Silicon is not classed as an essential element for most plants, yet for many crops it behaves like one. Plants take it up from the soil solution as monosilicic acid and deposit it in their tissues as amorphous silica, a process called silicification. That mineral armor strengthens stems, helps plants resist fungal pathogens and chewing insects, and buffers against drought, salinity and metal toxicity. The world’s most widely grown cereals, including rice, wheat, barley, maize and sugarcane, typically store more than 10 grams of silicon per kilogram of dry tissue, which is why silicon fertilizers are now applied in agroecosystems worldwide. But those fertilizers depend on finite mineral reserves, and they are often scarce or inaccessible in tropical regions, precisely where soils tend to be poorest in plant-available silicon.

The problem, the researchers note, is that most soil silicon is locked away. It sits inside primary and secondary silicate minerals, sorbed onto iron oxides, or embedded in weathering-resistant phases such as quartz, rather than floating free in the soil solution as monosilicic acid. Whether a crop can actually access silicon therefore depends on the rate at which these poorly available pools are dissolved. Laboratory work has long shown that low-molecular-weight organic anions, especially carboxylates such as citrate, oxalate and malate, accelerate the dissolution of silicate minerals. In one classic experiment, quartz dissolved roughly ten times faster in a citrate solution than in pure water. Recent theoretical work has proposed that root-released carboxylates might similarly unlock soil silicon in the field, raising an intriguing agricultural possibility: could a carboxylate-pumping legume feed silicon to a high-silicon cereal growing next to it?

Chickpea was an obvious candidate. Previous research on 20 chickpea accessions had documented large variation in how much carboxylate these plants release into their rhizosheath, the tight sleeve of soil that clings to living roots. The new study exploited that natural diversity. In a controlled glasshouse experiment at the University of Western Australia, wheat was grown either as two individuals per pot or paired with one of the 20 chickpea accessions, using a silicon-poor, iron-oxide-rich quartz sand representative of more than two-thirds of Western Australia’s cropping soils. After two months, the team measured wheat biomass, leaf and stem silicon concentrations using portable X-ray fluorescence, rhizosheath carboxylate amounts by high-performance liquid chromatography, and foliar manganese, which serves as an established proxy for carboxylate release, since manganese uptake in plants is poorly regulated and strongly tracks rhizosphere availability.

The results were striking. Wheat grown with chickpea produced more leaf, stem, root and total aboveground biomass than wheat grown with another wheat plant, and it also carried higher silicon concentrations in its leaves and a far greater total silicon content aboveground. Crucially, a follow-up experiment ruled out the simplest alternative explanation, competition. Wheat grown entirely alone in a pot still had lower leaf and stem silicon concentrations, and lower total silicon content, than wheat paired with chickpea, showing that the cereal genuinely benefited from its neighbor rather than merely suffering less competition for a limited resource. Tellingly, when pots were fertilized with abundant silicon, the chickpea advantage disappeared, suggesting that facilitation matters most exactly where silicon availability is limiting.

The rhizosphere data lent cautious support to the carboxylate hypothesis. Pots containing wheat and chickpea held significantly more rhizosheath carboxylates per unit of root dry weight than pots with two wheat plants, and accessions previously classified as high carboxylate releasers produced more carboxylates than low releasers. Wheat leaf silicon concentration was marginally correlated with rhizosheath carboxylate amounts, and wheat aboveground silicon content was positively, if weakly, associated with chickpea foliar manganese. Yet the mechanistic picture remained incomplete. Wheat leaf silicon showed no clear relationship with chickpea foliar manganese, a stronger proxy for carboxylate exudation, and within wheat itself, leaf silicon tracked leaf manganese, hinting that silicon and manganese may be mobilized by overlapping rhizosphere processes rather than by chickpea exudates alone.

