Effects of 22 herbicides on the synthesis of RNA and protein were investigated in excised tissues. The assays measured ATP and orotate incorporation into RNA, leucine incorporation into protein, and the gibberellin-controlled induction of a-amylase Statistical analysis of the average responses measured in the four assays suggested that 14 of the herbicides inhibited RNA and protein biosyntheses in vivo. The most inhibitory chemicals were 4-hydroxy-3,5-diiodobenzonitrile (ioxynil), 2-sec-butyl-4,6-dinitrophenol (dinoseb), 3',4'-dichloropropionanilide (propanil), 2,3,5-trichloro-4-pyridinol (pyriclor), and isopropyl m-chlorocarbanilate (chlorpropham). The activity of an RNA polymerase isolated from corn (Zea mays L.) tissue was inhibited maximally at approximately 20% by ioxynil, dinoseb, and pyriclor. Hence, interference with RNA polymerase, which performs a pivotal role in RNA and protein biosyntheses, does not fully account for all inhibitions.

Field pennycress (Thlaspi arvense L.) was seeded in rows at approximately 10-day intervals from June 1 to August 30, 1963, and from July 12 to August 31, 1966, in subarctic, south-central Alaska (61.5° N.). Plants from June 20 and earlier seedings produced mature seed as summer annuals; those from seedings during the first 3 weeks of July produced elongated stems and green pods, while those from later seedings produced unelongated, basal rosettes. Seedlings that emerged during July or later were potential winter annuals. No study plants survived the 1963-64 winter. The 1966 plantings survived the 1966-67 winter as follows: July 12, 50%, July 20, 54%, August 1, 93%, and August 12, 23, and 31, 100%. Morphology, time of flowering, and seed pod production of plants surviving the winter also were influenced by planting date the previous growing season. To prevent field pennycress from producing seed as a summer annual, plants that emerge before the middle of July must be eradicated. Plants that emerge during July or later should be destroyed as seedlings or prior to seed production time the following year.

Recovery of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), as the acid and ester, was significantly greater in live oak (Quercus virginiana Mill.) tissues treated with mixtures of the 2-ethylhexyl ester of 2,4,5-T (2 lb/A)-.potassium salt or isooctyl ester of 4-amino-3,5,6-trichloropicolinic acid (picloram) (1/2, 1 and 2 lb/A) than in tissues treated with 2 lb/A 2,4,5-T ester alone. Recovery of 2,4,5-T as the ester was noted in the middle and lower-stem tissues. Between 90 and 99% of the herbicide recovered 1 month after treatment was gone 6 months after treatment. Evaluation of brush reduction 2 years after treatment indicated that mixtures of picloram salt and 2,4,5-T resulted in greater reduction of brush than mixtures of picloram ester and 2,4,5-T or 2,4,5-T alone.