Title: THEORY AND PRACTICE OF DEVELOPING SPECIALTY AND HIGH-QUALITY TOBACCO LEAVES IN WEST HENAN PROVINCE OF CHINA
Description: Preface

The tobacco area of the west Henan Province is located at the border of Henan, Shanxi, and Shaanxi provinces, which is a transition zone of subtropical and warm temperate zone with mild climate and sufficient light. This area is suitable for the growth of high-quality tobacco leaves. However, in recent years, drought in the fast- growing period occurs often in tobacco leaf production, leading to late growth, late maturity, and declining quality of tobacco leaves. This study has found that the rainfall was low before July and had a high inter-annual variability by the analysis of the rainfall from April to September 1986-2022 in Sanmenxia [Sanmenxia, a city in Henan, China] tobacco-growing area and from May to October 1986-2022 in Luoyang [Luoyang, a city in Henan, China] tobacco-growing area. It subsequently carries out a randomized block design in three key stages of tobacco growth, including the root extending stage, the fast-growing stage, and the mature stage, in Liangjiazhuang, Zhuyang Town, Sanmenxia. The randomized block design studies the effects of four drought-resistance technologies on Yunyan87’s agronomic character, root activity, the content of reactive oxygen species (ROS), key enzyme activity in carbon-nitrogen metabolism, relative expression of key genes in carbon-nitrogen metabolism, field growth phase, conventional chemical component of top-three leaves and. The four drought-resistance technologies include water-holding agents and antitranspirant (no water-holding agents, using water-holding agents alone, using antitranspirant alone, and using water-holding agents and antitranspirant at the same time), different amount of water for irrigation (no irrigation when it is raining, and respectively irrigating to 40%, 60%, 80% of soil water content in the fast growing stage), different nitrogen application rates and basal-topdressing nitrogen ratios (total local conventional nitrogen fertilization of 3.5kg per acre, total nitrogen fertilization of 3kg and 6:4 of basal-topdressing nitrogen ratio per acre, total nitrogen fertilization of 3kg and 7:3 of basal-topdressing nitrogen ratio per acre, total nitrogen fertilization of 4kg and 6:4 of basal-topdressing nitrogen ratio per acre, and total nitrogen fertilization of 4kg and 7:3 of basal-topdressing nitrogen ratio per acre), and different substances of chemical manipulation (no chemical manipulation, spraying jasmonic acid, spraying abscisic acid, and spraying ethephon). This study is conducive to exploring the appropriate dry-land cultivation techniques for different places. It also subsequently carries out a randomized block design in Wangcun, Xiaojie Town, Luoyang. The randomized block design studies the effects of four drought-resistance technologies on LY1306’s agronomic traits, root activity, the content of reactive oxygen species (ROS), key enzyme activity in carbon-nitrogen metabolism, relative expression of key genes in carbon-nitrogen metabolism, the field growing period, conventional chemical components of top-three leaves. The four drought-resistance technologies include ridge tillage to preserve soil moisture (ridging in spring, ridging in winter, autumn ploughing and winter ridging), appropriate transplanting methods (conventional strong seedling transplanting, small seedling transplanting under film, and well-cellar seedling transplanting), different nitrogen fertilization and basal-topdressing nitrogen ratios (total local conventional nitrogen fertilization of 3.5kg per acre, total nitrogen fertilization of 3kg and 6:4 of basal-topdressing nitrogen ratio per acre, total nitrogen fertilization of 3kg and 7:3 of basal-topdressing nitrogen ratio per acre, total nitrogen fertilization of 4kg and 6:4 of basal-topdressing nitrogen ratio per acre, and total nitrogen fertilization of 4kg and 7:3 of basal-topdressing nitrogen ratio per acre), and different chemical regulators (no chemical regulators, spraying jasmonic acid, spraying abscisic acid, and spraying ethephon). This study is conducive to exploring the appropriate dry-land cultivation techniques for different places. Major research results are as follows:
(1) The variation of rainfall in the Sanmenxia tobacco-growing area from April to September from 1986 to 2022 shows a slow upward trend, and the rainfall of half of the years concerned of rainfall is lower than the average one. The variation coefficient of rainfall in September is the largest, followed by that in May, and the smallest is in July. According to the analysis of rainfall in each growing period of a flue-cured tobacco field, the variation of rainfall in the root stretching period, the fast growing period and the maturity period shows a slow downward trend respectively in general, and the relation is the root stretching period(262.23 mm)＞the fast growing period(85.80mm)＞the maturity period(81.84mm), which are inconsistent with the appropriate rainfall of tobacco-growing area field. The years of rainfall less than their own average rainfall accounts for 57%, 51% and 54% of all years, respectively.
