| In this paper, we studied the plant growing, photosynthetic process, molybdenum enzymes and carbon and nitrogen metabolism and hormone metabolism by pot experiment, hydroponic experiment and field experiment,investigated the lack critical value of soil molybdenum nutrition for the different traits (yield and quality) and suitable molybdenum content for tobacco,presented suitable application amount and method of molybdenum for soil molybdenum deficiency eares. The main results were as follows:l.The effects on photosynthetic pigment, gas exchange parameters,chlorophyll fluorescence parameters and chloroplast ultrastructure of tobacco were studied under molybdenum deficiency stress by the hydroponic experiment. The results showed that, compared with the control group, the photosynthetic pigment contents and net photosynthetic rate(Pn) of tobacco leaves under molybdenum deficiency stress were decreased,stomatal conductance(Gs), intercellular CO2 concentration (Ci), transpiration rate(Tr),Fo and non-photochemical quenching coefficient (NPQ) of PS II were increased, while photosynthetic electron transport rate(ETR) and the maximal photochemical efficiency (Fv/Fm) were reduced; The grana layer of the chloroplast ultrastructure under molybdenum deficiency stress expanded to deformation and loose at 10d. Most differences of photosynthetic fluorescence parameters between molybdenum deficiency and control tobacco were significant at 20d. In addition to the Tr, other indexes between the molybdenum deficiency and control tobacco were significant,and the number of amyloid was less and it grew worse,and the chloroplast of tobacco leaves was damaged seriously at 30d. Therefore, under the molybdenum deficiency stress, the chloroplast ultrastructure grows worse, the activity of PS II is inhibited, and the Pn reduces. With the extension of molybdenum stress time, the deficiency reaction is more obvious.In a day at 45d after culturing, under molybdenum deficiency, the net hotosynthetic rate(Pn) was declined earlier than that of Mo fertilized treatment, the maximal photochemical efficiency(Fv/Fm) was decreased significantly at 12:00 and increased slightly at 16:00.At 12:00,the electron transport rate(ETR) and the quantum yield(Y) began to decrease,but the initial fluorescence(FO)and the non-photochemical-quenching efficiency(NPQ) were increased sharply,then they did not recover to the level at 8:00.Under Mo fertilized treatment,the Pn of tobacco was a typical bimodal daily variation, Fv/Fm was stable, ETR and Y were reached the lowest point at 14:00 and then increased slightly at 16:00. F0 and NPQ were increased slowly during 12:00-14:00,and recovered to the level at 8:00.So,under molybdenum deficiency, the chlorophyll fluorescence parameters are sensitive to the bright light and high temperature.2.The effects on molybdenum enzymes, carbon and nitrogen metabolism and its related metabolites were studied in the developing process of tobacco under molybdenum deficiency. The results showed that the molybdenum enzymes and carbon and nitrogen metabolism enzymes of tobacco (XDH,NR, GS and INV) were increased at 10d more than that of Od, but the difference were not significant; in addition to sucrose phosphate synthase, molybdenum enzymes and nitrogen metabolism enzyme under molybdenum deficiency were decreased, and the difference between the molybdenum deficiency and CK was significant at 20d; molybdenum enzymes and carbon and nitrogen metabolism enzyme content or activity were decreased significantly under molybdenum deficiency tobacco at 30d. To illustrate, molybdenum deficiency reduces molybdenum enzyme activity or content of tobacco significantly, inhibits the nitrogen metabolism, and accelerates the metabolism conversion of nitrogen to carbon metabolism.3. The effects on dynamic changes of antioxidant system and endogenous hormone content of root and leaf tissues under molybdenum deficiency were studied. The results showed that, compared with the normal tobacco, the antioxidant enzymes (SOD, CAT, POD and APX) of tobacco were increased, MDA content was increased significantly, the ABA and CTK content of root and leaf were increased, GA and IAA content were decreased at 10d; under molybdenum deficiency,except that CAT enzyme was increased significantly, SOD, POD and APX activity were decreased, ABA, GA, CTK and IAA content of root and leaf were decreased at 20d; SOD, POD and APX enzyme activity of tobacco under molybdenum deficiency were decreased significantly, CAT enzyme was increased