The authors are candid about these limitations. Extracting and quantifying root exudates from an intertwined root system shared by two species is notoriously difficult; carboxylates are rapidly degraded by microbes or sorbed onto mineral surfaces between release and measurement, so the harvested pool may capture only a snapshot of a dynamic process. Other unmeasured exudates, notably the phytosiderophores that grasses themselves release, could also mobilize silicon, as has been shown for iron-deficient barley drawing silicon and iron from clay minerals. Shifts in rhizosphere pH, altered competition for manganese, or even physiological and gene-expression responses triggered simply by having a legume neighbor could all contribute. The correlation evidence, in other words, suggests carboxylates play a part, but the researchers emphasize that further studies are needed to confirm the mechanism and weigh it against alternatives.

The study delivered a second, unexpected discovery: chickpea itself varies enormously in silicon. Foliar silicon concentrations differed significantly among the 20 accessions, and, counterintuitively, the low-carboxylate group accumulated more silicon in their leaves than the high-carboxylate releasers. A principal component analysis revealed that high-silicon chickpeas formed a distinct syndrome: they were smaller, more branched, invested proportionally more biomass in roots, and exuded fewer carboxylates. The authors suggest a dilution effect may partly explain the pattern, since fast-growing accessions produce biomass faster than they take up silicon, effectively lowering concentration. The finding confirms that silicification varies not only within cereals like rice and wheat but also within a major legume crop, an area largely ignored because silicon research has traditionally centered on grasses, even though mounting evidence shows silicon also benefits legumes, potentially by alleviating metal toxicity and salinity and by promoting root nodulation in the rhizobia symbiosis.

For agriculture, the implications are tantalizing. If the facilitation observed in pots holds under field conditions, wheat-chickpea intercropping, a practice already common in many dryland farming systems, could enhance crop silicification without any added fertilizer, improving resistance to pests, diseases, drought and salinity while potentially lifting yields. The variation among chickpea accessions in their capacity to boost wheat silicon uptake suggests a breeding angle as well: lines that are especially good silicon facilitators could become targets for selection in silicon-limited regions. The authors also flag follow-up questions, including whether silicon supply alters wheat root architecture and water relations under drought, whether other carboxylate-releasing legumes such as soybean show similar facilitative effects, and how the broader community of rhizosphere organisms shapes silicon mobility. Field trials will be the decisive test, since soil chemistry and biology in the open ground differ substantially from controlled pot conditions. For now, the study adds a compelling chapter to a growing recognition that the microscopic traffic of organic molecules around roots, and the quiet cooperation between neighboring crops, can move elements once thought immovable.

Subject of Research: Legume-cereal intercropping and rhizosphere-mediated silicon mobilization in crops

Article Title: Chickpea enhances silicon accumulation in neighboring wheat: a role for rhizosheath carboxylates?

Article References: de Tombeur, F., Yan, L., Tang, D., Plouzeau, L., Gille, C. E., Thorne, S., Lambers, H., Violle, C., Hartley, S., & Pang, J. (2026). Chickpea enhances silicon accumulation in neighboring wheat: a role for rhizosheath carboxylates?. Plant and Soil. https://doi.org/10.1007/s11104-026-09070-w

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09070-w

Keywords: chickpea, wheat, silicon, silicification, rhizosheath carboxylates, intercropping, rhizosphere, root exudates, plant facilitation, soil chemistry, crop stress resilience, Plant and Soil

The scale of the problem the authors document is stark. Drought alone cuts rice yields by as much as 50 percent, soybean by 42 percent, maize by 40 percent, wheat by 21 percent, and chickpea by 27 to 40 percent. Soil salinity, which already degrades roughly 20 percent of the world’s irrigated farmland, inflicts comparable losses, and the authors cite projections that 30 to 50 percent of cultivated land could be lost to salinization by 2050. Temperature extremes and heavy metal contamination compound the damage by generating oxidative stress, disrupting nutrient uptake, and destabilizing cellular homeostasis. Because these stresses frequently strike crops simultaneously and repeatedly, their combined effect on food security is greater than the sum of their individual impacts—a reality that the authors argue demands a fundamentally more sophisticated toolkit than conventional breeding alone can provide.

