AbstractsBiology & Animal Science

The primary purposes of these studies were to investigate: (1) the effects of air temperature, soil moisture, and supplemental light on sprouting ability of quackgrass (Agropyron repens L. (Beauv. )) rhizome buds; (2) the influence of 2-chloroethylphosphonic acid (Ethrel) on growth, morphology, and regenerative capacity of quackgrass and field bindweed (Convolvulus arvensis L.); and (3) the efficacy of Ethrel in enhancing the phytotoxicity of a mixture of 3-aminos- triazole and ammonium thiocyanate (amitrol-T) and 2, 2 -dichloro propionic acid (dalapon) on the regenerative capacity of quackgrass rhizomes. The studies were carried out in a greenhouse or growth chambers. The percent sprouting of the single-node quackgrass rhizome buds was decreased if the plants were subjected to 70°F day and 60°F night air temperatures, a reduced level of light intensity, or severe soil moisture stress. Ethrel applied to mature quackgrass plants effectively induced the rhizome buds to grow and develop into either rhizome branches or into leafless, rhizome-like aerial shoots. The aerial shoots did not develop normal leaves for two to four weeks. Later, as the effect of Ethrel diminished, normal leaves developed on the upper parts of the new shoots. Higher rates of Ethrel (4 to 6 lb/A) were more effective in evoking growth of the rhizome buds than the lower rates, but the resulting shoots remained leafless for a longer time. A high level of soil-applied nutrients also induced growth of quackgrass rhizome buds. In this regard, the effect of Ethrel and high soil nutrient level was simply additive not synergistic. Ethrel applied to intact quackgrass plants or to its excised rhizome buds did not increase or decrease the percent sprouting of the single-node rhizome buds. But the excised rhizome buds from quackgrass plants growing at a high level of soil nutrients had a higher percent sprouting. Over a six-week period, Ethrel (6 lb/A) application doubled the fresh and the dry weight of the leaves plus the newly formed shoots, moderately reduced the dry weight but not the fresh weight of the rhizomes, and inhibited root growth of the treated quackgrass plants in comparison to the untreated plants. Pre-treating quackgrass plants with Ethrel did not enhance the effectiveness of amitrol-T, applied subsequently, as measured by the average weight of regrowth produced by the replanted rhizome segments. But Ethrel in combination with amitrol-T completely inhibited the rhizome segments of 60% to 80% of the plants from producing any regrowth. When amitrol-T alone was used, the rhizome segments of 30% to 50% of the plants failed to have any regrowth. The rhizome pieces from quackgrass plants treated with Ethrel and dalapon produced more regrowth dry weight than the rhizome segments obtained from similar plants treated with dalapon alone. The reason for this antagonistic relation between Ethrel and dalapon was not investigated. Mature field bindweed plants sprayed with Ethrel sustained severe to complete…