Ha-Il Jung

Arsenic (As) contamination poses a serious threat to rice production and food safety. Although sulfur (S) nutrition is known to alleviate As toxicity through thiol-based detoxification, the mechanisms underlying the relationship between S-induced As accumulation and tolerance remain poorly understood. We investigated the effects of contrasting S levels (0, 1, and 4 mM) on As accumulation, translocation, oxidative stress responses, thiol metabolite pools, and mineral nutrient profiles in hydroponically grown rice seedlings exposed to 15 µM As for 15 days. S supplementation alleviated As-induced growth inhibition in a dose-dependent manner despite increasing total As accumulation in both roots and shoots, demonstrating that S-mediated tolerance is independent of reduced As accumulation. Elevated S supply reduced oxidative stress markers (O₂^•–, H₂O₂, and MDA), while markedly enlarged the pools of γ-glutamylcysteine (γ-EC), glutathione, and phytochelatins (PCs), particularly in roots. S supplementation also improved the uptake of major essential nutrients, including nitrogen and potassium in shoots, while selectively modulating micronutrient distributions under As stress. Correlation analysis showed that root As content was strongly and positively correlated with γ-EC and PC2–PC4, and principal component analysis separated the treatments along the S gradient in both roots and shoots. Collectively, these results suggest that S enhances As tolerance in rice seedlings through thiol-dependent detoxification, thereby decoupling As tolerance from As accumulation rather than by restricting As accumulation.

Cadmium (Cd) is a potentially toxic element that impairs plant growth and threatens food safety and human health. This study aimed to investigate the effects of sulfur (S) supplementation on Cd uptake and tolerance in rice under hydroponic conditions. Rice seedlings were exposed to Cd stress and treated with S at different concentrations. Physiological traits, oxidative damage markers, thiol compounds, and ionomic profiles in rice plants were assessed. S supplementation reduced Cd-induced growth inhibition, restoring plant biomass. Although Cd accumulation increased with S treatment, it was accompanied by enhanced antioxidant responses, scavenging reactive oxygen species (ROS) and malondialdehyde. S application increased the production of thiol-containing compounds, including γ-glutamylcysteine, glutathione, and phytochelatins, which helped chelate Cd and sequester it in vacuoles, particularly in roots. Additionally, S supplementation altered the essential nutrient composition in rice tissues, particularly the uptake of N, P, and K, while influencing levels of Ca, Mg, and other essential elements. S supplementation enhanced rice tolerance to Cd stress by reestablishing ROS balance, activating thiol-based detoxification pathways, and regulating mineral nutrient balance. Furthermore, sulfur (S) exhibited a dual effect in plants, enhancing cadmium (Cd) uptake while also promoting its detoxification, underscoring its role in improving crop resilience in contaminated soils.

Potentially toxic elements (PTE), such as cadmium (Cd), lead (Pb), and arsenic (As), threaten rice (Oryza sativa L.) crop productivity and pose significant risks to human health when they are present in soil. This review summarizes the current understanding of soil and rice contamination with As, Cd, and Pb to provide an in-depth understanding of the dynamics of these contaminants and the mechanisms regulating their flow from soil to plants. It focuses on the following aspects: (1) these metals’ geochemical distribution and speciation in soil–rice systems; (2) factors influencing the transformation, bioavailability, and uptake of these metals in paddy soils; (3) metal uptake, transport, translocation, and accumulation mechanisms in rice grains; and (4) the roles of transporters involved in metal uptake, transport, and accumulation in rice plants. Moreover, this review contributes to a clearer understanding of the environmental risks associated with these toxic metals in soil–rice ecosystems. Furthermore, it highlights the challenges in simultaneously managing the risks of As, Cd, and Pb contamination in rice. The study findings may help inspire innovative methods, biotechnological applications, and sustainable management strategies to mitigate the accumulation of As, Cd, and Pb in rice grains while effectively addressing multi-metal contamination in paddy soils.

Soil electrical conductivity (EC) is widely used as an indirect indicator of salt accumulation. On-site diagnosis is a practical method for assessing soil conditions in real-time during crop cultivation. However, greenhouse soils often exhibit EC levels exceeding the standard osmotic stress threshold of 2 dS m-1 (On-site diagnosis standard), leading to frequent high-stress diagnoses that do not account for crop-specific salt tolerance. This study aimed to refine on-site diagnostic accuracy by evaluating early growth responses of tomatoes, a moderately salt-tolerant crop, across various EC levels. A 35-day cultivation experiment was conducted using soil with 4% organic matter, representative of greenhouse conditions. On-site diagnosis soil EC was adjusted from 1 to 20 dS m-1 in seven increments using KNO 3. Increased KNO 3 levels reduced soil-soluble phosphate, leading to a decrease in plant phosphorus content above EC 15 dS m-1. Growth analysis revealed that plant height, fresh weight, and dry weight significantly declined when EC exceeded 5 dS m-1 , with growth at EC levels above 15 dS m-1 dropping to less than 10% of the 2.5 dS m-1 treatment group. Based on soil and plant analyses, the optimal EC threshold for early tomato growth in soils with 43 g kg-1 organic matter was determined to be below 5 dS m-1. Therefore, in soils with EC exceeding 5 dS m-1 , young tomato cultivation should be avoided unless appropriate salt management strategies are implemented.

