| Nicotiana tabacum L.is one of the most important economic crops in Yunnan province,and it is also a traditional dominant crop in Yunnan Lincang area.At present,the middle or lower part of the middle of the tobacco leaves highest economic value often fracture from the base of the petiole under the influence of wind,rain or human and animal movement touch and other external factors in the stage of rapid growth has not yet reached a mature period in some of the tobacco areas in Lincang(the main cultivar is Yunyan 87).It brings huge economic losses to production.However,the causes and mechanisms of leaf fracture are not reported at present.In order to reduce the economic loss and explore the mechanism of tobacco leaf fracture,this study first compare the related physiological and biochemical indexes(including lignin content,the activity of lignin synthesis related enzymes POD and PAL)and the mechanical structure of petiole main vein,analyze the differences in the relative indexes of easy fracture leaves and fracture resistant leaves,and find out their physiological and morphological structures related to tobacco leaf fracture.Then,the effects of ecological factors such as light,humidity and temperature on the fracture of tobacco were specified by simulation experiment.In addition,increasing different fertilizers and exogenous growth regulators on the effect of related indexes tobacco leaf fracture.The experimental results are summarized as follows:1.Comparative analysis physiological and biochemical composition,the organizational structure of the petiole main vein in easy fracture leaves and fracture resistant leaves of Nicotiana tabacum cv.Yunyan87.Lignin content,the activity of POD and PAL were lower than those of fracture resistant leaves in the squaring stage,before the first harvesting and in the middle leaf harvesting stage,and all of them were significantly different.The vascular organization is underdeveloped in petiole main vein,the number of vessel elements in xylem was relatively small,the cell distribution was relatively sparse,the length of the vascular bundle was smaller,and the distance between the adjacent vascular bundles was relatively large of sand leaf,4-6-(th)leaf and lumbar leaf in easy fracture.It is suggested that the fracture of tobacco leaves may be related to the lignin content,activity of POD and PAL,and the fibrovascular tissue structure of the petiole main vein.2.Temperature,humidity,light three factors three horizontal orthogonal test results show that:Temperature,relative humidity and light all affect lignin content.Light intensity had the greatest effect on lignin synthesis.When the day and night temperature was 25/15 ?,the relative humidity was 65%,and the daylight illumination was 60%,the lignin content is the highest in the 9 groups of experiments.3.The effect of different fertilizers on the rate of mechanical fracture,lignin content,the activity of peroxidase(POD)and phenylalanine ammonialyase(PAL)of tobacco leaves in the field.Significantly reduced the rate of the fracture,significant increased lignin content,the activity of POD and PAL of sand leaf,4-6-(th)leaf and lumbar leaf of Nicotiana tabacum cv.Yunyan87 was treated with potassium sulfate,borax,water-soluble organic potassium,water-soluble organic potassium + spraying bacterial manure of containing trace elements and bacterial manure of containing trace elements decrease significantly in the squaring stage,before the first harvesting and in the middle leaf harvesting stage.Zinc sulfate,bacterial manure + bacterial manure of containing trace elements no significant effect to reduce the rate of the fracture,and increaselignin content,the activity of POD and PAL of tobacco leaves.4.Characteristics of anatomical structure of main vein of sand leaf,4-6-(th)leaf and lumbar leaf of easy fracture leaves and fracture resistant leaves treated with different fertilizers were studied by examining paraffin section.These examinations revealed that there is no significant difference between characteristics of anatomical structure of main vein of easy fracture leaves in all treatment groups and easy fracture leaves corresponding leaf position in control group in the squaring stage,before the first harvesting and in the middle leaf harvesting stage;There is no significant difference between characteristics of fibrovascular tissue structure of main vein of fracture resistant leaves in all treatment groups and fracture resistant leaves corresponding leaf position in control group.The vascular organization is underdeveloped in petiole main vein,the number of vessel elements in xylem was relatively small,the cell distribution was relatively sparse,the length of the vascular bundle was smaller,and the distance between the adjacent vascular bundles was relatively large of sand leaf,4-6-(th)leaf and lumbar leaf in easy fracture of all treatment groups.5.The effect of different fertilizers on the plant characters of Nicotiana tabacum cv.Yunyan87 in the field.Some agronomic traits were treated were found to be consistent in the squaring stage,before the first harvesting and in the middle leaf harvesting stage.The height of plant treated with fertilizers in all treatment groups was higher than that of control group.Stem diameter of plant treated with potassium sulfate,borax,water-soluble organic potassium,water-soluble organic potassium + spraying bacterial manure of containing trace elements and bacterial manure of containing trace elements were larger than control group,while there was no significant difference between Stem diameter of plant treated with Zinc sulfate,bacterial manure + bacterial manure of containing trace elements and control group.The cross sectional area(approximately 2 cm from the petiole base),leaf area,fresh weight of leaf were greater than the control group;There was no significant difference between water volume of leaf,specific leaf weight of tobacco leaves in all treatment groups and control group.6.The effect of different concentrations of exogenous auxin solution and gibberellin solution on the contents of lignin,the activity of POD and PAL in leaves of Nicotiana tabacum cv.Yunyan87.The measured indicators have an impact after treated 20 days,40 days and 60 days.The contents of lignin,the activity of POD and PAL in tobacco leaves treated respectively with 10-5mol/L auxin and 0.4mg/mL gibberellin has the extremely significant difference compared with CK group.In conclusion,the activity of POD and PAL in mesophyll tissue,the lignin content in the main vein,mechanical strength of stalk in tobacco leaves increased significantly,and the rate of the fracture in tobacco leaves treated with potassium sulfate,borax,water-soluble organic potassium,water-soluble organic potassium + spraying bacterial manure of containing trace elements and bacterial manure of containing trace elements decreased effectively.Spraying different concentrations of exogenous gibberellin and auxin solution may also effectively reduce the rate of the fracture Yunyan 87 tobacco in Lincang area.The results of this study provide a theoretical basis for further exploring the mechanism of tobacco leaf fracture,and put forward the corresponding control measures to reduce the field of fracture tobacco leaves. |
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