Dynamic changes in calcium signals during root gravitropism.

Gravitropism is a vital mechanism through which plants adapt to their environment. Previous studies indicated that Ca2+ may play an important role in plant gravitropism. However, our understanding of the calcium signals in root gravitropism is still largely limited. Using a vertical stage confocal and transgenic Arabidopsis R-GECO1, our data showed that gravity stimulation enhances the occurrence of calcium spikes and increases the Ca2+ concentration in the lower side of the root cap. Furthermore, a close correlation was observed in the asymmetry of calcium signals with the inclination angles at which the roots were oriented. The frequency of calcium spikes on the lower side of 90°-rotated root decreases rapidly over time, whereas the asymmetric distribution of auxin readily strengthens for up to 3 h, indicating that the calcium spikes, promoted by gravity stimulation, may precede auxin as one of the early signals. In addition, the root gravitropism of starchless mutants is severely impaired. Correspondingly, no significant increase in calcium spike occurrence was observed in the root caps of these mutants within 15 min following a 90° rotation, indicating the involvement of starch grains in the formation of calcium spikes. However, between 30 and 45 min after a 90° rotation, asymmetric calcium spikes were indeed observed in the root of starchless mutants, suggesting that starch grains are not indispensable for the formation of calcium spikes. Besides, co-localization analysis suggests that the ER may function as calcium stores during the occurrence of calcium spikes. These findings provide further insights into plant gravitropism.

Effects of Gaze Stabilization Exercises on Gait, Plantar Pressure, and Balance Function in Post-Stroke Patients: A Randomized Controlled Trial.

This study aims to explore the effects of gaze stabilization exercises (GSEs) on gait, plantar pressure, and balance function in post-stroke patients (≤6 months). Forty post-stroke patients were randomly divided into an experimental group (n = 20) and a control group (n = 20). The experimental group performed GSEs combined with physical therapy, while the control group only performed physical therapy, once a day, 5 days a week, for 4 weeks. The Berg Balance Scale (BBS) was used to test the balance function and the risk of falling, which was the primary outcome. The Timed Up and Go test (TUGT) evaluated the walking ability and the fall risk. The envelope ellipse area and the plantar pressure proportion of the affected side were used to measure the patient's supporting capacity and stability in static standing. The anterior−posterior center of pressure displacement velocity was used to test the weight-shifting capacity. Compared to the control group, the swing phase of the affected side, swing phase's absolute symmetric index, envelope ellipse area when eyes closed, and TUGT of the experimental group had significantly decreased after GSEs (p < 0.05); the BBS scores, TUGT, the anterior−posterior COP displacement velocity, and the plantar pressure proportion of the affected side had significantly increased after 4 weeks of training (p < 0.05). In conclusion, GSEs combined with physical therapy can improve the gait and balance function of people following stroke. Furthermore, it can enhance the weight-shifting and one-leg standing capacity of the affected side, thus reducing the risk of falling.

Gravity induces asymmetric Ca2+ spikes in the root cap in the early stage of gravitropism.

Gravitropism is an important strategy for the adaptation of plants to the changing environment. Previous reports indicated that Ca2+ participated in plant gravity response. However, present information on the functions of Ca2+ in plant gravitropism was obtained mainly on coleoptiles, hypocotyls, and petioles, little is known about the dynamic changes of Ca2+ during root gravitropism. In the present study, the transgenic Arabidopsis thaliana R-GECO1 was placed horizontally and subsequently vertically on a refitted Leica SP8 laser scanning confocal microscopy with a vertical stage. Real-time observations indicated that gravistimulation induced not only an increase in the Ca2+ concentration, but also an accelerated occurrence of Ca2+ sparks in the root cap, especially in the lower side of the lateral root cap, indicating a strong tie between Ca2+ dynamics and gravistimulation during the early stage of root gravity response.

Tunable multi-wavelength optofluidic Dammann grating with beam splitting property.

