Objective: The aim of this study is to demonstrate the potential of applying the contrast of the speckles obtained as noise in optical coherence tomography (OCT) images to monitor short term activity changes during foliar application of phytohormones to a plant leaf. Plant growth hormone, gibberellic acid (GA3) was sprayed onto the leaf of Chinese chives and after 60 min, OCT images (1 frame: 512 × 2048 pixels) were recorded at ten frames per second for a few tens of seconds. Results: Contrast across the temporal axis was calculated for each pixel of the structural images and biospeckle OCT contrast images were obtained under the conditions of before and after application of GA3 for different concentrations 0, 40, and 100 μM. Application of 40 μM GA3 failed to show any differences in the OCT structural images. However, bOCT contrast image was clearly different. Changes were found to be statistically significant. Although the mechanism for the contrast difference is not clear, it can be said there is a large change across the temporal scale with the application of GA3. Demonstration of OCT utilizing the speckle contrast is believed to have the potential as a promising tool in plant physiology.
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