Effect of Fungicide Metalaxyl on Dividing Root Cells of Allium Cepa L.

Abstract

The study throws light on the cytological effects of a systemic fungicide Metalaxyl on the somatic cell division. The root meristems of healthy onion bulbs (Allium cepa L.) were used as bioassay under lab condition. The water culture roots were made as control measure to study the chromosomal behavior. Metalaxyl solution of different concentrations was used to observe its cyto-toxic effects in dividing cells.

In agriculture, the field recommended dose of Metalaxyl is 0.5 gm/1000 ml. Such concentration is recognized as 100% solution. The test solutions of different concentrations were prepared by dilution, i.e. 25%, 50% and 75%. The cytological effect was observed in different concentration of metalaxyl solution at different treatment periods i.e. 3, 6, 12 and 24 hours separately.

Metalaxyl showed mito-depressive effect on higher concentration and also affected on all phase with different concentration with respect to different time periods. It is observed that higher the period of treated time lower will be the value of mean mitotic index. The mitotic indices values were observed between 22 to 25% in treated meristem whereas control value was 31%.

The value of prophase index was increased with increase in time of treatment and concentration. The prophase index was highest due to prophase poisoning and lowest was metaphase index among all of the other phase indices. The fungicide accomplished to induce the various type of chromosomal aberrations. The untreated root cells showed relatively less abnormalities than that of treated. The commonly found abnormalities were plasmolized cells, bi-nucleated cells, stickiness of chromosomes at prophase and metaphase, diagonal metaphase, C-metaphase, equatorial plate shifting, nonsynchronized arrangement of chromosomes, precocious chromosomes and arms, lagging

chromosomes, inhibition of cell plate formation and unequal cytokinensis. These were major physiological aberrations encountered in root treated cell of Allium cepa L. The abnormalities included chromosome breaks, chromatin bridges and micronuclei were the major clastogenic aberrations found on Metalaxyl treatment. Although, abnormalities were also encountered at control, but frequency was very low. Frequencies of physiological effects were found to be higher than that of clastogenic abnormalities. The statistical analysis showed that the frequency of aberrations induced with the entire dose and treatment period differed significantly from that of control. So, Metalaxyl has potential to physiological as well as clastogenic effects on plant cells.