Evaluation of natural dyes Curcuma longa and Nyctanthes arbor‐tristis with different mordants on plant tissues under fluorescence microscopy

The study reveals the effect of natural dyes Curcuma longa (rhizome) and Nyctanthes arbor‐tristis (corolla tube) on various plant tissues under fluorescence microscopy. The results indicated that the auto‐fluorescence was seen in some of the tissues of unstained monocot and dicot stem sections. The use of Curcuma longa dye along with different chemical mordants leads to various colors and intensity of fluorescence under different excitation filters (violet: 400–450; blue: 450–500; green: 500–570; yellow: 570–610 and red: 610–750 nm) examined. The extract of Nyctanthes arbor‐tristis along with the mordants lead to bluish‐orange fluorescence of vascular tissues under violet excitation filter. Among the dyes evaluated, Nyctanthes arbor‐tristis showed better fluorescence than the Curcuma longa dye. Hence, the dye extracted from the corolla tube of Nyctanthes arbor‐tristis is a potential natural dye and could be used as biological stain for staining plant tissues. Under fluorescence microscope nyctanthin from N. arbor‐tristis showed distinct fluorescence thereby differentiating the tissues in plants in all the excitation filters except green filter. Hence, the dye proved to be a good fluorescent dye.