Thallium accumulation by durum wheat and spring canola: The roles of cation competition, uptake kinetics, and transpiration

As a potassium analog, thallium (Tl) is readily accumulated by plants, with differential accumulation among species. Canola accumulated and translocated more Tl at a faster rate than durum wheat. Potassium reduced Tl+ uptake by both wheat and canola, although a higher ratio of K to Tl concentration was required to reduce Tl+ uptake in canola than wheat. Canola appeared to preferentially accumulate Tl over K and have a higher affinity for Tl+ than K+, although the K M values were not different due to low precision. Wheat had a similar affinity for K+ and Tl+ Thallium accumulation in wheat and canola roots was independent of transpiration. Thallium was concentrated in the transpiration stream of canola, but not wheat, and wheat shoots contained higher concentrations of Tl when transpiration rates were greater. Wheat and canola have different Tl+ uptake capacities which are influenced by transpiration, kinetics, and competition with K+ in different ways.