Identification of the sites of K leakage from imbibing seeds and grains

Seeds/grains of four species were imbibed for up to 90 minutes half embedded in agar. The agar was then freeze-dried and treated with a chromatographic reagent to detect the sites of potassium leakage from the imbibing seeds/grains. Soybean (Glycine max cv. Marathon) and pea (Pisum sativum cv. Little Marvel) leaked K across the entire surface of their testas. Aged pea seeds leaked much more extensively than seeds of a fresher lot of the same cultivar. Squash (Cucurbita maxima cv. Warted Hubbard) seeds leaked extensively from the flat sides of the seeds and at the hilum, but only slightly at the margins. Maize (Zea mays cv. Golden Beauty) leaked most extensively across the endosperm-only side (i.e. the side opposite the embryo) of the kernel, and kernels leaked more at the tip-cap end than at the broad end. Energy dispersive X-ray analysis determined that K was present in the testas/pericarps before imbibition in all species studied, and that the peak-to-background ratios of K were lower after the seeds/grains had been exposed to water. Neutron activation analysis verified that K was leaked out of the seeds/grains and absorbed into the agar. Seeds from all species studied showed varying amounts of seed-to-seed variation. These variations can be attributed in part to differences in testa/pericarp structure and condition.