Effect and localization of phenanthrene in maize roots

Area of Science:

• Environmental Science
• Plant Biology
• Toxicology

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants with known phytotoxicity.
• The precise mechanisms of PAH-induced plant toxicity, particularly their impact on root development and defense strategies, remain unclear.
• Phytomanagement of PAH-contaminated soils is hindered by plant toxicity, necessitating a better understanding of plant responses.

Purpose of the Study:

• To investigate the effects of phenanthrene (PHE), a representative PAH, on maize (Zea mays) root development and suberization.
• To elucidate the role of root exodermis and endodermis suberization in response to PHE exposure.
• To determine the localization and potential retention of PHE within the maize root system.

Main Methods:

• Maize seedlings were cultivated in sand spiked with phenanthrene (50 or 150 mg kg(-1) dry weight).
• Epi-fluorescence microscopy was employed to examine root sections for suberization of exodermis and endodermis.
• Phenanthrene localization was assessed along the primary root length in relation to suberized tissues.

Main Results:

• Exodermis and endodermis suberization were initially more extensive in PHE-exposed maize roots compared to controls after 10 days.
• After 20 days, control roots showed complete suberization, while PHE-exposed roots exhibited reduced suberization, indicating inhibited maturation.
• Phenanthrene was localized near suberized exodermis and endodermis, suggesting these tissues act as accumulation zones.

Conclusions:

• Early enhanced suberization may function as a temporary barrier against phenanthrene penetration.
• Prolonged phenanthrene exposure negatively impacts root maturation by inhibiting suberization.
• The suberized exodermis and endodermis act as retention sites for hydrophobic phenanthrene during radial transport in maize roots.