Translocation & re-use of boron in broccoli

Abstract

Broccoli was grown on a complete nutrient solution with 0.5 ppm B. At about 45 days before flowering the nutrient solution was changed to B-less nutrient. On this date and for the next 44 days at 4-day intervals, 4 plants were harvested, weighed, and the leaves stripped from the stem. Each leaf was dried and analyzed separately for B. At 24 days, B deficiency symptoms developed. As growth continued while the plants were without an external source of B, a re-distribution of the internal B occurred. It was continually moved to the youngest tissues. There was no loss from the basal leaves, but marked changes occurred in the younger leaves. For example, the 22d leaf from the base changed in concentration from 33 to 2 ppm and from 18 to about 6 tig.