The effects of abscisic Acid on growth and nucleic Acid synthesis in excised embryonic bean axes.

Abscisic acid (ABA) is an effective inhibitor of cell elongation in excised embryonic bean axes whether added prior to or after the initiation of cell elongation. Zeatin partially reverses this growth inhibition. ABA inhibits (32)P incorporation into ribosomal RNA, transfer RNA, and DNA but not into the tenaciously bound fraction of elongating axes in a manner resembling 5-fluorouracil, a compound which does not inhibit axis growth. The methylated albumin on kie-selguhr elution profiles of nucleic acids obtained from axes treated with either ABA, 5-fluorouracil, or a combination of the two are similar, and zeatin treatment has little apparent effect on these results. Our results suggest that the inhibition of growth in the axes by ABA is not due to its inhibition of DNA synthesis.ABA (1.9 x 10(-5)m) inhibits growth by 30 and 70% within 1 and 2 hours, respectively, after its addition to elongating axes. Its kinetics of inhibition are similar to those obtained with cycloheximide, and both compounds are more effective than 8-azaadenine. Based on these results, it is suggested that one possible effect of ABA may be at the level of translation.