Cytogenetic Effect of Chitosan on Mitotic Chromosomes of Root Tip Cells of Vicia faba

Chitosan is a biopolymer consisting predominantly of unbranched chain and derived from the natural product chitin. Three concentrations of chitosan during three different time periods were examined for its genotoxic and cytotoxic effects. The results show that treatments with chitosan increased the mitotic index compared with control, although treatment with high concentrations for (12&16houre) decreased the mitotic index but the effect were in significant at 005; furthermore, different treatments caused chromosomal aberrations similar to the chromosomal aberrations noticed in control which is normally observed during seed growing and before long would be insignificant. The study indicates that chitosan can be considered an excellent alternative to synthetic plants fertilizations. [Mona S. Al-ahmadi. Cytogenetic Effect of Chitosan on Mitotic Chromosomes of Root Tip Cells of Vicia faba. Life Sci J 2015;12(2):158-162]. (ISSN:1097-8135). http://www.lifesciencesite. com. 24 Key wards: Chitosan, Cytogenetic, Vicia faba, Root Tips. Introduction Chitosan (C6H11NO4)n is derived from a natural product, chitine (C8H13NO5)n (figure1-a) by deacylated chitin, cellulose-like biopolymer consisting predominantly of unbranched chain (figure 1-b), found in fungi, yeasts, marine invertebrates and arthropods, which is a principal component in the axoskeletons, and considered environmentaly friendly and easily degradable. The Chitosan has been applied in many fields; it had been found that chitosan regulates the immune system of plants (Boonlertnirun et al, 2008); also because chitosan is a natural biopolymer it contains a lot of nitrogen molecules that enhance germination index and shoot and root dry weight (Grant et al, 2009), it promotes seedling growth, accelerates the first flowering date (Ohta et al, 2004), can increase the microbial population by large numbers, and transforms organic nutrient into inorganic nutrients that are easily absorbed by plants’ roots (Somashekar and Joseph, 1996; Bolto et al, 2004), (Boonlertnirun et al, 2008) found that chitosan improved rice resistance to disease and insect infections. These studies encourage using chitosan in agriculture field with minimum side effects on plants. In this study, the cytotoxic and genotoxic effects of chitosan were investigated using the Vicia faba assay. Figure (1-a): Chitine (C8H13NO5)n Cellulose-like Biopolymer Consisting Predominantly of Unbranched Chain (The merck index, eleventh edition). Figure (1-b): Chitosan (C6H11NO4)n (Nair and Laurencin, 2007) Material and Methods 1-Preparation of samples: Seeds of Vicia faba were collected from the local market. They were first presoaked for 24 hours in distilled water and then transported to the tested concentrations for different periods of time, and then grown until the seedling secondary roots tip become 23 cm long, then were cut and fixed in freshly prepared 3:1 (v/v) alcohol: glacial acetic acid for 24 hours. For Cytological preparations, secondary root of Vicia faba were hydrolyzed in 1N HCL 60c for 5 minutes, and then washed with distilled water several times and staind with 1% acetocarmin, five temporary slides were prepared using the squash technique, two root tips on each slide were examined for the effects of the chitosan on mitotic index (MI). The same slides were analysed for the types and frequencies of chromosomal abnormalities (CA). 2-Treatments: IThree concentrations were prepared for each treatment (0.5%v, 1.5%v, 2.5%v) for four different periods of time (8, 12, 16, 24 hours) using Vicia faba for monitoring cytotoxicty and genotoxcity effects. IIControl (Negative treatment) using distilled water only. Life Science Journal 2015;12(2) http://www.lifesciencesite. com 159 3-Scoring of slides and data analysis The slides were viewed under light microscope (Phenix P H 50 DB047VU) using the 40X objective lens immersion. The most representative ones for each structural aberration were photographed using (Phenix micro Image analyzer Software 2008 En V2, 2). 4-Mitotic index: On one slide for each treatment, a total of 2000 cells, were scored. The mitotic index (MI) is expressed as the number of dividing cells per total cells scored. 5-Cytotoxicity: The mitotic index of the treated cells at each dose of chitosan were compared with that of the negative control group 6-Genotoxicity test: Chromosomal aberration per dose were examined; the percentage of cells with aberrations of each dose were compared with that of the negative control using the (SPSS 16.0 for Windows statistical package). Two-way Analysis of Variance was the statistical method used for determining the significance of difference at P = 0.05. Result and Discussion: 1-Mitotic index: Table (1) and figure (2 & 3) show the effect of different concentrations of chitosan for different time periods on mitotic index and chromosomes aberration frequency. Mitotic index (MI) measures the proportion of cells in the M-phase of cell cycle, inhibition could be considered as cellular death or delay in the cell proliferation kinetics (Rojas et al, 1993). The treatment with (0.5 %v) of chitosan for (12,16,24 hours) caused increase in (MI), while treatment for 8 hours decreased the (MI) compared with control and it was in significant at 0.05. The increase in mitotic index may be due to the effect of chitosan on biochemical activities as (Mondal et al, 2012) reported that foliar application of chitosan enhanced the biochemical activities and led to plant growth and development. (Apiradee et al, 2007) reported that chitosan can be used as a plant growth enhancer for immature plants or in tissue culture. The plants grow result from cells division, also chitosan increased the growth rates of roots and shoots of Raphanus sativa L. (Tsugita et al, 1993), (Boonlertnirun et al, 2012) found that chitosan stimulates plant growth and enhances yield of Oryza sativa. (Wanichpongpan et al, 2001) reported that chitosan significantly enhanced growth factors in terms of the average values of flower-stem length, the number of growing leaves, including leaf width and length as well as the number of flowers per bush. Also (Apiradee et al, 2007) conclude that chitosan may induce a signal to synthesize plant hormones such as gibberellins, and may induced secondary metabolites that enhances growth. (Guan et al, 2009) reported that chitosan contained a lot of nitrogen molecules and can enhance germination index and shoot and root weight. The nitrogen molecules is important for amino acids building compounds that inter in proteins synthesis. Similar result of the effect of chitosan on growth reported by (Abdel-Mawgoud et al, 2010; ElSawy et al, 2010). High concentrations of chitosan (1.5%v & 2.5%v) decrease the (MI) compared with control, this decrease of (MI) were in significant at 0.05. The effect of chitosan on plant growth is similar to the effect of gibberellic acid a plant hormone that enhance cell division. Table (1): Total Number of Examined Cells, Mitotic Index and Chromosomes Aberration Frequency after Treatment with Different Concentrations of Chitosan for Different Time Periods on Root Tip Cells of Vicia faba 0.03 13.9 10 333 2393 d. water 8 0.03 10.9 9 289 2642 d. water 12 0.06 10.8 14 235 2174 d. water 16 0.09 12 9 101 2121 d. water 24 0.034 9.8 7 204 2076 0.5 8 0.14 15.9 46 328 2057 0.5 12 0.17 16.4 55 33