Response of Corn at Different Leaf Stages to Shading by Redroot Pigweed (Amaranthus retroflexus)

The effects of shading by redroot pigweed (amaranthus retroflexus) on corn (zea mays) were determined in growth cabinets and growth rooms. corn was grown in a growth cabinet to different growth stages (4-,7- and 10 leaves) and then moved to a second growth cabinet where it was shaded by redroot pigweed plants at the 15 leaf growth stage. treatments were arranged in a completely randomized design with four replications. the results indicated that the rate of corn leaf appearance was reduced and tassel emergence was delayed when the corn was shaded by the weed at 4- and 7-leaf stages. shoot and root dry matter accumulations were influenced by shading. partitioning of dry matter was changed and corn root / shoot ratio was reduced when corn plants were shaded. leaf area per plant was reduced significantly only when light competition started at the 4-leaf stage.