The root of the problem lies in physics. Oxygen diffuses through water roughly ten thousand times more slowly than through air, so the moment soil pores flood, oxygen supply to buried tissues effectively collapses. Plants therefore experience submergence along a continuum of oxygen status, from normoxia through hypoxia to complete anoxia, and these states can shift across both time and space within a single root system. Deprived of oxygen, mitochondria can no longer oxidize sugars efficiently, ATP production plummets, and cells fall back on fermentation, a far less productive route to energy. Flooding also rewrites soil chemistry. Waterlogged ground turns reduced, accumulating soluble iron, sulfides and organic acids that are toxic in their own right, while carbon dioxide and ethylene build up around submerged organs. The review stresses that this combination of energy starvation, chemical toxicity and oxidative stress upon re-exposure to air explains why even brief floods devastate yields, and why tolerance demands coordinated responses spanning morphology, anatomy, physiology and metabolism rather than any single fix.

Remarkably, plants possess a dedicated first responder for this crisis: the gaseous hormone ethylene. Because ethylene diffuses slowly in water, it becomes trapped inside flooded tissues, accumulating within hours and acting as an internal signal that the plant is underwater. This entrapment converts a passive physical consequence of submergence into an active developmental cue. Ethylene signaling sets in motion nearly every adaptive strategy catalogued in the review: it promotes aerenchyma formation, stimulates adventitious root growth, drives hyponastic leaf movement and shoot elongation, and modulates the translation of hypoxia-response proteins through components such as EIN2 and GCN2. Cited studies show that ethylene can even pre-adapt plants before oxygen actually falls, allowing seedlings to brace for hypoxia before it arrives. Reduced ethylene sensitivity helps tomato maintain photosynthetic capacity during flooding, while in trembling aspen the hormone enhances root water transport through aquaporins. Ethylene, the authors conclude, is less a symptom of stress than the master switch of flooding survival, coordinating when plants should endure and when they should reach for air.

Downstream of ethylene sits one of the most elegant oxygen-sensing systems in biology: the group VII ethylene response factors, or ERF-VIIs. These transcription factors function as hypoxia-triggered switches. In well-aerated cells, a quality-control process known as the N-end rule pathway marks ERF-VIIs for immediate destruction, so they never accumulate. When oxygen drops, degradation stops, the proteins persist, enter the nucleus and switch on a battery of survival genes, among them pyruvate decarboxylase and alcohol dehydrogenase, the enzymatic heart of fermentative metabolism. Rice has co-opted this system spectacularly: SUB1A, a member of the ERF-VII family, underpins the celebrated SUB1 submergence-tolerance trait, restraining elongation growth so that seedlings conserve carbohydrates until floodwater recedes. Recent work highlighted in the review adds further layers of control, including the calcium-dependent protein kinase CPK12, which moves into the nucleus and phosphorylates ERF-VIIs to sharpen hypoxia sensing, and RBOH-type NADPH oxidases that shape reactive oxygen signaling during low-oxygen stress. The authors compile ERF-VII knowledge across major crops, positioning these factors as prime targets for engineering broad-spectrum flood tolerance.

At the very start of the life cycle, flooding poses a distinct threat: a germinating seed submerged in a paddy must sprout with almost no oxygen. Rice, uniquely among cereals, has evolved anaerobic germination, pushing out a coleoptile that stretches toward the water surface powered solely by fermentative energy. The review details the genetic architecture behind this trait, including the AG1 and AG2 quantitative trait loci and the trehalose-6-phosphate phosphatase gene OsTPP7, which boosts tolerance by mobilizing starch reserves to fuel coleoptile elongation. Genome-wide association studies across diverse rice collections continue to uncover fresh loci, and epigenetic pathways have been tied to anaerobic seedling establishment. The payoffs are practical. Varieties that germinate underwater enable direct seeding of rice, a practice that saves labor and irrigation water while suppressing weeds, and interactions between the SUB1 and anaerobic germination loci shape how seedlings fare when established underwater. Carbohydrate management under alternating light and darkness, along with auxin’s contribution to germination tolerance, illustrates how finely tuned this earliest phase of flood resilience has become.