At the heart of the review is the argument that no single layer of biological information is sufficient to understand how plants perceive and survive stress. The authors advocate for what they call “panomics”—the integration of genomics, transcriptomics, proteomics, metabolomics, epigenomics, ionomics, and phenomics into unified analytical frameworks. Plants respond to drought, salt, cold, heat, and toxic metals by activating elaborate regulatory networks: transcription factors of the MYB, MYC, NAC, bZIP/AREB, DREB, and HD-ZIP families bind to cis-regulatory elements such as ABRE and DRE/CRT in the promoters of target genes, while signaling cascades involving abscisic acid (ABA)-dependent and ABA-independent pathways, reactive oxygen species (ROS), and a suite of hormones coordinate adaptive physiological responses. By layering omics data across these levels, researchers can identify the key molecular operators—the genes, proteins, and metabolites—that actually determine whether a plant survives a stress event.

The review details how this approach has already paid dividends in dissecting drought responses. When water becomes scarce, plants close their stomata to conserve moisture, which curtails CO2 absorption and photosynthesis; water deficit also disrupts xylem and phloem function, disturbing nitrogen and phosphorus homeostasis. Against this backdrop, genomic studies have pinpointed genes whose manipulation enhances tolerance. In soybean, overexpression of the AtP5R gene, which drives proline biosynthesis, improves drought tolerance; in rice, elevated expression of the AtEDT1/HDG11 gene boosts water-use efficiency. Genes governing osmoprotectants matter enormously: bacterial BADH and choline oxidase genes enable the accumulation of glycine betaine, which—alongside zinc and salicylic acid—has been shown to improve drought tolerance and yield in maize, while mannitol biosynthesis genes confer dual protection against salinity and drought in wheat. Overexpression of the cytokinin oxidase genes CKX1 through CKX4 reduces cytokinin levels and increases drought resilience, a finding that foreshadows the review’s most striking example of applied genome editing.

Proteomics complements these genetic insights by revealing which proteins actually accumulate under stress. Techniques such as two-dimensional gel electrophoresis, LC-MS/MS, and DIGE have catalogued drought-responsive proteins including actin, which repairs stress-damaged membranes by densifying actin filaments, along with S-adenosyl methionine synthesis enzymes, homocysteine methyltransferase, aminoacylase-1, and cysteine synthase in chickpea. Comparative proteomics has identified protective proteins such as lactoyl glutathione lyase, p23, and Kunitz proteinase inhibitors in chickpea and rice, while pearl millet shows upregulation of aminomethyltransferase, a photorespiration enzyme implicated in drought management. Notably, levels of the molecular chaperones HSP70 and HSP90 decline under drought in several crops, and chlorophyll a, chlorophyll b, and carotenoid concentrations drop significantly—molecular signatures of the photosynthetic damage that ultimately drives yield loss.

Temperature stress receives equally detailed treatment. The authors trace the canonical cold-response pathway in Arabidopsis, where the DREB1/CBF transcription factor family—comprising DREB1A/CBF3, DREB1B/CBF1, and DREB1C/CBF2—activates genes bearing the 9-base-pair dehydration-responsive element (DRE), including the protective RD29A/COR78/LTI78 locus. Plants distinguish rapid from gradual temperature drops: calmodulin-binding transcription activators (CAMTAs) mount strong induction of DREB1B and DREB1C when temperatures plummet suddenly. On the heat side, the DREB2A protein is regulated through targeted degradation pathways, with CASEIN KINASE 1 anchoring and activating DREB2A by preventing phosphorylation within its negative regulatory domain. Proteomic surveys reveal the chaperone mobilization that follows: within 12 to 24 hours of heat exposure, dozens of proteins accumulate, including Cpn60, HSP70, HSP100, small HSPs, and the DnaK-type chaperone BiP, alongside antioxidant enzymes such as glutathione-S-transferase, dehydroascorbate reductase, and superoxide dismutase. Cold acclimation studies across Arabidopsis, rice anthers, pea mitochondria, and soybean have catalogued dozens of cold-responsive proteins involved in ROS scavenging, protein folding, energy storage, and the production of antifreeze proteins, which crops like wheat accumulate in the apoplast.

