The Macroscopic and Microscopic Effects of Borax on the Roots of Allium cepa var. aggregation

Abstract

Borax (sodium tetraborate decaliydrate) has been found by the BFAD used as a fbod additive in commercially sold tapiocas. The study was conducted to investigate on the toxicity and mutagenicity of borax on the roots of Allium cepa var' aggregatuni. Four series of 90 onion bulbs were grown on top of test tubes containing nine borax concentrations (0, 0.05, 0.10. 0.15, 0.20, 0.25, 0.30, 0.35 and 0.45% by weight in water). After 5 days of treatment, data were collected from the macroscopic parameters: the number of roots was counted; the longest and shortest roots were measured; root color (white and brown), form (straight and bent), turgescence (non-turgid, moderately turgid, and highly turgid), and root tip form (straight, broken, and crooked) frequencies were determined. Two separate set-ups with 90 onion bulbs each were used to examine the microscopic effects of borax on the Allium roots, with one set treated with colchicine and the otlier set untreated. Data on tlie microscopic parameters from the non-colchicine treated root tips comprised of the mitotic index and the frequencies of aberrant chromosomes. Colchicine treated root tips were counted fbr their chromosome numbers. Results of the experiment showed that borax restricted root production and growth, and increased the frequencies of brown, non-turgid and broken (desiccating) root tips. Root bending on the other hand was found to be a characteristic feature of the roots grown at 0.05, 0.10 and 0.15% borax concentrations. Microscopic analysis of the non-colchicine treated root tips showed that borax reduced the mitotic indices and increased the frequencies of chromosomal mutations (C-mitosis, abnormal prophase, sticky, hazy, and precocious chromosomes). Results of ANOVA established that the effects of borax on the all the macroscopic and microscopic parameters were significant. Moreover, Pearson Correlation Analysis ascertained the positive relationship between the production of unhealthy roots and increasing borax doses, as well as the induction of chromosomal aberrations and lowering of the mitotic index. Lastly, the colchicine and borax treated root tips exhibited aneuploid (monosomic and double monosomic) chromosomal aberrations. The resxilts of the experiment put forward the toxic and mutagenic effects of borax on the roots of Allium cepa var. aggregatum. These were attributed to the effects of borax on the osmotic potential of the growth medium, as well as to the involvement of its constituents (boric acid and sodium borate) in root growth and metabolism.