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Review

Advances in Nitrogen Uptake Preference and Physiological and Ecological Mechanisms in Mulberry

by
Fang Zhang
,
Shiqing Peng
,
Biao Chen
,
Yanjin Shi
,
Xiaohong Wang
and
Dan Xing
*
Institute of Sericulture, Guizhou Academy of Agricultural Sciences, Guiyang 550009, China
*
Author to whom correspondence should be addressed.
Nitrogen 2026, 7(1), 33; https://doi.org/10.3390/nitrogen7010033
Submission received: 20 January 2026 / Revised: 15 March 2026 / Accepted: 19 March 2026 / Published: 23 March 2026
(This article belongs to the Special Issue Nitrogen Metabolism and Degradation)
Versions Notes

Abstract

Mulberry (Morus alba L.) is a woody plant primarily cultivated for silkworm breeding, with significant economic and ecological functions. Its nitrogen use efficiency directly affects leaf yield, quality, and environmental adaptability. The main inorganic nitrogen forms available for plant uptake in soil are ammonium nitrogen and nitrate nitrogen, and plant uptake and assimilation of these two nitrogen sources often exhibit species-specific preferences. This review systematically summarizes the research progress on nitrogen uptake preferences in mulberry, confirming that this species generally shows a preferential uptake of nitrate. Specifically, when supplied with nitrate or a mixed nitrogen source dominated by nitrate, mulberry exhibits better performance in growth and development, photosynthetic efficiency, and accumulation of secondary metabolites. This review further discusses the physiological characteristics and underlying regulatory mechanisms responsible for this preference, and analyzes key factors affecting nitrogen uptake preferences, including soil properties, environmental stresses, and microbial interactions. It should be noted that while controlled experiments have yielded important insights, the applicability of these findings under complex field conditions still requires further validation through field trials. Finally, future research directions are prospected, including in-depth dissection of molecular mechanisms, field validation, plant-microbe interactions, and nutritional strategies for stress resistance, aiming to provide a theoretical basis for efficient cultivation and precise nitrogen management of mulberry.

1. Introduction

Mulberry (Morus alba L.) is an economically significant tree species in China. Its leaves serve as the exclusive food source for silkworms (Bombyx mori) and represent a promising high-protein feed resource for cattle, sheep and other livestock [1]. Moreover, mulberry has broad application prospects in ecological restoration, soil and water conservation, and the development of medicinal compounds [1]. Nitrogen is an essential mineral element for plant growth and development. It is directly involved in the synthesis of key biomolecules such as proteins, nucleic acids, and chlorophyll, thereby exerting a profound influence on photosynthesis, carbon–nitrogen metabolism, and ultimately, crop yield and quality [2].
In the soil–plant system, nitrogen exists in various forms. Among these, ammonium nitrogen and nitrate nitrogen are the primary inorganic nitrogen sources absorbed by plant roots [3]. Plant species often exhibit distinct preferences for these nitrogen forms, shaped by their genetic background, root architecture, and long-term adaptation to growth environments. Such preferences represent an integral component of nutrient acquisition strategies evolved over time [4].
Therefore, a precise understanding of mulberry’s nitrogen uptake preference is of critical importance. It provides essential theoretical insights into optimizing cultivation and fertilization practices, as well as practical guidance for their implementation. This knowledge is fundamental for enhancing nitrogen use efficiency, mitigating the risks of agricultural non-point source pollution, and ultimately achieving the dual goals of high yield and superior quality in mulberry leaf production. For instance, regulating the form and ratio of nitrogen fertilizer can optimize mulberry growth and development to meet its nitrogen demands. Furthermore, such targeted regulation holds the potential to steer the biosynthesis and accumulation of key medicinal compounds, such as 1-deoxynojirimycin (DNJ) [5]. Plant preference for nitrogen form is not fixed but is modulated by multiple factors, including soil properties, environmental stresses, and root–microbe interactions [6,7,8]. Consequently, studying the nitrogen absorption preference of mulberry must be considered within a broader ecosystem context encompassing the soil microenvironment, plant physiological dynamics, and microbial community interactions.
This review synthesizes current research on the nitrogen uptake preference of mulberry from physiological and agronomic perspectives, supplemented by ecological considerations. It aims to elucidate the underlying physiological mechanisms, compare the strategies employed by mulberry with those of other plant species, and propose future research directions. This work seeks to advance fundamental research on mulberry nitrogen nutrition and support the development of precise applications.

