Table 1. Stages of soybean seed development and summary of HPS detection in seed and endocarp.

Stage	Age (dpa)*	Observations
0	10 to 13	Small surface deposits present on endocarp epidermal surface, but no HPS signal within cell protoplasts or in the deposits.
1	18 to 28	Initial appearance of HPS signal within cells of the endocarp epidermis, including nucleus. Extracellular export of HPS-labelled material.
2	30 to 48	HPS signal is solely extracellular from this point on. HPS signal is typically associated with the endocarp surface, where that layer has separated from the seed coat.
3	50 to 60	At 50 dpa, HPS signal is present on the seed coat surface as well as the separated endocarp surface. By 55 to 60 dpa, endocarp epidermis and parenchyma cells are present along with HPS signal on the seed coat surface.
4	Mature	Pods and seed are dry, and the pod is ready to open. The seed coats are dull when the pod wall is dissected away. HPS is present on the seed coat surface together with other materials.

^*dpa, days post anthesis.