Histochemistry and identification of condensed tannin precursors in roots of cotton seedlings

Catechin (3,5,7,3′,4′-flavanpentol) and gallocatechin (3,5,7,3′,4′,5′-flavanhexanol) were isolated from methanol extracts of roots of 1-week-old Acala 4-42 cotton seedlings and identified by infrared spectrophotometry. Histochemical studies revealed the localization of the catechins in the hypodermis, endodermis, scattered cells of the xylem parenchyma, and the proximal portion of the root cap. The possible function of the catechins as chemical barriers to penetration and colonization of the root by plant pathogens is discussed.