Two species of annual nightshades were commonly found as agronomic weeds in Minnesota. Eastern black nightshade (Solanum ptycanthum Dun.), the most common species, was found throughout the southern half of the state. Hairy nightshade (Solanum sarrachoides Sendt. ♯3 SOLSA) was found only in a few scattered locations. Eastern black nightshade seedling emergence began in mid-April or early May, and more than 80% of the total yearly emergence occurred before June. Hairy nightshade emergence began in May, but less than 70% of its total yearly emergence occurred before June. Eastern black nightshade berries first contained viable seeds 4 to 5 weeks after flowering of the plants and a week or more before the berries began to turn black. Hairy nightshade generally required a week longer than eastern black nightshade for viable seed production after flowering.

Desert saltgrass [Distichlis stricta (Torr.) Rydb. ♯3 DISST] tolerated extremely high concentrations of boron in nutrient solution and was far more tolerant of this micro-nutrient than was reed canarygrass (Phalaris arundinacea L. ♯ TYPAR). Boron concentrations in nutrient solution necessary to reduce growth of desert saltgrass shoots and roots by approximately 50% after 28 days of exposure were 500 and 600 ppm, respectively. In contrast, shoot and root growth of reed canarygrass was decreased approximately 50% by boron concentrations of 82 and 29 ppm, respectively. After 28 days, reed canarygrass shoots contained approximately four times as much boron as desert saltgrass shoots. Reed canarygrass has a higher transpiration rate than desert saltgrass, but this difference did not appear to cause the differential boron concentrations in the shoot tissues of the two species.

Mature achenes from tansy ragwort (Senecio jacobaea L. ♯3 SENJA) capitula borne on lower branches had greater average dry weights and higher percentage germination than those closer to the apex, but these higher averages were obtained because more achenes in these samples were filled. Physiological maturity was attained in ray achenes 21 days past flowering (DPF), 24 DPF in peripheral disk achenes, and 27 DPF in central disk achenes. Maximum germination occurred at 18 DPF in ray and peripheral disk achenes and at 21 DPF in central disk achenes. Neither achene type was shown to have innate dormancy. Disk and ray achenes germinated most rapidly at alternating temperatures of 30/20 C.

Glyphosate [N-(phosphonomethyl)glycine] had several effects on carbon translocation in sugarbeet (Beta vulgaris L. ‘Klein E multigerm’): a) import of carbon by sink leaves was inhibited, b) net starch accumulation in source leaves was stopped, and c) carbon export from source leaves in the dark was stopped following 10 h of treatment in the light. During periods when no carbon was exported, glyphosate also was not transported from treated leaves. The limitation of glyphosate transport, resulting from disruption of carbon metabolism, appears important in the study and use of the herbicide.

In crop/weed interactions a method is needed to reduce the complex data derived from interference research to a simple form which can be utilized immediately. A response surface technique was utilized in analyses involving densities, duration of interference, interference abilities of different species, and weed growth rates. At high weed densities interfering for long durations, multispecies interference is not additive but at low densities additiveness is approached. Soybean [Glycine max (L.) Merr.] yield loss from multispecies weed interference was calculated by subtracting the percent yield loss from the most competitive weed and then repeating the same procedure for remaining weeds. Interference data for weed species in which fewer data were available were determined by linear interpolation for densities of more comprehensively researched, closely related species. Polynominal regression curves were utilized to predict weed age and future weed size from weed height. These analyses can produce information to assist soybean producers in recognizing economically detrimental threshold levels of weed infestations which require the initiation of control measures.