Relationship between reactive oxygen species and ultraweak luminescence in strawberry fruit during senescence under various reactive oxygen regulation treatments

GUO Jinli; LIU Huan; LIANG Shuang; ZHU Guanyu; BAI Yang; LI Lianguo

doi:10.13925/j.cnki.gsxb.20160175

Abstract：[Objective] The relationship between ultraweak luminescence (UWL) and growth and development of plants is a new research topic and the mechanism of UWL generation in plants is completely unknown.To examine the hypothesis that reactive oxygen species is related with the generation of UWL in plants,we carried out the experiment of soaking ‘Hongyan’ strawberry fruit with hydrogen peroxide (H2O2) and tea polyphenol (TP) and analyzed variations in UWL and reactive oxygen species under various treatments during the senescence process of the fruit.[Methods] The plants of strawberry ‘Hongyan’ used in this study were planted in the greenhouses in Nongfeng Fruit and Vegetable Farm Cooperation in the new urban district of Hohhot in September 2014.In April 2015,healthy mature fruit uniform in size were harvested and taken to lab immediately.The fruit were divided into 3 groups and were separately soaked for 30 minutes in 0.1 mmol· L 1 H2O2,100 mg·L-1 TP,and distilled water (as control).After soaking,the fruit were air-dried,put into preservative bags and stored under normal temperature.During the 6 days of storage,fruit samples were taken for physical index measurements every day.Part of each fruit sample were measured immediately for UWL intensity with a BPCL-2-SH instrument produced by Beijing Jianxin Science and Technology Company.The measurement procedure was according to the instrument instruction.The average value of 10 measurements from 10 fruit of each sample was assigned as the UWL intensity of that sample.The remaining part of each fruit sample were frozen in liquid nitrogen and stored under-80 ℃ in a freezer for the analyses of the indexes of lipoxygenase (LOX) activity,superoxide anion radical (O2·-)production rate,H2O2 content,malondialdehyde (MDA) content,and relative electricconductivity.[Results] During the senescence of fruit,the LOX activities in H2O2 treatment,TP treatmentand the control increased first and then decreased.O2·-production rates,MDA content and relative electric conductivity in the three treatments increased continuously.UWL intensity in three treatments showed a gradual declining trend.Based on the above results,during the senescence process of strawberry fruit,reactive oxygen species generated and accumulated constantly,and UWL intensity declined along with the accumulation of reactive oxygen species.Meanwhile,throughout the process of senescence,the O2·-production rate,MDA content and relative electric conductivity in H2O2 treatment were all higher but UWL intensity was lower than in the control.While the O2·-production rate,MDA content and relative electric conductivity in TP treatment were all lower,the UWL intensity was higher than in the control.The above resuits suggested that increasing reactive oxygen species led to decline in UWL intensify in fruit,while scavenging reactive oxygen species slowed the decline in UWL intensity.Correlation analysis between reactive oxygen levels and UWL intensity in fruit showed that UWL intensity had a significant negative correlation with OT production rate,MDA content and relative electric conductivity in all treatments and that the negative correlation between UWL intensity and reactive oxygen under H2O2 treatment was the most significant.The above correlation analyses further proved that reactive oxygen accumulation led to the decline in UWL intensity in fruit.[Conclusion] The radiant and active status formed from the interaction among reactive oxygen species has been suggested as the source of UWL.According to this suggestion,the accumulation of reactive oxygen species lead to enhanced UWL emission.The present study showed that UWL intensity declined with the accumulation of reactive oxygen species.Increasing reactive oxygen species in fruit intensified the decline in UWL intensity,while eliminating reactive oxygen slowed the decline in UWL intensity in fruit,indicating that reactive oxygen species might not be the direct source of UWL but can affect UWL by affecting other cellular metabolisms,which await further studies.