Effects Of Mild Drought Stress On Physiology Characteristics And Diterpenoids Synthesis Of Flue-cured Tobacco And Oriental Tobacco

In order to investigate the effects of mild drought stress on the synthesis of diterpenoids in flue-cured tobacco and oriental tobacco,In this paper,the effects of mild drought stress on growth and development,leaf defense enzyme activity,carbon and nitrogen metabolism enzyme activity,osmotic adjustment substance content,photosynthesis,glandular hair density and diterpenoid secretion of oriental tobacco and flue-cured tobacco were studied.The mechanism of diterpene synthesis difference of different types of tobacco and the response of key genes of diterpene synthesis to drought stress were analyzed by full-length transcriptome sequencing.The main results are as follows:1.Under mild drought stress,the growth and development of tobacco plants was slow.With the promotion of growth period,the plant height,effective leaf number,maximum leaf length and maximum leaf width of tobacco plants increased to some extent,but the overall growth of tobacco plants was weaker than that of the control.Especially when the water was controlled for 15 days,the development of tobacco plants was more significant;the dry matter accumulation of tobacco plants was less than that of the control.Mild drought stress promoted the growth and development of tobacco roots,but the plant height,stem circumference and leaf size were inhibited,and the root-shoot ratio were increased.The number of Basma leaves in the cultivars was higher than that of K326,and the leaf length and width was smaller than that of K326,and the dry matter weight and root development of Basma was weaker than K326.2.With the prolongation of drought stress,the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)in flue-cured tobacco and oriental tobacco increased first and then decreased.The peak was reached when the water was controlled for 15 days,and the antioxidant enzyme activity in Basma was higher than that of K326.The content of proline(Pro),an important osmotic adjustment substance,was higher than that of the control under drought stress,and the accumulation of proline in Basma was higher than that of K326.Under mild drought stress,the contents of endogenous hormones ZR,IAA and GA3 in tobacco plants were lower than those in the control,and they increased first and then decreased with the growth period;ABA content was higher than that of the control,with fertility The overall progress of the period is increasing,and the ABA content in Basma is higher than K326.3.Under the light drought stress,the photosynthetic pigments chlorophyll a,chlorophyll b and carotenoid content were lower than the control treatment;the relevant photosynthetic rate parameters:transpiration rate E,stomatal conductance Gs,intercellular CO2 and net photosynthetic rate Pn were lower than Compared with the treatment,the photosynthetic pigment content and photosynthetic rate parameters of Basma under drought conditions were lower than K326.4.Nitrate reductase(NR)and sucrose phosphate synthase(SPS)were key enzymes in plant carbon and nitrogen metabolism.Under drought stress,NR and SPS activities were lower than that of the control,and they increased first as the growth period progressed.The post-reduction trend reached a peak when the water was controlled for 15 days,and the activity of NR and SPS in Basma was higher than that of K326.5.Under the drought stress,the glandular hair density per unit leaf area increased,and the glandular hair density per unit area of K326 was higher than that of Basma.Among them,the density of Basma long-handled gland was lower than that of K326,and the difference of hair density of short-handled gland was not significant.Under drought stress,the secretion of diterpenoid glandular hairs in leaves was higher than that in the control.The content of gemular secretions in western cedars was higher in K326 leaves,and the content in larvae gland hair secretions was higher in Basma leaves.high.6.The Z-abienol and Labdene-diol catalytic enzyme gene sequences were analyzed and the CPS gene in the flue-cured tobacco variety K326 was mutated in the coding region,resulting in the leaves not containing Z-abienol and Labdene-diol;under the drought stress condition,the expression levels of CPS and ABS genes in the regulation of the synthesis of Labdene-diol compounds in oriental tobacco increased,which promoted the content of Z-abienol and Labdene-diol.Under normal water,the expression abundance of CBTS gene in Basma was lower than that of K326,and the competition of labdene-diols biosynthesis reduced the flow of CBT-ols branch,which resulted in lower CBT-ols content in Basma than that of K326.Under the condition of water stress,the expression of CBTS and P450,which are key genes regulating Sibutane diterpenoid,increased,and the content of α-,β-CBT-diol in flue-cured tobacco and oriental tobacco also the same.