Magnesium Deficiency Results in Increased Suberization in Endodermis and Hypodermis of Corn Roots

The composition of the aliphatic components of suberin in the stele and cortex of young corn (Zea mays L.) roots was determined by combined gas-liquid chromatography/mass spectrometry of the LiAlD(4) depolymerization products. omega-Hydroxy acids were shown to be the major class of the aliphatic components of both the hypodermal (35%) and endodermal (28%) polymeric materials with the dominant chain length being C(24) in the former and C(16) in the latter. Nitrobenzene oxidation of the roots generated p-hydroxybenzaldehyde and vanillin with much less syringaldehyde. Electron microscopic examination of the hypodermal and endodermal cell walls from roots of corn plants grown in a Mg(2+) -deficient (0.03 millimolar) nutrient solution showed that these walls were more heavily suberized than the analogous walls of roots from plants grown in normal (2 millimolar) Mg(2+) levels. Analysis of the LiAlD(4) depolymerization products of the suberin polymers from these roots showed that the roots grown in low Mg(2+) had 3.5 times as much aliphatic suberin monomers on a weight basis as the roots from plants grown in nutrient with normal Mg(2+) levels. Roots from plants grown in Mg(2+) -deficient nutrient solution released 3.8 times the amount of aromatic aldehydes upon nitrobenzene oxidation as that released from normal roots. As the degree of Mg(2+) deficiency of the nutrient solution was increased, there was an increase in the aliphatic and aromatic components characteristic of suberin. Thus, both ultrastructural and chemical evidence strongly suggested that Mg(2+) deficiency resulted in increased suberization of the cell walls of both hypodermis and endodermis of Zea mays roots. The roots from Mg(2+) -deficient plants also had a higher amount of peroxidase activity when compared to control roots.