Entry of Basic Macromolecules Into Barley Roots

The entry of labelled calf‐thymus histone, lysozyme, and poly‐L‐lysine into barley root tips was studied at concentrations which strongly inhibit root elongation. The macromolecules were suitably labelled and at these concentrations it was found, by autoradiography and fluorescence microscopy, that histone and lysozyme readily entered the roots and appeared to bind mainly to cell walls of the epidermis and cortex and to penetrate the cytoplasm occasionally. Except in cap cells, nuclei were rarely penetrated. Poly‐L‐lysine readily permeated cell walls and invaded cytoplasm and nuclei throughout the root tip. Some cells were damaged by contact with basic macromolecules, as evidenced by a change in appearance of protoplasts under phase contrast and by the inability of these same protoplasts to exclude labelled β‐lactoglobulin. Such damage was restricted to cells in contact with the outer solution. Interior to the epidermis, development of many cells was inhibited without visible signs of damage. Evidence supports the conclusion that in the presence of polybasic polymers the integrity of cell membranes is altered, thereby allowing leakage of some cell constituents essential for normal development.