Applications of glyphosate [N-(phosphonomethyl)glycine] to the leaves of pea (Pisum sativum L. ‘Burpee's Blue Bantam’), sunflower (Helianthus annuus L. ‘Mammoth’), and bean (Phaseolus vulgaris L. ‘Red Kidney’) reduced transpiration in all three species. The reduction varied with species and concentration applied. Eight-day-old bean leaves responded earlier than leaves on older plants. However, after 29 h, there was no difference in transpiration rates with seedling age, since treated leaves on both ages investigated were transpiring at about one-half the rate of control leaves. Addition of surfactant to the solution shortened the time interval between treatment and transpirational response but did not affect the final transpiration rate as compared to glyphosate without surfactant. The effect of glyphosate on transpiration was not due to changes in water availability or to the surface of the leaf that was treated. It is suggested that these results can give some insight into uptake, translocation, and mode of action of glyphosate.

Quackgrass [Agropyron repens (L.) Beauv.] was controlled by spring application of pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] in 1970 and 1971, but when spring rainfall was below nornal in 1973, only pronamide applied the previous fall gave control. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) gave 90% control of quackgrass for 2 yr at 2.2 kg/ha. Some control continued for 3 yr at 4.5 kg/ha. Three applications of glyphosate [N-(phosphonomethyl)glycine] at 3 kg/ha applied during a 2-yr period controlled quackgrass 97 to 100%. Phytotoxicity was not observed on 14-yr-old highbush blueberries (Vaccinium corymbosum L.) from pronamide or terbacil, on 4-yr-old blueberries from pronamide, or on 2-yr-old rhododendrons (Rhododendron × ‘A. Bedford’) from dichlobenil (2,6-dichlorobenzonitrile), pronamide, or directed sprays of glyphosate or amitrole (3-amino-s-triazole).