2. Physiological Responses and Growth Performance of Mulberry to Different Nitrogen Forms

As a core mineral element regulating growth and development, photosynthetic physiology, biomass accumulation, and nutrient use efficiency, nitrogen is a vital component of chlorophyll, proteins, nucleic acids, and various enzymes in plants [9]. In soil, the primary inorganic nitrogen forms available to plants are nitrate (NO3−) and ammonium (NH4+), which differ markedly in their uptake, transport, assimilation, signaling roles, and physiological effects (Table 1). These differences profoundly influence morphogenesis, biomass allocation, photosynthetic efficiency, and photosystem stability in mulberry [10]. Elucidating the regulatory mechanisms of different nitrogen forms on mulberry growth and physiological function can provide a crucial theoretical foundation for high-quality and high-efficiency cultivation, rational nitrogen resource allocation, and improved nutrient use efficiency.

2.1. Growth and Biomass Accumulation

Significant differences have been observed in the responses of mulberry to different nitrogen forms. Using the forage mulberry cultivar ‘Qinglong’ (Morus alba cv. ‘Qinglong’) as material, research found that under equal nitrogen supply, plant height, leaf number, leaf area, and root length were lower under sole nitrate or sole ammonium treatments compared to combined ammonium and nitrate applications. The highest seedling growth and biomass accumulation were achieved at NH4+:NO3− molar ratios of 50:50 and 25:75, indicating that forage mulberry prefers nitrate as a nitrogen source [10,11]. Under alkaline salt (Na2CO3) stress, increasing the proportion of NO3− significantly alleviated salt damage and promoted aboveground and root biomass accumulation in mulberry seedlings [12].
Therefore, the preference of mulberry for mixed nitrogen sources may stem from its intrinsic physiological and metabolic requirements. Nitrate uptake is typically accompanied by the efflux of anions (e.g., OH− or HCO3−) or the accumulation of organic acids, which helps maintain cellular pH homeostasis. In contrast, ammonium uptake is associated with H+ efflux, which can lead to rhizosphere acidification. While moderate acidification may promote root elongation and cation uptake, sole and high-concentration ammonium supply can induce ammonium toxicity, resulting in inhibited root growth and reactive oxygen species (ROS) accumulation [13,14,15]. This partially explains the poor growth performance of mulberry under sole ammonium treatments. Although mulberry can utilize both ammonium and nitrate, growth and biomass accumulation are maximized under mixed nitrogen supply, particularly when nitrate is the dominant form. This indicates a clear preference for nitrate-dominant conditions.

2.2. Photosynthetic Characteristics and Photosystem Function

Photosynthesis provides the material and energy foundation for plant growth, and nitrogen form profoundly influences photosynthetic performance in mulberry. Studies have shown that under an NH4+:NO3− ratio of 25:75, nitrate significantly enhances leaf net photosynthetic rate (Pn), stomatal conductance (Gs), and water use efficiency (WUE), thereby improving CO2 fixation and carbon assimilation capacity. In contrast, ammonium alone markedly inhibits stomatal opening and photosynthetic efficiency, leading to reduced photosynthetic capacity [10,11,16]. Numerous studies have reported that under ammonium treatment, mulberry seedlings exhibit significantly lower Pn, Gs, and transpiration rate (Tr), as well as reduced Fv/Fm, Fv/Fo, ΦPSII, ETR, and qP, compared to nitrate-treated plants. Conversely, the non-photochemical quenching coefficient (NPQ) is significantly higher under ammonium than under nitrate supply [11,14,15,16]. These findings indicate that ammonium treatment reduces PSII photochemical activity in mulberry leaves, leading to greater dissipation of excitation energy as ineffective heat [11,14,15,16]. Furthermore, Xu et al. demonstrated that under 50 mmol·L−1 Na2CO3 stress, increasing nitrate supply significantly enhanced photosynthetic electron supply and transfer capacity in mulberry leaves [17]. Nitrate also markedly promotes the synthesis of chlorophyll a, chlorophyll b, and total chlorophyll, thereby improving light energy capture and transfer efficiency. In contrast, ammonium inhibits chlorophyll synthesis and accelerates pigment degradation, ultimately reducing photosynthetic capacity [10,14].
The form of nitrogen directly affects PSII photochemical activity and electron transport. Ammonium nitrogen may impede electron transfer from QA to QB on the acceptor side of the PSII reaction center and weaken the activity of the oxygen-evolving complex (OEC). This disruption in electron transport on the PSII acceptor side can induce photoinhibition and damage to the photosystem [14,16,18]. These findings, from both photosynthetic physiology and photochemical perspectives, clearly explain why environments dominated by nitrate or with a higher proportion of nitrate are more favorable for maintaining efficient photosynthesis in mulberry.

