Histological changes of Berberis mikuna pollen grains in relation to viability and germinability

•Berberis mikuna is a spontaneous shrub grown in the Tucuman-Bolivian subtropical area.•Pollen grain germination and viability decreased after 45 days of storage.•Germination and viability decreased with increasing temperature.•Ultrastructure study revealed differences in the fibrillar structure of the intine.•A decrease in starch reserve in grains at 5 °C and at room temperature was observed.