Abstract
The protective effects of 5-aminolevulenic acid (ALA) on germination of Elymus nutans Griseb. seeds under cold stress were investigated. Seeds of E. nutans (Damxung, DX and Zhengdao, ZD) were pre-soaked with various concentrations (0, 0.1, 0.5, 1, 5, 10 and 25 mg l−1) of ALA for 24 h before germination under cold stress (5°C). Seeds of ZD were more susceptible to cold stress than DX seeds. Both seeds treated with ALA at low concentrations (0.1–1 mg l−1) had higher final germination percentage (FGP) and dry weight at 5°C than non-ALA-treated seeds, whereas exposure to higher ALA concentrations (5–25 mg l−1) brought about a dose dependent decrease. The highest FGP and dry weight of germinating seeds were obtained from seeds pre-soaked with 1 mg l−1 ALA. After 5 d of cold stress, pretreatment with ALA provided significant protection against cold stress in the germinating seeds, significantly enhancing seed respiration rate and ATP synthesis. ALA pre-treatment also increased reduced glutathione (GSH), ascorbic acid (AsA), total glutathione, and total ascorbate concentrations, and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), whereas decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and superoxide radical (O2 •−) release in both germinating seeds under cold stress. In addition, application of ALA increased H+-ATPase activity and endogenous ALA concentration compared with cold stress alone. Results indicate that ALA considered as an endogenous plant growth regulator could effectively protect E. nutans seeds from cold-induced oxidative damage during germination without any adverse effect.
Highlights
Cold stress is commonly defined as the low temperature range that is adequate to alter growth without stopping cellular processes [1]
Content aminolevulenic acid (ALA) concentrations ranging from 0 to 25 mg l21 were applied to E. nutans seeds to investigate the response for cold resistance
ALA concentrations above 1 mg l21 caused the ratio of germination percentage (GP) reduction in a dose dependent manner (Fig. 1A)
Summary
Cold stress is commonly defined as the low temperature range that is adequate to alter growth without stopping cellular processes [1]. Cold is one of severe environmental stresses that disrupts the metabolic balance of cells, resulting in membrane damage [3], reduction of cellular respiration [4], and production of reactive oxygen species (ROS) [5]. The antioxidant enzymes are important defense systems to detoxify ROS [6]. A large body of evidence has demonstrated that the antioxidant systems play important roles in protecting plants against oxidative damage induced by cold stress [3,9]
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