Rob A. Proulx and Seth L. Naeve. University of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108
Soybean (Glycine max L. Merrill) seed growth in field environments can be either source limited or sink limited, as the source-sink ratio during the seed filling period often depends on the environmental conditions present during seed fill relative to the conditions present during flower and pod set. As such, numerous studies have examined the effects of altered source-sink ratio on seed growth through the application of pod removal, shade, and defoliation treatments during the seed filling period. However, examinations of source and sink effects on protein and oil accumulation are less common, and few studies have evaluated the aforementioned treatments within a single experiment. Therefore, pod removal, shade, and defoliation treatments were used in field experiments near St. Paul, MN to examine the effect of altered source-sink ratio on protein and oil accumulation. Pod removal treatments significantly increased seed weight and shade treatments significantly decreased seed weight, while defoliation treatments resulted in seed weight decreases which were not always significantly different from the control. Pod removal treatments consistently increased seed protein concentration and decreased seed oil concentration, although both protein and oil content per seed were increased. Defoliation treatments resulted in decreased seed protein concentration and increased seed oil concentration, and when resulting in a significant seed weight decrease, defoliation treatments significantly decreased protein content per seed while oil content per seed remained unchanged. In contrast, shade treatments consistently decreased both protein and oil content per seed when compared to the control, resulting in increased seed protein concentration and decreased seed oil concentration. Preliminary results suggest that protein accumulation is more responsive than oil accumulation to increases in source-sink ratio, and that decreases in source-sink ratio have variable effects on protein and oil accumulation, dependent on the type of source limitation present.
PDF file