Metal-organic frameworks (MOF)-mediated improvement of cotton germination and early seedling resilience under salinity stress through explainable machine learning and non-destructive terahertz time-domain spectroscopy (THz-TDS)

Abstract

Cobalt-based metal-organic framework (Co-MOF) and nickel-cobalt bimetallic MOF (Ni-Co-MOF) systems were evaluated for their effects on cotton germination under saline conditions induced through NaCl seed priming treatments. Temporal germination dynamics, germination-related indices, explainable machine learning (ML), and terahertz time domain spectroscopy (THz-TDS) were integrated to characterize treatment-associated germination and THz responses. The results demonstrated clear treatment-dependent differences in germination initiation, progression, synchronization, and cumulative germination behavior. Co-MOF at 50 mg/L produced the strongest early germination responses, whereas Ni-Co-MOF at 50 mg/L achieved the highest cumulative germination (91.0%). A 4 h priming duration produced the most coordinated germination pattern under saline conditions. The random forest-based multi-output regression framework showed variable predictive performance among germination indices, with an average R2 of 0.372 and a maximum R2 of 0.507 for mean germination rate. Feature importance analysis further revealed that intermediate germination stages contributed most strongly to predictive performance. THz-TDS analysis revealed clear treatment-associated differences in time-domain attenuation and frequency-dependent absorption profiles within cotton leaf tissues. Stronger attenuation and absorption responses observed under specific MOF treatments indicated treatment-associated variation in hydration-associated dielectric behavior. Compared with 100 mM NaCl reference treatment without MOF supplementation,selected MOF treatments exhibited higher cumulative germination and distinct THz responses. The integration of MOF treatments, THz-TDS, and explainable ML provided a combined analytical approach for characterizing early germination patterns and leaf THz responses under controlled saline conditions. However, However, there is a need of further biochemical, physiological, ion-homeostasis, and plant growth assessments are needed to clarify the underlying mechanism.