Salinity is known to have a greater impact on shoot growth than root growth. Na⁺ buildup in plant tissue under salt stress has been proposed as one of the main issues that causes growth inhibition in crops via ionic imbalances, osmotic stress and pH disturbances. However, the evidence for apoplastic Na⁺ buildup and the role of silicon in Na⁺ accumulation at the subcellular level is still enigmatic. The current study focuses on the accumulation of Na⁺ in the apoplast and symplast of younger and older leaves of two maize varieties (Iqbal as salt-tolerant and Jalal as salt-sensitive) using hydroponic culture along with silicon supplementation under short-term salinity stress. Subcellular ion analysis indicated that silicon nutrition decreased Na⁺ concentration in both apoplastic washing fluid and symplastic fluid of maize under salt stress. The addition of silicon under NaCl treatment resulted in considerable improvement in fresh biomass, relative water content, chlorophyll content, and concentration of important subcellular ions (i.e., Ca²⁺, Mg²⁺, and K⁺). Knowledge of subcellular ion analysis is essential for solving the mechanisms underlying vital cellular functions e.g. in the current study, the soluble Na⁺ concentration in the apoplast of older leaves was found to be significantly greater (36.1 mM) in the salt-sensitive variety under NaCl treatment, which was 42.4% higher when compared to the Na⁺ concentration in the salt-tolerant variety under the same treatment which can influence permeability of cell membrane, signal transduction pathways and provides insights into how ion compartmentalization can contributes to salt tolerance. Calcium silicate enrichment can contribute to increased growth and improved ionic homeostasis by minimizing leaf electrolyte leakage, improving mechanical functions of cell wall and reducing water loss, and improved photosynthetic function. In current investigation, increased water content and intracellular ionic homeostasis along with reduced concentration of Na⁺ in the maize leaf apoplast suggest that calcium silicate can be used to ameliorate the adverse effects of salt stress and obtain yield using marginal saline lands.

The persistent nature of lead (Pb) and cadmium (Cd) in the environment severely affects plant growth and yield. Conversely, plants acquire zinc (Zn) from the soil for their vital physiological and biochemical functions. However, the interplay and coordination between essential and toxic metals for their uptake and translocation and the putative underlying epigenetic mechanisms have not yet been investigated in maize. Here, we report that the presence of Zn facilitates the accumulation and transport of Pb and Cd in the aerial parts of the maize plants. Moreover, the Zn, Pb, and Cd interplay specifically interferes with the uptake and translocation of other divalent metals, such as calcium and magnesium. Zn, Pb, and Cd, individually and in combinations, differentially regulate the expression of DNA methyltransferases, thus alter the DNA methylation levels at the promoter of Zinc-regulated transporters, Iron-regulated transporter-like Protein (ZIP) genes to regulate their expression. Furthermore, the expression of histone deacetylases (HDACs) varies greatly in response to individual and combined metals, and HDACs expression showed a negative correlation with ZIP transporters. Our study highlights the implication of DNA methylation and histone acetylation in regulating the metal stress tolerance dynamics through Zn transporters and warns against the excessive use of Zn fertilizers in metal contaminated soils.

Heavy metal like cadmium (Cd) is inessential and highly toxic and is posing serious environmental problems for agriculture worldwide. Presence of Cd gives rise to several physiological and structural disorders that leads to reduction in growth and performance of agricultural plants. Evidence related to subcellular distribution and accumulation of Cd is still enigmatic. Experiment was conducted using hydroponic culture to examine the subcellular accumulation of Cd in Spinacia oleracea L. leaves under Cd stress (50 μM and 100 μM); moreover, the Cd toxicity alleviation using 5 mM silicon (Si) was investigated. Our findings suggest that fresh and dry biomass, shoot and root length, leaf area and length of leaf declined when exposed to Cd stress (50 μM and 100 μM); however, an increase was noticed when Cd treated plants were supplied with Si (5 mM). The content of Ca²⁺, Mg²⁺ and Fe²⁺ in apoplastic washing fluid and symplasm were found to be lower in plants treated with alone Cd, when compared to control. Higher Cd²⁺:Ca²⁺, Cd²⁺:Fe²⁺ and Cd²⁺:Mg²⁺ ratios were detected under cadmium stress in both apoplast and symplast of leaves which were lowered by the addition of 5 mM Si. The novelty of the current study is the detection of increased apoplastic and symplastic Cd concentration in aerial part (i.e., spinach leaves) under alone Cd treatment which was considerably reduced when supplied with Si. Moreover, a noticeable increase in spinach growth and beneficial ionic concentrations suggest that Si can ameliorate the Cd stress in crop plants.

Salinity stress exerts a deleterious impact on crop growth, presenting a formidable challenge to sustainable agriculture, because of the prevalence of salt-affected arable land globally. The present investigation focused on mitigating the adverse effects of salinity on Triticum aestivum L. and employed integrated physical, chemical, and biological amendments, which were denoted as treatments T1 to T8. The findings unveiled higher pH, EC, and Na+ concentrations in the topsoil compared to the subsoil within the selected saline field. In comparison to the control treatment (T1), the combined application of gypsum, farmyard manure, and ridges (T8) demonstrated a significant enhancement in agronomic traits, chlorophyll contents, and total protein in wheat. Notably, T8 exhibited the lowest Na+ concentration and the highest levels of K+, Mg2+, Ca2+, and Mg2+ compared to all other treatments. Furthermore, the amalgamation of two reclamation approaches (T5, T6, and T7) surpassed single amendments (T2, T3, and T4) in terms of both agronomic traits and ionic analysis. Treatment T8 displayed the lowest phytochemical contents (i.e., antioxidant activity) in wheat, as indicated by total phenolic and flavonoid content, ferric and molybdate ion reduction, DPPH, and hydroxyl scavengers. These parameters exhibited a positive association in descending order, with 80.6%, 86.9%, 82.2%, 73%, 86%, and 84.5% in T1 and 71.4%, 81.2%, 73.4%, 68.1%, 79.3%, and 78.5% in T8, respectively. The observed alterations resulting from the combinations of amendments present promising targets, rendering them prospective in enabling wheat plants to successfully acclimatize to saline soil conditions.