[Inhibition of Elongation of Hypocotyls of Sinapis alba with FUDR].

Seedlings of Sinapis alba which were grown in light for 24, 48 and 72 h after 36 h of dark treatment renew elongation when transferred to dark again. The rate of elongation decreases with increased light treatment. The per cent as well as absolute inhibition of elongation by FUDR decreases with the duration of light treatment. The shortening of the hypocotyl is due mainly to the inhibition of cell elongation. The inhibition is not directly proportional to DNA synthesis at any particular time.Plants without cotyledons are less inhibited than those with cotyledons. Cytosine arabinoside is inhibitory only at high concentrations. According to these results elongation inhibition by FUDR does not involve the entire DNA-synthesis.