Specificity of Arsenic Stress Detection by Raman Spectroscopy During Co-Occurrences of Nitrogen Deficiency and Narrow Brown Leaf Spot.

Arsenic contamination in rice poses a potential health risk to populations dependent on their daily consumption. Previous work has shown that Raman spectroscopy is capable of nondestructively diagnosing arsenic uptake in rice; however, its diagnostic specificity in cases of concurrent abiotic and biotic stress remains unclear. As Raman spectroscopy relies on the detection of arsenic-induced stress patterns for diagnosis, the presence of additional stressors could potentially compromise diagnostic reliability. To address this gap, we evaluated the ability of Raman spectroscopy to detect arsenic uptake in the presence of both nitrogen deficiency (abiotic stress) and narrow brown leaf spot (biotic stress) across two Experiments. We found that nitrogen deficiency, while more severe than arsenic stress, did not affect arsenic detection. We also found that the diagnostic accuracy for both abiotic stressors (arsenic and nitrogen deficiency) depended on the plant growth stage, with arsenic detection being most reliable immediately after transplantation and nitrogen deficiency becoming more distinguishable as stress severity increased. Narrow brown leaf spot, though exhibiting minimal symptoms, remained sufficiently detectable. Altogether, these findings demonstrate that Raman spectroscopy remains a reliable method for diagnosing arsenic uptake and assessing overall rice health, even in the presence of additional stressors.