2.3. Accumulation of Secondary Metabolites

Research progress on the effects of nitrogen forms on the accumulation of active ingredients in medicinal plants indicates that nitrogen form significantly influences the synthesis and accumulation of secondary metabolites by regulating carbon–nitrogen allocation, key enzyme activities, and defense responses [19,20,21].
Secondary metabolites in mulberry, including DNJ, total flavonoids, and phenolic acids, constitute the core material basis for its medicinal, health-promoting, and forage values [22,23]. DNJ, a representative piperidine alkaloid in mulberry, exhibits synthesis and accumulation patterns highly dependent on nitrogen form. Under equivalent nitrogen supply levels, DNJ content is significantly higher under nitrate treatment than under ammonium treatment. Moreover, an appropriate nitrate-to-ammonium ratio can further enhance DNJ accumulation in mulberry leaves, with the optimal ratio of 25:75 (NO3−:NH4+) observed under hydroponic conditions [5]. Through integrated metabolomic and transcriptomic analyses, Sugiyama et al. found that nitrate upregulates the expression of key genes involved in DNJ biosynthesis, promoting the conversion of precursor compounds and thereby increasing both DNJ content and hypoglycemic activity [9]. Research by He Ningjia’s team further revealed that nitrate induces the expression of the transcription factor HDG11, which in turn activates downstream factors such as ZFHD6, TCP14, and ATHB40. This cascade specifically upregulates the key DNJ synthesis gene MnGutB1, ultimately promoting DNJ accumulation [24].
Flavonoids (e.g., total flavonoids, morin) and phenolic acids (e.g., chlorogenic acid) are important antioxidant secondary metabolites in mulberry, and their accumulation exhibits a typical preference for ammonium nitrogen [25]. Soil application of Bacillus subtilis modulates nitrogen form and consequently influences flavonoid synthesis in mulberry leaves [26]. These findings underscore that N form is a critical environmental factor regulating secondary metabolite accumulation in mulberry. Elucidating the underlying mechanisms will provide a theoretical basis and technical support for optimizing N management and enabling targeted production of high-value secondary metabolites.
Table 1. Effects of different nitrogen forms on physiological responses and growth performance of mulberry.
Table 1. Effects of different nitrogen forms on physiological responses and growth performance of mulberry.
Tested VarietyNitrogen TreatmentDetermination IndicatorsMain ConclusionsReferences
MulberryNitrate nitrogen, ammonium nitrogen, nitrate ammonium mixturesPlant height, stem diameter, biomass, net photosynthetic rate, stomatal conductanceNitrate nitrogen significantly promoted mulberry growth and biomass accumulation. Photosynthetic performance was optimal at a nitrate-to-ammonium ratio of 25:75, indicating that mulberry exhibits a nitrate-preferring characteristic.[10,11,12,14]
MulberryNitrate nitrogen, ammonium nitrogen, nitrate ammonium mixturesChlorophyll fluorescence parameters (Fv/Fm, ΦPSII, ETR, NPQ, PSII functionNitrate nitrogen maintained photosystem stability and enhanced photochemical efficiency; ammonium nitrogen inhibited electron transfer and induced photoinhibition.[10,11,14,16,17]
MulberryNitrate nitrogen, ammonium nitrogenDNJ, total flavonoids, phenolic acidsNitrate nitrogen promoted DNJ accumulation, whereas ammonium nitrogen favored the biosynthesis of flavonoid and phenolic acid compounds.[5,24,25,26]
Taken together, these studies suggest that mulberry exhibits pronounced physiological and metabolic differentiation in response to N form. Regarding growth and biomass accumulation, mulberry displays a preference for NO3−, with mixed N supply (particularly a higher NO3−:NH4+ ratio) being most conducive to plant development and biomass production. At the photosynthetic level, NO3− significantly enhances leaf photochemical efficiency, gas exchange parameters, and photosynthetic pigment contents, whereas NH4+ dominance tends to induce photoinhibition and energy dissipation. In terms of secondary metabolism, N form exerts specific regulatory effects: NO3− promotes DNJ biosynthesis and the expression of related key genes, whereas NH4+ favors the accumulation of antioxidant compounds such as flavonoids and phenolic acids. In conclusion, N form differentially shapes the growth, physiological traits, and quality formation of mulberry by coordinating carbon nitrogen metabolism, photosystem function, and secondary metabolic networks. It should be noted, however, that these conclusions are largely based on controlled condition studies, and their applicability under complex field conditions remains to be further validated.

