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

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Abstract
The composition of the aliphatic components of suberin in the stele and cortex of young corn (Z. mays L.) roots was determined by combined GLC/mass spectrometry of the LiAID4 depolymerization products. .omega.-Hydroxy acids were the major class of the aliphatic components of both the hypodermal (35%) and endodermal (28%) polymeric materials with the dominant chain length being C24 in the former and C16 in the latter. Nitrobenzene oxidation of the roots generated p-hydroxybenzaldehyde and vanillin with much less syringaldehyde. EM examination of the hypodermal and endodermal cell walls from roots of corn plants grown in a Mg2+-deficient (0.03 mM) nutrient solution showed that these walls were more heavily suberized than the analogous walls of roots from plants grown in normal (2 mM) Mg2+ levels. Analysis of the LiAID4 depolymerization products of the suberin polymers from these roots showed that the roots grown in low Mg2+ had 3.5 times as much aliphatic suberin monomers on a weight basis as the roots from plants grown in nutrient with normal Mg2+ levels. Roots from plants grown in Mg2+-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 Mg2+ deficiency of the nutrient solution was increased, there was an increase in the aliphatic and aromatic components characteristic of suberin. Thus, both ultrastructural and chemicl evidence strongly suggested that Mg2+ deficiency resulted in increased suberization of the cell walls of both hypodermis and endodermis of Z. mays roots. The roots from Mg2+-deficient plants also had a higher amount of peroxidase activity when compared to control roots.