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1 July 2006 Physiological and antioxidant responses of cotton and spurred anoda (Anoda cristata) under nitrogen deficiency
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Spurred anoda is a major competitor with cotton in the southern United States. Physiological and antioxidant responses of two species of cotton (Gossypium barbadense L. cv. ‘Pima S-7’ and Gossypium hirsutum L., Delta and Pine Land Company cv. ‘Delta Pine 5415’) and two accessions of spurred anoda [New Mexico (NM) and Mississippi (MS)] were investigated under nitrogen (N) -sufficient and -deficient conditions in the greenhouse. Pima S-7 had the highest leaf N content of all the plants regardless of treatment. Biomass decreased in all species when N was withheld, with Pima S-7 exhibiting the least reduction and MS the greatest. Plant height decreased in cotton but not spurred anoda under N stress. Height:node ratio increased 9% in MS, but decreased 8% in DP 5415 when they were 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 4% under N deficiency. Alpha-carotene decreased for all species when N was withheld, except for the NM accession, in which the levels increased. Total chlorophyll and lutein decreased under N stress regardless of species, but alpha-tocopherol and the xanthophyll cycle conversion state increased. Pima S-7 had the most chlorophyll and lutein, and both cotton species had more alpha-tocopherol, anthocyanins, and free-radical scavenging capacity than spurred anoda. These enhanced pigment and antioxidant profiles of cotton, particularly Pima S-7, may contribute to cotton's ability to compete for N with spurred anoda.

Nomenclature: Spurred anoda, Anoda cristata (L.) Schlecht. ANVCR; cotton, Gossypium barbadense L. ‘Pima S-7’; Gossypium hirsutum L. ‘DP 5415’.

Greg T. Bettmann, H. Harish Ratnayaka, William T. Molin, and Tracy M. Sterling "Physiological and antioxidant responses of cotton and spurred anoda (Anoda cristata) under nitrogen deficiency," Weed Science 54(4), 641-650, (1 July 2006).
Received: 26 December 2005; Accepted: 1 April 2006; Published: 1 July 2006

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