Integrative physio-biochemistry and transcriptomic insights into nitrogen-calcium interactions in pakchoi (Brassica chinensis L.) growth

Appropriate application of nitrogen (N) and calcium (Ca) can significantly enhance crop growth, photosynthetic efficiency, and yield formation. However, the physiological and molecular regulatory mechanisms underlying optimal N and Ca management in pakchoi remain poorly understood. To address this, a controlled soil pot experiment was conducted to systematically investigate the morphological, physiological, and transcriptomic responses of pakchoi to varying levels of N (0, 225 kg N·hm⁻ 2 ) and Ca (0, 75, 150, 225 kg CaO·hm⁻ 2 ). Results showed that the combined application of 225 kg N·hm⁻ 2 and 150 kg CaO·hm⁻ 2 (N225Ca150) maintained an optimal canopy microenvironment, significantly improved growth parameters, and increased chlorophyll content and photosynthetic efficiency. Compared to N225Ca0, the N225Ca150 increased fresh and dry weights by an average of 12.01% and 25.37%, respectively. Transcriptomic analysis revealed that under N-deficient conditions Ca enhanced the plant's adaptation by regulating the expression of genes involved in key metabolic pathways such as transcription factors and MAPK signaling cascades to modulate the growth, development, and stress response of pakchoi. However, Ca further promoted the expression of genes related to photosynthesis and N-Ca metabolism, metabolism, improving N assimilation and Ca fixation efficiency, and facilitated photosynthate production and yield enhancement under sufficient N conditions. Comprehensive analysis indicates that N and Ca exhibit synergistic effects at both physiological and molecular levels, collectively regulating the growth, development, and metabolic responses of pakchoi. Overall, the combined application of N and Ca (N225Ca150) is recommended as the optimal management practice. The findings provide a theoretical framework for understanding N-Ca interactions in pakchoi and offer practical insights for precision nutrient management in controlled cultivation systems. • N, Ca contribute to maintain optimal microenvironment and photosynthetic efficiency. • Ca enhance N balance and C accumulation under N-deficient by upregulating genes. • Ca promote the express genes related to hormone signaling under normal N supply. • N, Ca synergistically regulate optimal fine-tune metabolic pathways at molecular level.