Physiological responses of Coleus blumei to simulated drought stress
Author(s): LIU Ai-Rong, ZHANG Yuan-Bing, ZHANG Xue-Ping, WANG Xue-Juan, HUANG Shou-Cheng, XIE Yi-Qin
Pages: 656-662,630
Year: 2015 Issue: 5
Journal: Guihaia
Keyword: simulated drought stress; Coleus blumei; growth; osmotic adj ustment; antioxidant enzyme;
Abstract: In the present study,Coleus blumei seedlings were treated with PEG-6000 at the concentrations of 5%, 10%,15%,or 20% as the simulated drought stress,and without PEG-6000 treatment as control to investigate the changes of the growth,osmotic adjustment ability and the antioxidant enzyme activities of C.blumei.The results demonstrated that,comparing with the control,the fresh and dry biomass,water content and potential,root dehydro-genase activity and the contents of inorganic ion (K+,Na+,Ca2+,Mg2+)declined gradually as the increase of PEG-6000 concentrations.The content of NO-3 decreased at first and then increased,but lower than that of the control;On the contrary,nitrate reductase (NR)activity,soluble protein content and soluble sugar content increased at first and then decreased,and the contents of the latter two parameters were higher than that of the controls;in addition,proline and free amino acid content elevated in a PEG-6000-dose dependant manner.We noticed that the superoxide dis-mutase (SOD)activities also initially increased and then decreased,and reached the peak under 10%PEG-6000 treat-ment.However,peroxidase (POD)activities,catalase (CAT )activities,O-2?production rates and membrane permea-bility were greatly improved as the increase of PEG-6000 concentrations.Comprehensive analysis showed that moder-ate simulated drought stress (5%-10% PEG-6000)resulted in the decreased absorption of inorganic ion and water in C.blumei root,but enhanced ability of NO-3 reduction,suggesting that the inhibition on growth and the degree of water deficit were not detrimental,and thus ornamental values were hardly impaired.However,severe simulated drought stress (15%-20% PEG-6000),caused significant loss of inorganic ion absorption and deficit of water as well as the decrease of NO-3 assimilation,which further aggravated the inhibitory effect on growth and osmotic srt-ess,and finally destroyed its ornamental value.We observed that C.blumei seedlings did not accumulate inorganic ion,such as K+,Na+,Ca2+,Mg2+ and NO-3 ;however,it indeed accumulated organic small molecules,such as pro-line,soluble protein,soluble sugar and free amino acid,to maintain the osmotic balance in spite of the increasing rate of these molecules were not parallel.Although moderate simulated drought stress could enhance the antioxidant en-zyme activities (SOD,POD and CAT )of C.blumei seedlings,slight oxidative inj uries were observed.As the increase of PEG-6000 concentration,the notable elevation of O-2?generation rate might result from the decreasing activity of SOD,a key enzyme for scavenging O-2?;although POD and CAT ,another two important antioxidant enzymes,could be significantly induced when suffering from the drought stress.As a result of imbalance of these antioxidant en-zymes,the inj ury of membrane lipid peroxidation was inevitable.These findings will provide some useful experimental basis for elucidating the physiological mechanisms of C.blumei drought tolerance,and also contribute to water-saving planting and maintaining of C.blumei in practice.
Pages: 656-662,630
Year: 2015 Issue: 5
Journal: Guihaia
Keyword: simulated drought stress; Coleus blumei; growth; osmotic adj ustment; antioxidant enzyme;
Abstract: In the present study,Coleus blumei seedlings were treated with PEG-6000 at the concentrations of 5%, 10%,15%,or 20% as the simulated drought stress,and without PEG-6000 treatment as control to investigate the changes of the growth,osmotic adjustment ability and the antioxidant enzyme activities of C.blumei.The results demonstrated that,comparing with the control,the fresh and dry biomass,water content and potential,root dehydro-genase activity and the contents of inorganic ion (K+,Na+,Ca2+,Mg2+)declined gradually as the increase of PEG-6000 concentrations.The content of NO-3 decreased at first and then increased,but lower than that of the control;On the contrary,nitrate reductase (NR)activity,soluble protein content and soluble sugar content increased at first and then decreased,and the contents of the latter two parameters were higher than that of the controls;in addition,proline and free amino acid content elevated in a PEG-6000-dose dependant manner.We noticed that the superoxide dis-mutase (SOD)activities also initially increased and then decreased,and reached the peak under 10%PEG-6000 treat-ment.However,peroxidase (POD)activities,catalase (CAT )activities,O-2?production rates and membrane permea-bility were greatly improved as the increase of PEG-6000 concentrations.Comprehensive analysis showed that moder-ate simulated drought stress (5%-10% PEG-6000)resulted in the decreased absorption of inorganic ion and water in C.blumei root,but enhanced ability of NO-3 reduction,suggesting that the inhibition on growth and the degree of water deficit were not detrimental,and thus ornamental values were hardly impaired.However,severe simulated drought stress (15%-20% PEG-6000),caused significant loss of inorganic ion absorption and deficit of water as well as the decrease of NO-3 assimilation,which further aggravated the inhibitory effect on growth and osmotic srt-ess,and finally destroyed its ornamental value.We observed that C.blumei seedlings did not accumulate inorganic ion,such as K+,Na+,Ca2+,Mg2+ and NO-3 ;however,it indeed accumulated organic small molecules,such as pro-line,soluble protein,soluble sugar and free amino acid,to maintain the osmotic balance in spite of the increasing rate of these molecules were not parallel.Although moderate simulated drought stress could enhance the antioxidant en-zyme activities (SOD,POD and CAT )of C.blumei seedlings,slight oxidative inj uries were observed.As the increase of PEG-6000 concentration,the notable elevation of O-2?generation rate might result from the decreasing activity of SOD,a key enzyme for scavenging O-2?;although POD and CAT ,another two important antioxidant enzymes,could be significantly induced when suffering from the drought stress.As a result of imbalance of these antioxidant en-zymes,the inj ury of membrane lipid peroxidation was inevitable.These findings will provide some useful experimental basis for elucidating the physiological mechanisms of C.blumei drought tolerance,and also contribute to water-saving planting and maintaining of C.blumei in practice.
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