The role of cytokinins in root development of pea seedlings

Endogenous cytokinin-like activity was detected in pea seedlings using the soybean callus bioassay. Higher levels of activity were found in two-day-ol d seedling roots and in the root free zone of four-day-old seedlings compar ed to the lateral root zone of four-day-old seedlings. By day six, the leve ls of endogenous cytokinin-like activity was greatly reduced in both the la teral root zone and root free zone. Decapitation of the root tip disrupted the spatial organization of the root. Lateral roots were subsequently found along the entire length of the root rather than in a discreet lateral root zone. Application of 10(-3) M dihydrozeatin to decapitated root tips overc ame the effect of root tip removal and restored the situation to what is no rmally found in intact roots. There was little mobility of dihydrozeatin in the root, with applied H-3-DHZ not moving from the root free zone, even 24 h after application.