Frederiksen Dahlgaard (battlecell25)

Environmental stimuli such as gravity and light modify the plant development to optimize overall architecture. Many physiological and molecular biological studies of gravitropism and phototropism have been carried out. However, sufficient analysis has not been performed from a mechanical point of view. If the biological and mechanical characteristics of gravitropism and phototropism can be accurately grasped, then controlling the environmental conditions would be helpful to control the growth of plants into a specific shape. In this study, to clarify the mechanical characteristics of gravitropism, we examined the transverse bending moment occurring in cantilevered pea (Pisum sativum) sprouts in response to gravistimulation. The force of the pea sprouts lifting themselves during gravitropism was measured using an electronic balance. The gravitropic bending force of the pea sprouts was in the order of 100 Nmm in the conditions set for this study, although there were wide variations due to individual differences.The mechanical strength of a plant stem (a load-bearing organ) helps the plant resist drooping, buckling and fracturing. We previously proposed a method for quickly evaluating the stiffness of an inflorescence stem in the model plant Arabidopsis thaliana based on measuring its natural frequency in a free-vibration test. However, the relationship between the stiffness and flexural rigidity of inflorescence stems was unclear. Here, we compared our previously described free-vibration test with the three-point bending test, the most popular method for calculating the flexural rigidity of A. thaliana stems, and examined the extent to which the results were correlated. Finally, to expand the application range, we present an example of a modified free-vibration test. Our results provide a reference for improving estimates of the flexural rigidity of A. thaliana inflorescence stems.Xylem vessels, which conduct water from roots to aboveground tissues in vascular plants, are stiffened by secondary cell walls (SCWs). Protoxylem vessel cells deposit cellulose, hemicellulose, and lignin as SCW components in helical and/or annular patterns. The mechanisms underlying SCW patterning in the protoxylem vessel cells are not fully understood, although VASCULAR-RERATED NAC-DOMAIN 7 (VND7) has been identified as a master transcription factor in protoxylem vessel cell differentiation in Arabidopsis thaliana. Here, we investigated deposition patterns of SCWs throughout the tissues of Arabidopsis seedlings using an inducible transdifferentiation system that utilizes a chimeric protein in which VND7 is fused with the activation domain of VP16 and the glucocorticoid receptor (GR) (VND7-VP16-GR). In slender- and cylinder-shaped cells, such as petiole and hypocotyl cells, SCWs that were ectopically induced by the VND7-VP16-GR system were deposited linearly, resulting in helical and annular patterns similar to the endogenous patterns in protoxylem vessel cells. By contrast, concentrated linear SCW deposition was associated with unevenness on the surface of pavement cells in cotyledon leaf blades, suggesting the involvement of cell morphology in SCW patterning. When we exposed the seedlings to hypertonic conditions that induced plasmolysis, we observed aberrant deposition patterns in SCW formation. Because the turgor pressure becomes zero at the point when cells reach limiting plasmolysis, this result implies that proper turgor pressure is required for normal SCW patterning. Taken together, our results suggest that the deposition pattern of SCWs is affected by mechanical stimuli that are related to cell morphogenesis and turgor pressure.Arabinogalactan-proteins (AGPs) are extracellular proteoglycans, which are presumed to participate in the regulation of cell shape, thus contributing to the excellent mechanical properties of plants. AGPs consist of a hydroxyproline-rich core-protein and large arabinogalactan (AG) sugar chains, called type II AGs. The