Fig. 1

The structural morphology and ploidy of soybean endosperm. a Photographs of soybean seed. Parts of seed coat (sc) and endosperm (en) were removed. Endosperm is an independent and membrane-like tissue, located between the seed coat and cotyledon (co). b Flow cytometry of fresh leaves (green) from mature plants, and peeled endosperm (red) from soybean seed at 35 days after flowering (DAF). The diploid internal reference produced two peaks (green area), including a major peak with ×2DNA quantity and a minor peak corresponding to ×4 DNA. The peak of the red area corresponds to ×3 DNA. c Cryo-scanning electron microscopy (cryo-SEM) of soybean endosperm and cotyledon epidermis cells at 35 DAF. Cell wall ingrowth of soybean endosperm is identified in endosperm. d Fluorescence microscopy of propidium iodide-stained cell wall from soybean endosperm. sc, seed coat; en, endosperm; co, cotyledon. Scale bars = 1 mm for a, 100 μm for c and 10 μm for d