Physiological Responses Of Flue-cured Tobacco To Chloride Channel Inhibitors Under High Chloride Soil Condition

Flue-cured tobacco variety "Yuyan No.10" was used as experimental material in a pot experiment on the farm of Henan University of Science and Technology in 2015.Three different inhibitors were tested in this experiment,in which the used soil Clcontent was 50 mg/kg and the used Cl-channel inhibitor were Zn2+,NFA and 9-AC,with distilled water(CK)as control.The three inhibitor solutions were all made into two concentrations of 100?mol/L and 200?mol/L.The growth status,photosynthetic pigments contents,leaf mineral element contents,the accumulation and distribution of Cl-,K+,N03-in different organs,the ultrastructural structure of the leaves,the expression of CLC-Nt2 gene,the content of MDA and several antioxidant enzyme activity were analyzed.Based on the analysis of multiple indexes,the effects of the three inhibitors were evaluated comprehensively.Main results were as follows.1.Compared with CK,the plant height,stem circumference and maximum leaf area increased by applying inhibitors,and the effect on the maximum leaf area was significant(p <0.05),but there was no obvious influence on the effective leaves number.The enhancement of the inhibitors on the dry matter accumulation in different organs of tobacco plants was different,and the effect on the dry leaf weight of was especially significant(p<0.05).Compared with CK,the root-shoot ratio showed a downward trend.The effect of the 3 inhibitors was in the order of 9-AC,NFA,Zn2+,and high concentration is better than low concentration between two levels.2.Compared with CK,treatments with inhibitor increased the contents of chlorophyll a,chlorophyll b and chlorophyll(a+b).The maximum value of chlorophyll content appeared at 50-65 d after transplanting,which was conducive to improving the accumulation of dry matter and yield of flue-cured tobacco.The content of carotenoids did not show obvious regularity throughout the experiment.The results showed that the SPAD value of the leaves treated with Zn2+ was higher in the early growth period,treated with NFA was higher in the later stage of growth,while the SPAD value of the leaves treated with 9-AC had a higher value throughout the growth period.The SPAD values of leaves in different parts showed different laws.The SPAD of the upper leaves increased at first,then decreased,and the maximum value appeared at 65 days after transplanting.The middle leaves decreased at first,then increased and trend to stable at last.The lower leaves experienced a process from decrease to increase to decrease,while the maximum value appeared at 35 days after transplanting.The correlation between the photosynthetic pigments content and SPAD value of the upper,middle and lower leaves at 65 days after transplanting was analyzed.There was a significant positive correlation between chlorophyll a and SPAD in each part.Chlorophyll b and chlorophyll(a+b)also had a good correlation with the SPAD values of the upper and middle leaves.The effects of the inhibitors on the chlorophyll content at different leaf positions can be judged according to the SPAD value of different leaf positions,which can further explain the effects of the inhibitors on the physiological characters of flue-cured tobacco.3.Compared with the application of the inhibitors,the days after transplanting had a significant effects on the contents of the mineral nutrition in leaves.During the same period,the contents of the mineral nutrition was higher treated with 9-AC than other inhibitors.The high concentration is better than the low in the early growth of flue-cured tobacco,but in latter stage of growth was just the opposite.There were no significant advantages on the contents of the mineral nutrition treated with Zn2+ and NFA compared with CK.Compared with CK,the distribution of Cl-in the organs of leaf,stem and root were significantly reduced,but the distribution of K+ and the content of NO3-in the organs were increased.The treatments with inhibitors on the leaf showed a strong regularity,but not on the root and stem.The promotion effect of Zn2+ treatment on growth and development was bigger at the earlier stage of growth,while those of 9-AC and NFA treatments mainly at the middle and later stages of flue-cured tobacco growth.This may be related to the mechanism of the inhibitors.As to the concentration,the higher was the better.4.Inhibitors treatments resulted in the thylakoids well developed,which had more lamellae and strong stacking capability.There was not significant difference in the expressions of CLC-Nt2 gene in tobacco leaves among Zn2+?NFA and 9-AC three chloride channel inhibitors,but they were all significantly lower than those in control,which were 82.22%?75.39% and 72.19% respectively.In addition,inhibitors treatments obviously decreased the content of MDA by23.48%-35.67%,which represented the production of lipid peroxide.With the supply of inhibitors were favorable to maintaining the activities of SOD,POD and CAT at high level in flue-cured tobacco leaves.Based on the results above,irrigation of chloride channel inhibitors can alleviate chloride damage to tobacco plants planted in soil with relatively higher Cl-content,because of the positive reactions to growth and physiological activities of flue-cured tobacco.200?mol/L is better than100?mol/L in the two concentrations.Among there inhibitors,9-AC shows the best performance in the experimental condition,while Zn2+ could meet the needs of reduction of chlorine ion in tobacco leaves with low cost in practice.