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Competitive interactions in mixtures of broccoli and Chenopodium album grown at two UV‐B radiation levels under glasshouse conditions
Author(s) -
FURNESS N H,
JOLLIFFE P A,
UPADHYAYA M K
Publication year - 2005
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1111/j.1365-3180.2005.00476.x
Subject(s) - interspecific competition , intraspecific competition , chenopodium , competition (biology) , biology , horticulture , brassica , botany , chemistry , ecology , weed
Summary Ultraviolet‐B radiation effects on intra‐ and interspecific competition in broccoli ( Brassica oleracea ) and Chenopodium album were studied using bivariate factorial experiments. A randomized block design was used in which three monoculture densities for each species [144 (low), 256 (medium), and 400 (high) plants m −2 ] and all binary combinations were grown in a glasshouse at two (4 and 7 kJ m −2 day −1 ) UV‐B BE radiation levels for 4 weeks in 1999 and 5 weeks in 2000. Inverse yield–density relationships were more discernible at 4, compared with 7 kJ m −2 day −1 UV‐B BE radiation. Substitution rates, indicating the balance of intra‐ to interspecific competitive effects, declined for broccoli at 7, compared with 4 kJ m −2 day −1 UV‐B BE radiation, largely because of reduced interspecific competitive influences. Conversely, substitution rates increased for C. album grown at 7 kJ m −2 day −1 UV‐B BE radiation, as a result of both decreased intraspecific and increased interspecific competition. Interspecific competitive effects were influenced more than intraspecific competitive effects by UV‐B radiation. Based on relative magnitude of substitution rates, C. album was a stronger competitor than broccoli at 4 kJ m −2 day −1 UV‐B BE radiation in both years, and at 7 kJ m −2 day −1 UV‐B BE radiation in 1999. In 2000, broccoli was the stronger competitor at 7 kJ m −2 day −1 UV‐B BE radiation. Overall, the relative competitiveness of broccoli was enhanced, while that of C. album diminished at 7, compared with 4 kJ m −2 day −1 UV‐B BE radiation. These findings indicate that above‐ambient UV‐B radiation has the potential to alter crop–weed competitive interactions, which could change acceptable weed threshold levels.