Effects of some growth substances on mitosis

Effects of polyethylene terephthalate microplastic on germination, biochemistry and phytotoxicity of Cicer arietinum L. and cytotoxicity study on Allium cepa L

Accumulation of plastic materials in terrestrial systems threatens to contaminate food chains. The aim of the current study is to determine the impact of microplastics synthesized from PET plastics (control, 50, 250, 500, 750, 1000 mg/L) with respect to morphological, biochemical impact on Cicer arietinum using standardized 72 h assay and cytotoxicity study on Allium cepa root tips. The synthesized microplastics were characterized by Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR) studies. Germination studies clearly revealed that there is a sharp decrease in germination with increasing the concentration of microplastics. Both pigment and carbohydrate levels increased up to 500 mg/L concentration, although protein levels increased with increase of microplastic dose. Catalase activity also increased with increasing microplastic concentration. Finally, cytotoxicity studies revealed significant chromosomal aberration at higher dose of microplastics. Therefore, it may be concluded that the microplastics have significant biological and structural adverse effects on plant metabolism.

Does 2,4-dichlorophenoxyacetic acid (2,4-D) induce genotoxic effects in tissue cultured Allium roots?

2,4-Dichlorophenoxyacetic acid (2,4-D) is a synthetic plant growth regulator that is highly toxic to most broad leaved plants and relatively nontoxic to monocotyledonous plants; is frequently used as weed killer. The study aimed to investigate cytogenetic effects of different concentrations of 2,4-D (0.67, 1.34, 2.01, 2.68, 3.35 and 4.02 mg/L) on Allium cepa bulblets' root tips treated for 24 and 48 h. The results showed six types of structural aberrations: C-mitosis, stickiness, laggards, bridges, fragments and multipolarity that varied numerically compared to control. It significantly affected mitotic index (MI) at 24 and 48 h treatment. In the Allium test, MI increased significantly at three lower concentrations (0.67, 1.34, 2.01 mg/L) after treatment with 2,4-D for 24 h and decreased significantly at higher concentration. Whereas, 2,4-D treatment for 48 h increased MI at all concentrations with significantly decreased MI at the highest concentration. The experiment was extended using comet test that did not reveal significant difference among treatments except for application of 4.02 mg/L 2,4-D for 48 h; where cell damages were verified by comet test. Rest of the concentrations for any duration of time were not damaging and toxic to cells. The results showed, visible mitodepressive action of 4.02 mg/L 2,4-D when treated for 48 h that had tendency to become toxic if the roots had been in touch with 2,4-D for a longer time.

Testing of genotoxic effects of 2,4-dichlorophenoxyacetic acid (2,4-D) using multiple genetic assay systems of plants

The mutagenic activity of 2,4-D was assessed utilising cytogenetic, chlorophyll mutation, specific-locus and pollen viability endpoints in Allium cepa and Oryza sativa. In the Allium root-tip assay onion bulbs with roots were treated with 25, 50, 75 or 100 ppm 2,4-D for 4 h and the frequency of aberrations was estimated. With an increase in concentration there was rise in frequency of aberrant cells. In the case of mutation assays, presoaked rice seeds were treated with 100, 200 or 300 ppm 2,4-D for 4 h and sown in the field. Mutation frequency was estimated on M1 plant, spike and M2 seedling basis. With increasing concentration, there was a concomitant increase in mutation frequency. Highly significant chlorophyll-deficient and waxy mutants besides sterile pollen were observed as compared to both positive (EMS) and negative controls (H2O). The study demonstrates that 2,4-D has genotoxic potential.