Effects of reflected light on seed yield and photosynthetic rate of middle and lower leaves under different planting densities in soybean

摘要

The effects of light reflected from the ground by reflection sheets on the seed yield and photosynthetic rates of middle and lower leaves of the soyabean canopy were investigated. Soyabeans cv. Suzukari were grown at three different densities in thefield (14.3, 9.5, and 5.7 plants m-2). The light reflection treatment was carried out from the floral bud differentiation stage to maturity by covering the ground between rows with reflective sheets. Seed yields increased at the 2 lower plant densitiesin the reflection treatment. Yield depended on the number of pods and seeds at nodes lower than the 9th node. At the highest plant density, the number of pods increased at lower nodes but the total yield did not increase. Light intensity increased slightly between plants within a row on cloudy days due to reflection, and increased considerably between rows on both fine and cloudy days at the 2 lower densities. The photosynthetic rates of middle and lower leaves on the main stem increased at all plant densities as the result of reflection treatment. Between flowering and pod formation, crop growth rate (CGR) increased due to reflection treatment mainly because of an increase in LAI, while between pod formation and seed development stage, CGR increased as the result of reflection treatment mainly due to an increase in NAR.