Histological changes in Panicum miliaceum in response to phenanthrene contamination

Histological studies based on anatomical and histochemical changes can significantly contribute to our better understanding of cellular processes as well as how plants respond to biotic and abiotic stresses at different cell and tissue levels. Panicum miliaceum is a well-known crop in Poaceae family, however, there have not been many histological studies of the effects of abiotic stresses on this plant. Therefore, the aim of this study was to evaluate the anatomical changes in different parts of the plant (root, leaf and stem) under phenanthrene (PHE) contamination. Phenanthrene is an organic pollutant belonging to the group of polycyclic aromatic compounds (PAHs) which can penetrate into plants through different pathways, especially via roots, transport to different parts of the plant, and ultimately influence the morphological, anatomical, and physiological properties of plants. The seeds were hydroponically cultured within control and PHE-treated groups (۵۰۰ and ۱۰۰۰ ppm), after ۴۵ days, the samples were harvested and fixed in FAA solution. After sectioning and staining with Fast green and Safranin, they were studied with an optical microscope for changes in the anatomical structure. Examination of the anatomical traits showed that all plant tissues were undergone changes associated with PHE stress. The most important changes in roots include an increase in the number and size of cortex parenchymal cells, thickened xylem cells, and a general increase in the thickness and diameter of roots compared to the control. In leaves, the process of lignification was completely evident in samples treated with PHE. In stem of the treated plants, the number of vascular bundles as well as the amount of lignification increased and, thus they had more stability and resistance than the control samples. It can be concluded that the increased lignification probably obtained to increase the resistance of the plant as a defense mechanism against PHE stress.

کلیدواژه ها:

Polycyclic Aromatic Hydrocarbons ، Stress ، Anatomical structure ، Crop plant ، Microscopy