MicroRNA (miRNA) is a group of small, 2123-nucleotide-long, non-encoding RNA particles, which in the mature form regulate gene expression at the post-transcription level. Presently, over 3000 miRNAs are known, described in vertebrates and insects, but also in plants, fungi, unicellular organism and viruses. In the human genome, so far over 470 miRNAs have been discovered, although it is assumed that there are about 1000.

The unique feature of plant organisms is the presence of plasmodesmata (PD) between neigh- boring cells. Such plasmodesmatal continuum which exists within the plant body is termed symplasm. Classical view of plasmodesmata as static structures within the cell walls between neighboring cells must be reevaluated. According to our recent knowledge symplast is divided into functional domain. It appeared that symplasmic isolation/communication of cells or group of cells (symplasmic domains or symplasmic fields) is necessary for its proper differentiation within the plant body.

Root hairs are cylindrical in shape outgrowths of root epidermis. They are characterized by the tip growth which relies on the deposition of new components of cell membrane and cell wall at the tip of the growing hair. The main role of root hairs is to extend the root surface, uptake of water and mineral soils. They are responsible for building interactions with soil microorganisms, and in some species, they synthesize and secrete bioherbicides. The development of root hairs is a complex process that involves many proteins, enzymes and cellular structures.