Excised roots of corn (Zea mays L. ‘B73 × Mo 17′) and oat (Avena sativa L. ‘Goodfield’) and potato (Solanum tuberosum L. ‘Kennebec’) tuber slices absorbed 14C-atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] in a similar manner during short (1 to 30 min) absorption periods. Within 30 min, atrazine concentrations in tissues and ambient solution were equal. After 24 h of absorption, corn roots contained the most 14C, followed in order by velvetleaf (Abutilon theophrasti Medic.) roots, oat roots, and potato tuber slices. Corn and velvetleaf accumulated 14C to concentrations above the ambient solution. Efflux of 14C was slower for corn than oat, potato, and velvetleaf. Metabolism of atrazine to hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine] accounted for accumulation and slow efflux of 14C in corn. These experiments show that initial, rapid absorption of atrazine is comparable, but long-term accumulation differs among these tissues.

Greenhouse-grown honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] plants were treated with the propylene glycol butyl ether esters of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], the triethylamine salt or the ethylene glycol butyl ether esters of triclopyr {[(3,5,6-trichloro-2-pyridinyl) oxy]acetic acicd}, the potassium salt of picloram (4-amino-3,5,6-trichloropicolinic acid), or the monoethanol amine salt of 3,6-dichloropicolinic acid applied at the rate of 1.1 kg/ha to soil, foliage, or soil plus foliage. All herbicides were effective as foliar sprays in killing the stems of honey mesquite. When applied to the soil, picloram and 3,6-dichloropicolinic acid killed all above ground stems, and the ester and amine formulation of triclopyr killed 70 and 91% of the stem tissue, respectively, but 2,4,5-T was ineffective. Accumulation of herbicides in leaves 10 days after foliar spray was 28, 167, and 266 μg/g fresh wt for triclopyr, 3,6-dichloropicolinic acid, and picloram, respectively. Upward transport of picloram and 3,6-dichloropicolinic acid (2.7 to 5.9 μg/g) was also more extensive than that of 2,4,5-T or triclopyr after soil treatment. Higher concentrations of 3,6-dichloropicolinic acid than 2,4,5-T, triclopyr, or picloram usually was found in honey mesquite stems and roots 3, 10, or 30 days after application to soil or foliage. This may be one reason that 3,6-dichloropicolinic acid is highly effective in controlling honey mesquite.