Uptake, distribution and metabolic fate of 3H-triforine in plants. II. Long-term experiments

Uptake of 3H‐triforine by tomato and barley seedlings from soil with a high organic matter content was much less efficient than from aqueous suspensions, even though the period of exposure was much longer—at least 1 week (“long‐term treatment”) vs 1 day (“short‐term treatment”). After transplanting to fresh soil, part of the label in the roots was lost probably by desorption. Distribution of label in tomato shoots was as irregular as after short‐term treatment; label was virtually confined to the leaves which expanded before about 14 days after cessation of the treatment. In shoots of barley seedlings which were pretreated in an aqueous suspension of 3H‐triforine for 1 day before being subjected to a long‐term soil treatment, almost all radioactivity present could be ascribed to uptake during the pretreatment phase. The distribution pattern strongly resembled that obtained after short‐term treatment, hardly any label being found in leaves which unfolded after the pretreatment phase. Rates of conversion of 3H‐triforine in barley shoots depended to some extent on whether or not seedlings were transplanted to fresh soil after 1 week.