Dammann grating (DG) is a binary beam splitter. Traditional DG is pure solid and cannot be modulated for different working wavelength. We report a tunable multi-wavelength DG based on a liquid-solid hybrid structure. Two glass plates are bonded by UV adhesive strips, one has a periodic grooves structure made by photoresist, the other has two drilled holes as inlet and outlet, respectively. A microfluidic mixer connected the inlet mixes of two miscible liquids with different flow rates to adjust the refractive index of the mixed liquid entering DG from 1.351 to 1.473. In the experiment, the real-time tunability has shown the DG achieves well beam splitting effect when parameter N is integer, 7 × 7 light spots are arranged in order with good uniformity. For λ = 632.8 nm, spot size uniformity is about 78.38% and power uniformity is ∼71.01%. For λ = 532 nm, the spot size and power uniformity are about 77.17% and 64.32%, respectively. The experiment also demonstrates this DG's suitability for near-infrared light. This work is the first study of tunable DG based on liquid-solid hybrid structure and possesses special merits as compared to its solid counterpart, such as simple fabrication, tunability and multi-wavelength applicability, which make it have an extensive prospect in optofluidic networks and optical devices.

Design and characteristics of tunable in-plane optofluidic lens actuated by viscous force.

In this Letter, we report a tunable in-plane optofluidic lens based on a new regulation method. The viscous force (VF) adjusts a 68# white mineral oil-air interface and focal length (f). Two glass plates bonded by ultraviolet adhesive strips form a lens chamber. Liquid enters the chamber by capillary action and forms a convex interface due to VF. As the liquid filling amount increases, VF is enhanced, and the interface deforms. Because of the uneven VF, interface is aspheric, which can reduce the lens aberration. Bendings on both sides of the interface caused by edge effect lead to an even polynomial profile of the entire interface, and they can be used for aberration correction of an in-plane spherical reflector. Experiments demonstrate the continuous tuning of f from 17.7 to 45.1 mm. The positive longitudinal spherical aberration (LSA) is effectively suppressed below 0.078 when f<35.5mm. Interface with a large negative LSA is used for spherical reflector aberration correction. Simulation results proved that the light spot improvement rate is>90%, and the maximum reached 99%.

Design and characteristics of a Maxwell force-driven liquid lens.

Varifocal lenses (especially large-aperture lenses), which are formed by two immiscible liquids based on electrowetting and dielectrophoretic effects, are usually modulated by an external high-voltage power source, with respect to the volume of the liquid. Hence, a Maxwell force-driven liquid lens with large aperture and low threshold voltage is proposed. With the polarization effect, the accumulated negative charges on the surface of the polyvinyl chloride/dibutyl adipate gel near the anode results in the generation of Maxwell force and deformation with cosine wave. The effect of surface roughness on wettability is linear with the cosine of the contact angle, leading to a sharp reduction in the threshold voltage when the volume of liquid is increased. When the volume of the droplet increases to 80 µl, the threshold voltage is about 10 V. Hence, the aperture of polarization effect-driven liquid lenses can potentially reach the centimeter level. Moreover, when Maxwell force increases, the lens ranges from concave to convex lens, which holds great promise in rich application such as those in light-sheet microscopes and virtual reality systems.

Latrunculin B facilitates gravitropic curvature of Arabidopsis root by inhibiting cell elongation, especially the cells in the lower flanks of the transition and elongation zones.

Gravitropism plays a critical role in the growth and development of plants. Previous reports proposed that the disruption of the actin cytoskeleton resulted in enhanced gravitropism; however, the mechanism underlying these phenomena is still unclear. In the present study, real-time observation on the effect of Latrunculin B (Lat B), a depolymerizing agent of microfilament cytoskeleton, on gravitropism of the primary root of Arabidopsis was undertaken using a vertical stage microscope. The results indicated that Lat B treatment prevented the growth of root, and the growth rates of upper and lower flanks of the horizontally placed root were asymmetrically inhibited. The growth of the lower flank was influenced by Lat B more seriously, resulting in an increased differential growth rate between the upper and lower flanks of the root. Further analysis indicated that Lat B affected cell growth mainly in the transition and elongation zones. Briefly, the current data revealed that Lat B treatment inhibited cell elongation, especially the cells in the lower flanks of the transition and elongation zones, which finally manifested as the facilitation of gravitropic curvature of the primary root.