大田期烟草根系构型参数的动态变化

Dynamic changes of morphological parameters of tobacco root in field.

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56～70d．栽后57d（打顶）前，烟草根系的分枝密度表现为10～20〉0～10〉20～30〉30～40cm，此后随土层的加深呈递减趋势．在主根上，以7～21cm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90d，比根长随土层的加深而递减．1级侧根根长密度在0～10cm土层内的变化呈“S”型曲线，10～20、20～30和30～40cm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0～10cm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 soll 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.