Total chlorophyll and lutein declined under N stress regardless of species, but the antioxidant alpha-tocopherol and the xanthophyll cycle conversion state increased. Pima had the most chlorophyll and lutein, and both cotton species contained more alpha-tocopherol, had detectable levels of anthocyanins, and were better at scavenging free-radical DPPH. These enhanced characteristics of cotton, particularly Pima, may contribute to cotton’s ability to compete for N with spurred anoda.