Protein storage vacuoles (PSVs) from radicles and cotyledons of dry cotton seeds were isolated by differential centrifugation following homogenization in glycerol. Protein complement analysis of isolated PSVs with one dimensional SDS-PAGE gels revealed similar major storage proteins, viz. 53 and 48 kDa, with differences in lower molecular mass proteins. Radicle PSVs have apparently more 35-kDa and less 22-kDa storage protein than do cotyledon PSVs. The mineral composition of whole radicles, cotyledons and isolated PSVs from radicles and cotyledons was determined by atomic absorption spectroscopy and colorimetric elemental analyses. The concentration of calcium (Ca), magnesium (Mg), potassium (K) and phosphate (P) was lower in isolated PSVs from radicles than from cotyledons, resulting in a marked difference in the Mg/Ca and (Mg+Ca)/K ratios in PSVs from these two sources. Analysis of radicle and cotyledon tissue from dry seeds for mineral distribution with EDX and scanning electron microscopy revealed major concentrations of Mg, K and P in PSVs. These observations indicate that PSVs in radicles are similar in protein and mineral composition to PSVs in cotyledons. PSVs in radicles have the potential function as storage organelles to provide minerals and nutrients for radicle growth during imbibition and germination.