| In order to prove the mechanism of the regulation of exogenous auxin on the opening of the upper leaves of flue-cured tobacco,in this paper,the flue-cured tobacco （Nicotiana tabacum L.）variety’Yunyan 87’was used as the test material,and six treatments were set,that is,CK conventional topping and T1 bud removal Leaf（remove all leaves of the top bud and keep removing the inflorescence and keep the top bud）,T2 ring stripping（ring peeling the phloem of the top bud,remove all the leaves of the top bud and keep removing the inflorescence,keeping the top bud）,T3 low concentration growth Auxin(concentration 25mg·kg-1 auxin 0.5mg for topping wound site),T4 medium auxin concentration(50mg·kg-1 auxin 0.5mg for topping wound site),T5 high concentration auxin(topping The wound site used a concentration of 100mg·kg-1 auxin（0.5mg）,which was carried out in Hengnan County,Hengyang City,Hunan Province in 2018 and 2019.To study the effects of exogenous auxin on the agronomic traits,tissue structure,endogenous hormones,photosynthetic characteristics,conventional chemical composition,and economic benefits of the upper leaves of flue-cured tobacco,and to provide a theoretical basis for the production of high-quality upper leaves.The main results of this study are as follows:1.Before the current stage of flue-cured tobacco,there is basically no significant difference in agronomic traits of each treatment,and the difference begins to manifest until the mature stage.With the increase of auxin concentration,the flue-cured tobacco plant height, maximum leaf length of the upper leaf and maximum leaf width showed an upward trend,but the concentration was too high,the effect was reduced instead,the maximum lea length of the lower leaf showed a downward trend.Compared with the control T4,the concentration of auxin plant height increased by 5.81%,the upper leaf maximum leaf length and leaf width increased by 3.36%and 9.11%,respectively,and the upper 6 leaves increased by 3.48%-19.92%,indicating that mainly by increasing the leaf width To improve the opening degree.2.Compared with the control T2 ring stripping,the thickness of the upper 6 leaves of the flue-cured tobacco increased by 7.49%-13.47%,and the thickness of the upper epidermal cells was reduced by 17.03%-28.12%.The cell thickness generally showed an upward trend.When the auxin concentration reached 100 mg·kg-1,it increased by 1.35%-22.91%and 10.11%-61.79%,respectively;T1 removal of buds and T2 ring stripping reduced the thickness of the upper leaf palisade 0.07%-10.14%and 6.24%-27.92%,increase the thickness of sponge tissue 0.11%-28.53%and 2.67%-24.11%,medium and low concentrations of auxin can reduce the thickness and tissue ratio of the 6 leaves of the upper part of flue-cured tobacco,increase the sponge tissue Thickness,of which the concentration of auxin in T4 can reduce the thickness of the palisade tissue by 13.33%-34.87%,the tissue ratio by 31.08%-44.8%,and increase the thickness of the sponge tissue by 20.96%- 51.24%.3.The peak of IAA content in each treatment was 28 days after treatment,which was 45.58%higher than that of the control T2 ring stripped upper leaves,and the concentration of auxin in T4 increased by 88.72%;the IBA content of each treatment showed a trend of“inverted S”,The peak reached 28 days after treatment,the IBA content of the upper leaves of T2 ring stripping increased by 30.04%,the concentration of auxin in T4 increased by 27.78%,and the removal of bud leaves by T1 decreased by 4.12%;the ABA content of each treatment showed a"double peak"The trend changed,and the"peak"appeared at 14 days after the treatment.The ABA content of the upper leaf of T2 ring stripping was decreased by 17.64%,the concentration of auxin in T4 was decreased by 19.56%,and the concentration of auxin in T5 was increased by 13.31%;the upper leaf of control SA content showed a"double peak"trend,while the remaining treatment showed a"inverted S"trend in the upper leaves.Seven days after treatment was the peak of the SA content in the upper leaves except for the control,the T4 medium concentration auxin The SA content of the upper leaves increased by 122.75%.4.28 days after the treatment,compared with the control,the net photosynthetic rate of the upper leaves of flue-cured tobacco can be increased by 34.89%-67.16%by applying auxin;the stomatal conductance of each treatment in the 35 days of treatment showed a"bimodal"trend,compared with 7 days after treatment The control was reduced by 6.48%-18.88%,and at 14 days and 28 days,that is,"two peaks",the treatments were increased by 13.14%-23.17%and 13.48%-29.24%respectively;the transpiration rate of the control was 21 days after the treatment There was a sudden downward trend,and this trend was eliminated by applying auxin.At this time,the transpiration rate of each treatment increased by 25.64%-45.07%compared with the control.5.With the increase of auxin concentration,the nicotine content of flue-cured tobacco showed a downward trend,which was 22.6%and 19.79%lower than the control T5 high-concentration auxin for two years.Medium and low concentrations of auxin can reduce the total sugar content.T1 removal of buds and leaves will increase the reducing sugar content of flue-cured tobacco,increasing by 6.46%and 14.67%in two years respectively.Through treatment,the total nitrogen content of flue-cured tobacco can be reduced,and the total potassium content can be increased.Only a low concentration of auxin will reduce the nitrogen-alkali ratio.In 2018,high-concentration auxin actually reduced the yield by 6.8%,while cyclic stripping and low-and medium-concentration auxin can increase the yield and output value of tobacco leaves,and have better economic benefits. |
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