Abstract
Chilling stress is an important constraint for maize seedling establishment in the field. To examine the role of salicylic acid (SA) and hydrogen peroxide (H2O2) in response to chilling stress, we investigated the effects of seed priming with SA, H2O2, and SA+H2O2 combination on maize resistance under chilling stress (13°C). Priming with SA, H2O2, and especially SA+H2O2 shortened seed germination time and enhanced seed vigor and seedling growth as compared with hydropriming and non-priming treatments under low temperature. Meanwhile, SA+H2O2 priming notably increased the endogenous H2O2 and SA content, antioxidant enzymes activities and their corresponding genes ZmPAL, ZmSOD4, ZmAPX2, ZmCAT2, and ZmGR expression levels. The α-amylase activity was enhanced to mobilize starch to supply metabolites such as soluble sugar and energy for seed germination under chilling stress. In addition, the SA+H2O2 combination positively up-regulated expressions of gibberellic acid (GA) biosynthesis genes ZmGA20ox1 and ZmGA3ox2, and down-regulated GA catabolism gene ZmGA2ox1 expression; while it promoted GA signaling transduction genes expressions of ZmGID1 and ZmGID2 and decreased the level of seed germination inhibitor gene ZmRGL2. The abscisic acid (ABA) catabolism gene ZmCYP707A2 and the expressions of ZmCPK11 and ZmSnRK2.1 encoding response receptors in ABA signaling pathway were all up-regulated. These results strongly suggested that priming with SA and H2O2 synergistically promoted hormones metabolism and signal transduction, and enhanced energy supply and antioxidant enzymes activities under chilling stress, which were closely relevant with chilling injury alleviation and chilling-tolerance improvement in maize seed.Highlights:Seed germination and seedling growth were significantly improved under chilling stress by priming with SA+H2O2 combination, which was closely relevant with the change of reactive oxygen species, metabolites and energy supply, hormones metabolism and regulation.
Highlights
Chilling stress is one of the most severe abiotic stresses inhibiting obviously seed germination and plant growth (Allen and Ort, 2001)
We found that maize seeds germinated obviously faster after Salicylic acid (SA)+H2O2 combined priming as compared with priming treatment with SA or H2O2 alone
Endogenous SA content was analyzed using HPLC according to the method of Wang et al (2013)
Summary
Chilling stress is one of the most severe abiotic stresses inhibiting obviously seed germination and plant growth (Allen and Ort, 2001). One of sensitive crops to chilling stress (Hola et al, 2007), often encounters low temperature when sowed in early spring, resulting in reduction of seed emergence and seedling growth (Farooq et al, 2008b; Guan et al, 2009; Imran et al, 2013). It is necessary to develop novel methods to enhance the chilling tolerance of maize seed (Maslak et al, 2007). Hydrogen peroxide (H2O2) at proper concentration was conducive to seed dormancy-broken and germination enhancement (Müller et al, 2009; Lariguet et al, 2013). There are few reports on chilling resistance improvement of maize seeds through H2O2 application
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