TRANSLATABLE RNA POPULATIONS ASSOCIATED WITH MAINTENANCE OF PRIMARY ROOT ELONGATION AND INHIBITION OF MESOCOTYL ELONGATION BY ABSCISIC-ACIDIN MAIZE SEEDLINGS AT LOW WATER POTENTIALS

Previous work indicated that accumulation of abscisic acid (ABA) acts differentially to maintain elongation of the primary root and inhibit elongation of the mesocotyl of maize (Zea mays L.) seedlings at low wa ter potentials (psi(w)). Subsequent results indicated specific locatio ns in the elongation zones where elongation is maintained, inhibited, or unaffected by endogenous ABA at low psi(w). This information was ut ilized in this study to identify in vitro translation products of RNA associated with the maintenance or inhibition of elongation in the pri mary root and mesocotyl, respectively, by endogenous ABA at low psi(w) . The results distinguished products associated specifically with the elongation responses from those nonspecifically associated with ABA ac cumulation or low psi(w), as well as normal cell development and matur ation. In the primary root, the maintenance of elongation at low psi(w ) by ABA was associated with the maintenance of expression of three pr oducts that were also expressed during elongation at high psi(w), the expression of a novel product, and the suppression of two products. In the mesocotyl, the inhibition of elongation by ABA after transplantin g to low psi(w) was associated with the induction of a novel translati on product. However, the induction of this product, as well as accumul ation of ABA and inhibition of elongation, occurred without a decline in tissue water content. The results demonstrate the necessity of exam ining the association of gene expression with elongation responses to low psi(w) with a high degree of spatial resolution.