Longitudinal Gradients of Ion Transport in Corn Roots

Abstract

Excised roots of corn, 8 cm long, were mounted for collection of xylem exudate, submerged in aerated, labeled salt solutions, and left while steady‐state exudation developed. After 19 hr, additional portions of the roots were removed and all apical ends which had been severed were sealed with wax. Collection of exudate samples began 1 hr later and continued for 8 hr. The results showed that removal of only 1 cm from the apex of the root reduced the output of rubidium to the exudate by as much as 74%. They also showed that the longitudinal changes in ion contribution to the exudate were not linear, but were closely correlated with the longitudinal gradient of Rb content in the root.

Electrical signalling and cytokinins mediate effects of light and root cutting on ion uptake in intact plants

“…Another important issue is the role of root integrity and, specifically, of the root apex in regulating ion uptake at the mature root zone. Some reports that included measurements of transport processes after removing the root tip are available from the literature (Hong & Sucoff 1976;Smith & Majeed 1981), but again, changes only became apparent after a delay of more than an hour. No information on short-term effects is available.…”