Foliar application of Beta amino butyric acid to mitigate the heavy metal stress in sunflower (Helianthus annus L.)

Nickel is heavy metal that can drastically lower plant growth and development. This study aimed to evaluate the role of foliar application of beta amino butyric acid under nickel stress. The variety of sunflower (HYSUN − 33) was used under the treatments of study nickel stress (control, 50 µM, and 100 µM) and beta amino butyric acid (BABA) (control, 200 µM, 400 µM). The results nickel stress (100 µM) decreased the shoot length by 37.8%, shoot fresh weight by 46.2%, shoot dry weight by 70.9%, and total chlorophyll content by 39.2%, compared to control. However, foliar application of BABA (400 µM) improved the shoot length up to 71.7%, shoot fresh weight 124.8%, shoot dry weight up to 382.3%, total chlorophyll content by 45.3%, respectively. Ni stress (100 µM) decreased the water potential (Wp) and relative water content (RWC) by 27.3%, respectively. Conversely, applying BABA (400 µM) to the leaves improved the water potential by 37%, and relative water content by 124.2% respectively. BABA (400 µM) applied via foliar spray further improved the SOD by 26%, POD up to 45.6%, and CAT up to 63.8% respectively under stress condition. Foliar application of 400 µM BABA significantly reduces the negative effects of Ni stress by improving anti-oxidative defense system. It improves key growth and the activity of enzymatic antioxidants like peroxidase, superoxide dismutase, and catalase. Further research is needed to explore the large-scale use of beta amino butyric acid in field settings, using different application methods.