| Cigar smoke has a strong and full aroma,and the quality of tobacco is special.With the rapid growth of the economic development in the domestic cigar,the demand for cigar raw materials is also increasing.Generally,there are high requirements for the appearance quality of cigar coated tobacco leaves.The growth of cigar coat is greatly affected by fertilization and light.As a metal atom in the center of the chlorophyll porphyrin ring,magnesium(Mg)has a regulatory effect on the photosynthesis and appearance color of cigar coat leaves.Therefore,in order to improve the appearance and color of the cigar coat and improve the yield of high-quality cigar coats.This study took the variety of cigar coat Chuxue 26(CX26)as the research object,applied different amounts of magnesium fertilizer(T1:0 kg/Mg O hm~2,T2:0 kg/Mg O hm~2,T3:37.5 kg/Mg O hm~2,T4:75 kg/Mg O hm~2,T5:100 kg/Mg O hm~2)in the field,and installed LED lights in the airing room to control different light qualities(conventional airing(CK),red light(R),yellow light(Y),blue light(B),green light(G),White light(W)and light intensity(5 Watts(W5),10 Watts(W10),15 Watts(W15),20 Watts(W20),and 30 Watts(W30)).It were used to quantitatively analyze the color of cigar coat,revealing the mechanism of color formation of cigar tobacco leaves under magnesium fertilizer and light conditions,providing guidance for improving the yield of cigar coat and production technology of cigar coat.The main conclusions were as follows:(1)Applying 75 kg/Mg O hm~2(T4 treatment)magnesium fertilizer deepened the color of the leaves.During the topping period,the leaf width,leaf length,and chlorophyll content value(SPAD)of cigar tobacco treated with T4 were higher than those of other treatments,respectively 32.4 cm,58.0 cm,and 40.0 cm.In terms of biological characteristics,the growth of tobacco leaves in the field under T5 treatment were less than that of T4 or T3.At maturity,the color of T1 leaves were yellow green;while T2,T3,and T5 leaves were cyan green;T4 appeared dark green,darker than other processed colors.During the airing period,leaf color changes concentrated in the first 10 days.The brightness value(L*),yellow-blue value(b*),and total color difference(△E)all increased,then decreased,and then stabilized during the airing process,reaching the maximum on the 6th day.The average values of each index on the 6th day were 61.68,41.44,and 28.06,respectively.The red and green values(a*)showed a gradual increase and tended to stabilize,reaching the maximum on the 10th day of each treatment.The value of a*in T1,T2,T3,T4 and T5 was 4.56,9.46,8.90,9.15,and 9.47,respectively.The L*and b*values of T1 treatment were significantly higher than those of other treatments at the early stage of airing,while the values of a*and△E were opposite.The L*,a*,and b*values of T4 treatment were significantly lower than those of other treatments.Applying 75 kg/Mg O hm~2deepened the color of leaves,making them appear dark green and dark brown at the end of harvest and airing.It was the appropriate amount of magnesium fertilizer.(2)Magnesium mainly affected the Pheophytin pheophorbide hydrolase(PPH)degradation pathway of chlorophyll degradation in cigar tobacco leaves to regulated changes in leaf color.The activity of Mg-Dechelatase(MDCase)first increased and then decreased with the advance of the airing process,and reached the highest level on the fourth day.The value of MDCase in T1,T2,T3,T4 and T5 was 15.00 U/g,18.27 U/g,18.91 U/g,16.71 U/g and 19.24 U/g,respectively.The PPH activity gradually decreased with the advance of the airing process,and the PPH activity of T4 treatment was significantly higher than that of other treatments.T2 treatment reduced the activity of Pheophorbide a oxygenase(PAO).Therefore,the PPH deplantation pathway was the main pathway for the degradation of chlorophyll in cigar tobacco leaves.Magnesium deficiency accelerated the rate of water loss in the early stages of airing,inhibit the activity of PAO,and hinder the degradation of chlorophyll.Applying magnesium fertilizer reduced the brightness and redness of the leaves to a certain extent,resulting in brown tobacco leaves and dark apparent color of cigar tobacco leaves.(3)Light quality accelerated the yellowing and browning of tobacco leaves,with the most obvious effects of R and B lights.The results of this study showed that the impact index of light quality on the browning stage of tobacco leaves.The index of the browning stage in CK,R,Y,B,G and W was 1.23,33.1,36.6,17.6,3.9 and 42.5 percentage points,respectively,and it was higher than that of the yellowing stage.The effect of Y light on the yellowing index of tobacco leaves was lower than that of other treatments,with 21.6,19.7,23.5,23.8,and 41.2 percentage points lower than CK,R,B,G,and W,respectively.Light quality treatments all increased the browning index of tobacco leaves,with R and B lights browning indexes of 80.0%and 63.7%,both significantly higher than other treatments.The proportion of cigar coats produced under conventional airing conditions was relatively high(35.3%).It was 10.6,21.2,27.3,16.9 and 8.2 percentage points higher than R,Y,B,G and W,respectively.However,R-light treatment produced first-class cigar coats with a yield of 3.0%.(4)Appropriate light intensity(15 W)deepened the color of tobacco leaves.The color of tobacco leaves treated with W15 was darker than that of other treatments,with a total color difference△E of 25.3.It was greater than that of other treatments.The chromaticity values of L*,a*and b*were 47.5,9.6 and 30.2,respectively.This indicated15-watt light was the best light intensity for deepening the color of the leaves.Light accelerated the browning of tobacco leaves,and the maximum browning index was81.5%when the light intensity was 10 W.For the yellowing index of tobacco leaves,W30treatment decreased by 22.8 percentage points compared to conventional airing treatment,while W5 treatment increased by 13.3 percentage points.The content of unsaturated fatty acids such as linoleic acid and linolenic acid in tobacco leaves decreased with the increase of light intensity.The relative content of linoleic acid and linolenic acid in the browning stage was lower than that in the yellowing stage.This indicated that light decomposed the content of unsaturated fatty acids in the leaves,and affected the rate of water loss of tobacco leaves,accelerating cell membrane lipid damage,and changed the appearance and color of the leaves,resulting in rapid browning of tobacco leaves.In summary,this study suggested that applying 75 kg/Mg O hm~2fertilizer in the field deepened the color of cigar tobacco leaves.On the basis of applying an appropriate amount of Mg fertilizer,using 30 W of red light and 15 W of white light for 12 hours at night produced first-class high-quality cigar clothing,with yield rates of 3.0%and 11.5%,respectively. |
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