Abstract:

The purpose of this paper is to explore the effects of acid treatment and exogenous application of calcium to nutrient solution on the functions of antioxidant systems and mitochondria in Malus hupehensis var. pingyiensis roots. The M. hupehensis var. pingyiensis rootstock seedlings were cultured in 1/2 Hoagland nutrient solutions of different pH (3, 4, 5 and 6) and different Ca²⁺ concentrations (10, 20 and 30 mmol·L^-1) with pH 3, respectively. The antioxidant enzyme activities and the characteristics of mitochondria were measured in day 0, 2, 3 and 4. Compared with the control (pH6), the maximum activity of SOD, CAT in the treatments occurred in day 2, and the change of POD activity was different, the maximum activity of POD occurred in day 2 in pH 3 and pH 4, and in day 3 pH 5. Meanwhile, the mitochondrial membrane permeability, potential (Δψ_m) and cytochrome c/a decreased with the increasing of the acidity and the treatment time and the content of H₂O₂ was decreased at first and then increased. The exogenous application of calcium (10 and 20 mmol·L^-1) in the nutrient solution under acid treatment (pH 3) increased the activities of SOD, POD and CAT, relieved the damage of the mitochondrial functions by the acidity and inhibited the accumulation of H₂O₂(the decline, with 10 and 20 mmol·L^-1, was 6.78% and 13.43% of the accumulation caused by the single acid treatment, respectively). The 20 mmol·L^-1 Ca²⁺ had better effect whereas the 30 mmol·L^-1 Ca²⁺ increased the damage and increased the content of H₂O₂ by 8.96%. The above results suggested that the acid treatments would damage the roots of M. hupehensis var. pingyiensis and the exogenous application of dilute calcium in the nutrient solution could relieve the damage of acid treatment to the roots.

Key words: Malus hupehensis var. pingyiensis, acid treatment, calcium, antioxidant systems, mitochondria