slightly, GA, CTK and IAA content were decreased and ABA content was increased slightly at 30d. To illustrate, at the early period under molybdenum deficiency, the antioxidant system of tobacco is inspired,and the hormone metabolic responses obviously.With the extension of molybdenum stress time, the oxidation resistance and capacity of resisting the bad environment will be close or exceed the limit, so that the body’s ability to resist adverse environment decreases.4.The effects on the dry matter accumulation of tobacco plant, molybdenum distribution in different organs and molybdenum utilization rate under different doses molybdenum nutrition by pot experiment and field experiment were studied.The results showed that, dry matter accumulation amount was also increased with the extension of growth period, and molybdenum content had different variations. The leaf had the most distribution of molybdenum in different organs by defferent molybdenum application level. The molybdenum content of tobacco leaf was increased with the increasing of soil available molybdenum content.The molybdenum accumulation in tobacco plant was increased with the increasing of the molybdenum nutrition level. Molybdenum element promotes the accumulation of dry matter of different organs, improves the molybdenum accumulation amount of the plant.To a certain extent,appropriate molybdenum nutrition affects molybdenum allocation in different organs of tobacco plant and improves distribution ratio in tobacco leaves.5.The lack critical level of the soil available molybdenum of different quality characters of flue-cured tobacco and suitable molybdenum content of tobacco leaf were studied. The results showed that,in the condition of pot experiment, the lack critical value of soil available molybdenum for yield was about 0.30mg/kg, and the lack critical value of soil available molybdenum for oil was about 0.10mg/kg;In the conditions of field experiment, the lack critical value of soil available molybdenum for yield was about 0.15mg/kg, and the lack critical value of soil available molybdenum for proportion of high class tobacco and variegated tobacco were also about 0.20mg/kg.There was a significant logarithmic relationship between the molybdenum content in tobacco leaves and soil available molybdenum content. We can draw a conclusion that molybdenum content in the range of 2-4mg/kg is appropriate from critical value of soil available molybdenum for different traits.6.Field experiments were carried out to study the effects on yield and quality of flue-cured tobacco by different molybdenum fertilizers. The results showed that the contents of nicotine and total nitrogen were decreased, but the reducing sugar and total sugar content were increased with the increasing of molybdenum amount. The amounts of aroma components, yield and output value were increased by molybdenum, and the ratio of variegated tobacco was decreased. Based on the analysis on chemical components, aroma component,economic attributes and smoking evaluation of tobacco leaves, the optimum molybdenum dose is 80ml(2mg MoO3) per plant of special fertilizer dilution for flue-cured tobacco.7.Field experiments were carried out to study the effects of different molybdenum measures on growth, yield and quality of flue-cured tobacco. The results showed that the yield and values were increased significantly,nicotine accumulation of upper leaves were reduced,the potassium content and aroma components were increased, and the overall quality was improved by molybdenum. Under the condition of same molybdenum fertilizer diluent of 80ml per plant, the mode of watering at the transplanting stage and spraying at the squaring stage (B2) has the best effect; and the mode of spraying molybdenum fertilizer at the rosette stage and the squaring stage respectively (B3) was the second.In summary, for the very lack of region "whose soil available molybdenum belows 0.10 mg/kg, we need add specific fertilize molybdenum by 80-120ml per 666.7m2 to tobacco;for the deficient region whose soil available molybdenum between 0.10-0.15 mg/kg, we need add specific fertilize molybdenum by 80ml per 666.7m2; for the deficient slightly region whose soil available molybdenum between 0.15-0.20 mg/kg, we need add specific fertilize molybdenum by 40-80ml per 666.7m2.We can water root one time at transplanting period and spraying one time at squaring stage, or spray two times respectively at the rosette stage and squaring stage and focus in upper leaves. |
PDF Full Text Request