Gibberellic acid-induced generation of hydrogen sulfide alleviates boron toxicity in tomato (Solanum lycopersicum L.) plants.

It was aimed to examine the role of gibberellic acid (GA) induced production of hydrogen sulfide (HS) in alleviating boron toxicity (BT) in tomato plants. Two weeks after germination, a solution consisting of GA (100 mg L) was sprayed once a week for 14 days to the leaves of cv. "SC 2121" of tomato under BT stress (BT; 2.0 mM). Before starting BT treatment, half of the seedlings were retained in a solution containing a scavenger of HS, 0.1 mM hypotaurine (HT), for 12 h. Boron toxicity led to a substantial decrease in dry biomass, leaf water potential, leaf relative water content, chlorophyll a, chlorophyll b, photosynthetic quantum yield (Fv/Fm), ascorbate (AsA) and glutathione (GSH) in the tomato plants. However, it increased the accumulation of hydrogen peroxide (HO), malondialdehyde (MDA), endogenous hydrogen sulfide (HS), and free proline as well as the activities of catalase, superoxide dismutase and peroxidase. The supplementation of GA mitigated BT by increasing the endogenous HS, and leaf Ca and K, and reducing the contents of leaf HO, MDA, and B as well as membrane leakage. GA-induced BT tolerance was further enhanced by the supplementation of sodium hydrosulfide (0.2 mM NaHS), an HS donor. A scavenger of HS, hypotaurine (0.1 mM HT) was supplied along with the GA and NaHS treatments to assess if HS was involved in GA-induced BT tolerance of tomato plants. Addition of HT reversed the beneficial effect of GA on oxidative stress and antioxidant defence system by reducing the endogenous HS without changing L-DES activity, suggesting that HS participates in GA-induced tolerance to BT of tomato plants.