Studies On Physiological And Biochemical Responses Of Different Flue-cured Tobacco Genotypes To Different Light Intensity And Thermal Environments

Flue-cured tobacco cultivars, K326and CB-1, were employed as materials, the responses of physiologicaleffects and proteomics of different flue-cured tobacco genotypes at seedling stage to different light intensityand thermal environments as well as their possible physiological and biochemical adaptive mechanisms wereanalyzed in a pot culture experiment. The results can provide the theory reference for the study of themechanism of tobacco aroma style and quality formation in the production of tobacco material with highquality and good characteristics in Fujian Province. The major results of this paper are given below.(1) The photosynthetic responses of the two flue-cured tobacco seedlings to different light intensity andthermal environments were different. In the paper, the chlorophyll (Chl) content in leaves at seedlings stage ofthe flue-cured tobacco was different with different genotypes as well as the light intensity and temperature,while the carotenoid (Car) content was different with the interaction of genotypes as well as the light intensityand thermal environments. Stomatal conductance (Gs), the intercellular CO₂concentration (Ci), thetranspiration rate (Tr) and carboxylation efficiency (CE) were affected by different genotypes, the lightintensity and thermal environments, and their interactions. Ribulose1,5-bisphosphate carboxylase (Rubisco)activity was affected by the light intensity and thermal environments and the interaction of genotypes as wellas the light intensity and thermal environments, but mainly influenced by the light intensity and thermalenvironments. The net photosynthetic rate (Pn) was affected only by the light intensity and thermalenvironments. Minimal fluorescence (Fo), photochemical quenching (qP), actual photochemical efficiency(ΦPS Ⅱ) and excess of PSⅡ reaction centers (Ex) of chlorophyll fluorescence parameters were affected onlyby the light intensity and thermal environments, while the variable fluorescence (Fv) was affected by the lightintensity and thermal environments as well as the interaction of genotypes and environments. Although thephotosynthetic capacity of the two genotype flue-cured tobacco seedlings was enhanced, the photosyntheticapparatus was sensitive to higher light intensity and higher temperature, the degree of openness of the PSIIreaction center reduced, the proportion of the light energy that could be used for the photochemical reactionwas decreased relatively, and the more absorption of light energy was used for the antenna thermal dissipationand the energy dissipation of non-photochemical reaction in the reaction center after artificially higher lightintensity and higher temperature treatment. The PSII activity of CB-1decreased quickly with higher lightintensity and higher temperature treatment.(2) The responses of dry matter accumulation and its allocation in the two flue-cured tobacco seedlings todifferent light intensity and temperature were different. Lower temperature condition contributed to theaboveground biomass accumulation of CB-1, while higher light intensity and temperature showed a obviouslygrowth advantage to K326.The result indicated that higher light intensity and higher temperature environmentcan not improve the yield and quality of CB-1.(3) The responses of total soluble sugar, sucrose and starch content in each organ of the two flue-curedtobacco seedlings to different light intensity and thermal environments were also different. The sucrose contentin each organ of flue-cured tobacco seedlings was affected by genotypes, light intensity and temperature, and their interactions. The factors that impact the total soluble sugar and starch content in each organ of flue-curedtobacco seedlings were different and the influence degree of each factor also differed. The responses of theactivity of sucrose phosphate synthase (SPS), acid invertase (AI), sucrose synthase (SS), nitrate reductase (NR)and glutamine synthelase (GS) in leaves of the two flue-cured tobacco seedlings to different light intensity andthermal environments were different. Under higher light intensity and higher temperature treatment, theactivities of SPS, AI, SS and GS in leaves of the two flue-cured tobacco seedlings both increased, but theactivity of NR in leaves of the two flue-cured tobacco seedlings both decreased. The activity of SPS in leavesof flue-cured tobacco seedlings was affected by genotypes as well as the light intensity and thermalenvironments. The activity of AI, SS and NR in leaves of flue-cured tobacco seedlings were affected bygenotypes, the light intensity and thermal environments, and their interaction. The activity of GS was affectedonly by the light intensity and thermal environments.