3. Key Factors Influencing Nitrogen Uptake Preference in Mulberry

3.1. Soil Environmental Factors

The potential influence of soil pH on nitrogen uptake strategies in mulberry should not be overlooked, as pH not only affects the relative availability and transformation rates of NH4+ and NO3−, but also directly influences the activity and selectivity of nitrogen transporters on root cell membranes [27,28]. Zhang et al. reported that in paper mulberry and mulberry seedlings, nitrate utilization peaked at pH 7.3, while ammonium utilization was highest at pH 6.3, with both forms showing reduced uptake under more acidic or alkaline conditions [29]. However, contrasting patterns have been observed in other species, highlighting the species-specific nature of pH effects on nitrogen uptake. For instance, in maize (Zea mays L.), nitrogen form preference shifts with pH: seedlings tend to prefer NO3− in strongly acidic soils, but shift to NH4+ preference under neutral to alkaline conditions [30]. In Eucalyptus nitens, ammonium uptake at pH 4 was 200% higher than at pH 6, while nitrate uptake remained unchanged across this pH range [31]. These divergent responses indicate that there is no universal optimal pH for nitrogen uptake; rather, pH effects are modulated by factors such as ecological adaptation, nitrogen form interactions, and root zone conditions. Therefore, while Zhang et al.’s findings offer a valuable reference for Moraceae species, the nitrogen uptake response of mulberry to pH warrants further systematic investigation.
The relative concentration and spatial distribution of different nitrogen forms in the soil also play a decisive role. Plants are capable of sensing the dominant nitrogen source in their environment and dynamically adjusting their uptake systems, exhibiting environmental plasticity. For example, seedlings of four subtropical tree species preferentially absorbed ammonium when it was the dominant form, but shifted to nitrate preference under nitrate-dominated conditions [32]. Studies on strawberry seedlings under varying nitrogen concentrations revealed that the plants preferred ammonium, nitrate, and ammonium under low, medium, and high nitrogen supply, respectively [33]. Zhang et al. found that increasing nitrate supply enhanced nitrogen assimilation in mulberry seedlings, with nitrogen accumulation increasing progressively as nitrate concentration increased; however, carbon accumulation showed no significant change between 2.0 mmol·L−1 and 8.0 mmol·L−1 nitrate treatments [34]. Based on these findings, it can be inferred that mulberry may also exhibit dynamic adjustments in nitrogen uptake preference under different soil nitrogen concentrations, thereby optimizing the utilization of available nitrogen sources in the environment.

