Effects of Deltamethrin on the Ultrastructures of the Root Meristem Cells of Allium cepa

Abstract

The EC50 value of commercially formulated deltamethrin (Decis 2.8% EC) was determined to be 0.87 ppm against Allium root growth. Root meristem cells were exposed to deltamethrin (0.5–2 ppm) for 6 to 24 h and examined by transmission electron microscopy. Deltamethrin induced various morphological abnormalities in the cell wall, plasma membrane, and Golgi apparatus dictyosomes. The microfibrillar arrangement of cell wall appeared to be amorphous in treated cells. The plasma membrane showed extensive dehiscence from the cell wall. The stacked cisternal membrane of dictyosomes were seem to be degenerated and the vesicles emanating from the dictyosomes were found to be accumulated around the degenerated dictyosome remnants. Sporadic dilation of dictyosome cisternae was also observed in the treated cells. Most nuclei in treated cells were observed to contain condensed chromatin material. The number of microtubles in the preprophase band was significantly reduced in 24 h treatment. Deltamethrin frequently disturbed the parallel array of spindle microtubules in metaphase cells. Telophase cells exposed to deltamethrin revealed incomplete, if not irregular, cell wall formation. Present findings suggest that the action of deltamethrin on microtubules is to an extent similar to that of microtubule depolymerizing drugs, which is the primary cause of toxicity leading to the induction of various mitotic aberrations. However, induction of structural and functional aberrations in the Golgi apparatus dictyosomes indicates the effect of deltamethrin on intercisternal elements and microfilaments, which possibly keeps the cisternal stack intact and directs the intracellular transport of vesicles.