Constructing a Cross-Instrument Transfer Learning Method for Chlorophyll a Fluorescence OJIP Transient Using OJIP-SNV and CGAN: A Case Study for Cotton Salt Stress Diagnosis
摘要
Cross-instrument comparability of O-J-I-P (OJIP) chlorophyll fluorescence transients remains limited because blue and red excitation strategies generate fluorescence curves with different spectral responses and temporal morphology. This study aimed to develop a transfer learning framework for standardizing heterogeneous OJIP data and improving cotton salt stress diagnosis.
MethodsOJIP measurements from 14,145 cotton leaf samples collected in greenhouse and field experiments were used. FluorPen-FP110 and Pocket PEA data were compared under blue and red excitation. A phase-specific OJIP-Standard Normal Variate (OJIP-SNV) preprocessing method was developed and evaluated with support vector machine (SVM), bidirectional long short-term memory (Bi-LSTM), one-dimensional convolutional neural network (1D-CNN), and Cotton Salt Stress-OJIP-Net (CSS-OJIP-Net). A conditional generative adversarial network framework, FluoToFluo, combined OJIP-SNV preprocessing with a Bi-LSTM transform for cross-instrument fluorescence migration.
ResultsBlue- and red-excitation measurements showed clear differences in fluorescence intensity distributions, with weak correlations for several intensity parameters but stronger agreement for relative fluorescence parameters. OJIP-SNV improved SVM and Bi-LSTM classification performance. CSS-OJIP-Net achieved 87.80% accuracy and 84.70% recall on Pocket PEA data. After FluoToFluo (OJIP-SNV) transfer and sample-search augmentation, accuracy and recall increased to 90.29% and 90.97%, respectively.
ConclusionOJIP-SNV and FluoToFluo reduced instrument-dependent fluorescence discrepancies and provided a practical route for multi-instrument OJIP databases and precision diagnosis of cotton salt stress.