Effect of brassinosteroids and its biosynthesis inhibitor in two varieties of tomato´s seedlings under salt stress

Abstract

Brassinosteroids (BRs) are currently considered the sixth class of plant hormones. In recent years, several authors have studied the BR protection conferred to the plants to certain types of biotic and abiotic stress. In this study, germination, early growth, levels of proline and malondialdehyde (MDA) and the peroxidase activity of two tomato varieties (INCA 9(1) and Amalia) subjected to salt stress and treated with a natural brassinosteroid (24-epibrassinolide, EBL), an spirostanic analogue of brassinosteroid (Biobras-16) and an inhibitor of the biosynthesis of brassinosteroids (Brz2001) were evaluated. Seeds of these varieties were treated for four hours with EBL (0,1?mol.L-1) Biobras-16 (0,1?mol.L-1) Brz2001 (10 ?mol.L-1), and the combination of brassinosteroids with the inhibitor. Later, they were then placed in Petri dishes for seven days in the presence or absence of NaCl 75 mmol.L-1. It was evidenced that both brassinosteroids regained the germination of NaCl stressed-seeds, while the Brz2001 with NaCl inhibited germination. In the case of growth, EBL protected the stem length and the dry mass of the stressed seedlings, while it had a negative effect on root length. Proline levels and peroxidase activity increased in all treatments except the control, whereas MDA levels remained unchanged in all treatments. EBL reduced proline levels in stressed seedlings.