Improvement of Salinity Tolerance in Rice Seedlings by Exogenous Magnesium Sulfate Application

Abstract

This study was conducted to develop the salt tolerance of rice by exogenous application of magnesium sulfate supplement (MgSO4). The salinization was carried out on 7-day-old rice seedlings including BC15 (salinity tolerant) and DT84DB (salinity susceptible) varieties with 0.5 mM MgSO4. The exogenous application of MgSO4 significantly improves the growth of seedlings of both varieties. In addition, antioxidant activities increase in line with the raise of total phenolic and total flavonoid contents. Remarkably, the contents of momilactone B (MB) and phenolic compounds including tricin, ρ-coumaric, salicylic, cinnamic, benzoic, and ferulic acids simultaneously rise in both varieties treated by salinity and 0.5 mM MgSO4. Interestingly, MB was not found in the salt-treated samples but presents with considerable contents in the salt and MgSO4-treated cultivars. The findings imply that MgSO4 may significantly improve the salt tolerance of rice seedlings through the enhancement of secondary metabolic synthesis pathways, of which phenolic acids and momilactone B may play a crucial role in the response of rice to salt stress. In contrast, momilactone A (MA) did not show any contribution in salinity tolerance of examined rice cultivars at the early seedling stage. Further investigations on the effect of MgSO4 exogenous application in improving salinity tolerance of various rice varieties at other growing stages should be carried out.

Salinity Treatments Promote the Accumulations of Momilactones and Phenolic Compounds in Germinated Brown Rice

“…Accordingly, tricin, ρ -coumaric acid, ferulic acid, salicylic acid, and cinnamic acid were found in increasing quantities in B2 treatment (75 mM salinity and 4-day germination), which accounted for 107.63, 93.77, 139.03, 46.05, and 596.26 µg/g DW, respectively. The elevated contents of ρ -coumaric, salicylic, and ferulic acids are in line with those in rice seedlings subjected to salinity (100 mM) in a previous study [ 38 ]. Meanwhile, cinnamic acid and tricin amounts decreased [ 38 ], which does not align with our findings.…”

“…The elevated contents of ρ -coumaric, salicylic, and ferulic acids are in line with those in rice seedlings subjected to salinity (100 mM) in a previous study [ 38 ]. Meanwhile, cinnamic acid and tricin amounts decreased [ 38 ], which does not align with our findings. This might be due to the differences in genetic diversity among tested rice varieties.…”

“…On the other hand, the highest TFC (11.06 mg RE/g DW) was detected in B2, while the lowest TFC (2.54 mg RE/g DW) was found in A2. Previous studies indicated that TPC and TFC increased in rice seedlings under salinity effects [ 38 , 39 , 40 ], which might be due to the upregulation of genes encoding the major biosynthetic enzymes (e.g., phenylalanine ammonia lyase and chalcone synthase) in plant responses to biotic stresses [ 33 , 41 , 42 ]. In this study, TPC and TFC were remarkably stimulated in treatments with 75 mM salinity.…”

“…This might be due to the differences in genetic diversity among tested rice varieties. In fact, different rice varieties (tolerant and susceptible cultivars) exhibit dissimilar mechanisms in phenolic accumulation to cope with stress conditions [ 33 , 38 , 39 , 40 ]. On the other hand, the present study revealed a notable decrease in the quantities of these phenolics in GBR when exposed to extreme levels of salinity (150 mM).…”

Fulvic Acid Improves Salinity Tolerance of Rice Seedlings: Evidence from Phenotypic Performance, Relevant Phenolic Acids, and Momilactones

“…Recently, exogenous applications of fertilizers, biostimulants, and bio-preparations for improving plant tolerance to environmental stresses have received increasing attention from researchers worldwide [ 11 , 12 , 20 , 21 ]. However, their effectiveness is limited due to physical properties such as solubility and pH persistence [ 11 , 12 ].…”