Cell elongation in the soybean root: The influence of inhibitors of RNA and protein biosynthesis

A possible requirement for RNA and protein synthesis duringcell elongation of intact seedling tissue was studied usingthe soybean seedling foot with the elongating zone being delineatedby India ink marks at 2 and 7 mm back of the root tip. In contrastto most excised plant tissues, there was marked net synthesisof RNA and protein during cell elongation of the intact root.AD and CH were potent inhibitors of cell elongation in the soybeanroot. CH essentially eliminated protein synthesis, whether measuredby net accumulation of protein or by ¹⁴C-leiicine incorporation,while completely inhibiting cell elongation after a short lag.AD, on the other hand, only partially inhibited protein synthesiswhile causing almost total inhibition of cell elongation aftera lag. The capacity of the tissue to synthesize protein in thepresence of AD was correlated with the maintenance of functionalpolyribosomes, thus suggestive that m-RNA associated with theregulation of cell elongation is more unstable (i.e., a shortermean life) than total root m-RNA. FU did not inhibit cell elongation,protein synthesis or the level of functional polyribosomes.The requirement for RNA synthesis during cell elongation ofthe seedling root, as in excised plant tissues, appears to berestricted to the AMPrich species of RNA presumed to be m-RNA. ¹This research was supported by NIH grant GM 10157. ²Purdue University AES paper No. 3359. ³Present address: Dept. of Botany, National Taiwan University,Taipei, Taiwan.