Exogenous Application of Ethylenediaminetetraacetic Acid and Oxalic Acid Improve the Seed Germination and Enzymes Activities of Sunflower (Helianthus annuus) Under Cadmium Stress

The study was conducted to examine the deleterious effects of cadmium (Cd) on metabolic enzymes and their end products during seed germination and the effect of ethylenediaminetetraacetic acid (EDTA) and oxalic acid (OA) in easing the Cd toxicity in two sunflower hybrids (Hysun-33 and FH-533). To accomplish this, a pot experiment was carried out in small sand-filled plastic pots under normal environment temperature (28+/-2 degrees C). Seeds of both sunflower hybrids were exposed to Cd levels (250 and 450 mg/kg) alone and in combination of optimized level of chelating agents EDTA and OA (each at the rate of 1g/kg) at the time of sowing. The enzymes activities of two germinating hybrids were recorded over time from 24 to 120 h after sowing. When Cd was applied alone it reduced the germination rate, enzymes activities and total soluble sugars contents. Mobilization of stored proteins and amino acids were also suppressed in germinating seeds of both hybrids. However, application of EDTA and OA in combination with Cd improved the germination rate of seeds by surpassing the biochemical metabolism and enhanced the activities of a-amylase and protease revealing the ameliorating effect to Cd toxicity. Results revealed that minimum values of all the attributes are obtained at 450 mg/kg of Cd level, while chelators treatments proved effective in relieving Cd stress of which OA had 10% more pronounced germination percentage than EDTA and 30% more as compared to control. Interactive studies showed that both the chelators detoxify the 250 mg/kg of Cd more as compared to 450 mg/kg of Cd. Results clearly indicated that sunflower hybrid Hysun-33 showed greater activities of two hydrolyzing enzymes and efficient mobilization of reserved sugars and proteins than hybrid FH-533 under Cd stress, so it can be grown on Cd contaminated soils for higher plant productivity. Thereafter EDTA and OA could be supportive to improve the seed germination security in Cd polluted soil. (C) 2015 Friends Science Publishers