Pretreatment with NaCl Promotes the Seed Germination of White Clover by Affecting Endogenous Phytohormones, Metabolic Regulation, and Dehydrin-Encoded Genes Expression under Water Stress

Abstract

This study was designed to examine the effects of NaCl pretreatment on the seed germination of white clover (Trifolium repens cv. Ladino) under water stress induced by 19% polyethylene glycol (PEG) 6000. Lower concentrations of NaCl (0.5, 1, and 2.5 mM) pretreatment significantly alleviated stress-induced decreases in germination percentage, germination vigor, germination index, and radicle length of seedlings after seven days of germination under water stress. The soaking with 1 mM of NaCl exhibited most the pronounced effects on improving seed germination and alleviating stress damage. NaCl-induced seeds germination and growth could be associated with the increases in endogenous gibberellic acid (GA) and indole-3-acetic acid (IAA) levels through activating amylases leading to improved amylolysis under water stress. Seedlings pretreated with NaCl had a significantly lower osmotic potential than untreated seedlings during seed germination, which could be related to significantly higher soluble sugars and free proline content in NaCl-treated seedlings under water stress. For antioxidant metabolism, NaCl pretreatment mainly improved superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione reductase activities, transcript levels of FeSOD, APX, and DHAR, and the content of ascorbic acid, reduced glutathione, and oxidized glutathione during seed germination under water stress. The results indicated that seeds soaking with NaCl could remarkably enhance antioxidant metabolism, thereby decreasing the accumulation of reactive oxygen species and membrane lipid peroxidation during germination under water stress. In addition, NaCl-upregulated dehydrin-encoded genes SK2 expression could be another important mechanism of drought tolerance during seeds germination of white clover in response to water stress.

Diethyl Aminoethyl Hexanoate Priming Ameliorates Seed Germination via Involvement in Hormonal Changes, Osmotic Adjustment, and Dehydrins Accumulation in White Clover Under Drought Stress

“…Moreover, DA-6 (2 mM) also exerted distinct beneficial effects by mitigating drought-induced decreases in GV, GI, SVI, FW, RL, and SL of white clover seedlings ( Figures 1 , 2 ). These results are consistent with study of Cao et al (2018) about exogenous NaCl pretreatment during germination in white clover seeds under drought stress. The present findings indicate that seed priming with DA-6 (2 mM) could be an effective strategy to ameliorate tolerance in white clover under water deficient conditions.…”

“…A previous study has shown that exogenous polyamines application ameliorated seed germination and growth of young seedling via alteration of endogenous phytohormones in cotton (Gossypium hirsutum) under drought stress (Yang et al, 2016). Moreover, seed priming with sodium chloride enhanced germination of white clover (Trifolium repens) seeds by regulating hormonal and carbohydrate metabolism under water stress (Cao et al, 2018).…”

“…At this stage, carbohydrates, fats, and proteins metabolism supply energy for seeds germination and subsequent seedling growth ( Jie and Kentian, 1993 ). On the other hand, different types of solutes including water soluble carbohydrates (i.e., sucrose, glucose, and fructose), sugar alcohols (mannitol), proteins (dehydrins), and free amino acids (proline) tend to accumulate, which play a vital function in osmotic adjustment (OA) for reducing water potential of cells during seed germination under water deficient condition ( Cao et al, 2018 ). These solutes also perform function as antioxidants for reactive oxygen species (ROS) scavenging, membrane protection, and other defense mechanisms under drought stress ( Bartels and Sunkar, 2005 ; Seki et al, 2007 ).…”

Pengaruh Osmopriming Benih terhadap Pertumbuhan dan Morfofisiologi Tanaman Kangkung Darat (Ipomoea reptans Poir) pada Cekaman Kekeringanngkung Darat (Ipomoea reptans Poir) pada Kondisi Kekeringan

“…Dampak positif dari priming tersebut terhadap kadar prolin juga telah dibuktikan pada biji gandum (Tabassum et al, 2018), biji padi varietas Nagina-22 (N-22) dan Pusa-Sugandh-5 (PS-5) (Samota et al, 2017), dan biji Trifolium repens cv. Ladino (Cao et al, 2018).…”

Exogenous Gibberellin Promotes the Germination of Phellodendron Chinense Schneid Seeds by Regulating the Expression of Phytohormone Related Genes and Anabolic Proteins

“…Seed germination is a complex and ordered reaction process, which is regulated by endogenous phytohormones, and the phytohormone contents are controlled by key synthesis enzymes and genes [34,35]. The ratio of GA 3 and ABA in seeds is an important factor in seed germination, and their synthesis and accumulation are regulated by genes [31,36].…”