| Potassium is a quality element of tobacco,and its adequate supply not only ensures the normal growth and development of tobacco,but also has an important impact on the quality and production value of tobacco leaves,such as appearance quality,physical characteristics and chemical composition.Under drought stress,tobacco roots have a reduced ability to absorb water,the root cell membrane structure is damaged,and the absorption of nutrients such as potassium is weakened,causing potassium deficiency in tobacco plants.For example,the frequent droughts in the Luoyang tobacco area in western Henan Province tend to reduce the effective potassium content of soil due to potassium fixation and reduce the utilization of potassium fertilizer,resulting in a lower amount of potassium available for uptake and utilization by the tobacco plant,which seriously restricts the improvement of potassium content and quality of local tobacco leaves.To address the above problems,this study investigated the potassium uptake characteristics of flue-cured tobacco under simulated drought stress and alternating wet and dry conditions at different potassium levels,and the accumulation of potassium and yield benefits of flue-cured tobacco under water-fertilizer integration technology,using flue-cured tobacco as the material.(2)the effect of alternating wet and dry conditions on the growth and potassium uptake of flue-cured tobacco seedlings under different levels of potassium supply;(3)the effect of water and fertilizer integration on the growth and development of flue-cured tobacco and potassium nutrition.The main research results are as follows:1.Mild drought had a good promotion effect on the growth of flue-cured tobacco seedlings,but the inhibitory effect of drought stress on physiological functions such as material accumulation,photosynthesis and potassium uptake of flue-cured tobacco increased with the increase of drought level.When PEG-6000 was not added,the root dry weight,chlorophyll content,root vigor,and potassium content of all parts of the tobacco plant were significantly lower at low potassium levels than at normal potassium levels.At both levels of potassium supply,the relative conductivity,reactive oxygen content and malondialdehyde content of the tobacco plant tended to increase,chlorophyll content and potassium content of each part tended to decrease,while the soluble protein content,root vigor,SOD and CAT activities of the leaves increased and then decreased with increasing concentration of PEG-6000 and were maximum at 10% PEG concentration.The net photosynthetic rate,stomatal conductance,water utilization,and leaf POD activity increased and then decreased with the increase of PEG-6000 concentration,and all of them reached the maximum at 10% PEG-6000 concentration,and the increases were 27.87%,73.68%,78.57%,and 179.11%,respectively,compared with the drought-free control,179.11%.At low potassium levels,net photosynthetic rate,stomatal conductance,transpiration rate,and water utilization decreased gradually with increasing PEG-6000 concentration,and the largest decrease was achieved at 20% PEG-6000 concentration,with 56.25%,41.94%,57.14%,and 36.90% lower than the control,respectively.2.Appropriate drought alternation could promote the growth of tobacco seedlings,improve antioxidant enzyme activity and photosynthesis,and enhance the stress tolerance of tobacco seedlings.Without the addition of 10% PEG treatment,aboveground and root dry and fresh weight,root vigor,chlorophyll content,net photosynthetic rate,stomatal conductance,water utilization,and potassium content of all parts of the tobacco plant were significantly higher at normal potassium level than at low potassium level,while the opposite was true for root malondialdehyde content,malondialdehyde leaf and root SOD activity,root POD activity,and leaf CAT activity.The above-ground and root dry and fresh weights,root vigor,leaf and root antioxidant enzyme activities showed a gradual increase in the order of CK(normal control)-DT(drought treatment)-AWD(alternating wet and dry)at both potassium levels,where the leaf SOD and POD activities,root dry and fresh weights,SOD and POD activities of AWD treatment normal potassium levels increased compared to CK and DT treatments by and 1.91-fold,87.77%,74.86%,100.12%,103.61%,1.27-fold and 71.05%,48.14%,47.53%,57.57%,29.78%,74.60% at low potassium levels and 73.89%,1.10-fold,45.66%,1.43-fold,62.25%,86.34% and 42.31%,81.64%,27.06%,39.08%,33.98%,34.12%;soluble protein content,relative conductivity,malondialdehyde content and reactive oxygen species content of leaves and roots of tobacco plants gradually decreased;chlorophyll content and potassium content of all parts first decreased