Relationship between ethylene and spermidine in the leaves of Glycyrrhiza uralensis seedlings under root osmotic stress

The correlation between ethylene (ETH) production and spermidine (Spd) content was studied in the leaves of Glycyrrhiza uralensis seedlings under root osmotic stress. After 4-h root osmotic stress, Spd inhibited ETH production significantly while ETH had no significant influence on Spd content in leaves. After 24-h root osmotic stress, ETH production and Spd content showed significant negative correlations in leaves, and the negative correlations were still significant even if the common precursor S-adenosylmethionine (SAM) was abundant. This result suggested that the significant negative correlations were not mainly caused by the competition for the common precursor SAM. The results also showed that, after 24-h root osmotic stress, ETH enhanced while Spd reduced the production rate of H2O2 and markedly in leaves; furthermore, exogenous H2O2 accelerated the increase in ETH production and the decrease in Spd content caused by deep stress. So it could be concluded that reactive oxygen species played important roles in the significant negative correlations in the deeply stressed leaves of G. uralensis seedlings.