Abstract: Based on the large farmland soil moisture control experimental and root observational field in Jinzhou and minirhizotron method,water stress treatments were carried out during jointing and tasseling stages of maize with the way of continuous no-water complementing for a long time.Dynamics of root distributions at the soil depth of 40 cm,120 cm and 160 cm and their responses to drought stress (DS) were observed and investigated.Results show that the number of fine roots with the diameter below 1 mm is greater than that of thick roots and ac-counts for a large proportion at the soil depth of 40 cm.The proportions of thick roots at the soil depth of 120 cm and 160 cm increase compared with those at shallow soil layer.At the early stage of DS,root length density (RLD) at the soil depth of 40 cm is increasing with the aggravated DS and the DS promotes roots growing toward deep soil layer.In addition,after tasseling stages,the roots in the upper soil layer indicate premature and acceler-ated aging when suffering the DS in jointing stage.Moreover,the DS during tasseling stage of maize is able to prompt roots growing toward deep soil layer too,but the later DS results in the effect of DS on root growth weak-ened.Besides,a quick and compensatory growth of root is possibly caused by re-watering after maize suffering a long DS.

Key words: Spring maize, Key growth period, Root, Drought stress