Study on the combined toxic effects of benzotriazole and cadmium on growth of rice seedlings

This study investigated the toxic effects of benzotriazole (BTA) (2.5, 5, and 10 mg/L) and its combination with cadmium (Cd) (5 μmol/L)on rice (Oryza sativa L.) seedling growth. Results showed that with increasing concentration, BTA significantly decreased chlorophyll content,inhibited rice seedling growth, decreased soluble sugar and starch content, enhanced soluble protein content, free amino acid content, and nitrate reductase (NR) activity, and inhibited glutamine synthase (GS) and glutamate synthase (GOGAT) activity compared with the control. Compared with Cd alone, BTA and Cd in combination facilitated chlorophyll degradation and suppressed rice seedling growth. In addition, 2.5 and 5 mg/L BTA combined with Cd decreased starch and soluble sugar content, while high-concentration BTA (10 mg/L) combined with Cd elevated starch and soluble sugar content. Joint exposure also enhanced free amino acid content and NR activity but reduced GOGAT activity. Different concentrations of BTA in combination with Cd also resulted in high enhancement and low suppression of GS activity. Thus, BTA either alone or in combination with Cd affected nitrogen and carbon metabolism in the leaves of rice seedlings, indicating that 2.5~10 mg/L BTA inhibited carbon and nitrogen metabolism. However, increasing BTA combined with Cd exhibited high promotion and low suppression of carbon and nitrogen metabolism to a certain extent.