Heavy metal accumulation imparts structural differences in fragrant Rosa species irrigated with marginal quality water.

Ecotoxicol Environ Saf. 2018 Sep 15;159:240-248. doi: 10.1016/j.ecoenv.2018.05.003. Epub 2018 May 21. Ahsan M1, Younis A2, Jaskani MJ2, Tufail A3, Riaz A2, Schwinghamer T4, Tariq U5, Nawaz F6. Author information 1 Department of Horticultural Sciences, University College of Agriculture & Environmental Sciences, The Islamia University of Bahawalpur, Pakistan. Electronic address: ahsan.horti@iub.edu.pk. 2 Institute of Horticultural Sciences, University of Agriculture Faisalabad, Pakistan. 3 Department of Botany, Division of Science and Technology, University of Education Lahore, Pakistan. 4 Department of Plant Science, McGill University, Montréal, Québec, Canada. 5 College of Agriculture, Bahadur sub-campus Layyah, Bahaudin Zakariya University, Multan, Pakistan. 6 Department of Agronomy, Muhammad Nawaz Sharif University of Agriculture, Multan, Pakistan. Abstract Wastewater is an alternative to traditional sources of renewable irrigation water in agriculture, particularly in water-scarce regions. However, the possible risks due to heavy metals accumulation in plant tissues are often overlooked by producers. The present study aimed to identify heavy metals-induced structural modifications to roots of scented Rosa species that were irrigated with water of marginal quality. The chemical and mineral contents from the experimental irrigation canal water (control) and treated wastewater were below the limits recommended by the Pakistan Environmental Protection Agency (Pak-EPA) for medicinal plants. The experimentally untreated wastewater contained electrical conductivity (EC), chemical oxygen demand (COD), biological oxygen demand (BOD), and heavy metals (Co, Cu, Cd, Pb) that were above the recommended limits. The responses by wastewater-treated Rosa species (Rosa damascena, R. bourboniana, R. Gruss-an-Teplitz, and R. centifolia) were evaluated. The experimental data revealed that treated wastewater significantly increased the thickness of collenchyma (cortex and pith) and parenchyma tissues (vascular bundle, xylem, and phloem) of R. Gruss-an-Teplitz. Root dermal tissues (epidermis) of R. bourboniana also responded to treated wastewater. R. damascena and R. centifolia were the least affected species, under the experimental irrigation conditions. Collenchyma and dermal tissues were thicker in R. damascena and R. Gruss-an-Teplitz under untreated wastewater conditions. In parenchyma tissues, vascular bundles were thicker in R. damascena in untreated wastewater conditions, while the xylem and phloem of R. Gruss-an-Teplitz were thicker where treated wastewater was applied. In tissues other than the vascular bundle, the differences in anatomical metrics due to the experimental irrigation treatments were greater during the second year of the experiment than in the first year. The contents of metals other than chromium in the roots and stems of roses were below the WHO limits, under all of the experimental irrigation conditions. Rosa centifolia contained higher heavy metals content than the other experimental species, and heavy metals content was associated with anatomical changes due to the treatments. We conclude that, under conditions of wastewater irrigation, R. Gruss-an-Teplitz was highly resistant; R. damascena was moderately resistant while R. bourboniana and R. centifolia were the most susceptible to irrigation with marginal quality water. This is the first report of plant tissue responses to wastewater irrigation by the experimental species. Regarding the accumulation of heavy metals in rose plant tissues, the results confirm that untreated wastewater must be treated to grow Rosa species where water is scarce. KEYWORDS: Environmental pollution; Metal toxicity; Scented roses; Tissues alteration; Water purification