The water pipes of elongating plant organs are the result of programmed cell death and are formed by the walls of dead and empty protoxylem elements. These protoxylem elements are passively elongated many times by the surrounding tissue before they are replaced and collapse. Well-known adaptations for this unique task include the characteristic secondary wall thickenings, forming rings and heli...

Protoxylem plays an important role in the hydraulic function of vascular systems of both herbaceous and woody plants, but relatively little is known about the processes underlying the maintenance of protoxylem function in long-lived tissues. In this study, embolism repair was investigated in relation to xylem structure in two cushion plant species, Azorella macquariensis and Colobanthus muscoid...

Plants precisely control lignin deposition in spiral or annular secondary cell wall domains during protoxylem tracheary element (TE) development. Because protoxylem TEs function to transport water within rapidly elongating tissues, it is important that lignin deposition is restricted to the secondary cell walls in order to preserve the plasticity of adjacent primary wall domains. The Arabidopsi...

The phytohormone cytokinin regulates various aspects of plant growth and development, including root vascular development. In Arabidopsis thaliana, mutations in the cytokinin signaling components cause misspecification of protoxylem cell files. Auxin antagonizes cytokinin-regulated root protoxylem differentiation by inducing expression of Arabidopsis phosphotransfer protein6 (AHP6), a negative ...

Cell-cell communication is critical for tissue and organ development. In plants, secretory CLAVATA3/EMBRYO SURROUNDING REGION-related (CLE) peptides function as intercellular signaling molecules in various aspects of tissue development including vascular development. However, little is known about intracellular signaling pathways functioning in vascular development downstream of the CLE ligands...

A polyclonal antibody was used to localize a glycine-rich cell wall protein (GRP 1.8) in French bean hypocotyls with the indirect immunogold method. GRP 1.8 could be localized mainly in the unlignified primary cell walls of the oldest protoxylem elements and also in cell corners of both proto- and metaxylem elements. In addition, GRP 1.8 was detected in phloem using tissue printing. The labeled...

Land plants evolved xylem vessels to conduct water and nutrients, and to support the plant. Microarray analysis with a newly established Arabidopsis in vitro xylem vessel element formation system and promoter analysis revealed the possible involvement of some plant-specific NAC-domain transcription factors in xylem formation. VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7 can induce transdifferen...

The glycine-rich structural protein GRP1.8 of French bean (Phaseolus vulgaris) is specifically localized in the modified primary cell walls of protoxylem elements. Continuous deposition of GRP1.8 into the cell walls during elongation growth of the plant suggests that GRP1.8 is part of a repair mechanism to strengthen the protoxylem. In this work, a reporter-protein system was developed to study...

Regulation of water flow in an interconnected xylem vessel network enables plants to survive despite challenging environment changes that can cause xylem embolism. In this study, vulnerability to embolisms of xylem vessels and their water-refilling patterns in vascular bundles of maize leaves were experimentally investigated by employing synchrotron X-ray micro-imaging technique. A vascular bun...

BACKGROUND AND AIMS Development and architecture of plant roots are regulated by phytohormones. Cytokinin (CK), synthesized in the root cap, promotes cytokinesis, vascular cambium sensitivity, vascular differentiation and root apical dominance. Auxin (indole-3-acetic acid, IAA), produced in young shoot organs, promotes root development and induces vascular differentiation. Both IAA and CK regul...