The important roles of reactive oxygen species in the relationship between ethylene and polyamines in leaves of spring wheat seedlings under root osmotic stress

The important roles of reactive oxygen species (ROS) in the relationship between ethylene (ETH) and polyamines (PAs) were investigated in leaves of spring wheat seedlings under root osmotic stress. The results showed that the increase in polyamine content reduced (while the decrease in polyamine content promoted) the production of ROS and ETH significantly in the deeply and not deeply stressed leaves. The promotion and inhibition in ETH production had no significant influence on the production of ROS, the activities of diamine oxidases (DAOs) and polyamine oxidases (PAOs), the content of putrescine (Put), spermidine (Spd) and spermine (Spm) in the not deeply stressed leaves. But in the deeply stressed leaves, the promotion in ETH production significantly promoted the production of ROS and the activities of DAOs and PAOs, thus reduced the content of these amines; the inhibition in ETH production significantly reduced the production of ROS and the activities of DAOs and PAOs, and thus alleviated the decline in the content of these amines that was caused by deep stress. It was also found that exogenous H2O2 promoted ETH production and the activities of DAOs and PAOs, and reduced the content of these amines in the deeply stressed leaves. The above results suggested that ROS played extremely important roles in the relationship between ETH and PAs: through reducing ROS levels, PAs inhibited ETH production in the deeply and not deeply stressed leaves; through promoting ROS levels, ETH promoted polyamine oxidation and hence reduced its content in the deeply stressed leaves; but in the not deeply stressed leaves, ETH had no significant influences on ROS levels and the activities of DAOs and PAOs, so the content of these amines was not significantly influenced. (C) 2003 Elsevier Ireland Ltd. All rights reserved.