Ultrastructural effects of polycyclic aromatic hydrocarbons in the mangroves Avicennia marina and Rhizophora mucronata

- In roots oil caused disorganization of cells in the root cap, meristem, and conducting tissue.
- Oil damaged membrane integrity and caused fragmentation and disorganization of the nucleus, mitochondrion and chloroplast.
- Adverse effects of oil were greater in Avicennia marina than in Rhizophora mucronata.

The effects of polycyclic aromatic hydrocarbons (PAHs) on cell ultrastructure in the mangroves Avicennia marina and Rhizophora mucronata were investigated. One-year-old seedlings of both species were subjected to sediment oiling with Bunker fuel oil 180. In both species, fresh sections of root tips from the control, stained with fluorescein diacetate, exhibited green fluorescence indicating living cells, while those in the oiled treatment, stained with propidium iodide, exhibited red fluorescence indicating dead cells. In roots of both species, ultrastructural changes induced by oil included disorganization of cells in the root cap, epidermis, meristem and conducting tissue. Oil distorted and disorganised cells as well as their internal structure. Ultrastructural changes included loss of cell contents and fragmentation of organelles such as the nucleus and mitochondria. In the leaves of both species, oil caused dilation and distortion of chloroplasts and disintegration of grana and lamellae. This study demonstrated that in both species, oil damaged membrane integrity and caused disorganisation of critical organelles, such as nuclei, chloroplasts and mitochondria which are responsible for cell vitality and energy transformation.