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UV‐absorbing compounds and susceptibility of weedy species to UV‐B radiation
Author(s) -
DAI QIUJIE,
FURNESS NANCY H.,
UPADHYAYA MAHESH K.
Publication year - 2004
Publication title -
weed biology and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.351
H-Index - 36
eISSN - 1445-6664
pISSN - 1444-6162
DOI - 10.1111/j.1445-6664.2004.00125.x
Subject(s) - weed , biology , botany , ozone depletion , distilled water , shoot , ultraviolet b radiation , sunlight , stellaria media , ultraviolet radiation , chemistry , ozone , physics , astronomy , radiochemistry , organic chemistry , chromatography
Stratospheric ozone (O 3 ) depletion has led to increased terrestrial ultraviolet‐B (UV‐B) radiation (290–320 nm). Leaves exposed to this radiation produce UV‐absorbing compounds in the epidermal cells, which protect plants from UV‐B damage. To determine the role of UV‐absorbing compounds in the UV‐B sensitivity of weeds (common chickweed ( Stellaria media ), downy brome ( Bromus tectorum ), green smartweed ( Polygonum scabrum ), redroot pigweed ( Amaranthus retroflexus ), spotted cat’s‐ear ( Hypochoeris radicata ), and stork’s‐bill ( Erodium cicutarium )) seedlings were exposed to 0, 4 (field ambient), 7 (18% O 3 depletion) and 11 (37% O 3 depletion) kJ m −2 d −1 of biologically effective UV‐B radiation in a greenhouse. Ultraviolet‐absorbing compounds were extracted from the second true‐leaf (0.5 cm 2 samples) with methanol : distilled water : HCl (79 : 20 : 1) in an 85°C water bath for 15 min, and the absorbance of the extracts measured at 300 nm. The shoot dry biomass was recorded to determine the susceptibility to UV‐B radiation. Common chickweed was the most sensitive and green smartweed the least sensitive weed to UV‐B radiation. The latter accumulated more UV‐absorbing compounds and this accumulation occurred earlier compared with common chickweed. As UV‐B BE radiation levels increased from 0 to 11 kJ m −2 d −1 , the green smartweed shoot biomass did not decline. However, the biomass of all five susceptible species declined despite an increase in the UV‐absorbing compounds in response to increased UV‐B radiation. Therefore, formation of a ‘UV‐screen’ in these species is not sufficient to fully prevent UV‐B damage. When the concentration of UV‐absorbing compounds in the six species was plotted against their susceptibility to UV‐B radiation, no relationship was observed. Thus, while the accumulation of UV‐absorbing compounds may be a major factor in the protection of certain species against UV‐B radiation and may offer some degree of defence in other species, it does not explain UV‐B susceptibility differences in weedy species in general.