Effects Of Shading And Waterlogging At Different Growth Stages On Growth And Physiological Characteristics Of Flue-cured Tobacco

A pot experiment was conducted to study the effects of shading&waterlogging at different growth stages on growth and physiological characteristics offlue-cured tobacco Zhongyan100in Henan University of Science and Technology in2010. The test was made up of ten treatments, those were normal supplying light andwater during the whole growth stage (CK); shading at root elongation stage (S shen);water logging at root elongation stage (W shen); shading and water logging at rootelongation stage (SW shen); shading at vigorous growth stage (S wang); waterlogging at vigorous growth stage (W wang); shading and water logging at vigorousgrowth stage (SW wang); shading at ripe stage (S cheng); water logging at ripe stage(W cheng); shading and water logging at ripe stage (SW cheng). The treatments werefirstly analysed in three parts: root elongation stage test (CK, S shen, W shen, SWshen), vigorous growth stage test (CK, S wang, W wang, SW wang), ripe stage test(CK, S cheng, W cheng, SW cheng) and on the basis of comparison among differenttreatments of each test, the difference compares of shading&water logging atdifferent growth stages (CK, SW shen, SW wang, SW cheng) were studied. Themain results were as follows:1. Effects of shading&waterlogging at different growth stages on growth offlue-cured tobaccoShading at root elongation stage, vigorous growth stage and ripe stage, waterlogging at root elongation stage and vigorous growth stage and shade&waterflooding at root elongation stage and vigorous growth stage had a great impacton the morphology of the flue-cured tobacco. The plant height and maximum leafarea of flue-cured tobacco were increased under shading at three stages, ratio oflength to breadth of the largest leaf showed a significant increase and the stem girth was significantly reduced in S wang and S cheng, while the S shen was contrary. Theplant height, stem girth, maximum leaf area and ratio of length to breadth of thelargest leaf of flue-cured tobacco were decreased in W shen and W wang. Stem girthof SW shen was reduced, ratio of length to breadth of the largest leaf was increased,plant height and maximum leaf area firstly increased and then decreased. In addition,the plant height, stem girth and maximum leaf area of SW shen were lower than theS shen, but higher than W shen. Stem girth of flue-cured tobacco of SW wangdecreased, plant height and maximum leaf area increased. Moreover, plant heightand stem girth of SW wang were higher than S Wang. Comparing the results ofshading&water logging in three different stages, the plant height increased aftershading&waterlogging at the early stage of root elongation and the vigorous growthstage. The stem girth and maximum leaf area decreased and increased respectivelyafter shading&waterlogging at every growth stage. The maximum leaf length/widthratio increased significantly in the root elongation; in the late period of tobacco plantgrowth, plant height of shading&waterlogging at vigorous growth stage was thehighest and stem girth in the same treat was the minimum.2. Effects of shading&waterlogging at different growth stages on the contentsof photosynthetic pigments of flue-cured tobaccoChlorophyll a, b, and their total and carotenoid contents of shading at threestages were significantly higher than that of the control, while each pigment contentswere significantly lower than that of the control after waterlogging at three stages.Effects of shading&waterlogging at different growth stages on the contents ofpigments of flue-cured tobacco were more complicated. Compared with control, thecontent of chlorophyll in SW shen and SW wang showed a trend of increased-reduced-increased–reduced, while the contents of each pigment of SW cheng washigher than control; in the late growth period, pigment contents of the flue-curedtobacco was highest in SW cheng, then control followed by, SW wang was slightlylower than the control, SW shen was lowest, which significantly lower than control.3. The effects of shading and waterlogging at different growth stages onantioxidants of flue-cured tobacco There were different effects of shading and waterlogging at different growthstages on the activities of superoxide dismutase (SOD), peroxidase (POD) andcatalase (CAT) of flue-cured tobacco. The effects of shading&waterlogging atvigorous growth stage on the antioxidase activity were relatively great. After eachstress treatment at root elongation stage, the three antioxidase activities of shadingtreatment were the highest at the early and middle growth stage, and thewaterlogging treatment took the second place; the SOD and POD activities ofwaterlogging treatment were the highest at the late growth stage, and the shadingtreatment took the second place. Shading at vigorous growth stage made the SODactivity increase in the whole growth stage and the POD activity increase at the earlygrowth stage; the SOD and CAT activities of each stress treatment were both lowerthan the control group and the POD activity was close to the control group at the lategrowth stage. Shading at ripe stage was conducive to improve three antioxidasesactivities, while the waterlogging stress made the activities lower; antioxidasesactivities of shading&waterlogging were between the two, and were close to thecontrol group except POD activity. Comparing the differences among shading&waterlogging at three growth stages, after shading&waterlogging at root elongationstage, the activities of SOD and CAT were significantly lower than the control group,the POD activity was significantly higher than the control group, and the treatment atvigorous growth stage was in contrast; SOD and POD activities of shading&waterlogging at ripe stage were significantly higher than the control group, but CATactivity was significantly lower than the control group; at the end of the growth stage,SOD activity of the control group was the highest and that of shading&waterlogging at vigorous growth stage was the lowest; POD activitiy of shading&waterlogging at three growth stages were all higher than the control group, and thatof shading&waterlogging at ripe stages was highest; CAT activity was highest inshading&waterlogging at root elongation stage, and lowest in shading&waterlogging at vigorous growth stage.Glutathione (GSH) contents of flue-cured tobacco had a greater fluctuationafter suffering from outside environment stresses, and the impact on the GSH content was bigger with the aggravation of the stresses. During the growth stage offlue-cured tobacco, GSH content showed a twisted and turning upward trend.Shading, waterlogging and shading&waterlogging at the three growth stages madeGSH contents reduce, the GSH content of took on a greater degree of volatility thanthe control group. The GSH contents of shading&waterlogging treatments were theminimums at the end of the growth stages, which showed a greatest reduction at rootelongation stage.4. Effects of shading and waterlogging at different growth stages on themalondialdehyde (MDA) contents of flue-cured tobaccoThere were different effects of shading and waterlogging stress at differentgrowth stages on the MDA contents between early and late growth stages offlue-cured. At the early growth stages, the MDA content rose because of sufferingfrom the outside environment stresses, while at the late growth stages, it reduced tosome extent, which showed that the senescence of leaves was delayed after sufferingstress. After stress treatments at root elongation stage and the vigorous growth stage,the MDA contents were all significant higher than the control group; moreover, atroot elongation stage, the content of waterlogging treatment was highest, and at thevigorous growth stage, the content of shading treatment was higher than the others.At the end of the root elongation stage and vigorous growth stage, the MDA contentsof shading&waterlogging were all higher than the other treatments, while S shen, Scheng and SW cheng all made MDA contents reduce at the end of the growth stage.The MDA contents of shading&waterlogging at the three stages were allsignificantly higher than the control group, but until to the end of the growth stages,the MDA contents of that were all lower than the control group and the contents ofshading&waterlogging at ripe stage were the lowest.5. The relationship between the MDA content and antioxidant systemCorrelation analysis showed that: the MDA content of the control group had ahighly significant negative correlation with POD activity. The MDA content undershading&waterlogging at root elongation stage had a highly significant negativecorrelation with CAT activity. After shading&waterlogging at the vigorous growth stage, the MDA content had significant or highly significant negative correlationswith the activity of POD, CAT and SOD. After shading&waterlogging at the ripestages, the MDA content had highly significantly negative correlations with the GSHcontent and the activity of POD and CAT.