(2) In the study on the application of water-holding agent and antitranspirant, the application of water-holding agent and antitranspirant at the same time has the best effect on the growth and development of flue-cured tobacco, achieving the fastest fading of flue-cured tobacco and the most coordinated chemical components of flue-cured tobacco leaves. There is little difference between the application of a water-holding agent and the application of an antitranspirant, whose effect is just followed by the application of a water-holding agent and the antitranspirant at the same time. The agronomic traits of the group under treatment are better than those of the control group, and the agronomic traits of the application of a water-holding agent and antitranspirant at the same time are the best. 60 and 90 days after transplanting, the soil moisture content and root activity of groups under treatments are significantly higher than those of the control group and the highest soil moisture content and root activity are obtained when water-holding agent and antitranspirant are applied at the same time, followed by the application of water-holding agent alone. 120 days after transplanting, the root activity decreases significantly in groups under treatments, and the root activity of the application of a water-holding agent and antitranspirant at the same time is the lowest and its root aging is the deepest. The contents of O2- and H2O2 in groups under treatments are significantly higher than those in the control group, and the hydroxyl radical clearance in groups under treatments is significantly lower than those in the control group. Meanwhile, the accumulated active oxygen species in the application of a water-holding agent and antitranspirant at the same time is the highest. The nitrate reductase (NR) enzyme activity and glutamine synthetase (GS) enzyme activity in groups under treatments are significantly lower than those in the control group, and the expressions of NtNR and NtGS in groups under treatments are significantly lower than those in the control group. Meanwhile, the expressions of NtNR and NtGS genes in the application of water-holding agent and antitranspirant at the same time are 0.23 and 0.22 times of those in the control group. The sucrose phosphate synthetase (SS) enzyme activity of groups under treatments is significantly lower than that in the control group, and the gene expression of NtSPS and NtSS in groups under treatments are significantly lower than that in the control group. The gene expression of NtSPS and NtSS treated with water-holding agent and antitranspirant at the same time are 0.21 and 0.20 times that of the control group. The enzyme activity and gene expression related to carbon and nitrogen metabolism are the lowest when water-holding agent and antitranspirant are applied at the same time. The growing period of the field treated with water-holding agent and antitranspirant at the same time is 126 days, which is 6 days, 6 days, and 19 days shorter than that of the application of water-holding agent, that of the application of antitranspirant alone and the control group. Compared with the control group, the contents of total sugar, reducing sugar and potassium increased, while the contents of total nitrogen, nicotine, and chlorine decreased. At the same time, the contents of total sugar, reducing sugar, the ratio of potassium to chlorine and the nitrogen-nicotine ratio in groups under treatments are the highest, and the chemical components of tobacco leaves are the most coordinated under the above treatment.
(3) On the study of different irrigation, flue-cured tobacco first enters the maturity period and has the shortest growing period under the condition of irrigation to 80% soil moisture content. Compared with the control group, 60 and 90 days after transplanting, the agronomic traits of groups under treatment are better, among which that of the irrigation to 80% of soil moisture content is the best, followed by 60%. The root soil moisture content and root activity in groups under treatments are significantly higher than those in the control group, and that of group with irrigation to 80% soil moisture content is the largest. 120 days after transplanting, the root activity of flue-cured tobacco is the lowest when irrigating to 80% of soil moisture content. The contents of O2•− and H2O2 in groups under treatments are significantly higher than those in the control group, and that of the group with irrigation to 80% of soil moisture content is the highest, followed by 60%. The hydroxyl radical scavenging rate in groups under treatments is significantly lower than that in the control group, and that of the group with irrigation to 80% of soil moisture content is the lowest, followed by 60%. The NR enzyme activity, GS enzyme activity, SPS enzyme activity and SS enzyme activity are significantly lower than those in the control group, and those of the group with irrigation to 80% of soil moisture content is the lowest, followed by 60%. The gene expression of NtNR, NtGS, NtSPS and NtSS in groups under treatments are significantly lower than those in the control group, and those of treatment with irrigation to 80% soil moisture content is the lowest, followed by 60%. The field growing period of treatment with irrigation to 80% soil moisture content is 126 days, which is shortened by 6 days, 6 days and 19 days compared with treatment with irrigation to 60% soil moisture content, irrigation to 40% soil moisture content and the control group. Compared with the control, the reducing sugar and total sugar of cured tobacco increase with the increase of irrigation amount, while the content of nicotine, chlorine and total nitrogen decrease with that. In the treatment with irrigation to 80% soil moisture content, the ratio of potassium to chlorine and nitrogen-nicotine ratio of flue-cured tobacco is the highest, and the chemical components of them are most coordinated, followed by 60%.
