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

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.