Survival underwater also demands architectural renovation, and the review devotes sustained attention to aerenchyma, the spongy networks of gas-filled space carved into roots and stems through programmed cell death of cortical cells. Formed by lysigenous or schizo-lysigenous mechanisms, aerenchyma lowers the resistance to oxygen diffusion and creates internal conduits that channel air from aerated shoots down to drowned roots. Its construction is orchestrated by ethylene, reactive oxygen species, nitric oxide and RBOH-derived signals, with cell-wall-remodeling enzymes executing the demolition. Complementing these internal channels, many species sprout adventitious roots from stem nodes; in deepwater rice, aquatic adventitious roots can even extract oxygen directly from floodwater, sustaining growth through prolonged submergence. A third anatomical weapon is the barrier to radial oxygen loss: suberized and lignified layers in the outer root cortex act as a fence that keeps precious oxygen from leaking back into the anoxic soil. Experiments show that even low concentrations of organic acids, or sulfides in the rhizosphere, can trigger this barrier in rice roots.

Underneath the morphology lies a metabolic emergency plan. With oxygen scarce, pyruvate is diverted from mitochondrial respiration into fermentation: pyruvate decarboxylase and alcohol dehydrogenase convert sugars to ethanol while regenerating the NAD+ needed to keep glycolysis running, and lactate dehydrogenase helps manage cytosolic acidification. Overexpressing the lactate dehydrogenase gene OsLdh7 in rice improves submergence tolerance by tuning anaerobic glycolysis, ethanolic fermentation and amino acid metabolism, while mutants defective in starch mobilization fail to induce hypoxia genes properly, underlining that carbohydrate supply is non-negotiable. The review also spotlights nitric oxide, whose behavior at low oxygen is paradoxical. Through the phytoglobin–nitric oxide cycle, plant hemoglobins scavenge the gas and help sustain ATP production under anoxia, while nitrite can serve as an alternative electron acceptor in mitochondria. Ethylene-mediated depletion of nitric oxide pre-adapts Arabidopsis to hypoxia, and the alternative oxidase links nitric oxide turnover to redox balance. Selenium seed priming, chemical priming and nanomaterial-delivered nitric oxide donors are emerging as experimental routes to bolster these defenses in the field.

For some plants the winning strategy is not endurance but escape. Submerged rosette plants such as Rumex palustris execute hyponastic growth, curving their leaves upward while petioles elongate rapidly through ethylene- and auxin-driven apoplastic acidification and expansin activity, lifting foliage back toward light and air. Deepwater rice performs the same logic at scale: internodes elongate dramatically in a snorkeling response, and hydrophobic leaf gas films, conferred by wax-synthesis genes such as LGF1, preserve a thin layer of air against the leaf surface that sustains gas exchange under water. Noninvasive imaging has revealed how partial-pressure gradients drive long-distance gas movement through aerenchyma from the leaf blade down to submerged organs. The review frames escape and quiescence as antithetical but complementary strategies: genotype and flood regime determine which is fitter, since quiescence conserves resources during short flash floods while escape suits prolonged, shallow inundation. Misreading the environment carries a cost, because traits tuned for one type of flooding can backfire badly under another.

Those nuances carry weighty consequences for agriculture. The SUB1 gene has been successfully introgressed into popular rice varieties such as Swarna, protecting millions of hectares from flash floods, yet the review highlights evidence that SUB1 introgression can aggravate susceptibility to stagnant, medium-depth flooding in certain genetic backgrounds, a reminder that tolerance traits must be matched to the hydrological reality of a given region. Breeders are responding by pyramiding multiple traits, combining submergence quiescence with the aeration traits needed for stagnant water, favorable root architecture and anaerobic germination to build layered resilience. Beyond marker-assisted selection, the review surveys an expanding toolkit: waterlogging priming that hardens wheat offspring to hypoxia, silicon application that fortifies rice against submergence, beneficial fungi that modulate ethylene metabolism in maize, and nitric oxide donors delivered through nanomaterials. Proteomic and transcriptomic studies across soybean, sweet potato, mulberry, banana, watermelon, grapevine and lotus are mapping conserved and species-specific flood responses, handing breeders a growing catalogue of candidate genes and regulatory networks for crops facing ever more erratic water regimes.

The authors close by charting where the field must go next. They call for integrated multi-omics studies connecting oxygen sensing to metabolism at fine anatomical resolution, better field phenotyping to bridge the gap between controlled hypoxia experiments and the mud and variability of real paddies, and deeper exploration of the crosstalk among ethylene, nitric oxide, reactive oxygen species and calcium signaling. Unresolved questions abound: how ERF-VII networks differ among crops, how phytoglobins and the alternative oxidase can be exploited to maintain energy under anoxia, and how flooding tolerance can be stacked with salinity and heat resilience, since floods rarely arrive alone. What the review makes unmistakably clear is that flooding tolerance is not a single trait but a symphony, an interplay of gas-diffusion physics, oxygen-sensing switches, remodeled anatomy, rerouted metabolism and calibrated growth, all conducted by ethylene. As extreme weather intensifies, translating that symphony into the genomes of staple crops may determine whether agriculture can keep pace with a changing climate and a growing world.