(4) In the study of appropriate nitrogen fertilization and basal-topdressing ratio of flue-cured tobacco, 30 days and 60 days after transplanting, the agronomic traits of groups under treatments are significantly better than those of the control group, among which those of (T2) 3 kg total nitrogen and 7:3 basal-topdressing ratio is the best, followed by (T4) 4 kg total nitrogen and 7:3 basal-topdressing ratio, indicating that with the progress of field growing period, the total biomass of T2 is the largest, and the growth and development of flue-cured tobacco are the fastest. 90 days after transplanting, T2 still performs best in agronomic traits. 120 days after transplanting, the enzyme activities of carbon and nitrogen metabolism in groups under treatments are significantly lower than those in the control group, and the relative expression of NtNR, NtGS, NtSPS and NtSS genes in groups under treatments are significantly lower than those of the control group. the enzyme activities of carbon and nitrogen metabolism and the relative expression of NtNR, NtGS, NtSPS and NtSS genes in T2 are lowest, followed by T4. The contents of O2•− and H2O2 in groups under treatments are significantly higher than those in the control group, and the hydroxyl radical scavenging rate of T2 is the lowest, and the content of reactive oxygen species of T2 is the highest. This experiment shows that with the increase of basal-topdressing nitrogen ratio, the capacity of carbon sequestration, transformation and metabolism in flue-cured tobacco decrease, the nitrogen metabolism and nitrogen use efficiency decrease, the content of reactive oxygen species increases, and the maturity and senescence of flue-cured tobacco are deepened. With the increase of basal-topdressing nitrogen ratio, the contents of total sugar and reducing sugar in flue-cured tobacco increase, while the contents of nicotine and total nitrogen decrease. Among them, the ratio of potassium to chlorine and sugar alkali ratio of T2 are the best, where the chemical components of flue-cured tobacco are most coordinated. It is followed by T4.
(5) In the study on spraying chemical regulators, spraying ethephon has the best effect of yellowing, and under this treatment, the growing period of the field is the shortest. It is followed by spraying jasmonic acid. 120 days after transplanting, the contents of chlorophyll a, chlorophyll b, carotenoid and total chlorophyll in groups under treatments are significantly lower than those in the control group. As spraying abscisic acid, the content of total chlorophyll is significantly higher than that of spraying jasmonic acid, which is significantly higher than that of spraying ethephon. Compared to the control group, the content of O2- content in groups under treatment are significantly higher, which are 1.31, 1.29 and 1.58 times of that in the control group, respectively. Compared to the control group, the content of H2O2 content in groups under treatments is significantly higher, which are 1.12, 1.19 and 1.47 times of that in the control group, respectively. The hydroxyl radical scavenging rate of groups under treatments is significantly lower than that of the control group, and that of the group with spraying ethephon is the lowest. The NR enzyme activity, GS enzyme activity, SPS enzyme activity and SS enzyme activity in groups under treatment are significantly lower than those in the control group, and the key enzyme activity of carbon and nitrogen metabolism in the group with spraying ethephon is the lowest. Compared to the control group, the expressions of NtNR, NtGS, NtSPS and NtSS genes in groups under treatments are significantly lower, which are, in treatment of spraying ethephon, 0.23, 0.21, 0.15 and 0.14 times of those in the control group. In the treatment of spraying ethephon, the growing period is the shortest (126 days), which is 6 days, 6 days and 19 days shorter than that of spraying abscisic acid, jasmonic acid and the control group. The content of total sugar in group of spraying ethephon is the highest (33.73%), an increase of 1.23% and 1.96% compared with that in the group of spraying jasmonic acid and abscisic acid respectively. The ratio of potassium to chlorine and sugar alkali ratio in the group of spraying ethephon are the best, which can better coordinate the chemical components of flue-cured tobacco.
(6) The average rainfall in the Luoyang tobacco-growing area from May to October from 1986 to 2022 is 446.84 mm, showing a slow upward trend. Among all the years, the rainfall of 1997 is the lowest, and the rainfall of half of the years concerned of rainfall are lower than the average one. According to the analysis of rainfall in each growing period of a flue-cured tobacco field, the variation of rainfall in the root stretching period, the fast growing period and the maturity period shows a slow downward trend respectively in general, and the relation is the root stretching period(218.52mm)＞the fast growing period(105.72mm)＞the maturity period(89.49mm), which are inconsistent with the appropriate rainfall of tobacco-growing area field. The years of rainfall less than their own average rainfall accounts for 57%, 62% and 65% of all years, respectively.
