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

به منظور بررسي اثرات سايه اندازي تاج خروس بر روند رشد ذرت، آزمايشي در شرايط كنترل شده اجرا شد . در اين آزمايش ابتدا ذرت در يك اتاقك رشد و در شرايط عاري از علف هرز رشد داده شد و در مراحل مختلف رويشي ( 4 ،7 و 10 برگي) به اتاقك رشد ديگر انتقال داده شده تا تحت سايه اندازي علف هرز تاج خروس وحشي قرار گيرد. نتايج آزمايش نشان داد، هنگامي كه بوته هاي ذرت در مراحل ر ويشي 4 و 7 برگي در سايه انداز تاج خروس وحشي قرار داشتند، سرعت ظهور برگ كاهش يافته و ظهور سنبله در آنها به تاخير افتاد. افزون بر آن، وزن خشك اندام هوايي و ريشه و همچنين نسبت ريشه به اندام هوايي اين گياه تحت تاثير رقابت نوري با تاج خروس كاهش يافت . در اين آزمايش ميزان سطح برگ در واحد گياه تنها در زماني كه بوته هاي ذرت درمرحله 4 برگي به شرايط رقابت نور انتقال يافتند كاهش معني داري نشان داد.

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.