The need for such tools is becoming increasingly urgent. Atmospheric carbon dioxide concentrations have risen to roughly 420 parts per million, intensifying warming and contributing to shifts in precipitation, sea-level rise, ocean acidification and more frequent climate extremes. Agriculture is affected not only by heat and drought, but also by the spread of saline soils. Reduced rainfall, high evaporation, seawater intrusion and irrigation with poor-quality water can all cause salts to accumulate in farmland. Excess sodium and chloride interfere with water uptake, nutrient balance and cellular metabolism. At high concentrations, sodium can enter plant cells and disrupt enzyme activity, while chloride can become toxic in tissues. The combined effect is known as salinity stress: an initial water deficit caused by the soil’s low water potential, followed by ion toxicity and oxidative damage. At the same time, warmer temperatures can accelerate insect development, alter pest ranges and strengthen resistance to conventional pesticides, while weeds adapt rapidly to changing conditions and continue competing with crops for water and nutrients.

Halophytes have evolved a remarkable collection of mechanisms to withstand these pressures. Some exclude salt at their roots, others sequester ions in specialized tissues or salt glands, and many accumulate compatible solutes—small molecules such as sugars, amino acids and polyols that help cells retain water without disrupting biochemical reactions. Their physiology is also shaped by constant exposure to oxidative stress. Salinity, heat and intense sunlight can cause excessive production of reactive oxygen species, chemically reactive molecules that damage membranes, proteins and DNA. In response, halophytes often produce large quantities of antioxidant compounds and defensive secondary metabolites. The review highlights phenolic acids, flavonoids, alkaloids, tannins, saponins and volatile terpenoids as particularly promising. These compounds are not simply passive by-products of survival; they can act as chemical defenses against herbivores and pathogens, and may be extracted for use in crop production.

Essential oils from halophytes are among the most striking examples. In one study discussed in the review, oil distilled from the aerial parts of Lobularia maritima caused high mortality in the cowpea beetle Callosobruchus maculatus, with a reported LC50 of 7.48 microliters per liter of air. The same oil had moderate effects on the red flour beetle and rice weevil. Chemical analysis found that the oil was dominated by azeleonitrile, trans-3-pentenenitrile and 4-isothiocyanato-1-butene. The trans-3-pentenenitrile component acted as a fumigant respiratory toxin, disrupting cellular respiration in exposed insects. Other halophyte extracts have shown antifeedant, repellent or growth-inhibiting effects against stored-grain pests. Extracts from Halocnemum strobilaceum, for example, produced complete mortality in red flour beetles at a high experimental dose and inhibited acetylcholinesterase, the enzyme responsible for breaking down the neurotransmitter acetylcholine. When that enzyme is blocked, acetylcholine accumulates at synapses, causing uncontrolled muscle activity, paralysis and eventually death.

The chemistry of these plant oils may also make resistance more difficult for pests to evolve. Many synthetic insecticides are designed around a single molecular target, allowing insects with a protective mutation or enhanced detoxification system to survive and reproduce. Terpenoids, by contrast, can attack several physiological systems simultaneously. They may alter insect behavior by interacting with octopamine receptors, disrupt development by mimicking or blocking juvenile hormones, and interfere with molting pathways linked to ecdysone. Because terpenoids are highly lipophilic, they can also insert into cell membranes, disturbing their structure and causing the leakage of ions. Some inhibit cytochrome P450 enzymes, which insects use to metabolize and neutralize toxic substances. The resulting combination of neurotoxicity, endocrine disruption, membrane damage and impaired detoxification is sometimes described as a multi-target mode of action. That complexity could slow resistance, although the review emphasizes that the evidence remains uneven and that field performance cannot be inferred from laboratory mortality alone.

Halophyte chemistry may be useful against weeds as well as insects. The review describes experiments in which extracts from Inula crithmoides caused complete mortality in Peganum species and substantial mortality in thistle when applied at high concentrations. Research on the facultative halophyte Cynara cardunculus, or cardoon, has provided more detailed clues about how plant-derived herbicides might work. Extracts rich in flavonoids such as myricitrin and naringenin induced severe oxidative stress in treated seedlings. Phenolic compounds can associate with cell membranes and promote the formation of phenoxyl radicals, disturbing the balance of cellular redox reactions. In chloroplasts and mitochondria, the resulting surge of reactive oxygen species can trigger lipid peroxidation, a chain reaction that degrades membrane lipids. Rising levels of malondialdehyde, a marker of lipid damage, are followed by electrolyte leakage, chlorosis and necrosis. Other cardoon compounds, including p-coumaric acid, syringic acid, quercetin and several sesquiterpene lactones, have been linked to blocked germination and suppressed growth in weeds such as Phalaris minor, Silybum marianum and Echinochloa crus-galli.

