Effects Of Rare Earth Element Concentration And Application Method On Growth And Aroma Precursors Of Flue-cured Tobacc

Plant growth was generally promoted at low concentrations of rare earth elements,but it was inhibited by the high concentration of rare earth elements.In this study,pot experiments with Yunyan 87 were carried out with different concentrations of lanthanum nitrate(0、25、50、90、130、170、210 mg/L),cerium nitrate(0、15、30、45、60 mg/L)and lanthanum nitrate application methods(foliar spraying and root irrigation).The differences in agronomic traits,photosynthetic characteristics,chemical components,plastid pigments and polyphenols content of tobacco among treatments were analyzed to explore the effects of rare earth elements on the growth quality and aroma precursors of tobacco and their appropriate concentrations.The main results are as follows:(1)Effects of lanthanum nitrate on the growth of the shoots and roots of tobacco,photosynthetic properties(transpiration rate,stomatal conductance and net photosynthetic rate),total nitrogen,total potassium,reducing sugar,total sugar,plastid pigments(chlorophyll a,chlorophyll b and carotenoids)and polyphenols(neochlorogenic acid),chlorogenic acid,total phenols,rutabin)content were significant,which could be called the effect of "low promotion and high inhibition".However,the contents of total phosphorus,nicotine,chlorine,cryptochlorogenic acid and scopolamine decreased with the increase of lanthanum nitrate concentration.Overall,50-130mg/L lanthanum nitrate was more beneficial to promote the growth of flue-cured tobacco and the production of aroma prerequisite substances.(2)With the concentration increasing of cerium nitrate,the photosynthetic characteristics,total nitrogen,reducing sugar,total sugar,and polyphenols content also showed the phenomenon of "low promotion and high inhibition";while the total root length,root surface area,root average Diameter,root volume,nicotine and chlorine content increased;and the number of root tips,total phosphorus and total potassium,and scopolamine content showed decreased.In addition,with the growth of tobacco,the inhibitory effect of high concentration of cerium nitrate was more obvious.Overall,15-30mg/L cerium nitrate was beneficial to promote the growth of tobacco and improve its quality.(3)In terms of the application method of rare earth elements,root irrigation was more helpful to promote the improvement of agronomic traits and root growth of flue-cured tobacco above ground,however,f oliar spraying was more conducive to improve the quality of tobacco leaves,especially in the accumulation of mineral nutrients,organic matter content,two types of aroma precursors,such as plastid pigments and polyphenols in tobacco leaves...