Polar auxin transport , which takes place with the carrier protein , is a unique way to distribute auxin in plant enabling the formation in particular cells or tissues phytohormone concentration gradient . The auxin transport protein involved belong to three families : media PIN (PIN -formed ) , the pump PGP / ABCb ( P-glycoprotein/ATP binding cassette ) and permease AUX1/LAX ( auxina RESISTANT1/LIKE-AUX1 ) . The results of recent studies have confirmed that five of the eight PIN proteins in A. thaliana , functioning as carriers transporting auxin out of the cell .

A breakthrough in the study of polar auxin transport proved to be the results obtained through the use of molecular biology techniques - characteristics of the respective mutants , cloning of genes AUX1 and PIN , encoding putative auxin transport carriers that control dokomórkowy and extracellular transport of the hormone. Specific demonstrated by immunocytochemistry , polar location of these proteins in cells, stem and root of Arabidopsis thaliana.