Nanometer accuracy statistical interferometric technique in monitoring the short-term effects of exogenous plant hormones, auxin and gibberellic acid, on rice plants

Abstract

Statistical interferometric technique (SIT) is a highly sensitive, high speed non-contact, and non-destructive optical technique developed by our group capable of measuring instantaeoues sub-nanometer displacements. SIT applied to plant leaf elongation revealed nanometric intrinsic fluctuaitons (NIF) that are robust and sensitive to variations in the environment making NIF as a measure of healthiness of the plants. In this study, exogenous plant hormones, auxin (2,4-dichlorophenoxyacetic acid-2,4-D), and gibberellic acid (GA 3 ), along with an auxin transport inhibitor 2,3,5-triiodobenzoic acid-TIBA, that affect plant growth were used to investigate their effects on NIF. Rice (Oriza sativa) seedlings were used, and their roots were exposed to 1, 2, and 4 µM 2,4-D, and the auxin transport inhibitor, TIBA, of 10, and 20 µM for 22 h and GA 3 solution of different concentrations of 10, 40, and 100 µM for 5 h. Results showed significant increment in NIF for 1 µM and reduction for 4 µM 2,4-D while applicaiton of both 10, and 20 µM TIBA led to reduction in NIF. On the other hand, significant increment in NIF for 40 µM, and a significant reduction at a higher concentration of 100 µM for 5 hours of GA 3 were also observed in comparison to those of control. Our results indicate that NIF as revealed by SIT could show both the positive and negative effects depending on the concentration of exogenous hormones, and transport inhibitors. Results suggest that SIT could be a valuable tool being sensitive enough to speedily assess the effects of plant growth hormones.

Biospeckle optical coherence tomography in speedy visualizing effects of foliar application of plant growth hormone to Chinese chives leaves

“…where Here R was defined as the difference in grand average bOCT contrast obtained before and after 60 min divided by that obtained before and expressed as a percentage. Results at different concentrations revealed 40 μM to have significant effect agreeing with our earlier results [9]. At higher GA3 concentrations, the layered structure got affected significantly corresponding to dramatic reduction in the temporal changes and thus in the activity within the leaf.…”

Evaluation of sub-nanometric plant growth activities under far-red light illumination using Statistical Interferometry Technique (SIT)

“…These new findings brought some informative hints. Since we have ever successfully demonstrated that NIF is correlated to plant growth parameters such as plant height, stress indicators etc., NIF could be used as an indicator to assess plant healthiness, stress, and environmental pollution in a short time [2][3][4][5][6] . Although further research must be required, even just the single FR and B illumination results here strongly implied that NIF does not simply reflect good or bad of plant healthiness or environmental condition, also suggested that NIF may reflect growth potential, how large and tall it will be in the future.…”

“…In general, endogenous indole-3-acetic acid (known as IAA, natural auxin) level in plant body is increased by FR illumination, then plant growth is induced (as SAR) 10 . In our previous study, we found that the exposure of low concentration of 2,4-D (artificial auxin) to rice seedlings increased NIF of their leaves 3 . Based on these findings, in this study we investigated how NIF changes in their leaves when the plant is exposed to FR.…”

“…Interestingly, we found that NIF seems to reflect a plant healthiness or a biological activity in response to environmental condition highly sensitively. For example, exposure of plants to plant growth promoters, e.g., micronutrient, such as low concentrations of zinc and auxin, plant growth hormone, promotes plant growth and increases the magnitude of NIF 2,3 . On the other hand, exposure to plant growth inhibitors such as cadmium and ozone drastically decreases NIF 2,4,5 .…”

Label-free optical interferometric microscopy to characterize morphodynamics in living plants

“…To this end, the plant is fixed using a holder (see Figure 1F ) and the in-plane displacement relative to the fixed point is measured: , where is the wavelength of the laser, is the angle between the illumination beam and the normal to the detection plane, and , represents the phase difference between the two interfering biospeckle fields. This method has been used for multiple applications in plants: instantaneous tracking of nano-scale growth fluctuations of leaves under stress (see Figure 1G ) ( Muthumali DeSilva et al., 2017 ), monitoring both the quality of pine seedlings through root elongation rate ( Wang L. et al., 2021 ) and the short-term effects of exogenous plant hormones on rice ( Kabir et al., 2020 ), studying the nano-scale growth behavior of fungi-infected ( Rathnayake et al., 2008 ) and uninfected seedlings under ozone exposure at different concentrations ( Rathnayake et al., 2007 ). The authors observed that fungal infection results in higher root growth.…”