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Investigation of ozone (O3) effects on 14C distribution in Ladino clover

1983; Elsevier BV; Volume: 23; Issue: 4 Linguagem: Inglês

10.1016/0098-8472(83)90013-8

1873-7307

Udo Blum, Edward Mrozek, Emanuel L. Johnson,

Atmospheric chemistry and aerosols

Ladino clover plants were exposed to 0, 0.05, 0.10 or 0.15 ppm O3 for 4 hr per day for 6 days starting 32 days after planting. Leaf injury was estimated and 14CO2 exposures were given 48 hr after the last O3 exposure. One mature leaf per plant with visible injury roughly equivalent to whole plant injury was exposed to 14CO2 in a plexiglass chamber for 15 min. Twenty-four hours later, plants were harvested, placed on herbarium sheets, frozen and freeze-dried. Radioautographs were subsequently used to determine the distribution of 14C and as a guide in partitioning plant material for quantification of radioactivity. Ozone exposures reduced root dry weight more than shoot dry weight of ladino clover. The maximum reduction for shoot dry weight was 24% while the maximum reduction for root dry weight was 42%. Total plant radioactivity values, determined 24 hr after the 14CO2 exposure, indicated that increasing O3 concentrations reduced net photosynthesis of clover plants. The proportion of carbon allocated to the roots increased gradually from 35 to 52% with increasing O3 levels up to 0.10 ppm and then decreased rapidly to 21% at 0.15 ppm. Carbon allocation to developing leaves decreased from 64 to 48% with increasing O3 levels up to 0.10 ppm and then increased to 79% at 0.15 ppm.