EFFECTS OF SHADING ON THE GROWTH OF NUTSEDGES (CYPERUS SPP.)

Greenhouse studies were carried out to determine the effects of differ ent shading levels on biomass accumulation of purple and yellow nutsed ge. Artificial shading levels provided were 20, 40, 60, and 80% of inc ident sunlight in addition to the full sunlight control (0% shading). Yellow nutsedge shoot and tuber number, plant height, and shoot and tu ber dry weight were less affected by 20% shading than were these varia bles for purple nutsedge. Shoot and tuber dry biomass for both species responded linearly to shading level. In yellow nutsedge, 80% shading reduced dry matter partitioning to the tubers and increased partitioni ng into tile shoots. In contrast, biomass partitioning to purple nutts edge tubers was decreased under high shade conditions without increase s in partitioning to the shoots. The light compensation point was lowe r for yellow nutsedge than for purple nutsedge. This could possibly ex plain the wide distribution of yellow nutsedge in relatively low light intensity environments, in contrast with purple nutsedge, which gener ally occurs in tropical areas where higher light intensities are the n orm.