POLYAMINE CATABOLISM IN DORMANT EMBRYOS OF THE SPINDLE TREE (EUONYMUS-EUROPAEUS L) AND IN DORMANCY BREAK OBTAINED AFTER TREATMENT WITH GIBBERELLIC-ACID
N. Berangernovat et al., POLYAMINE CATABOLISM IN DORMANT EMBRYOS OF THE SPINDLE TREE (EUONYMUS-EUROPAEUS L) AND IN DORMANCY BREAK OBTAINED AFTER TREATMENT WITH GIBBERELLIC-ACID, Plant growth regulation, 21(1), 1997, pp. 65-70
Previously we showed that dormancy break of spindle tree embryos after
gibberellic acid (GA(3)) treatment was followed by an increase in arg
inine decarboxylase (ADC) activity (Beranger-Novat N. et al., Plant Sc
. 102: 139-145, 1994). These results indicated that arginine decarboxy
lase pathway mediate hormone-induced growth responses in spindle tree
embryos. In the present investigation we show that in GA(3)-treated em
bryos diamine oxidase (DAO) increases immediately after putrescine con
tent and the increase in DAO activity paralleles the accumulation of p
utrescine at the beginning of the culture (before the visible appearan
ce of the radicle). In this system polyamine oxidase (PAO) increases i
mmediately after DAO activity and follows closely the increase in sper
midine content. These results demonstrate a direct correlation between
the biosynthesis and oxidation of putrescine and spermidine. At every
stage of development DAO and putrescine levels are lower than spermid
ine and PAO levels. Dormant embryos can be distinguished from GA(3)-tr
eated embryos by a complete lack of putrescine accumulation. In dorman
t embryos compared to GA(3)-treated embryos DAO changed more or less i
n parallel and on the whole seemed to follow the same content and dist
ribution, but the kinetics of the activation of DAOs were different in
dormant embryos with a delay of 1.5 day for the first and 1 day for t
he second peak. During the first days of culture at least up to 4 days
the distribution of spermidine and PAO in GA(3)-treated embryos follo
wed the same pattern observed in dormant embryos, but the levels of sp
ermidine and PAO were greatly reduced in dormant embryos. On the other
hand the kinetics of the activation of PAOs were different in dormant
embryos with a delay of 1 day. The results suggest that dormant embry
os are deficient in their ability to synthesize polyamines efficiently
and support the view that spermidine catabolism (via PAO pool) is lim
iting in untreated embryos during the first days of culture.