Abstract
Two types of ATP-dependent calcium (Ca2+) transport systems were detected in sealed microsomal vesicles from oat roots. Approximately 80% of the total Ca2+ uptake was associated with vesicles of 1.11 grams per cubic centimeter and was insensitive to vanadate or azide, but inhibited by NO3. The remaining 20% was vanadate-sensitive and mostly associated with the endoplasmic reticulum, as the transport activity comigrated with an endoplasmic reticulum marker (antimycin A-insensitive NADH cytochrome c reductase), which was shifted from 1.11 to 1.20 grams per cubic centimeter by Mg2+.