(4) The responses of total nitrogen, phosphorus, potassium, and nicotine content in each organ of the twoflue-cured tobacco seedlings to different light intensity and thermal environments were different. Thephosphorus and nicotine content in each organ of the two genotype flue-cured tobacco seedlings were affectedmainly by genotypes. The factors that impact the total nitrogen and potassium content in each organ offlue-cured tobacco seedlings were different and the influence degree of each factor were also different.(5) The responses of the antioxidant system and membrane lipid peroxidation in leaves of the twoflue-cured tobacco seedlings to different light intensity and thermal environments were different. The activityof superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), lipoxygenase (LOX),polyphenol oxidase (PPO) and phenylalanine aminolyase (PAL) in leaves of the two flue-cured tobaccoseedlings both increased, the activity of catalase (CAT) in flue-cured tobacco seedling leaves of CB-1decreased, malandialdehyde (MDA) content in leaves of the two genotype flue-cured tobacco seedlings bothdecreased, and H₂O₂content in leaves of the two genotype flue-cured tobacco seedlings both increased afterartificially higher light intensity and higher temperature treatment. The increasing of the activity of SOD, POD,APX, PPO and PAL in flue-cured tobacco seedling leaves of K326were bigger than CB-1, while theincreasing of the activity of LOX in flue-cured tobacco seedling leaves of CB-1were bigger than K326afterhigher light intensity and higher temperature treatment. The activity of SOD, POD, APX and PAL in flue-curedtobacco seedling leaves of CB-1were lower than that of K326, and MDA content were higher than that ofK326under the higher light intensity and higher temperature in the plant growth chamber. The activity of LOXin the flue-cured tobacco seedling leaves of CB-1was higher than that of K326under both light intensity andthermal environments. This result suggested that CB-1was susceptible to the oxidative damage of higher lightintensity and higher temperature environment, while K326was tolerant to higher light intensity and highertemperature environment. The activities of SOD, POD, CAT, APX, LOX, PPO and PAL in leaves of flue-curedtobacco seedlings were affected by genotypes, the light intensity and thermal environments, and theirinteraction. MDA content was affected by genotypes as well as the light intensity and thermal environments,but mainly influenced by the light intensity and thermal environments. H₂O₂content was affected by genotypes, the light intensity and thermal environments, and their interactions.(6) Proteomics tools was applied to investigate the differential expression of proteins in leaves of the twoflue-cured tobacco seedlings under different light intensity and thermal environments.25protein spots wereregulated by light intensity and temperature, but only22different proteins were identified by analysis anddatabase retrieval. The proteins related to the light reaction of photosynthesis and defenses, as well as theenzymes participating in the carbon dioxide fixation, photorespiration and energy metabolism wereup-regulation, but the proteins participating in photosynthetic electron transport, the components of PS Ⅱandcell material synthesis metabolism were down-regulation in leaves of the two flue-cured tobacco seedlingsafter artificially higher light intensity and higher temperature treatment. The light intensity and temperatureshowed impact on the expression of leaf proteins in flue-cured tobacco seedlings. CDSP32protein influe-cured tobacco seedling leaves of CB-1was specifically expressed in both light intensity and thermalenvironments, and the protein was up-regulated after artificially higher light intensity and higher temperaturetreatment.The expressing patterns of differential proteins were different with the different tobacco genotypeunder the same light intensity and temperature treatment. The twenty-five differentially expressed protein spotswere induced mainly by the light intensity and temperature except for CDSP32protein which was inducedmainly by genotypes.The results showed that lower temperature contributed to the growth of the flue-cured tobacco of CB-1,Therefore, CB-1is suitable to be planted in early season, but the flue-cured tobacco of K326is not suitable tobe planted in early season. CB-1was susceptible to the damage of higher light intensity and highertemperature, while K326was tolerant to higher light intensity and higher temperature. In conclusion, CB-1should be planted as early as possible to avoid high light intensity and temperature to reach high yield andquality of flue-cured tobacco leaves in Fujian.