Chlorophyll-a Fluorescence Analysis Reveals Differential Response of Photosynthetic Machinery in Melatonin-Treated Oat Plants Exposed to Osmotic Stress

Abstract

In this study, the effects of melatonin-induced enhancement on the principal photosynthetic parameters and antioxidant machinery were investigated in Avena sativa (oat) plants exposed to polyethylene glycol (PEG)-induced osmotic stress. The parameters of growth, chlorophyll content, stomatal conductance, proline accumulation, lipid peroxidation, and electrolyte leakage showed noteworthy improvements between the groups. Melatonin treatment caused upregulation of the genes that encode the three major antioxidant enzymes: ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT). Chlorophyll-a fluorescence kinetic analyses revealed that melatonin treatment improved performance indices (PIABS and PItotal), quantum yields, and efficiencies of photosystem II (PSII) in oat plants subjected to PEG-induced osmotic stress. Furthermore, upregulation of five genes (PsbA, PsbB, PsbC, PsbD, and PsbO) that encode the core proteins of PSII implied melatonin exerted a positive influence on photosynthesis under conditions of osmotic stress.

Melatonin Enhanced the Tolerance of Arabidopsis thaliana to High Light Through Improving Anti-oxidative System and Photosynthesis

“…The decrease of photosynthesis efficiency in plants after being exposed to adverse environmental might be a key reason for the reduction of crop. The previous studies showed abiotic stress induced irreversible damage to PSII in tomato, oat seeds, Ligustrum vicaryi and maize seedlings thereby decreasing photosynthetic rate (Ding et al, 2017;Chen et al, 2018;Alyammahi and Gururani, 2020;Kanwar et al, 2020;Yuan et al, 2020). The decrease of stomatal conductance could result in a declined P n and reduced assimilation products, thus causing an inhibited growth and a lower yield (Rao and Chaitanya, 2016).…”

Synergistic Effects of Melatonin and Gamma-Aminobutyric Acid on Protection of Photosynthesis System in Response to Multiple Abiotic Stressors

“…Therefore, stomatal opening would improve gas exchange efficiency; as a result, this improves stress tolerance by maintaining a steady state photosynthesis [ 77 ]. It has been reported that melatonin enhances osmotic stress tolerance by promoting the efficiency of CO 2 assimilation [ 78 ] and obstructing the inhibitory effects of osmotic stress on g s [ 79 ]. Melatonin takes part in increasing g s by maintaining cell turgor that facilitates the stomatal opening and conductance [ 76 ].…”

“…It can be concluded that the stronger correlation in primed plants compared with the control was due to higher initial PI abs parallel with increase in NPQ under PEG stress. In this regard, GABA has been reported to enhance PEG-induced stress tolerance in Piper nigrum through increasing PSII activity [ 102 ], and melatonin showed to improve PI abs in oat plants exposed to PEG stress, which minimizes the inhibitory effects of PEG [ 78 ].…”

Low Light Alters the Photosynthesis Process in Cigar Tobacco via Modulation of the Chlorophyll Content, Chlorophyll Fluorescence, and Gene Expression

“…The activity of the PSII system is restricted by various environmental stresses affecting the synthesis of proteins required for its repair and proper functioning [58]. The expression of PsbA, PsB, and PsbD is repressed in oat plants under saline conditions, exhibiting damage to the PSII system [59], while 5-aminolevulinic acid application increases the PsbA and PsbD expression in wheat under drought, which represents the damage repair of the PSII system [60]. In our study, the expression levels of these genes are increased under T50 relative to the control, which indicates PSII damage repair under a low light environment.…”