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Magnesium Deficiency Results in Increased Suberization in Endodermis and Hypodermis of Corn Roots ¹

Instituto De Edafologia y Biologia Vegetal, Madrid, Spain, Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340

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 LiAlD₄ depolymerization products. -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 C₂₄ in the former and C₁₆ 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 Mg²⁺ -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) Mg²⁺ levels. Analysis of the LiAlD₄ 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 chemical evidence strongly suggested that Mg²⁺ deficiency resulted in increased suberization of the cell walls of both hypodermis and endodermis of Zea mays roots. The roots from Mg²⁺ -deficient plants also had a higher amount of peroxidase activity when compared to control roots.