Hello Vladimir,

This is pollen of Malva.

This is Malvaceae, though looks more like Alcea sp.

Check it in: Salah M. EL NAGGAR (2004): Pollen Morphology of Egyptian Malvaceae: An Assessment of Taxonomic Value, Turk J Bot 28 (2004) 227-240

Definetly a Malvaceae, from its diameter and the presence of echini of different size it could fit Culhane and Blackmore's (1988) Althaea hirsuta type or Malva alcea type. But the fine exine structure and apertures of this grain are covered by some residue (did you use glycerol or silicon oil?).

see:

Culhane, K.J. Blackmore S. 1988. The Northwest European Pollen Flora, 41: Malvaceae. Review of Palaeobotany and Palynology 57: 45–74

Best regards

Johannes Martin Bouchal 

It is simply not possible to name the species for these pollen grains without sampling local flora from where the wild bees were collected

Malvaceae family