EFFECTS OF REFLECTED LIGHT ON SEED YIELD AND PHOTOSYNTHETIC RATE OF MIDDLE AND LOWER LEAVES UNDER DIFFERENT PLANTING DENSITIES IN SOYBEAN

The effects of reflected light from the ground, using reflection sheet s, on the seed yield and photosynthetic rates of middle and lower leav es of soybean canopy were investigated. The curtivar Suzukari was grow n at three different planting densities in the field (i.e., 14.3 (10 c m plot), 9.5 (15 cm plot): and 5.7 (25 cm plot) plants m(-2)). The lig ht reflection treatment was carreied out from the floral bud different iation stage to maturity by covering the field ground between rows wit h reflective sheets. Seed yields increased in both 15 and 25 cm plots as the result of reflection treatment. It depended on the number of po ds and seeds at nodes lower than the 9th node. In the 10 cm plot, the number of pods increaed at lower nodes, however, the total yield did n ot increase. Light intensities increased slightly between plants withi n a row on the cloudy day, however, it increased considerably between rows on both fine and cloudy days in both the 15 and 25 cm plots. The photosynthetic rates of middle and Lower leaves on the main stem incre ased in all planting densities as the result of reflection treatment. During the period from flowering to the pod formation stage, CGR incre ased as the result of reflection treatment mainly due to the increase in LAI. Whereas, during the period from pod formation to the seed deve lopment stage, CGR increased as the result of reflection treatment mai nly due to the increase in NAR.