Seedling Growth of Soybeans (Glycine max) and Selected Weeds

Seedling growth of soybean[Glycine max(L.) Merr. ‘Forrest’], common cocklebur (Xanthium strumariumL. # XANST), and tall morningglory[Ipomoea purpurea(L.) Roth. # PHBPU] was compared in field studies. Root growth was determined by measuring roots restricted to the inside of a permeable membrane that contained no soil. Leaf area duration and net assimilation rate between 4 and 9 weeks were greatest for common cocklebur compared to the other species. At 9 weeks, shoot and root dry weight and leaf area were greatest for common cocklebur compared to soybean and tall morningglory. Relative growth rate of common cocklebur roots was greater than the other species between 4 and 9 weeks. Tall morningglory had greater shoot length or height at 4 and 9 weeks and greater shoot or height elongation rate between 2 and 4 weeks, and 4 and 9 weeks than the other species.