Plants may be quietly rewriting the rules of fertilizer use. A new review argues that nitrate—the dominant form of nitrogen applied to many crops—is not merely a raw material for making proteins, chlorophyll and DNA. It is also a chemical signal that helps plants decide where to grow, how aggressively to forage for nutrients, when to expand their leaves and how long to keep photosynthesizing. At the center of this decision-making system are cytokinins, a class of plant hormones that connect the nitrogen status of roots with the growth and productivity of shoots. The review, published in Plant and Soil, brings together decades of molecular, physiological and agronomic research to show how the nitrate–cytokinin partnership could become a target for improving nitrogen-use efficiency while reducing fertilizer waste and environmental damage.

Nitrogen is one of the most powerful levers in modern agriculture. When supplies are inadequate, crops often produce less biomass, fewer seeds and smaller grains. Yet applying more nitrogen is not a simple solution. Crops commonly absorb only a fraction of the fertilizer supplied to fields; the remainder can leach into waterways, escape as nitrous oxide or undergo chemical transformations that contribute to air and climate pollution. Farmers therefore face a biological paradox: plants need enough nitrogen to build a productive canopy, but excessive applications are expensive and can damage ecosystems. Nitrogen-use efficiency, or NUE, describes how effectively a plant converts available nitrogen into harvestable yield. According to the review by Dmitry Veselov, Jiangzhe Zhao, Alla Korobova and colleagues, improving NUE will require understanding not just how nitrate enters roots, but how plants interpret its presence and coordinate their entire body in response.

The first step is nitrate perception. Plant roots use transporter proteins to acquire nitrate from soil, but some of these transporters also act as “transceptors”—molecules that combine transport activity with sensory functions. One of the best studied is NRT1.1, also known as CHL1 or NPF6.3 in Arabidopsis. Its activity changes with nitrate concentration, allowing roots to respond across a broad range of nutrient availability. At low nitrate levels, high-affinity NRT2 transporters help capture scarce ions; at higher concentrations, other transport systems become more important. NRT1.1 can also influence the distribution of auxin, another plant hormone, thereby altering the formation and elongation of lateral roots. This allows a plant to proliferate roots in nutrient-rich patches rather than spending the same amount of energy everywhere. Once nitrate is detected, calcium signals, protein phosphorylation and transcription factors such as NLP6 and NLP7 help activate a rapid nitrogen-response program.

Cytokinins add a second layer of control to this nutrient-sensing network. These hormones are produced in roots and shoots, and their concentration depends on a balance between biosynthesis, transport and breakdown. Nitrate availability can stimulate the expression of isopentenyl transferase, or IPT, enzymes involved in cytokinin production. In particular, nitrate-responsive changes in root IPT activity can increase the synthesis of cytokinin precursors, including forms that are converted into trans-zeatin, a biologically active cytokinin. Other enzymes, including cytokinin oxidases and dehydrogenases known as CKXs, remove or deactivate the hormones. The result is a dynamic system rather than a simple on–off switch: a change in nitrate supply can alter cytokinin production, chemical form and movement through the plant. Recent evidence highlighted in the review suggests that fluctuations in nitrate may even influence IPT3 through changes in chromatin and histone modification, allowing roots to adjust hormone production as nutrient conditions shift.

The direction of cytokinin movement is crucial. Root-derived cytokinins can travel upward through the xylem, carrying information about soil conditions to leaves and growing shoots. Transporters such as ABCG14 and related proteins help load and move cytokinin compounds over long distances, while purine permeases and other transport systems contribute to local distribution and hormone homeostasis. The shoot is not simply a passive recipient of this chemical message. It also sends information back to the roots through sugars, nitrogen-containing metabolites and mobile peptides. CEP peptides produced in roots under nitrogen limitation can be processed into signals that travel upward and stimulate shoot-to-root messages, including CEPD-like proteins that regulate nitrate uptake. Cytokinins therefore participate in a two-way conversation: roots report the availability of nitrate, while shoots communicate their demand for additional nitrogen. This feedback prevents the plant from absorbing nutrients indiscriminately when its leaves cannot use them efficiently.

The most visible consequence of this communication appears below ground, where nitrate and cytokinin signals help reshape root architecture. When nitrate is scarce, plants may favor deeper or more extensive roots capable of exploring a larger volume of soil. In a localized nitrate-rich patch, they can stimulate lateral root growth near the nutrient source. Cytokinins interact with auxin in this process, often exerting opposing effects on root and shoot development. High cytokinin activity in some root zones can limit primary root elongation, while reduced cytokinin levels may permit a larger root system. This explains why genetically or chemically reducing cytokinin degradation in roots can produce plants with enhanced root growth, improved mineral accumulation in shoots and greater drought tolerance. The effect is context-dependent, however. A root that grows farther is not automatically more efficient; constructing and maintaining extra tissue requires carbon. The plant must balance the energetic cost of exploration against the expected benefit of finding and absorbing more nitrate.

