采用“根箱”法研究了大田期烟草根系构型参数在时间、空间上的动态变化.结果表明， 烟草2级侧根总长度的增加明显大于1级侧根,根快速增长期分别出现在移栽后26～40和56～70 d.栽后57 d(打顶)前，烟草根系的分枝密度表现为10～20＞0～10＞20～30＞30～40 cm，此后随土层的加深呈递减趋势.在主根上，以7～21 cm范围内的分枝密度最大.打顶前，比根长随着入土深度的加深而递增;栽后90 d，比根长随土层的加深而递减.1级侧根根长密度在0～10 cm土层内的变化呈“S”型曲线，10～20、20～30和30～40 cm内表现为双峰曲线；2级侧根根长密度随生育期的进程而增加，其中0～10 cm根长密度的变化为“S”曲线，其它层次为单峰曲线.
The study with rhizotron showed that the total length of tobacco’s second order lateral root had a much more increase than that of first order one,and the root length developed rapidly during 26～40 d and 56～70 d after transplanting for the second and first order lateral root,respectively.Before tip pruning,the branch root density of tobacco was decreased in order of 10～20＞0～10＞20～30＞30～40 cm soil layer.The branch density of main root was the highest in 7～21 cm soil layer.The deeper the soil layer,the bigger the ratio of dry weight and root length,but the distribution was reverse at 90 d after transplanting.The first order lateral root length density distributed in “S” curve in 0～10 cm soil layer and in double climax curve in 10～20,20～30 and 30～40 cm soil layers,while the second order lateral root length density became bigger with the course of growth period,which was in “S” curve in 0～10 cm soil layer and in single climax curve in other soil layers.
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