title: Changes in oxidative patterns during dormancy break by warm and cold stratification in seeds of an edible fruit tree.
abstract: The transition from seed dormancy to germination is triggered by environmental factors, and in pomegranate (Punica granatum) seeds higher germination percentages are achieved by warm + cold stratification rather than by cold stratification alone. Our objective was to define the pattern of internal oxidative changes in pomegranate seeds as dormancy was being broken by warm + cold stratification and by cold stratification alone. Embryos isolated from seeds after 1-42 days of warm stratification, after 56 days of warm stratification + 7, 28 or 56 days of cold stratification, and after 1-84 days of cold stratification alone, were used in biochemical tests. Hydrogen peroxide (H2O2), nitric oxide (NO), proline, lipid peroxidation, protein carbonylation, and activities of the scavenging enzymes superoxide dismutase (SOD), hydrogen peroxide enzyme and peroxidase in the embryos were assessed by colorimetric methods. Our results indicated that warm + cold stratification had a stronger dormancy-breaking effect than cold stratification (85% versus 50% germination), which may be attributed to a higher yield of H2O2, NO, lipid peroxidation and protein carbonylation in warm + cold stratification. Furthermore, warm + cold stratification-induced H2O2 change led to greater changes (elevation followed by attenuation) in activities of the scavenging enzymes than that induced by cold stratification alone. These results indicated that restriction of the level of reactive oxygen species change within a positive and safe range by such enzymes promoted seed germination. In addition, a relatively strong elevation of proline during warm + cold stratification also contributed to dormancy breakage and subsequent germination. In conclusion, the strong dormancy alleviating effect of warm + cold stratification on pomegranate seeds may be attributed to the corresponding active oxidative change via H2O2, NO, proline, malondialdehyde, protein carbonylation and scavenging enzymes.
authors.affiliation: National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
authors.forename: Dilinuer
authors.initials: D
authors.lastname: Shalimu
authors.affiliation: National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506, USA Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.affiliation: National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China yjliubio@163.com lsun2013@bjfu.edu.cn.
authors.forename: Liwei
authors.initials: L
authors.lastname: Sun
authors.affiliation: National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China yjliubio@163.com lsun2013@bjfu.edu.cn.
authors.forename: Yujun
authors.initials: Y
authors.lastname: Liu
keywords: H2O2; NO; lipid peroxidation; physiological dormancy; pomegranate seeds; protein carbonylation; scavenging enzymes