Exogenous Melatonin Alleviates Alkaline Stress in Malus hupehensis Rehd. by Regulating the Biosynthesis of Polyamines

Abstract

Since melatonin was identified in plants decades ago, much attention has been devoted to discovering its role in plant science. There is still a great deal to learn about the functional importance of melatonin, as well as its functional mode. In this paper, we examine the role of melatonin treatment in the response of Malus hupehensis Rehd. to alkaline conditions. Stressed seedlings showed chlorosis and suppressed growth. However, this phenotype was ameliorated when 5 µM melatonin was added to the irrigation solution. This supplementation was also associated with a reduction in cell membrane damage and maintenance of a normal root system architecture. Fewer reactive oxygen species (ROS) were accumulated due to the enhanced scavenging activity of antioxidant enzymes superoxide dismutase, peroxidase, and catalase. In addition, alkaline-stressed seedlings that received the melatonin supplement accumulated more polyamines compared with untreated seedlings. Transcript levels of six genes involved in polyamine synthesis, including SAMDC1, -3, and -4, and SPDS1, -3, and -5, -6, were upregulated in response to melatonin application. All of these results demonstrate that melatonin has a positive function in plant tolerance to alkaline stress because it regulates enzyme activity and the biosynthesis of polyamines.

Exogenous Dopamine Application Promotes Alkali Tolerance of Apple Seedlings

“…The most obvious phenotype is the yellowing phenomenon of leaves in response to alkaline conditions, which showed a decrease of chlorophyll content [5,28]. In this study, compared with control, the contents of chl a, chl b, and chl t significantly decreased under alkali stress, as seen in Figure 5A-C.…”

“…The effects of alkali stress on plant growth mainly manifested in the damage of partial root function, decreases of water content and root activity, destruction of the photosynthetic system, and a decrease of photosynthetic pigment levels [3]. Previous studies have shown that alkali stress can significantly inhibit the growth of apple seedlings, damage plasma membrane, and cause a series of reductions of physiological functions [4][5][6].…”

Melatonin: Awakening the Defense Mechanisms during Plant Oxidative Stress

“…Similarly, greater SOD activity has been reported during chilling stress [42], waterlogging [44], alkaline stress [46], heavy metal stress [38], and drought stress [26]. Campos et al [25] reported that SOD activity was lower following the rehydration of Coffea arabica L. plants that had initially been exposed to drought stress, whereas Hodžić et al [40] described changes in SOD activity following the addition of melatonin under Cd and Zn stress in Melissa officinalis L. and Valeriana officinalis L. Interestingly, lower SOD activity was observed in Valeriana officinalis L. supplemented with both Zn and melatonin, whereas it increased when Zn was replaced with Cd.…”

“…POD, CAT [44] Pisum sativum L. Oxidative stress SOD [45] Malus hupehensis Rehd. Alkaline stress SOD, POD, CAT [46] Citrullus lanatus Vanadium stress SOD, CAT [47] Arabidopsis thaliana High light stress APX [48] Trigonella foenum graecum L. Lead and acid rain stress SOD, CAT [49] Solanum lycopersicon cv. Salinity and heat stress CAT, APX, GR, GST, GPX MDHAR SOD [50] Cynodon dactylon L. Salinity, drought and cold stress POD, SOD, CAT, GSH [51] Table 2.…”

Antioxidative response of Melissa officinalis L. and Valeriana officinalis L. leaves exposed to exogenous melatonin and excessive zinc and cadmium level

“…17 There is broad evidence that melatonin protects plants from oxidative damage and harmful environmental conditions. 18,19 In addition to direct ROS scavenging, melatonin protects plant cells by chelating heavy metals and preventing the formation of free radical species. 20 The available knowledge about the effect of melatonin on the antioxidant metabolism of plants exposed to various types of abiotic stress is summarized in Table S-I of the Supplementary material to this paper.…”