Picloram effects on ribonucleic acid and protein biosynthesis in excised plant tissues

Abstract

Picloram (4-amino-3,5,6-trichloropicolinic acid), both at growth-promoting (10 μg/ml) and growth-inhibiting (500 μg/ml) concentrations decreased the loss of RNA (ribonucleic acid) and protein of excised soybean (Glycine max (L.) Merr. cv. Harosoy 63) hypocotyl, barley (Hordeum vulgare L. cv. Parkland) coleoptile, barley leaf, and Canada thistle (Cirsium arvense (L.) Scop.) leaf tissues during an 8-h incubation. At a growth-promoting concentration picloram enhanced RNA and protein biosynthesis (incorporation of 14C-labeled precursors), whereas at a growth-inhibiting concentration it inhibited such synthesis. Incorporation of radioactivity into RNA and protein of particulate and supernatant fractions (separated at 20 000 × g) appeared to be equally sensitive to picloram. Actinomycin D and cycloheximide in the incubation medium markedly inhibited both normal and picloram-induced growth and RNA and protein biosynthesis. Puromycin was less effective in inhibiting growth and protein biosynthesis. Picloram, gibberellic acid, and indoleacetic acid all promoted growth and RNA and protein biosynthesis though they did so at different concentrations and to varying degrees. Our results indicate that picloram has a role in altering both net synthesis of RNA and protein and some processes in the degradative metabolism of these constituents.