| Water is indispensable to all life activities of tobacco,it is one of the important environmental factors that affect tobacco growth and development.It is an important material transportation channel and storage organ of crops,and it has great significance to the construction of ideal plant type and the improvement of yield and quality of tobacco.In this study,flue-cured tobacco variety K326 was used as the material,through indoor control experiment and set three water gradients: CK: control(70 %-80 % relative water content);T1: drought treatment(50 %-60 % relative water content);T2: waterlogging treatment(90 %-100 % relative water content)in root spreading stage and in time of seedling desired to plant to study the effects of water on the growth index,morphological structure,anatomical structure and substance content of main stem during the growth and development of tobacco seedlings,the main research results are as follows:1.In root spreading stage and in time of seedling desired to plant,drought and waterlogging stress reduce the fresh and dry weight of tobacco seedlings,and the fresh and dry weight in each treatment stage is CK > T2 > t1.Drought stress can increase root-shoot ratio of tobacco seedlings.After 10 days of water treatment,the water content of tobacco seedlings in each treatment was not significantly different,but the water content of tobacco seedlings treated by drought stress increased after the stress was relieved.2.In root spreading stage and in time of seedling desired to plant,water stress,especially drought stress,inhibited the growth of main stem.After 10 days in root spreading stage,compared with CK,the average pitch of TI decreased by 71 %,the average stem diameter decreased by 15 %,the average pitch of T2 decreased by 17 %,and the average stem diameter decreased by 8 %;After 10 days in time of seedling desired to plant,compared with CK,the average pitch of TI decreased by 85 %,the average stem diameter decreased by 16 %,the average pitch of T2 decreased by 21 %,and the average stem diameter decreased by 8 %.Water stress inhibited the elongation of main stem internode and the increase of node number,thus affecting the growth of plant height.The stem circumference of each internode of the main stem gradually thickens from top to bottom,and water stress inhibits the thickening of the stem circumference of each internode of the main stem.3.After 10 days in root spreading stage,compared with CK,TI cortex thickness decreased by 34 %,cell length decreased by 75 %,marrow diameter decreased by 41 %,cell length decreased by 38 %,T2 cortex thickness decreased by 13 %,cell length decreased by 17 %,marrow diameter decreased by 10 %,and cell length decreased by 20 %;After 10 days in time of seedling desired to plant,the thickness of TI cortex decreased by 32 %,the length of cells decreased by 34 %,the diameter of marrow decreased by 40 %,the length of cells decreased by 12 %,the thickness of T2 cortex decreased by 9 %,the length of cells decreased by 27 %,the diameter of marrow decreased by 10 %,and the length of cells decreased by 12 %.Water stress,especially drought stress,is not conducive to the increase of each structure of the main stem,thus affecting the thickening of the main stem.Elongation of cells and increase of cell number are the main reasons for internode elongation.Elongation of cortical cells and pith cells is inhibited under drought stress,while cells can elongate rapidly under suitable water conditions.4.The transportation and storage of substances in the main stem are closely related to the morphological and structural characteristics of the main stem.In root spreading stage and in time of seedling desired to plant,the contents and accumulation of nonstructural carbohydrates,nitrogen compounds and nutrients in stems are CK > T2 > T1 after 14 days of the stress was relieved.Plant height and the average pitch is longer,the number of nodes is more much,the average stem circumference is larger,the transportation and storage function of stem are stronger;on the contrary,the main stem is shorter,the stem circumference is reduce,the pitch is shorter,the transportation and storage function of stem are weaker. |
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