Abstract

The effects of calcium on respiratory and nitrogen metabolism of apple roots (Malus baccata Borkh.) exposed to temperature stress (5°C ~ 20°C ~ 0°C) were investigated. Seedlings were treated with distilled water (control), calcium chloride (CaCl2) or calmodulin antagonist trifluoperazine (TFP) before temperature stress. Temperature was increased from 5°C to 20°C (1°C h -1 ) and then decreased to 0°C (1°C h -1 ). Temperature stress decreased root vitality and increased root malondialdehyde (MDA) concentration, the effect of which was exacerbated by TFP treatment. Treatment with CaCl2 improved root vitality and decreased root MDA concentration. At 20°C, exogenous CaCl2 alleviated the negative effects of temperature stress on the total respiration rate by enhancing the activity of tricarboxylic acid cycle (TCA). Activities of key enzyme in nitrogen metabolism were strongly inhibited by temperature stress. Exogenous CaCl2 significantly increased key enzyme activities of nitrogen metabolism compared to the control. However, the TFP treatment markedly reduced the activity of glutamate synthase (GOGAT) at 20°C and noticeably inhibited glutamate dehydrogenase (GDH) activity during the entire temperature stress period. The data showed that the Ca 2+ -calmodulin (Ca 2+ -CaM) signal system was involved in increase of GOGAT and GDH activity that occurred with an increase in temperature, and played a role in the increase in the total respiration rate and GDH activity which occurred with a decrease in temperature. Cultural practices that improve plant calcium (Ca) status in the early spring may mitigate damage induced by temperature stress. © 2016 Friends Science Publishers

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