In a previous work, we observed a longitudinal decrease in Cd2+ influx starting from the root tip in first order lateral roots of sunflower (Helianthus annuus L.) grown in hydroponics. This variable influx was expected to impact the total Cd2+ uptake depending on the root system architecture and on how steep was the decrease of the influx. Here, we examined the influence of the culture substrate, of the age and order of lateral roots on the longitudinal variation of Cd2+ influx. By using short-term exposures to Cd-109-labelled solution (5 to 200 nM), we compared the longitudinal variations in Cd2+ roots influx depending on the growth substrate (hydroponics or sand), on the root age and order. In second order laterals, Cd2+ influx decreased from the apex to the root base, as for first order laterals. For sand cultures compared to hydroponics, the mean Cd2+ influx was lower and decreased more steeply with the distance from the apex. The influx also decreased with increasing root age and order, markedly in hydroponics but less for sand cultures. Results suggested that for a given root surface area, the Cd2+ uptake by a root system should increase with increasing number of root tips and decreasing individual root length.Read less <