Salinity responses are dissected through the lens of ion homeostasis, with the SOS (Salt Overly Sensitive) transcriptional gene family identified as among the most powerful drivers of salt tolerance by regulating the balance of sodium and potassium ions. In Arabidopsis, the AtWRKY8 gene is frequently induced by salt stress and directly binds the RD29A promoter. In rice, the salt-responsive transcription factor SERF1 shows root-specific activation following treatment with salt and hydrogen peroxide, while the receptor-like kinase gene OsRMC negatively regulates salt-stress responses. Proteomic analyses across 34 plant species have identified 2,171 salt-responsive proteins, and work on the halophyte Bruguiera gymnorrhiza revealed 23 salt-responsive proteins tied to photosynthesis, cell organization, and protein folding—explaining how this mangrove survives conditions that kill conventional crops. Four salt-induced late embryogenesis abundant (LEA) proteins in rice, and the successful transfer of the barley HVA1 LEA gene into rice, illustrate how these discoveries translate into engineering strategies. Heavy metal stress, the authors note, is being tackled similarly: 46 heavy-metal-associated proteins have been catalogued in rice and 55 in Arabidopsis, with two cysteine residues on these proteins mediating metal binding, transport, and detoxification, and the HMA transporter family playing a central role in metal absorption, translocation, and sequestration.

The review’s most consequential section examines how CRISPR/Cas9 editing is converting this mechanistic knowledge into actual crops. In wheat, protoplast-based CRISPR/Cas9 systems have been used to target the stress-responsive transcription factor genes TaERF3 and TaDREB2. In rice, knockout of OsAnn3 and OsAnn5—annexin genes involved in stress signaling—produced mutants with altered cold tolerance, with OsAnn5’s promoter bearing MYB recognition sites and dehydration-responsive elements that suggest multi-transcription-factor control. The authors highlight off-target effects as a persistent concern, along with inefficiencies in particle bombardment and Agrobacterium-mediated transformation that result in random transgene insertion; newer delivery methods such as electroporation and ribonucleoprotein (RNP) delivery promise more precise distribution of editing components. They also flag pleiotropic trade-offs, in which enhanced stress tolerance comes at the cost of growth or yield, and stress that genotype-by-environment interactions mean controlled-condition results must be validated across multiple locations and seasons before varieties reach farmers.

The proof of concept, the authors argue, is already growing in Indian fields. DRR Dhan 100 (Kamala), a genome-edited rice variety released in India, carries a novel allele of the cytokinin oxidase gene OsCKX2 created by CRISPR/Cas9; the edit reduces cytokinin degradation in reproductive tissues, promoting tillering, grain number, and earlier maturity while sustaining performance under drought and low-input conditions. Pusa Rice DST1, by contrast, knocks out DST, a negative regulator of stress responses, yielding reduced stomatal density and transpiration, improved water-use efficiency, enhanced tillering, and better ion homeostasis under salt stress. These edited varieties are complemented by marker-assisted lines such as CR Dhan 416 and CR Dhan 801, which stack quantitative trait loci including qSaltol, Sub1A, the qDTY drought-tolerance series, and Xa/Pi resistance genes—integrating osmotic adjustment, ion exclusion, submergence survival, and pathogen immunity into elite backgrounds without yield penalty. Analogous CRISPR-guided work on ethylene, ABA, and heat-shock pathways in wheat, maize, and soybean—targeting genes such as ARGOS8, ZmHDT103, and GmHsp90A2—has produced lines that maintain or increase yields under combined drought and heat.

Looking forward, the authors call for the fusion of multi-omics data with artificial intelligence-driven analytics, phenomics, and single-cell genomics, which together would allow cell-type-specific stress responses to be resolved and complex datasets to be integrated at scale. They also stress the governance side of the genome-editing revolution: national and international databases of genome-edited sequences would ensure transparency and traceability, support regulators and policymakers with reliable molecular information, and smooth compliance with international trade rules—critical steps in a world where regulatory frameworks for edited crops vary dramatically between nations and remain a significant barrier to adoption. If these scientific and institutional pieces align, the review concludes, the convergence of omics-informed mechanistic understanding and precise genome editing offers a genuinely robust framework for developing the next generation of cultivars: crops that are not only higher-yielding but inherently equipped to withstand the multifaceted stresses of a rapidly changing climate.