Absorption and translocation in both leaves and roots is less under low temperatures. Seasonal response of wheat to 2,4-D is conditioned by the stage of growth as well as environment. The response of wheat and downy bromegrass to triazine herbicides is seasonal, whereas the response to carbamate herbicides appears to be influenced by local environmental conditions at time of spraying. Physiological condition of fiddleneck is more important than age, i.e., plants in the rosette stage were always far more sensitive than bolting plants of the same age. Sensitivity to 2,4-D was greater at 26 C than at 10 C or 5 C at all stages of growth. Applications of certain metabolites, especially thiamin, increased the sensitivity of fiddleneck to 2,4-D at low temperatures.

Birdsfoot trefoil, timothy, and sterile pea plants treated with 4-(2,4-dichlorophenoxy) butyric acid [4-(2,4-DB)], formed 2,4-dichlorophenoxyacetic acid (2,4-D) to about the same extent. Apparently the enzymatic ability for beta oxidation can reside in the plant as well as in microorganisms.

Black henbane (Hyoscyamus niger L.) has invaded cultivated land, pastures, and disturbed areas in east central Saskatchewan. This species flourishes during cycles of abundant moisture and disappears during dry cycles, surviving in Saskatchewan only in moist depressions or disturbed areas. Summerfallow, fall tillage, and competition from vigorous perennial grasses provide effective control of the weed. Black henbane is not likely to become a serious deterrent to crop production in Saskatchewan.