Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

Soil acidification has shown detrimental effects on rice plants that lead to decreased rice production. In the present study, we aim to study the microstructural changes in rice leaves under acidic stress through swept-source optical coherence tomography (SS-OCT). To achieve this, rice seeds were germinated, subsequently these germinated seedlings were further grown under varying pH conditions for 14 d. Growth in root and shoot of plants and chlorophyll content of leaf samples were studied at varying pH levels. Similarly, acidic stress treated rice leaves were also subjected to SS-OCT image analysis revealing several features present in the layers of leaves. Seedling growth was greatly reduced at pH 3.5 while it was maximum at pH 6.5 treatment, which might be the result of cumulative altered physiological parameters. The thickness between different layers of leaves starts disintegrating at low pH conditions, thickness of parenchyma cells was greatly reduced. The attenuated growth of rice seedlings at low pH conditions, as inferred from results of SS-OCT, was further corroborated by decreased root and shoot growth and chlorophyll content. Therefore, cross-sectional OCT images are very much helpful in identifying the morphological changes occurring in the leaves under low pH that cannot be observed by the naked eye. Results of the study could be applied for the identification of cross-sectional changes in the leaf of low pH affected plants and to take remedial measures towards boosting rice production and benefiting the agriculture sector. (paper)