Effect Of Root-promoting Regulators On The Growth Of Tobacco Plants And Tobacco Leaf Production And Quality

As to the problem of poor root growth due to low temperature and less sunshining during transplanting of tobacco seedlings,a tobacco root-promoting regulator was made according to the contents of nutrients in tobacco-planting soils.Effects of root-promoting regulators on the root growth,leaf physio-chemical characteristics and leaf quality were investigated using pot culture experiments,rhizo-box experiments and field experiments.The results were as follows:Results with pot culture experiments indicated that treatment with root-promoting regulators with different dilution folds influenced the time of seedling significantly.Root-promoting regulators with 200-fold dilutions reduced seedling time obviously.No differences of seedling times were observed when grown on 3 soils.Twenty days after transplanting,shoot and root biomass of tobacco seedlings with 200-fold dilution treatment were the biggest in comparison to other dilution treatments.The size of plant biomass grown on 3 soils was sandy soil > Nugantu soil > purple soil.Observation of leaf morphology parameters indicated that tobacco leaves grew fast at the 35 to 60 day after transplanting.The length and width of tobacco leaves with root-promoting regulator treatment were bigger than those of the control treatment.During the time,leaf SPAD value decreased gradually.Variation of leaf morphology parameters showed similar tendencies among 3 soils.Microscopic analysis of leaf structure showed that leaf thickness with root-promoting regulator treatment was bigger than that of the control obviously during 35 to 63 days after transplanting.Rate of palisade tissue thickness / sponge tissue thickness is correlated with leaf quality.The value was the biggest with root-promoting regulator treatment in purple soils,which was 0.93.The corresponding values were 0.91 and 0.84 in N ugantu soil and sandy soil.The ratios of palisade tissue / sponge tissue with the control treatment were 0.88,0.84 and 0.84 in Nugantu soil,sandy soil and purple soil respectively.Measurement of root activity indicated that root activity varied according to transplanting days.Root activity increased gradually and then decreased during 27 to 63 days after transplanting.Root activity with root-promoting regulator treatment was increased at early-transplanting periods.After topping,root activity reached the maximal value,the size of root activity grown in 3 soils was purple soil > sandy soil > Nugantu soil.Observation of root morphology with rhizobox experiments indicated that the total root length and lateral root numbers with 200-fold dilution treatment reached the maximal values,similar varying tendencies of the total root lengths and lateral root numbers were found in 3 soils.Results from the permeation of root-promoting regulators in soils indicated that with the elongation of permeation time,root-promoting regulators permeated deeply.At 12 h after permeation,root-promoting regulators reached the maximal depth.The permeating depth with root-promoting regulator treatment was bigger than that with the control treatment in purple soil,while no difference was observed in N ugantu soil and sandy soil.Results from field experiments indicated that treatment with root-promoting regulator raised the leaf potassium content in N ugantu soil and the content of reducing sugar of tobacco leaves in sandy soil.In purple soils,treatment with root-promoting regulators increased the content of reducing sugar and improved leaf qua lity.Analysis of tobacco smoking index indicated that treatment with root-promoting regulators increased the volume of aroma grown in Nugantu soil,and improved tobacco smoking indices grown in purple soil.Economic analysis of tobacco leaves indicated that treatment with root-promoting regulators increased the leaf production in Nugantu soil by 61.1 kg/ha,and the ratio of output to input is 2.22.In sandy soil,treatment with root-promoting regulators did not increase the leaf production obviously,and the ratio of output to input is 1.33.In purple soil,treatment with root-promoting regulators enhanced tobacco leaf production by 113.6 kg/ha,and the ratio of output to input is 2.44.Taken together,the above results indicated that root-promoting regulator had beneficial effects on tobacco growth in purple soil.This might be related to a faster permeating rate of root-promoting regulators,tobacco roots could grow deeply,which enhanced the resistance of tobacco roots to environmental stress such as low temperature and less sunshining.After topping,root activity was enhanced again,and more water and nutrients were uptake,thus the ratio of palisade tissue / sponge tissue was increased,finally,the production and quality of tobacco leaves were improved in purple soils.