and then increased,in which the above-ground and root potassium content of DT treatment at low potassium level was lower than that of CK and AWD treatment,respectively.The above-ground and root potassium contents decreased by 26.55% and 18.68%,45.34% and 31.78% in DT treatment and 37.55% and 31.08%,50.00% and 22.65% in AWD treatment,respectively,compared with CK and AWD treatments.The highest net photosynthetic rate,stomatal conductance and transpiration rate were observed in AWD treatment at normal potassium level,which significantly increased by 25.42%,36.81% and 40.66% compared to CK treatment.Under low potassium level,in the order of CK-DT-AWD,net photosynthetic rate,stomatal conductance and transpiration rate of tobacco leaves decreased first and then increased,while water utilization and intercellular CO2 concentration were reversed,in which net photosynthetic rate and stomatal conductance of AWD treated leaves significantly increased by 36.22% and 59.30%,0.99 times and 2.61 times compared with CK and DT treatments.3.To investigate the effect of water and fertilizer integration on potassium uptake and yield quality of flue-cured tobacco,and to provide a basis for enhancing the potassium content of tobacco leaves.Using flue-cured tobacco LY1306 as the test material,a single-factor randomized group trial was conducted in the field with three treatments: blank control(CK),conventional fertilization(T1)and water-fertilization integration(T2),to compare the dry matter accumulation,potassium accumulation and accumulation rate of each part,chemical composition and economic traits of postbaking tobacco leaves.Compared with CK and T1 treatments,the dry matter accumulation in T2 treatment was always the highest,and the dry matter accumulation rate increased by 70.03% and 36.72%,and the maximum dry matter accumulation rate appeared at 53.370 d,7.884 d and 5.777 d earlier than that of CK and T1 treatments;as the fertility process progressed,the potassium accumulation in each part showed an obvious " The average and maximum accumulation rates of potassium in all parts of the T2 treatment were significantly higher than those of the CK and T1 treatments,and the time of maximum accumulation rate was significantly earlier than those of the CK and T1 treatments,and it was most obvious in the tobacco root system,where the average accumulation rate of potassium was significantly higher than that of the CK treatment by 64.33% and the maximum accumulation rate of potassium was significantly higher than that of the CK treatment.The average accumulation rate of potassium in tobacco roots was significantly higher than that of CK by 64.67%,the maximum accumulation rate of potassium was significantly higher than that of CK and T1 by 72.28% and 33.72%,and the maximum accumulation rate of potassium appeared 7.28 d and 8.78 d earlier than that of CK and T1;the potassium content and potassiumchlorine ratio of tobacco leaves were the highest in all parts of T2 treatment after baking,and the potassium content of its leaves was significantly higher than that of CK and T1 by 33.70% and 20.59%.The potassium content and potassium-chlorine ratio of the T2 treatment were the highest in all parts of the tobacco leaves after baking,and the potassium-chlorine ratio was 31.60% higher than that of the CK treatment,and the production value was 50.45% higher than that of the CK treatment and 9521.25 Yuan/hm2 higher than that of the T1 treatment.Water fertilizer integration technology can significantly increase the dry matter accumulation of tobacco plants,effectively promote the accumulation of potassium in all parts of flue-cured tobacco,coordinate the chemical composition of tobacco leaves,and improve the economic traits of fluecured tobacco.In summary,the inhibitory effects of drought stress on physiological functions such as material accumulation,photosynthesis and potassium uptake in flue-cured tobacco increased with the increase of drought degree.The moderate drought alternation can promote the growth of flue-cured tobacco seedlings based on further promotion of material accumulation and enhanced photosynthesis,and effectively alleviate the increase in cell membrane permeability,reactive oxygen species accumulation,chlorophyll degradation and decrease in above-ground and root potassium content of tobacco due to persistent drought.The water-fertilizer integration technology can effectively promote the growth and potassium uptake of flue-cured tobacco,prompt the maximum accumulation rate of dry matter and potassium in fluecured tobacco to move forward in time,and significantly improve the quality of tobacco leaves in Luoyang tobacco area. |
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