Effects Of Four Chemical Regulators On Chilling, Flooding, And Shade Tolerance And Photosynthetic Characteristics In Tobacco Seedlings

Tobacco is an important cash crop, how to improve its yield and quality has beenwidely concerned. However, tobacco plantation is inevitably affected by theenvironmental factors such as temperature, precipitation, illumination and so on.Environmental stresses is not only threaten the growth of tobacco plants, but also mayreduce its yield and quality. Therefore, it’s significant to study the stress tolerance oftobacco plants. This study, using Yunyan97as experimental materials, pretreated theseedlings with the solution of CaCl2(3.0or6.0mmol/L), gibberellin (GA3)(100or200mg/L), salicylic acid (SA)(1.0or2.0mmol/L) or paclobutrazol (PP333)(100or200mg/L), and distilled water was used as the control. We studied the effects of thepretreatments with the four chemical regulators on tolerance of treated tobaccoseedlings to low temperature, flood, and weak light and their photosyntheticphysiological characteristics. The results are stated as follows:1. The effects of pretreatments with the four chemical regulators on growth andbiochemical characteristics of tobacco seedlingsAfter pretreatments with the four chemical regulators for four times, ascompared with the control spraying distilled water, the pretreated seedlings with thefour chemical regulators generally had higher the dry matter accumulation rate,relative growth rate, root vigor, proline content and net photosynthetic rate, reduce theMDA content and the electrolyte permeability, which totally enhanced the quality oftobacco seedlings.2. The effects of pretreatments with the four chemical regulators on chilling toleranceof tobacco seedlings under low temperature stress.Tobacco seedlings were treated under low temperature at10°C for20days inartificial climate chamber. The results showed that spraying chemicals partiallyalleviate the harmful influence of low temperature to tobacco seedlings and improvethe cold resistance of tobacco seedlings. Compared to the controls,1.0mmol/L SAhas the better ability to increase the fresh weight and dry weight of tobacco seedings, the relative growth rate, dry matter accumulation rate, the proline content, root vigor,and reduce the electrolyte leakage and MDA content.1.0mmol/L SA and100mg/LPP333have the ability to increase the total chlorophyll content, net photosyntheticrate, intercellular CO2concentration, stomatal conductance and transpiration rate.3. The effects of pretreatments with the four chemical regulators on floodingtolerance of tobacco seedlings under waterlogging stress.Treated the tobacco seedlings6days in artificial climate chamber under thesimulated flooding. The results showed that spraying chemicals can improve thewaterlogging resistance of tobacco seedings. Compared to the contols,1.0mmol/LSA L has the ability to increase the relative growth rate, the accumulation of drymatter in tobacco seedings.1.0mmol/L SA and100mg/L PP333have the ability toreduce electrolyte permeability, improve root vigor.100mg/L GA3and200mg/LPP333have the ability to increase increase net photosynthetic rate and transpirationrate.4. The effects of pretreatments with the four chemical regulators on shade toleranceof tobacco seedlings under weak light stress.Treated the tobacco seedlings6days in artificial climate chamber under thesimulated weak light. The results showed that spraying chemicals partially alleviatethe damges of weak light to tobacco seedings. Compared to the controls,200mg/LPP333promote the yield of tobacco seedings dry weight, relative growth rate, the rateof dry matter accumulation.1.0mmol/L SA enhance the root vigor, reduce theelectrolyte permeability, MDA content.1.0mmol/LSA and3.0mmol/L CaCl2improved the net photosynthetic rate.Based on the above results, it can be showed that four kinds of chemicalregulators (CaCl2, GA3, SA, PP333) pretreatments could generally enhance thequality of tobacco seedlings. Under low temperature, waterlogging, weak lightconditions, as compared with the control, the pretreated seedlings with the fourchemical regulators could maintain higher dry weight, relative growth rate, dry matteraccumulation rate, root vigor, proline and chlorophyll content, net photosynthetic rate,intercellular CO2concentrations, stomatal conductance and transpiration rate,alleviate the MDA content accumulation and electrolyte leakage induced by these stresses, which finally enhanced chilling, flooding and shade tolerance of tobaccoseedlings. The pretreatments with the four chemical regulators all could increasestress tolerance in tobacco seedlings to different content, in general, SA pretreatmentreceived the best effect.