Influence of Seed Maturation on Germinability in Soybean1

Abstract

Few studies have related seed formation to germinability in soybean [Glycine max (L.) Merrill]. Our objectives were to evaluate seed growth, seed maturation, and germination capacity of ‘Chippewa 64’ soybean seeds and isolated axes in greenhouse and field environments. Flowers were tagged on the main stem, and pods were harvested at 4‐day intervals between 22 and 58 days after flowering (DAF). Seeds and embryonic axes were removed, weighed, and rapidly desiccated. Germination and axis growth were determined upon rehydration. Mean growth rates were 7.8 and 4.9 mg seed−1 day−1 in greenhouse and field‐grown seeds, respectively. Mature seed weights were 200 and 160 mg seed−1 for greenhouse and field‐grown seeds, respectively, and percent moisture at maximum seed dry weight was 59 and 61% at 50 DAF. Air‐dried immature seeds had increasing capacity for germination between 34 and 46 DAF (73 and 140 mg seed−1 dry weight). Embryonic axes reached maximum dry weight 4 days before maximum dry weight of seeds. Upon rehydration germination of air‐dried seeds and isolated axes was similar. Immature seeds and isolated axes harvested before one‐half maximum seed weight did not germinate after desiccation. When seeds reached 140 mg dry weight seed−1, whole seeds and isolated axes had developed the capacity to withstand desiccation and had a high percentage germination upon rehydration. We conclude: 1) the capacity for germination of soybean is developed before the seed reaches maximum seed weight, and 2) seed maturation is not a major factor altering the sensitivity of isolated axes to hydrational stress.