Germination induction of dormant Avena fatua caryopses by KAR(1) and GA(3) involving the control of reactive oxygen species (H2O2 and O-2(center dot-)) and enzymatic antioxidants (superoxide dismutase and catalase) both in the embryo and the aleurone layers

摘要

Avena fatua L. caryopses did not germinate at 20 degrees C in darkness because they were dormant. However, they were able to germinate in the presence of karrikinolide (KAR(1)), a key bioactive compound present in smoke, and also in the presence of gibberellin A(3) (GA(3)), a commonly known stimulator of seed germination. The aim of this study was to collect information on a possible relationship between the above regulators and abscisic acid (ABA), reactive oxygen species (ROS) and ROS scavenging antioxidants in the regulation of dormant caryopses germination. KAR(1) and GA(3) caused complete germination of dormant A. fatua caryopses. Hydrogen peroxide (H2O2), compounds generating the superoxide (O-2(center dot-)), i.e. menadione (MN), methylviologen (MV) and an inhibitor of catalase activity, aminotriazole (AT), induced germination of dormant caryopses. KAR(1), GA(3), H2O2 and AT decreased ABA content in embryos. Furthermore, KAR(1), GA(3), H2O2, MN, MV and AT increased alpha-amylase activity in caryopses. The effect of KAR(1) and GA(3) on ROS (H2O2, O-2(center dot-)) and activities of the superoxide dismutase (SOD) and catalase (CAT) were determined in caryopses, embryos and aleurone layers. SOD was represented by four isoforms and catalase by one. In situ localization of ROS showed that the effect of KAR(1) and GA(3) was associated with the localization of hydrogen peroxide mainly on the coleorhiza. However, the superoxide was mainly localized on the surface of the scutellum. Superoxide was also detected in the protruding radicle. Germination induction of dormant caryopses by KAR(1) and GA(3) was related to an increasing content of H2O2, O-2(center dot-) and activities of SOD and CAT in embryos, thus ROS homeostasis was probably required for the germination of dormant caryopses. The above regulators increased the content of ROS in aleurone layers and decreased the activities of SOD and CAT, probably leading to the programmed cell death. The presented data provide new insights into the germination induction of A. fatua dormant caryopses by KAR(1) and also by GA(3). In A. fatua, KAR(1) or GA(3) is included in the induction germination of dormant caryopses through regulation level of ABA in embryos and ROS-antioxidant status both in embryos and aleurone layers. (C) 2014 Elsevier GmbH. All rights reserved.