Chemical compositon of apoplastic transport barriers in roots

Abstract

The lipophilic biopolymer suberin is deposited to endodermal and hypodermal root cell walls forming apoplastic transport barriers. Comparing 10 different species, it becomes evident that suberization of apoplastic barriers of roots is strongly species-dependent and can vary by more than 2 orders of magnitude. In response to environmental stress factors, suberization of apoplastic barriers can significantly increase (salt stress) or decrease (nutrient deficiency). Radial hydraulic conductivity in the apoplast of corn roots decreased as a result of an increased suberization of the apoplastic barriers. Based on the suberin determination in apoplastic barriers in roots of different species, it must be concluded that (i) there is a large variability in the degree of suberization of apoplastic barriers in roots due to internal and external factors and (ii) suberization per se does not necessarily lead to complete impermeability of the apoplast for water and dissolved solutes.