(7) In the study of ridge tillage to preserve soil moisture, ridging in winter, and autumn ploughing and winter ridging can significantly increase the soil moisture in the early growing period, improve the root activity of flue-cured tobacco during flue-cured tobacco’s growth and development, and reduce it in the maturity and aging period. With the maturity and aging of flue-cured tobacco, the capacity of nitrogen metabolism gradually decreases, and the capacity for carbon sequestration and transformation decreases. This study finds that in the late growing period of flue-cured tobacco, the key enzyme activity in carbon and nitrogen metabolism and the expression of related genes are significantly reduced by ridging in winter, and autumn ploughing and winter ridging. In addition, under these two treatments, the contents of nicotine, total nitrogen and chlorine are reduced, the contents of reducing sugar, total sugar and potassium are increased, the ratio of potassium to chlorine and sugar alkali ratio are more coordinated, and the quality of flue-cured tobacco is higher. The picking time of the upper leaves in the treatment of ridging in winter, and autumn ploughing and winter ridging is advanced by 11 days and 16 days respectively.
(8) In the study of appropriate transplanting methods, small seedling transplanting under film and well-cellar seedling transplanting significantly reduce the root activity in the maturity period, which are 81.06% and 75.06% of CK, the name of the control group, respectively. As for well-cellar seedling transplanting, the key enzyme activity and the relative expression of carbon and nitrogen metabolism in flue-cured tobacco in the maturity period are significantly decreased, and the relationship is CK>T1>T2. The peroxidase activity in small seedling transplanting under film and well-cellar seedling transplanting are significantly lower than that in CK, 67.90% and 62.50% of that of CK respectively. The conventional chemical components of flue-cured tobacco leaves are more coordinated in well-cellar seedling transplanting, and the quality of tobacco leaves is better. At the same time, small seedling transplanting under film and well-cellar seedling transplanting can advance the picking time and shorten the growing period of flue-cured tobacco.
(9) In the study of appropriate nitrogen fertilization and basal-topdressing ratio of flue-cured tobacco, (T4) 4 kg total nitrogen and 7:3 basal-topdressing ratio shows higher photosynthetic rate and excellent agronomic traits in the early periods, and can be picked earlier in the maturity period. In general, before and during the fast growing period, when the nitrogen fertilization is the same, the content of plastid pigment, the capacity for material accumulation, root activity and antioxidant activity of tobacco plants increase with the increase of basal-topdressing nitrogen ratio. However, when the basal-topdressing nitrogen ratio is the same, the content of plastids pigment increases with the increase of nitrogen fertilization. The trend is opposite to that in the fast growing period. The carbonitase activity and the relative expression of carbazitase genes in tobacco plants decrease with the increase of basal-topdressing nitrogen ratio. Compared with the control group, all treatments promote the ratio of potassium to chlorine and sugar alkali ratio in chemical components of flue-cured tobacco. T4 is the best, which is followed by T2. In T4, the growing period is the shortest, which is 140 days, 8 days, 3 days, 5 days, and 18 days shorter than that of T1, T2, T3 and the control group.
(10) In the study on spraying chemical regulators, the contents of chlorophyll a, chlorophyll b, carotenoid and total chlorophyll in groups under treatments are significantly lower than those in the control group. 120 days after transplanting, the NR enzyme activity and GS enzyme activity in groups under treatments are significantly lower than those in the control group, and the effect of (T3) spraying ethephon is the most obvious. 120 days after transplanting, the SPS enzyme activity and SS enzyme activity in groups under treatments are significantly lower than those in the control group, and the effect of T3 is the best. 120 days after transplanting, the POD enzyme activity, SOD enzyme activity and CAT enzyme activity in groups under treatments are significantly lower than those in the control group. 120 days after transplanting, the relative expression of NtNCET1, NtPR1b, and NtEFE26 are promoted significantly. In general, the effect of T3 is the best. From the whole growing period of flue-cured tobacco fields, the growing period of T3 is the shortest, lasting 138 days, which is 3 days, 6 days and 21 days shorter than the growing period of spraying jasmonic acid, spraying abscisic acid and the control group. Compared with the control group, different treatments can promote the ratio of potassium to chlorine and sugar alkali ratio in chemical components of flue-cured tobacco, among which T3 is the best in all dictators.
We are confident that people in the field of tobacco cultivation will derive valuable knowledge from reading this monograph.