Anatomical Responses of Zinnia violacea Cav. Roots and Stems to Batik Wastewater

Batik industry is one of the most developed textile industries in Yogyakarta. Synthetic dyes used for batik coloring contain some toxic components for the environment, such as heavy metals. Zinnia violacea Cav. is one species of Asteraceae family potential to be heavy metal phytoremediator. This research aimed to determine the effects of batik wastewater on plant growth, as well as its root and stem anatomy. One and a half months old zinnia plants were treated with batik wastewater on different concentrations (0%, 25%, 50%, 75%, 100%). The treatment was done every 5 days using 400 mL of wastewater according to field capacity. The parameters observed were plant morphology, plant growth, as well as root and stem anatomy. The transverse section of root was prepared using the paraffin embedding method, while the anatomical slides of stem were obtained by non-embedding method. The results showed that increasing concentration of batik wastewater decreased the number of fresh leaves, the length and volume of the roots, and also plant biomass. Treatment of 50% to 100% of wastewater caused leaf chlorosis and necrosis. Plant height increased up to 50% concentration but decreased at 75% and 100%. Anatomically, batik wastewater decreased the diameter of roots and stele, with the highest was obtained in control. Trachea diameter increased by 75% and 100%, while cortex thickness decreased by 100% treatment. Increasing wastewater concentration also caused damage to epidermal and cortical cells of roots, as seen by the shape of the cells, from round to ellipsoid cells with a number of cells showed a damaged cell wall. In stem, the diameter increased in plants with wastewater of up to 75% and then decreased by 100%. Epidermal cell thickness in the stem has no significant change between control and treated plants, however, 100% of wastewater gave the thinnest stem cortex. For vascular bundles, the thickness increased along with the increasing concentration of wastewater.