The effects of 2-thiouracil on growth and metabolism in the root. Ι. Growth of excised root tissue

Abstract

In this investigation isolated 2 to 4 mm subapical pea root segments were used to study the effect of 2-thiouracil on extension growth. 2-Thiouracil stimulated an increase in the lengths, fresh and dry weights, and polysaccharide material of the expanding segments, but only in the presence of a simple sugar. To produce the maximum stimulation it must be in contact with the tissue through out the entire cell expansion period. Uracil was an antagonist of 2-thiouracil stimulation. The analogue did not alter the morphological development of cells, xylem an d phloem formation being unaffected. Substances which are known to affect either growth (indole-3-acetic acid) or metabolism (D-threochloramphenicol and actinomycin D) were found to decrease or even abolish the stimulation caused by 2-thiouracil. 2-Thiouracil stimulation was also dependent on temperature, the maximum stimulation being observed at 25 to 30 °C.