ABSCISIC-ACID INCREASES THE CONTENT OF FREE POLYAMINES AND DELAYS MITOTIC-ACTIVITY INDUCED BY SPERMINE IN ISOLATED EMBRYONIC AXES OF CHICKPEA SEEDS

The effects of abscisic acid (ABA) on the free polyamine: spermine (Spm), spermidine (Spd), putrescine (Put) and cadaverine (Cad) content, mitotic index (MI) and DNA synthesis have been studied in embryonic axes isolated from chick-pea (Cicer arietinum L.) seeds. Spermine and spermidine decreased in controls during the first 24 h of germination, the former by 70% and the latter by 20%. This decrease was slowed down by ABA (5-mu-M or 25-mu-M) in response to its concentration, at 24 h the values for Spm and Spd were 3-fold and 1.5-fold those of the controls, respectively. Exogenous ABA induced the synthesis of Put from 0 to 24 h, by which time the content of this polyamine had doubled. The controls at 24 h registered the same Put content as those with 25-mu-M ABA, suggesting that ABA had ceased to induce Put synthesis. The pattern for cadaverine ABA-induced synthesis was similar to that of Put. From 18 to 24 h. however, the level of Cad in the controls was 3 times higher than in the treatments. The mitotic index in meristem cells reached a maximum at 30-36 h, when cell elongation stopped in the sub-apical region. This maximum was lowered by exogenous ABA in response to the concentration and occurred 12 h earlier in the presence of Spm (0.1-1.0 MM), which induced high MI levels during thc period studied. With 10 mM Spm, two complete waves of mitosis were observed, but when Spm and ABA were added together, the tetramine had no observable effect. Spermine stimulated H-3-thymidine uptake as well as DNA synthesis, with a maximum at 12 h. but did not counteract the inhibitory effect of ABA. Our results suggest that ABA causes changes in mitotic activity that Spm cannot overcome.