Physiological responses of flue-cured tobacco under the high chloride to chloride channel inhibitors

ObjectivesHigh Cl^– content in soil is one of the main factors for high Cl^– content in tobacco leaves, which plagues tobacco production in some tobacco-growing area of China. Studying the effect of Cl^– channel inhibitors on the physiological and biological indexes of flue-cured tobacco would provide reference for approaching reasonable way of relieving the adverse impaction in tobacco production.

MethodsThree Cl^– inhibitors, Zn²⁺, NFA and 9-AC, were tested in a pot experiment, in which the used soil Cl^– content was 50 mg/kg. All the three Cl^– inhibitors were made into water solution of 200 μmol/L, each time irrigated 1 L per pot and consecutively for 3 days after the tobacco plants were transplanted for 30, 45, 60 and 75 days. The expression ofCLC-Nt2 gene, photosynthetic pigments content, chlorophyll fluorescence parameters, the related elements accumulation and plant biomass were measured in maturing leaves.

Results1) There was no significant difference in the expressions ofCLC-Nt2 gene in tobacco leaves among the Zn²⁺, NFA and 9-AC treatments, but they were all significantly lower than those in control, which were 82.22%, 75.39% and 72.19% respectively. 2) Inhibitor treatments could obviously raise the content of chlorophyll, with the increasing rate of 20.15% (Zn²⁺), 29.10% (NFA) and 45.52% (9-AC) separately compared with CK. The chlorophyll fluorescence in each treatment was higher than the control to a certain degree, which had remarkable benefit to decrease the damage of the PSⅡ photosynthetic apparatus in tobacco leaves. 3) Compared with control, the leaf Cl^– contents were significantly decreased by 18.17%～33.48%, while the K⁺ and NO₃^– were apparently increased by 5.28%–10.20% and 12.19%–25.24%, with the best effect in 9-AC. 4) Tobacco biomass were significantly affected by the use of inhibitors. Compared with CK, the dry weight of leaf, stem and the total biomass were significantly promoted and increased by 17.02%–32.45%, 10.54%–20.66% and 13.21%–25.50%, while the root dry weight increased only by 5.94%–11.43%. Therefore, the root-shoot ratio was comparatively lower. The biomass was showed in the order of 9-AC > NFA > Zn²⁺ > CK.

ConclusionsIrrigation 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 μmol/L 9-AC shows the best performance in the experimental condition, 200 μmol/L Zn²⁺ could meet the needs of reduction of chlorine ion in tobacco leaves with low cost in practice.