Low nitrogen stress severely impedes crop growth and productivity. There has been substantial research on root adaptation to low nitrogen conditions in many plant species. However, the mechanism underlying the morphological response of the strawberry (Fragaria × ananassa Duch.) root to low-NO₃⁻ or low-NH₄⁺ stress remains poorly understood. Strawberry plants were hydroponically cultivated under 1 mM NO₃⁻, 1 mM NH₄⁺, and control (15 mM NO₃⁻) conditions to assess the physiological responses of their roots to low nitrogen stress. As a result, low nitrogen stresses increased the fresh weight of root, lateral root density, and root surface area, as well as enhanced the accumulation of indole-3-acetic acid and jasmonic acid while significantly reducing salicylic acid in the roots. Correspondingly, low nitrogen stresses increased PM H⁺-ATPase activity. Low-NO₃⁻ stress enhanced the activities of nitrate reductase and glutamine synthetase, whereas low-NH₄⁺ treatment led to higher glutamine synthetase and glutamate synthase activities. Collectively, the present results demonstrate that low nitrogen stresses enhance nitrogen uptake of strawberry roots by regulating hormones (indole-3-acetic acid, jasmonic acid, and salicylic acid) and thereby mediating PM H⁺-ATPase activity, while promoting nitrogen metabolism by upregulating the activities of nitrate reductase, glutamine synthetase, and glutamate synthase. In conclusion, low nitrogen conditions may facilitate more efficient acquisition of available N from the soil by strawberry root system.

Improving soil organic carbon (SOC) has been considered as a “win-win way” for ensuring high crop productivity and mitigating chemical N input. Improving SOC can achieve higher wheat yield and simultaneously improve nitrogen (N) productivity (defined as kg grain produced per kg total N input from both indigenous and applied N). Two treatments were tested for improving SOC level. The manure treatment involved applying manure for 6 successive years, and the EM treatment involved adding peat and vermiculite once, both combined with optimized in-season N management. The performance of these two systems were compared with a traditional farming system (Control, where only straw was returned each season). N fertilizer input under all three treatments was optimized by in-season N management and was increased by 90.1% and 48.1% under EM and Manure treatments, respectively, as compared with Control. The average wheat yield for the EM and Manure treatments was 9.1 and 9.2 Mg ha^–1, respectively, across all three years, which was 18.8% and 19.7% higher, respectively, than that of the Control treatment (7.7 Mg ha^–1). The average chemical N application rates for the EM and Manure treatments were 139 and 146 kg ha^–1, which were 24.9% and 21.1% lower than those of the Control treatment, respectively. The N productivity was 15.1% and 14.9% which was higher under Manure and EM treatments than that of the Control treatment. The high yield and N productivity were attributed to improved aboveground dry matter and N uptake by wheat, with optimal soil N supply of the root zone. The higher stem number and weight seen in individual plants with increasing SOC resulted in larger spikes and grains at harvest. Our results determined that increasing SOC combined with optimal N management achieve low chemical N input and higher grain yield by increasing productive stems and grains per spike for improving wheat individual growth.

Anthocyanin is the primary determinant of visual quality in red-fleshed apples. Iron (Fe) contributes to alleviating chlorosis and improving fruit quality, including anthocyanin accumulation. However, the mechanism linking Fe nutrition to anthocyanin content remains unclear, particularly in red-fleshed cultivars. Here, we evaluated how foliar Fe application influenced anthocyanin and soluble sugar contents in apple flesh and investigated the associated transcriptional responses using RNA-seq. Fe increased leaf chlorophyll content and promoted the accumulation of soluble sugars and anthocyanins in fruits grown in calcareous soil. RNA-seq analysis identified 323 differentially expressed genes (DEGs) in response to Fe treatment. Specifically, multiple DEGs were associated with sugar biosynthesis and transport, anthocyanin biosynthesis, and phytohormone biosynthesis. Based on RNA-seq and physiological analyses, we proposed that Fe may promote anthocyanin accumulation through three putative mechanisms: (i) elevating sugar levels via increased leaf chlorophyll content, thereby providing substrates and signals; (ii) activating key anthocyanin structural genes and related transcription factors; and (iii) stimulating ethylene and brassinosteroid biosynthesis and signaling pathways involved in anthocyanin accumulation. This work provides new insight into the Fe-mediated regulatory network underlying anthocyanin accumulation, offering a practical basis to refine fertilization strategies for fruit quality improvement in red-fleshed apples.