3.2. Microbial Interactions

AMF play a key role in regulating plant nitrogen nutrition. Zhang et al. demonstrated that AMF inoculation modulates soil nitrogen transformation processes, significantly increasing nitrate (NO3−) and dissolved organic nitrogen (DON) content, promoting plant growth, enhancing soil microbial activity, diversifying the nitrogen sources available to plants, and consequently improving root nitrogen nutrition [35]. As demonstrated by Xing et al., inoculation with arbuscular mycorrhizal fungi AMF, specifically Funneliformis mosseae and Rhizophagus intraradices, significantly reduces soil nitrate content while concurrently increasing ammonium levels and promoting nitrogen accumulation in plants. This mechanism not involves AMF enhanced nitrate uptake by mulberry but may also facilitate the dissimilatory nitrate reduction to ammonium (DNRA) process in the soil, thereby altering the composition of nitrogen forms in the rhizosphere [8]. Under low-nitrogen conditions, AMF inoculation significantly upregulated the expression of the ammonium transporter gene LjAMT2;2 in legumes, promoting ammonium uptake and ultimately increasing nitrogen content in plant roots [36]. Shiva et al. reported that AMF inoculation suppressed nitrification and denitrification in deeper soil layers while enhancing dissimilatory DNRA [37]. In addition, multiple studies have shown that AMF hyphal exudates not only stimulate soil microbial activity and accelerate nitrogen mineralization but also reduce nitrogen loss through leaching [38,39,40].
Therefore, it is inferred that AMF may optimize nitrogen nutrition in mulberry through multiple synergistic pathways. These include regulating soil nitrogen-transforming microorganisms to reshape the NO3−/NH4+ ratio, activating the expression of ammonium transporter genes in host roots, and driving nitrogen mineralization and DNRA via hyphal exudates, thereby reducing nitrogen loss. Such coordinated regulation within the soil–plant system significantly enhances nitrogen accumulation and use efficiency in mulberry and other plants, although further validation is required.

3.3. Environmental Stress

Abiotic stresses such as drought and salinity can also alter plant nitrogen uptake preferences. For instance, under drought stress, Populus cathayana exhibits suppressed nitrate uptake capacity and shifts toward ammonium preference [41]. In mulberry, studies have shown that under salt stress (e.g., Na2CO3 stress), increasing nitrate supply alleviates stomatal limitation and improves CO2 utilization in mesophyll cells, thereby enhancing photosynthetic carbon assimilation and salt tolerance [12]. Su et al. found that salt stress weakens ammonium assimilation via the glutamine synthetase–glutamate synthase (GS-GOGAT) cycle in mulberry but enhances ammonium assimilation through the glutamate dehydrogenase (GDH) pathway, while also affecting nitrate reduction processes, thereby influencing nitrogen nutrition. Therefore, under saline soil cultivation conditions, ammonium-based fertilizers may exhibit superior fertilizer effectiveness compared to nitrate-based fertilizers for mulberry [42]. Zhang et al. reported that with increasing drought intensity, nitrate utilization significantly decreased in both paper mulberry and mulberry, whereas ammonium utilization did not show a linear reduction [29]. These findings suggest that under stress conditions, mulberry may undergo adaptive adjustments in its demand and uptake strategies for specific nitrogen forms to enhance stress tolerance.
Collectively, these findings indicate that the nitrate uptake preference of plant is shaped by the combined effects of soil conditions, microbial interactions, and environmental stresses (Table 2). In production practice, measures such as regulating soil pH, inoculating with growth-promoting microorganisms, and optimizing water and nutrient management can stabilize and enhance nitrate uptake and utilization in mulberry, thereby achieving the coordinated goals of high nitrogen use efficiency, high yield, and superior quality.
Table 2. Integrative Regulation of Nitrogen Utilization in Mulberry.
Table 2. Integrative Regulation of Nitrogen Utilization in Mulberry.
Upstream FactorsIntermediate ProcessesDownstream Physiological EffectsReferences
Nitrate dominant or mixed nitrogen supplyRoot nitrate uptake via nitrate transporters (NRTs), coupled with OH−/HCO3− efflux, thereby maintaining intracellular pH homeostasisEnhanced chlorophyll biosynthesis and PSII photochemical efficiency; DNJ accumulation via the HDG11-MnGutB1 regulatory pathway[10,11,14,24]
Ammonium dominant nitrogen supplyRoot ammonium uptake via ammonium transporters (AMTs), accompanied by H+ efflux, leading to rhizosphere acidification and potential ROS accumulationInduced photoinhibition (reduced ETR, increased NPQ; favored the biosynthesis of flavonoids and phenolic acids[13,15,25]
AMFModulates soil dissimilatory nitrate reduction to ammonium (DNRA); upregulates root ammonium transporter expressionImproved plant nitrogen accumulation and use efficiency; alleviated stress induced inhibition of nitrogen uptake[8,35,37]
Soil pHRegulates the activities of NRT and AMTs; affects soil nitrogen transformation (nitrification, DNRA)Optimized nitrate utilization and photosynthetic carbon assimilation[29,34]
Salinity or drought stressSuppressed nitrate uptake; shifted ammonium assimilation toward the GDH pathwayAlleviated stress injury by supplementary nitrate; modified the accumulation pattern of secondary metabolites[12,29,42]

