Effects Of Different Growth Temperatures On Growth,Development And Metabolism Of Some Key Aroma Constituents Of Tobacco Plants

Tobacco?Nicotiana tabacum L?,originated from tropical and subtropical area,which is sensitive to environmental temperature changes.As an important economic crop and model plant,tobacco plants are entensively planted and sudied around the world.Our previous study demonstrated that environmental temperature is one of the most key ecological factors that affects the quality and style of tobacco leaves in different territery of the China.Moreover,plastid pigments,polyphenols,fatty acids and non-structural carbohydrates?NSCs?are vital compounds and aroma constituents in tobacco plants,which are closely associated with the growth,development,yield and quality of tobacco plants.However,the effects and regulatory mechanism of different growth temperatures on the growth and development,metabolism of these 4compounds in tobacco plants are not completely clear.Based on the present research advances in this field,using Nicotiana tabacum L.as experimental materials,the following contents were studied and the results were as follow:?1?Effects of different growth temperatures?18.5,23.5 and 28.5°C,daily average?on growth,development and plastid pigments metabolsim of tobacco plants.Compared with tobacco plants grown under 23.5°C,treatments with 18.5 and28.5°C inhibited the expansion of leaves.The contents of superoxide anion?O₂.^-?,hydrogen peroxide?H₂O₂?and malonaldehyde?MDA?significantly increased but soluble protein remarkably decreased in leaves under 28.5°C,which in turn accelerated the flowering and senescence of tobacco plants.By contrast,treatment with 18.5°C remarkably decreased O₂.^-,H₂O₂,MDA,and increased soluble protein in leaves,followed by delaying the flowering and senescence.Furthermore,treatment with 18.5°C significantly up-regulated the expressiones of glutamyl-tRNA reductase?Glu-TR?and magnesium chelatase?MgCH?,and down-regulated the ferri chelatase?FeCH?,protochlorophyllide oxidoreductase?POR?,chlorophyllase?CHLase?,phaeophorbide a monooxygenase?PaO?and phytoene synthase?PSY?,which further promoted the accumulation of chlorophyll?Chls?and reduced the cartenoids?Cars?in leaves.On the contrary,treatment with 28.5°C remarkably reduced the Glu-TR and MgCH,and increased the FeCH,CHLase,PaO and PSY,which in turn decreased the Chls and increased the Cars in leaves.The results suggest that growth temperature could regulate growth,development,and plastid pigments metabolism of tobacco plants,and 23.5°C could be the optimal ones.?2?polyphenols metabolism responses to different growth temperatures in tobacco leaves.Chlorogenic acid,rutin and scopoletin were predominant polyphenols in leaves,and chlorogenic acid was the most abundance ones.The contents of these polyphenols gradually increased during the growth and development of leaves.Compared with plants grown under 23.5°C,treatment with 18.5°C remarkably enhanced the activity and its expression of the phenylalanine ammonia-lyase activity?PAL?,but significantly decreased the activities and their expressiones of the polyphenol oxidase?PPO?and peroxidase?POD?,which in turn increased the accumulation of chlorogenic acid and total polyphenols in leaves.In contrast,treatment with 28.5°C significantly reduced the activity and its expression of the PAL,but remarkably increased the activities and their expressiones of PPO and POD,followed by decreasing the chlorogenic acid and total polyphenols.The results indicated that polyphenols metabolism were remarkably controled by different gorwth temperatures,and treatment with 18.5°C is more profitable for the accumulation of polyphenols in tobacco leaves.?3?Effects of different growth temperatures on fatty acids metabolism in tobacco leaves.The contents of saturated fatty acids:lauric aicd,myristic acid,palmitic acid,stearic acid and total saturated fatty acids increased and then decreased,but the unsaturated fatty acids:oleic acid,linoleic acid,linolenic acid and total unsaturated fatty acids decreased during the growth and development of leaves.Moreover,the unsaturated fatty acids is the predominant fatty acids in leaves.Palmitic acid and linoleic acid and linolenic are the most abundance saturated and unsaturated fatty acids in leaves,respectively.Compared with plants grown under23.5°C,treatment with 18.5 and 28.5°C remarkably down-regulated the expressiones of acetyl-CoA carboxylase?ACCase??stearoyl ACP desaturase?SAD?and fatty acid desaturase?FAD 2?3 and 7?,wich in turn decreased the contents of these saturated fatty acids,unsaturated fatty acids and total fatty acids in leaves under18.5°C and 28.5°C.And the contents of these fatty acids under different growth temperatures from high to low was:23.5>28.5>18.5°C.The results suggested that the fatty acids metabolism were remarkably regulated by different gorwth temperatures in tobacco leaves,and 23.5°C could be the optimal ones.?4?NSC metabolism responses to different growth temperatures?16.5,23.5 and30.5°C,daily average?in tobacco leaves and roots.Compared with plants grown under 23.5°C,treatment with 16.5°C remarkably enhanced the activity and gene expression of sucrose phosphate synthase?SPS?,but decreased the activities and their expressiones of sucrose synthetase?SuSy?and invertase?Inv?,which in turn increased the accumulation of sucrose in leaves and roots.In contrast,treatment with30.5°C significantly decreased the activity and expression of SPS,but increased the activities and their expressiones of SuSy and Inv,followed by decreasing the contents of sucrose in leaves and roots.Treatment with 16.5°C remarkably enhanced the activities and their gene expressiones of ADP-glucose pyrophosphorylase polypetide?AGPase?,soluble starch synthase?SSS?and starch branching enzyme?SBE?,but decreased the activity of Amylase,which in turn increased the accumulation of starch in leaves and roots.In contrast,treatment with 30.5°C significantly decreased the activities and their expressiones of AGPase,SSS and SBE,but increased the activity of amylase,followed by decreasing the starch in leaves and roots,compared with plants grown under 23.5°C.In conclusion,treatment with 16.5°C increased the sucrose,starch,reducing sugar and soluble sugar in leaves and roots,reduced the respriration rate of tobacco plants,which in turn increased the accumulation of total NSC in leaves and roots.In contrast,treatment with 30.5°C decreased the sucrose,starch,reducing sugar and soluble sugar,and enhanced the respriration rate,followed by decreasing the total NSC,compared with plants grown under 23.5°C.The results indicated that the NSC metabolism in tobacco plants were remarkably controled by different gorwth temperatures,and the treatment with 16.5°C is more profitable for the accumulation of NSC in tobacco leaves and roots.