## 1 Introduction  
Maize (_Zea mays_ L.) is one of the most important agricultural crops with the largest yield and acreage in the world. Since maize originated from tropical and subtropical regions, the plant is sensitive to low temperature (LT), mainly during germination and post-germinative growth period [1, 2]. The agricultural praxis is to sow maize when the soil temperature is approximately above 10 \({}^{\circ}\)C. Under condition of soil temperature below 10 \({}^{\circ}\)C, seed germination and post-germinative growth are significantly inhibited, that result to the reduction of crop yield [3, 4]. In addition, periods of LT occasionally encountered at higher latitudes regions significantly threaten maize cultivation. Therefore, selection of elite maize inbred accessions should take into account the seed germination and post-germinative growth potential under LT stress. Low temperature impaired plant stomatal function, photosystem activity, Calvin cycle, or photosynthetic enzyme activities, as well as altered electron transport chain reactions, which finally leading to the excessive accumulation of reactive oxygen species (ROS) and subsequently oxidative damage [5, 6]. On the other hand, the generation of ROS is a fundamental process in higher plants and function to transmit signal response to the changing environment. Thus, plant developed a suit of antioxidant defense systems to maintain the equilibrium between generation and scavenging of ROS [6; 7]. In general, the antioxidant defense system consists of nonenzymatic antioxidants and some antioxidant enzymes, both of them participate in the redox reaction by electron transfer to eliminate the oxidative damage. The enzyme superoxide dismutase (SOD) functions in the first line of ROS defense, converting superoxide (O\({}_{2}\)\({}^{\bullet}\)) into hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)). The generated H\({}_{2}\)O\({}_{2}\) can be further converted into H\({}_{2}\)O by the enzymes catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), or by the ascorbate-glutathione pathway (AsA-GSH pathway). AsA-GSH pathway, also known as Asada-Halliwell pathway, is the major pathway that detoxifies the H\({}_{2}\)O\({}_{2}\) in a plant cell [8]. This pathway comprises two nonenzymatic antioxidants, AsA and GSH, and four antioxidant enzymes, including APX, GR, monode-hydroascorbate reductase (MDHAR), and dehydrorosorbate reductase (DHAR). AsA and GSH both have high redox potentials; the maintenance of their redox state is important in conferring stress tolerance in plants. Redox state of AsA and GSH mainly depends on the activities of the four enzymes that catalyze the conversion between their redox and oxidative form. First, the enzyme APX converts H\({}_{2}\)O\({}_{2}\) into the water with the help of AsA as an electron donor. The produced monodehydroascorbate (MDHA) recycled back to AsA by ferredoxin at photosystem I (PSI) and by MDHAR, or spontaneously converted into dehydrorosorbate (DHA). DHA is then recycled to AsA by the activity of GSH-dependent DHAR. In this reaction, one electron is transferred from GSH to DHA, and GSH is oxidized to oxidized glutathione (GSSG) that is further reduced back to GSH by NADPH-dependent GR activity [6; 8; 9; 10]. AsA and GSH function as the electron carrier and play pivotal role in ROS detoxification, the ratio of AsA/DHA and GSH/GSSG are considered as oxidative stress sensor for the surveillance of cellular redox homeostasis [11]. Plants activate the AsA-GSH pathway to cope with LT stress. For example, LT stress increased GSH/GSSG and AsA/DHA ratios in _Citrullus lanatus_[12]. Similarly, rice seedlings exposed to LT stress had enhanced GSH/GSSG ratio and along with increased SOD and CAT activity [13]. Antioxidants enzymes play key role in plant fitness to LT stress. For example, overexpression of _APX_ gene from _Camelia azale_ improves ROS scavenging and cold tolerances in tobacco [14].