SCREENING OF SOME INDIGENOUS HERBAL DYES FOR USE IN PLANT HISTOLOGICAL STAINING

This paper examined the efficacy of some indigenous non-toxic and eco-friendly herbal stains for staining plant materials with the aim of improvising for the toxic, expensive and non-available artificial exotic stains used in plant histology. Dye extracts from Bixa orellana, Curcuma domestica, Lonchocarpus cyanescens and Pterocarpus osun were used to stain wood sections using the existing standard staining procedures with little modification. The affinities of Wood fibres and tissues to the natural plant dyes were noted. They all had affinity for the fibre and vessel elements except the extract from L. cyanescens. While P. osun extracts behaved as a general purpose stain, C. domestica and B. orellana dye extracts had high selectivity for fibre. From the results of the absorbance curves, each of the dye extract had minimum of two peaks indicating that they had two or more colour imparting chromophores except Curcuma domestica with one peak resulting in its only one colour imparting chromophore. All the dye extracts were acidic having pH range of 3.77 to 6.77. Therefore, this study has showed that dye extracts from Bixa orellana, Curcuma domestica and Pterocarpus osun could be solitarily used or in combination with artificial dyes for Plant histological staining.