Effects Of Light Intensity On The Growth, Photosynthetic Characteristics And Quality Of Flue-cured Tobacco

Abstract The experiments of potted planting and field condition were carred out separately in the Education Technical Center of Henan Agriculture University during 2005-2006.Tobacco used as materials,different light intensities were set in whole tobacco growing period to discussion effects of light intensity on tobacco growth and photosynthetic characteristics and quality.The Main results of the experiments were showed as follows:1 Effects of Light Intensity on the Growth of Flue-cured Tobacco.Light can regulate growth,development and morphogenesis of plants and effects the accumulation of dry matter and chemical components.The paper analyzed the effects of light intensity on agoronomic character of tobacco.The results showed light intensinty had a very great impact on growth indicators of tobacco wich,With the declince of light intensity,their stem gradually became thinner,length to width ratio of leaf increased,leaf growth rate was slower,dry weight gradually reduced,R/S ratio decreased and growth period was extended.However.80%of all light conditions of plant height and leaf area was higher than other three treatments of theirs.2 The Effects of Light Intensity on Accumulating Regularity and Content of Nutrient Element of Flue-cured Tobacco.This study indicated nutrient absorption significantly related to different light intensity treatment duration,wich absorption of N,P,K,Ca,Cu,Zn had presented the trend of decling in front growth stage of flue-cured tobacco,with the light intensity and the reduction of the extended growth period,in which absorption K of 80%under natural light potassium higher than it of full light in controlling 35 days.But low light on the nitrogen uptake had increased in accompany of prolong of growth age, especially changes were most noticeable in 50%and 20%of natural light growth stack.Controlling 35 days,50%and 80%of natural light and natural light growth under the leaves of tobacco plants in the absorption of magnesium over control. Controlling 55 days,80%of natural light is still higher than the control treatment,in line with the growth period of the extension and reducing light intensity declined. Under low light,absorption of Cl,Mn and Fe dramtically accumulated in tobacco growth stage and late.Handling 35 days,except Cl,light intensity,net photosynthetic rate and the other nutrients were significantly correlated.3 The Effects of Light Intensity on the Physiological Characteristics of the Flue-cured tobacco.Different light intensity has created a great impact on biological activity during the process of growth and development of flue-cured tobacco.SOD activity,POD activity and CAT activity were basically in the strong light impoved.In tobacco growth stage,SOD,POD,CAT increased,Hence POD activity continued to increase in the late growth of tobacco while CAT activity decreased.Content of MDA dramatically increased in the early stage,and then that had become stable until maturity under 100%and 80%natural light.The content of soluble protein had no significant difference under 100%,80%,50%of light intensity in front growth of tobacco.However it still greater more than 20%of natural light.But,due to becoming mature and photosynthetic ability decreasing in natural light intensity of tobacco,later content of soluble protein was lower while that remained at a high level 80%natural light intensity.As the light intensity increasing,phenylalanine ammonia-lyase activity increased,so aroma from tobacco leaves was sensitive to light reaction.4.The Effects of Light Intensity on the Photosynthetic Characteristics of Flue-cured Tobacco.Fluorescence and photosynthetic parameters of cutters were measured when controlling light intensity during 35 days,the results showed that chlorophyll content and intercellular CO2 concentration(Ci)gradually increased,while the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Evap) decreased with light intensity reducing,chlorophyll fluorescence parameters Fm,(?) PSâ…¡,Fv.QP value decreased with the light gradually increased,so it fully explained tobacco leaves can be more absorbed light allocated to photochemical way and high-intensity conditions will be more absorption of light energy to distribute heat dissipation channels in low light conditions and the same plant under different light conditions can greatly adapt to environment.Day changes of chlorophyll fluorescence parameters showed that value of Fv/Fm and(?)PSâ…¡reached to the utmost point in the change morning and evening,while that at noon had been gradually declining. With the light intensity increases,chlorophyll fluorescence noticably declined,naturally,tobacco plants under the high light intensity will happen photoinhibition at noon.So appropriate shading would reduce photoinhibition and raise photochemical efficiency.5.The Effects of Light intensity on Chemical Constituents and Quality of Flue-cured Tobacco.Light intensity had effect on chemical constituents,quality indicators and Neutral aroma compound.As the reducing of light intensity,single leaf weight, thickness,weight decreased leaf,leaf-stem ratio,total sugar,reducing sugar,total phenol and nicotine content reduced,while total N,K and Cl content increased,but the ratio of K/Cl showed the trend decreasing.Neutral aroma compounds with reduced light intensity increased,which the new plant diene content with the weakening of light intensity significantly improved,while carotenoids and degradation products, aromatic amino acid metabolites,maillard reaction products,cyberSchoolBus alkane degradation products in proportion of Neutral aroma declined.