Spectral balance and UV-B sensitivity of soybean: A field experiment

CALDWELL MM; FLINT SD; SEARLES PS

PLANT, CELL AND ENVIRONMENT (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Año: 1994 vol. 17 p. 267 - 276

0140-7791

Soybean [Glycine max (L.) Mem] cultivar Essex was grown and tested for sensitivity to UV-B radiation (280— 320 nm) under different combinations of UV-A (320-400 nm) and PFD (400-700 nm) radiation in four simultane-ous field experiments. The radiation conditions were effected with combinations of filtered solar radiation and UV-B and UV-A lamps electronically modulated to track ambient radiation. Significant UV-B-caused decreases in total aboveground production and growth were seen only when PFD and UV-A were reduced to less than half their flux in sunlight. When PFD was low, UV-A appeared to be particularly effective in mitigating UV-B damage. How-ever, when PFD was high, substantial UV-A did not appear to be required for UV-B damage mitigation. Leaf chlorophyll fluorescence did not indicate photosynthetic damage under any radiation combination. With UV-B, leaves in all experiments exhibited increased UV-absorb-ing pigments and decreased whole-leaf UV transmittance. Results of these field experiments indicate difficulties in extrapolating from UV-B experiments conducted in glasshouse or growth cabinet conditions to plant UV-B sensitivity in the field. Implications for UV radiation weighting functions in evaluating atmospheric ozone reduction are also raised.