Effect of Tannery Wastewater on the Growth and Yield of Sunflower (helianthus Annuus L.)

The effects of tanneries wastewater on growth and yield of three cultivars (SF-187, CRN-1435 and DK3915) of sunflower (Helianthus annuus L.) showed that wastewater was not fit for irrigation due to extremely high mineral and heavy metal contents. In addition, effluents were highly alkaline with high load in EC, BOD, COD and SAR values. The amount of iron, manganese, zinc and chromium was also quite high. The growth and yield of plants was adversely affected by effluents treatment, especially at higher doses from seedling stage to maturity leading to reduce biomass and seed production as compared to control. Effluents of tanneries used for irrigation purposes proved to be alarmingly toxic to the growth and yield of the important crop in Kasur region, Pakistan. Introduction There are as many as 800 tanneries including small tannin units located in Pakistan. Out of these, 237 units are located in Kasur District (Anonymous 2009). Effluents of tanning industries containing Cr and other metals are discharged into the local water bodies which are used for irrigation purposes. Presence of chromium beyond the tolerance limit (< 2 ppm) makes water unsuitable for crop growth (Sahu et al. 2007). The high level of Cr and nutrient contents in the effluent has been reported to inhibit the seed germination and seedling growth, which might be due to the presence of excessive amount of dissolved solids, chlorides, sulphides, chromium, high BOD and COD values of the effluent (Mishra and Bera 1995). Wastewater laden irrigation water affects the plant growth and yield (Barman and Lal 1994) and the accumulation of toxic heavy metals are biomagnified at different trophic levels through food chain (Rai et al. 2002, Saxena et al. 2007, Perez and Sarma 2008). The accumulation, however, depends on the plant species, the elements, its bioavailability, redox, pH, cation exchange capacity, dissolved oxygen, temperature and secretion of roots. Marked toxicity of chromium has been reported with respect to photosynthetic pigments in algae and other higher plants (Nath et al. 2005). Chromium toxicity produces chlorosis and necrosis in plants (Cervantes et al. 2001). The decrease in chlorophyll contents is due to chromium, competing for iron at functional site which might be interfering with the functional metal (Mg) in the porphyrin ring (Mengel and Kirkby 2001). Chromium exposure results into complete loss of growth in lateral roots while lesser concentration starts damaging root cap, stomata and cotyledonary hair seem to be collapsed and plasma membrane appears to be detached from the cell wall under cytological studies (Mariappan et al. 2001). The present study was undertaken to investigate the chemical composition of the effluents released by the tanneries and their effects on the growth and yield of three cultivars of sunflower. *Author for correspondence: Departmernt of Environmental Sciences, Bahauddin Zakariya University, Multan, Pakistan.