4. Comparison of Nitrogen Uptake Preferences Between Mulberry and Other Plants and Its Ecological Significance

4.1. General Patterns of N-Form Preference in Trees and Crops

Plant preferences for nitrogen (N) forms can be broadly categorized as ammonium-preferring, nitrate-preferring, or dual-use types. These preferences are closely linked to phylogeny, life form, and native habitat. Traditionally, many coniferous tree species (e.g., pine, fir) have been considered ammonium-preferring, which aligns with their typical growth in acidic forest soils where organic matter decomposition is slow [43,44]. However, recent field studies using 15N labeling have revealed that nitrate uptake in mature coniferous trees can contribute 39–90% of total N uptake [45], challenging conclusions drawn from hydroponic experiments and underscoring the profound influence of microbial competition and soil processes on actual plant N utilization.
Mulberry, as a broadleaf tree species, exhibits a nitrate preference that is consistent with trends observed in many broadleaf trees and crops. Such species are typically adapted to well-aerated soils with active nitrification. The high mobility of nitrate drives the development of extensive root systems for effective foraging, and the processes of nitrate uptake and reduction contribute to maintaining intracellular redox and pH balance—traits particularly advantageous for rapid growth under high photosynthetic activity.

4.2. Plasticity and Dual-Use Strategies

Plant N preference is not absolute; many species exhibit considerable plasticity. For instance, seedlings of subtropical tree species can shift their preference in response to the dominant N source in the environment [46]. Mulberry exemplifies this flexibility: it does not perform optimally under pure nitrate conditions but instead thrives under mixed N supply with nitrate dominance, reflecting its dual-use capacity and dependence on synergistic effects among different N forms.

4.3. Ecological Implications and Coexistence

From an ecological perspective, variation in plant N form preferences serves as a mechanism for species coexistence and niche differentiation, potentially reducing direct competition for limited N resources [47]. For example, N uptake preferences within grassland plant communities can shift in response to N and water additions [48]. In agroforestry systems or mixed forests, the performance of mulberry may be influenced by its N niche relationships with neighboring plants.
Furthermore, plant N preferences profoundly affect ecosystem N cycling processes—including nitrification, denitrification, litter decomposition, and N mineralization—thereby creating feedback loops that shape soil N pools. In the context of global change, the continuous increase in atmospheric N deposition and shifts in its form ratio (NH4+/NO3−) will have profound effects on plants and ecosystems [49,50]. The nitrate-preferring characteristic of mulberry may confer advantages under scenarios where the proportion of nitrate deposition increases. However, excessive N deposition can also induce negative effects such as soil acidification and nutrient imbalances. Therefore, assessing the response of mulberry to future N deposition requires integrated consideration of its uptake preferences, tolerance limits, and physiological adaptability.

