Widespread use of plastics and mishandling has resulted in severe environmental issues affecting seed germination and seedling growth. This study investigates the effect of polyethylene microplastics (740-4990 nm PEMPs) on lentil (Lens culinaris) seed germination and seedling growth using Biospeckle Optical Coherence Tomography (bOCT), a technique that we successfully demonstrated earlier in visualizing the internal activity of plants. Lentil seeds were exposed to PEMPs bioassay for seven days with 10, 50, and 100 mg L^-1 concentrations. The average speckle contrast was calculated after 0 h, 6 h, 12 h, and 24 h of exposure, and statistically significant differences were observed just after 6 h of exposure under all the treatments. However, with conventional parameters, germination viability, germination rate, root and shoot lengths, fresh and dry seedling weights, and antioxidative enzymes, no significant effect was observed until 2 d of exposure. The results revealed that the presence of PEMPs significantly reduced the internal activity at the initial stages that could be visualized only by the use of bOCT, which has never been observed till now. Our results demonstrated for the first time the effect that microplastics indeed could hinder the internal activity during germination of the seeds, possibly resulting from the physical blockage of pores leading to stunted growth at later stages.

We have examined whether blood volume changes induced by neural activation are controlled precisely enough for us to visualize the submillimeter-scale functional structure in anesthetized and awake cat visual cortex. To activate the submillimeter-scale functional structures such as iso-orientation domains in the cortex, visual stimuli (gratings) were presented to the cats. Two methods were used to examine the spatial precision of blood volume changes including changes in total hemoglobin content and changes in plasma volume: (i) intrinsic signal imaging at the wavelength of hemoglobin's isosbestic point (569 nm) and (ii) imaging of absorption changes of an intravenously injected dye. Both measurements showed that the visual stimuli elicited stimulus-nonspecific and stimulus-specific blood volume changes in the cortex. The former was not spatially localized, while the latter was confined to iso-orientation domains. From the measurement of spatial separation of the iso-orientation domains, we estimated the spatial resolution of stimulus-specific blood volume changes to be as high as 0.6 mm. The changes in stimulus-nonspecific and -specific blood volume were not linearly correlated. These results suggest the existence of fine blood volume control mechanisms in the capillary bed in addition to global control mechanisms in arteries.

Surface neural activity has been widely visualized using optical intrinsic signal imaging (OISI) from various cortical sensory areas. OISI of the cortical surface with a CCD camera gives integrated information across a depth of a few hundred micrometers. We visualize depth-resolved activation patterns of cat primary visual cortex by functional optical coherence tomography (fOCT). A comparison of the depth-integrated results of fOCT maps with the optical intrinsic signal profiles shows fairly good agreement. Our results reveal layer-specific activation patterns and indicate that the activation was not homogeneous.