| Tobacco industry is one of the important economic pillars in Yunnan where is also one of the major tobacco production places in China.Therefore,the quantity and the quality of tobacco production are essential for promoting economic efficiency of tobacco.In recent years,some of the middle-lower parts of the tobaccos(mainly were Yunyan87 and K326)in Lincang,Yunnan province have been easily broken from their petiole bases during the three growing stages(from vigorous to mature stages)due to storm and touch by animals and people.As a result,the tobacco production in Lincang has been decreased,which led to great economic losses for the local development.On the basis of such research background,the present study was designed to investigate the reasons for tobaccos’ fracturing by finding out the types of tobaccos that would be most likely break.Specifically speaking,on the one hand,the present study explored the influence of transplantation density,plastic film mulching and transplantation date on the tobaccos’ physiological and biochemical indexes of their middle-lower parts(including sand leaves,4-6-(th)leaves and lumbar leaves),respectively,on the other hand,in order to find out the main factor for the tobaccos’ resistance to fracture,the effects of temperature,humidity and light intensity on the related biochemical indexes of the tobaccos’ resistance to fracture were explored on the basis of the results of the three ecological modeling research.The explored indexes consisted of the following aspects:tobaccos’ middle-lower parts’ fracture rate,lignin content,POD and PAL activities as well as their specific leaf weight.Furthermore,the tissue anatomy of the tobaccos’ main veins were also observed and the research results were presented as follows:1.Using weight test to examine the fracture rate of the Yunyan87 and K326,the results showed that the fracture rate of the sand leaves,4-6(th)-leaves and lumbar leaves of Yunyan87were all higher than those of the tobaccos K326.What is more,such results lasted through all the three tobaccos’ growing stages.2.The results of the effects of transplanting density on the tobaccos’ resistance to fracture and on the related physiological and biochemical indexes of Yunyan87:compared to the transplanting density as 16,500 tobaccos per hectare,the fracture rate of the middle-lower parts of the tobaccos transplanted as 13,500 per hectare were lower through the three growing stages;in addition,the lignin content,POD and PAL activities of the middle-lower parts of the tobaccos that were transplanted as 13,500 per hectare were stronger than those of the tobaccos transplanted as 16,500 per hectare during the three growing stages;besides,the lignin content of the tobaccos was positively related to their resistance to fracture to some extent;meanwhile,the tobaccos’ resistance to fracture would be strengthen if they were transplanted as 13,500 per hectare.In another word,if the tobaccos transplanted few and for between,they would be stronger to resist fracturing.the specific leaf weight in all the positions of Yunyan87 transplanted as 13,500 per hectare were higher than those in the tobaccos that were transplanted as 16,500 per hectare.Such results indicated that the closer the transplanting density is,the lower the tobaccos’ illumination and water using efficiency will be.At the same time,the illumination and water using efficiency of the 4-6(th)～leaves were stronger than those of the sand leaves and lumbar leaves between the two types of transplanting density tobaccos.3.The results of the impact of transplanting density on the tissue anatomy of the main veins among Yunyan87:during the three growing stages,the main veins’ tissues of the middle-lower parts of the tobaccos transplanted as 13,500 per hectare were all more flourishing compared to those of the tobaccos that were transplanted as 16,500 per hectare.4.The results of the effect of plastic film mulching on the resistance to fracture and on their physiological and biochemical indexes of Yunyan87:the fracture rate of the middle-lower parts of the tobaccos that were covered with plastic films were relatively lower than those of the tobaccos that were uncovered with films through the three growing stages.The lignin content,POD and PAL activities in the tobaccos with plastic films were higher compared to those in the tobaccos without plastic films.there were no significant differences in the specific leaf weight in the middle-lower parts between the tobaccos with plastic film and those without plastic film.That is to say,plastic film mulching exerted little influence on the illumination and water using efficiency of the middle-lower parts of Yunyan87,furthermore,there was no direct or necessary connection between the specific leaf weight and weight capacity of Yunyan87.5.The results of the impact of plastic film mulching on the tissue anatomy of the main veins of Yunyan87:the area of vascular bundle of the main veins in the middle-lower of Yunyan87 parts were bigger,the number of vessel element were more,and their ability to resist fracturing were stronger among the tobaccos with plastic films.6.The results of the effect of transplanting date on the resistance to fracture and on their physiological and biochemical indexes of Yunyan87:During the squaring stage,the fracture rate,lignin content,POD and PAL activities of the middle-lower parts of the tobaccos transplanted on 4th,May were not significantly different from those of the tobaccos transplanted on 26th,May.Besides,before the first harvesting and during the middle leaf harvesting time,the resistance to fracture of the tobaccos which were transplanted on 26th,May was stronger than that of the tobaccos which were transplanted on 4th,May.Transplanting date did not exert significant effect on the specific leaf weight of all the part of the tobaccos during the three growing stages.7.The results of the impact of transplanting date on the tissue anatomy of the main veins of Yunyan87:Transplanting date did not show great impact on the fibrovascular tissues in the main vein of Yunyan87 in the squaring stages,with the maturing of tobaccos,the intensity of the fibrovascular tissues in the main veins of all the part of the tobaccos transplanted at the end of May was stronger than that of the tobaccos transplanted at the beginning of may.8.The influence of three ecological factors on the resistance to fracture of the yunyan87:The order of the impact of the three factors on POD and PAL activities was temperature first,then light intensity and relative humidity last.The tobaccos’ POD and PAL activities were strongest when the day and night temperature was between 25-15,relative humidity was 65%and the light intensity was 60%in days. |
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