Soil plowing depth is very important in improving soil quality and promoting of crop production system. The relationship between soil plowing depth and soil chemical properties and crop yield was analyzed. Soils were sampled from 20 watermelons, 19 muskmelons, and 22 squash farms of plastic film house. The results showed that the average soil plowing depth of watermelon, melon, and squash cultivated in the plastic film house were 22 cm, 21 cm, and 27 cm, respectively. when the soil depth of watermelon and squash was deepened to 31 cm (26-39 cm), the levels of nitrate ion (NO 3-), electrical conductivity (EC), and exchange cations (Ex. cations) decreased by 2-42% compared to 18 cm (14-24 cm). The concentration of NO 3-, EC, and Ex. Potassium (Ex. K) of muskmelon cultivation with soil depth of 28 cm (26-36 cm) tended to decrease by 5-39% compared to 17 cm (14-22 cm). The yield of watermelon, muskmelon, and squash were increased by 6-22% when the soil plowing depth was 39 cm compared to 25 cm. The contribution of plowing depth to yield of 3 crops was highly significant at 13.1-28.2%. Therefore, deep tillage is necessary to improve soil health and increase yield of watermelon, muskmelon, and squash under plastic film house.

Climate change is causing a variety of environmental issues globally, and the frequency and intensity of droughts in the country are expected to increase. This has heightened the importance of managing agricultural water resources and necessitated the adoption of more efficient farming practices. In this study, we evaluated water inflow, outflow, nutrient concentration, and rice yield under continuous flooding (CF), alternate wetting and drying (AWD) in paddy soils with two different soil textures. AWD proved effective in saving water, as it increased rainfall infiltration and reduced irrigation water input compared to CF. Specifically, in silty clay loam (SiCL) soils, AWD resulted in less water and nutrient outflow than CF. Rice yields increased by 16.4% under AWD compared to CF in SiCL soils, and by 31.9% in sandy loam (SL) soils. These results suggest that water management practices can help mitigate the impact of climate change on irrigation water shortages and increase rice yields across various soil textures compared to conventional farming practices.

Cadmium (Cd) contamination in agricultural land poses a serious threat to human health due to the absorption of this toxic element by crops. This research aims to evaluate the effects of Cd at different soil contamination levels on yield and Cd concentration of rice (Oryza sativa L.). Rice was grown under controlled greenhouse conditions with seven different concentrations of Cd (0.1 [control], 1.9, 3.6, 7.2, 8.5, and 10.3 mg kg-1) to investigate changes in soil chemical properties and their effects on rice growth and yield. The total Cd content in the soil was significantly and positively correlated with organic matter (OM) and P 2 O 5 levels. As soil Cd concentration increased, negative correlations were observed with key rice growth parameters, including the panicle number per plant, yields, and tiller number after 60 days. The total (Cd Total) and plant-available (Cd Mehlich3) Cd concentrations in soil were found to be 4.787 and 2.733 mg kg-1 , respectively, and the Cd concentration in polished rice reached the edible limit of 0.2 mg kg-1. This study provides valuable insights into the relationship between soil Cd contamination, plant-available Cd concentration, and Cd accumulation in polished rice. By understanding these dynamics, effective standards can be established to assess and mitigate the risk of Cd contamination in agricultural environments.

Effects of Three Inorganic Amendments on Stabilization of As and Pb in Heavy Metal Contaminated Paddy Soil • 151 As (A and B) and Pb (C and D) concentration in the soils with the extracting solution of Mehlich3 as affected by CaSO 4 , FeSO 4 , CaCO 3 + CaSO 4 (1:1), FeSO 4 + CaCO 3 (1:1), FeSO 4 + CaCO 3 (2:1), and FeSO 4 + CaSO 4 (1:1), treated before transplanting rice seedlings. The Mehlich3-extractable As and Pb concentration in soil were measured at 6 and 12 weeks after transplant (WAT) of rice seedlings, respectively. Means denoted by the same letter are not significantly different at the p < 0.05 level according to Fisher's least significant difference (LSD) test.