Glasshouse experiments on the uptake of foliar applied lead

The radioactive tracer ²¹⁰Pb has been used to examine the foliar uptake and redistribution of lead in three plant species grown under glasshouse conditions for periods of 8–12 weeks. In radish a small amount (0.05–0.28%) of the lead applied to the leaf surfaces was transported to the swollen storage organ. This movement occured through intact and damaged cuticles, with an indication of an enhanced effect for damaged cuticles. Carrot plants absorbed and transported a fraction (0·43%) of the applied activity. By the end of the experiment this had reached the lower portion of the leaf petiole. Transport of lead to the tap root was <0·01% of that applied. In the case of dwarf French beans no movement of lead into pod or seed tissue was detected. It is estimated for radish that foliar absorption of lead and transport to the root could account for about 35% of the internal lead burden of root storage tissues. For carrot this pathway contributes about 3%.