5. Summary and Outlook

This paper systematically reviews the research progress on nitrogen uptake preference in mulberry, with the main conclusions summarized as follows:
Mulberry exhibits a general preference for nitrate nitrogen. Compared with a single nitrogen source, mixed nitrogen sources dominated by nitrate are generally more conducive to promoting its growth, enhancing photosynthetic efficiency, and facilitating the accumulation of secondary metabolites. This preference is subject to the comprehensive regulation of multiple factors, including soil conditions, microbial interactions, and environmental stresses, demonstrating considerable ecological plasticity. This nitrate-preferring characteristic aligns mulberry with many broadleaf tree species and crops in terms of nitrogen utilization strategies, potentially conferring a competitive advantage in specific ecological niches and exerting certain influences on ecosystem nitrogen cycling processes. Current understanding of mulberry’s nitrogen preference is primarily derived from hydroponic and pot-based experiments, with results indicating superior performance under nitrate-dominated mixed nitrogen conditions, whereas exclusive ammonium nitrogen treatment may produce adverse effects. However, field-based empirical data remain relatively limited, and research outcomes may vary depending on environmental conditions, underscoring the necessity for further in situ investigations.
To further advance this research field and provide stronger support for practical applications, future studies should prioritize the following directions:
(1) Molecular mechanism dissection: Systematically identify the ammonium transporter (AMT) and nitrate transporter (NRT) gene families in mulberry, and elucidate their expression regulatory networks and functional mechanisms under different nitrogen forms and environmental stress conditions. (2) Field validation and long-term effect assessment: Conduct systematic long-term field experiments combined with 15N isotope tracing techniques to quantitatively assess the contribution, uptake rate, and utilization efficiency of different nitrogen sources by mulberry in authentic soil environments, and evaluate the long-term effects and ecological impacts of various nitrogen management strategies. (3) Deepening research on microbial interactions: Given that colonization by AMF can alter rhizosphere nitrogen availability and nitrogen form composition (e.g., by enhancing the ammonium pool while reducing nitrate content), optimal nitrogen fertilization strategies—including nitrogen form and application rate—may shift accordingly in mulberry cultivation systems managed with AMF. In-depth investigation of the synergistic mechanisms between AMF and nitrogen fertilization could provide a theoretical basis for developing microbe-integrated precision fertilization technologies aimed at simultaneously enhancing mulberry productivity and secondary metabolite accumulation. (4) Nitrogen nutrition strategies under stress conditions: Investigate the response patterns of mulberry nitrogen uptake preference under abiotic stresses such as drought, salinity–alkalinity, and heavy metal exposure, and elucidate the physiological and molecular mechanisms by which different nitrogen forms regulate stress tolerance, thereby providing theoretical support for stress-resistant cultivation and adaptive planting on marginal lands. (5) Integrated management and ecosystem services: Integrate nitrogen nutrition regulation in mulberry into the broader framework of whole-industry-chain management and ecosystem service assessment, and explore its application potential in areas such as nitrogen-polluted water remediation, nutrient cycling optimization in agroforestry systems, and development of low-carbon ecological planting models, thereby promoting the green and sustainable development of the mulberry industry.
Through multidisciplinary and multi-level collaborative research, thoroughly elucidating the physiological basis and key influencing factors of mulberry nitrogen uptake preference will provide a solid scientific foundation for improving mulberry industry quality and efficiency, as well as for ensuring ecological security.

Author Contributions

F.Z.: Writing and editing; S.P.: literature screening; B.C.: data verification; Y.S.: review; X.W.: review; D.X.: review and editing, funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the Guizhou Provincial Outstanding Young Scientific and Technological Talents Program (Qiankehe Platform Talents—YQK [2023]019), the Guizhou Provincial Scientist Workstation (Qiankehe Platform Talent KXJZ(2025)028), the Guizhou Provincial Science and Technology Program Projects (Qiankehe Support [2023] General 011, Qiankehe Support [2024] General 076), and the National Modern Agricultural Industry Technology System (CARS-18-SYZ20).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Acknowledgments

We used language-editing software to improve readability and take full responsibility for the content. We also thank colleagues from the Mulberry Breeding and Cultivation Laboratory of the Guizhou Institute of Sericulture for their insightful discussions and constructive suggestions, which have greatly improved the quality of this paper.

Conflicts of Interest

The authors declare no conflict of interest.

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MDPI and ACS Style

Zhang, F.; Peng, S.; Chen, B.; Shi, Y.; Wang, X.; Xing, D. Advances in Nitrogen Uptake Preference and Physiological and Ecological Mechanisms in Mulberry. Nitrogen 2026, 7, 33. https://doi.org/10.3390/nitrogen7010033

AMA Style

Zhang F, Peng S, Chen B, Shi Y, Wang X, Xing D. Advances in Nitrogen Uptake Preference and Physiological and Ecological Mechanisms in Mulberry. Nitrogen. 2026; 7(1):33. https://doi.org/10.3390/nitrogen7010033

Chicago/Turabian Style

Zhang, Fang, Shiqing Peng, Biao Chen, Yanjin Shi, Xiaohong Wang, and Dan Xing. 2026. "Advances in Nitrogen Uptake Preference and Physiological and Ecological Mechanisms in Mulberry" Nitrogen 7, no. 1: 33. https://doi.org/10.3390/nitrogen7010033

APA Style

Zhang, F., Peng, S., Chen, B., Shi, Y., Wang, X., & Xing, D. (2026). Advances in Nitrogen Uptake Preference and Physiological and Ecological Mechanisms in Mulberry. Nitrogen, 7(1), 33. https://doi.org/10.3390/nitrogen7010033

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