Nitrogen use efficiency in crops under salt stress: from molecular networks to intelligent breeding
A four-tier closed-loop conceptual framework comprising signal perception, transport reprogramming, metabolic redistribution, and genetic redesign is developed that yields three testable predictions: the sequential activation of regulatory tiers; a quantitative relationship between Ca2+ signal amplitude and the extent of C–N metabolic redistribution; and salt-concentration thresholds that distinguish basal homeostatic buffering from full adaptive reprogramming.