The review’s second major theme is resilience: halophyte-derived substances may help ordinary crops withstand salty conditions. Plant biostimulants are materials or microorganisms that activate natural processes involved in nutrient uptake, growth and stress tolerance rather than supplying nutrients in the same way as conventional fertilizers. Extracts made from halophytes and marine plants can contain minerals, vitamins, amino acids, oligosaccharides and hormone-like compounds. In soybean experiments, foliar application of Arthrocnemum macrostachyum extract improved growth and survival under 75 and 150 millimolar sodium chloride treatments, while treated plants retained higher levels of soluble sugars, proteins and photosynthetic pigments. Seagrass extracts produced different results depending on how they were delivered to okra: foliar sprays favored flowering and pod formation, whereas soil drenches improved pod weight and length. In tomato, liquid extract from the seagrass Zostera marina increased the activity of antioxidant enzymes including superoxide dismutase, catalase and ascorbate peroxidase. These enzymes convert damaging reactive oxygen species into less harmful molecules, helping cells maintain metabolic function during salt exposure.

The roots of halophytes offer another resource: microbial communities already adapted to difficult environments. Their rhizospheres can harbor bacteria, fungi and actinomycetes that tolerate high salt while producing substances beneficial to plants. Some synthesize indole-3-acetic acid, a plant hormone that promotes root growth; others release siderophores that capture iron, solubilize phosphate or improve soil structure. In experiments summarized by the authors, microorganisms isolated from Suaeda salsa increased maize resistance to salt stress and boosted antioxidant and soil-enzyme activity. A consortium of Bacillus zhangzhouensis and Pseudarthrobacter oxydans isolated from halophytes improved the performance of Swiss chard in soil containing 85 millimolar sodium chloride. Bacteria from Distichlis spicata promoted growth in watermelon, cucumber and Arabidopsis. Halotolerant actinobacteria from Limonium sinense also helped tomato seedlings cope with salinity while showing antifungal potential. In some cases, cell-free fungal filtrates—not living organisms—stimulated tobacco biomass, suggesting that purified microbial metabolites could offer more predictable products than live inoculants.

Yet “natural” does not automatically mean harmless, and the review warns against assuming that botanical pesticides are environmentally risk-free. Essential oils often break down rapidly under ultraviolet radiation and heat, reducing their long-term persistence compared with some synthetic chemicals. That apparent advantage creates a persistence paradox: concentrated exposure can be intense immediately after application even if the compound disappears quickly. Rain, wind, soil adsorption and temperature fluctuations can also reduce effectiveness in the field, producing a gap between promising laboratory results and reliable agricultural control. Encapsulation, nanoemulsions and other controlled-release systems may protect volatile compounds and extend their activity; experiments with encapsulated sea-fennel oil, for example, produced toxicity against cotton leafworm larvae and pupae while reducing insect fecundity and longevity. But improved stability can change exposure patterns. Certain terpenoids, including menthol and thymol, can harm honey bees at elevated concentrations, and nanoformulations may alter the behavior of predatory mites. Repeated application of antimicrobial oils could also temporarily suppress beneficial soil bacteria and fungi involved in nutrient cycling.

The authors therefore present halophyte-based agriculture as a promising but unfinished technology rather than an immediate replacement for synthetic chemicals. They call for multi-location field trials, standardized extraction and formulation methods, precise molecular characterization of active compounds, and long-term monitoring of pollinators, soil microbiota and other non-target organisms. Production must also be scalable: harvesting wild halophytes could damage fragile coastal or desert ecosystems, while domestication and cultivation would need to avoid creating new pressures on water and land. A circular model could eventually link saline agriculture with biorefineries, using halophytes grown on marginal land to produce oils, extracts, feedstocks and microbial products without competing directly with food crops. If the biological activity observed in controlled experiments can be translated into safe, consistent field applications, plants that evolved to survive the planet’s most hostile soils may help agriculture do the same. The review’s central message is that climate resilience may depend not on a single miracle compound, but on combining plant chemistry, beneficial microbes and ecological caution into a more adaptive farming system.