Above ground, cytokinins help determine whether newly acquired nitrogen becomes productive leaf area or is diverted elsewhere. Adequate cytokinin signaling promotes cell division, leaf expansion and chloroplast development, the process by which cells build the photosynthetic machinery that captures light. In rice, wheat and other cereals, higher cytokinin status has been associated with increased photosynthetic capacity under favorable nitrogen conditions. This connection is chemically logical: nitrogen is required to build chlorophyll and many photosynthetic proteins, including Rubisco, the enzyme that fixes carbon dioxide. Cytokinins can also influence stomatal behavior, chlorophyll maintenance and the expression of genes involved in carbon assimilation. By coordinating nitrogen uptake with photosynthetic activity, the plant can convert absorbed nitrate into sugars more efficiently. Those sugars, in turn, provide energy and carbon skeletons for nitrate assimilation, creating a feedback loop between carbon and nitrogen metabolism.

The review also draws attention to cytokinin’s role in delaying leaf senescence, the orderly deterioration of leaves as plants age or face nutrient stress. During grain filling, cereal crops depend heavily on flag leaves to continue producing carbohydrates that are transported into developing seeds. Nitrogen availability and cytokinin signaling can help maintain these leaves for longer, preserving photosynthetic activity at a stage when grain weight is being determined. At the same time, cytokinin metabolism must be carefully controlled. Excessive or poorly timed signaling can disrupt the balance between vegetative growth and reproduction. Enzymes such as CKXs act as important regulators of this balance. Research in rice has shown that altering CKX activity can affect grain number, grain filling and the relationship between carbohydrate-producing leaves and developing grains. Some transport proteins may even carry both sugar and cytokinin, linking the movement of energy and growth signals directly within developing cereal grains.

Nitrogen and cytokinin signaling may also help crops cope with drought, salinity, heat and flooding—stresses that are becoming more consequential as climates change. Nitrate can influence stress-related gene expression, antioxidant defenses and the production of reactive oxygen species, molecules that serve as signals at controlled levels but can damage cells when they accumulate excessively. Cytokinins interact with abscisic acid, the hormone strongly associated with drought responses, as well as with ethylene and other signaling pathways. Under water deficit, changes in cytokinin production and transport can alter the balance between shoot growth and root investment, helping plants conserve resources while continuing to search for water. In some systems, stress-induced cytokinin synthesis has been linked to coordinated regulation of carbon and nitrogen assimilation. Nitrate nutrition has also been associated with improved tolerance to salinity and heat, although the benefits depend on dose, timing, species and environmental conditions. Too much nitrogen can intensify stress by stimulating growth that the plant cannot support with available water.

The authors emphasize that these findings do not justify simply adding hormones or more fertilizer to fields. Cytokinins are powerful regulators, and their effects vary with tissue, developmental stage, nitrate concentration and interactions with other hormones. Instead, the review points toward precision strategies that might match fertilizer placement and timing to the plant’s signaling capacity. Localized fertilizer application could encourage roots to forage in nutrient-rich zones without saturating the entire soil profile. Breeding or gene editing might target nitrate sensors, cytokinin transporters, IPT biosynthetic enzymes or CKX catabolic enzymes to create crops that maintain productivity with less nitrogen. Beneficial soil microbes that produce or modify cytokinins could provide another route, particularly under drought or nutrient stress, although field performance remains difficult to predict. The central message is that future high-efficiency crops may be designed not only to absorb more nitrate, but to make better decisions about when, where and why to use it. By treating nitrate as both food and information, agriculture could move closer to producing more grain with less fertilizer—and make the plant’s own communication network part of the solution.

Subject of Research: Interaction between nitrate signaling and cytokinin hormones in plant nitrogen-use efficiency, growth, stress resistance and crop productivity

Article Title: Interaction between nitrates and cytokinins in the regulation of nitrogen use efficiency, plant growth, abiotic stress resistance and productivity

Article References: Veselov, D., Zhao, J., Korobova, A. et al. “Interaction between nitrates and cytokinins in the regulation of nitrogen use efficiency, plant growth, abiotic stress resistance and productivity.” Plant and Soil (2026). Original research page

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09011-7

Keywords: nitrate uptake, nitrogen-use efficiency, cytokinin signaling, cytokinin transporters, root architecture, crop productivity, drought resistance, cereal grain filling

Tags: crop yield improvement through hormonal pathwayscytokinin hormone regulationenvironmental impact of nitrogen fertilizersfertilizer optimization strategiesNitrate signaling in plantsnitrogen leaching and pollution reductionnitrogen use efficiency in agricultureplant growth and developmentplant molecular and physiological responses to nitrogenplant nutrient sensing and decision-makingstress tolerance mechanisms in cropssustainable fertilization practices