Ethylene Supplementation Combined with Split Application of Nitrogen and Sulfur Protects Salt-Inhibited Photosynthesis through Optimization of Proline Metabolism and Antioxidant System in Mustard (Brassica juncea L.)

Abstract

In the present study, the potential of ethylene as ethephon (an ethylene source) was investigated individually and in combination with split doses of nitrogen (N) and sulfur (S) soil treatments for removal of the damaging effects of salt stress (100 mM NaCl) in mustard (Brassica juncea L.). Plants were grown with 50 mg N plus 50 mg S kg−1 soil at sowing time and an equivalent dose at 20 days after sowing [N50 + S50]0d and 20d. Ethephon at 200 μL L‒1 was applied to combined split doses of N and S with or without NaCl. Plants subjected to NaCl showed a decrease in growth and photosynthetic characteristics as well as N and S assimilation, whereas proline metabolism and antioxidants increased. The application of ethephon to plants grown with split N and S doses significantly enhanced photosynthetic efficiency by increasing the assimilation of N and S, improving the concentration of proline and induction of the antioxidant system with or without NaCl. The regulation of ethylene and/or split forms of N and S application may be potential tools for not just overcoming salt stress effects in this species and in related Brassicaceae but also enhancing their photosynthesis and growth potential through increased nutrient assimilation.

Coordinated Role of Nitric Oxide, Ethylene, Nitrogen, and Sulfur in Plant Salt Stress Tolerance

“…It has been observed that growth becomes reduced in plants due to damage of PS II and electron transport rates under stress [41]. In B. juncea, the increased concentration of salt significantly impacted net photosynthetic rate, stomatal conductance, intercellular CO 2 , quantum yield of PS II, Rubisco activity, and PNUE [10]. The study of Singh et al [42] showed the response towards variable concentration of salt, which hampered the photosynthetic apparatus and the water splitting efficiency complex.…”

“…Salinity-impact on the germination has been reported in several crop plants including Brassica juncea [10], Oryza sativa [26], and Triticum aestivum [27]. In salinity (EC 12 dS m -1 )exposed B. juncea genotypes, a significant correlation existed between tolerance index and shoot length, dry matter and also salt tolerance efficiency [28].…”

“…Varied reactive oxygen species (ROS) generated at higher level can occur due to salinity stress in plant cells, can act as signaling molecules, and help in mediating numerous key physiological processes [8]. However, overproduced or non-metabolized ROS can be toxic to plants and cause oxidative damage to cellular constituents including macromolecules (DNA, lipid, and proteins), and, eventually, cause cell death [9,10].…”

“…Various studies have shown the interaction of NO and ETH with N and S under abiotic stress. Studies have reported the interactive effects of NO with N and S [2] and ETH with N and S [10]. N-availability was reported to influence ETH -production and improve salt tolerance in mustard [23], whereas NO was found to enhance the photosynthetic nitrogen use efficiency (PNUE) and photosynthetic sulfur use efficiency (PSUE).…”

Methyl Jasmonate Protects the PS II System by Maintaining the Stability of Chloroplast D1 Protein and Accelerating Enzymatic Antioxidants in Heat-Stressed Wheat Plants

“…The adaptive reaction of plants to oxidative stress consists in the rise of the activity of antioxidants enzymes [ 8 , 9 , 10 ]. Remarkably, several studies reported the association between antioxidant activity, heat tolerance, and plant hormones [ 3 , 11 , 12 , 13 ].…”