Water transport, mechanical support and storage are the vital functions provided by the xylem. These functions are carried out by different cells, exhibiting significant anatomical variation not only within species but also within individual trees. In this study, we used a comprehensive dataset to investigate the consistency of predicted hydraulic vessel diameter widening values in relation to the distance from the tree apex, represented by the relationship Dh ∝ Lβ (where Dh is the hydraulic vessel diameter, L the distance from the stem apex and β the scaling exponent). Our analysis involved 10 Fagus sylvatica L. trees sampled at two distinct sites in the Italian Apennines. Our results strongly emphasize that vessel diameter follows a predictable pattern with the distance from the stem apex and β ~ 0.20 remains consistent across cambial age and climates. This finding supports the hypothesis that trees do not alter their axial configuration represented by scaling of vessel diameter to compensate for hydraulic limitations imposed by tree height during growth. The study further indicates that within-tree variability significantly contributes to the overall variance of the vessel diameter-stem length exponent. Understanding the factors that contribute to the intraindividual variability in the widening exponent is essential, particularly in relation to interspecific responses and adaptations to drought stress.

• Klíčová slova
• allometry, architecture, diffuse-porous, hydraulic, quantitative wood anatomy, vessels, xylem traits,
• MeSH
• buk (rod) * růst a vývoj   fyziologie   anatomie a histologie   MeSH
• kambium * růst a vývoj   MeSH
• podnebí * MeSH
• stonky rostlin * růst a vývoj   anatomie a histologie   fyziologie   MeSH
• stromy růst a vývoj   fyziologie   anatomie a histologie   MeSH
• voda metabolismus   MeSH
• xylém * růst a vývoj   anatomie a histologie   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Itálie MeSH
• Názvy látek
• voda MeSH

Polar auxin transport in the Arabidopsis (Arabidopsis thaliana) root tip maintains high auxin levels around the stem cell niche that gradually decrease in dividing cells but increase again once they transition toward differentiation. Protophloem differentiates earlier than other proximal tissues and employs a unique auxin "canalization" machinery that is thought to balance auxin efflux with retention. It consists of a proposed activator of PIN-FORMED (PIN) auxin efflux carriers, the cAMP-, cGMP- and Calcium-dependent (AGC) kinase PROTEIN KINASE ASSOCIATED WITH BRX (PAX); its inhibitor, BREVIS RADIX (BRX); and PHOSPHATIDYLINOSITOL-4-PHOSPHATE-5-KINASE (PIP5K) enzymes, which promote polar PAX and BRX localization. Because of a dynamic PAX-BRX-PIP5K interplay, the net cellular output of this machinery remains unclear. In this study, we deciphered the dosage-sensitive regulatory interactions among PAX, BRX, and PIP5K by their ectopic expression in developing xylem vessels. The data suggest that the dominant collective output of the PAX-BRX-PIP5K module is a localized reduction in PIN abundance. This requires PAX-stimulated clathrin-mediated PIN endocytosis upon site-specific phosphorylation, which distinguishes PAX from other AGC kinases. An ectopic assembly of the PAX-BRX-PIP5K module is sufficient to cause cellular auxin retention and affects root growth vigor by accelerating the trajectory of xylem vessel development. Our data thus provide direct evidence that local manipulation of auxin efflux alters the timing of cellular differentiation in the root.

• MeSH
• Arabidopsis * metabolismus   genetika   růst a vývoj   MeSH
• biologický transport MeSH
• fosfotransferasy s alkoholovou skupinou jako akceptorem metabolismus   genetika   MeSH
• kořeny rostlin metabolismus   růst a vývoj   genetika   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• membránové transportní proteiny metabolismus   genetika   MeSH
• protein-serin-threoninkinasy * MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• xylém metabolismus   růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AT1G66150 protein, Arabidopsis MeSH Prohlížeč
• BREVIS RADIX protein, Arabidopsis MeSH Prohlížeč
• fosfotransferasy s alkoholovou skupinou jako akceptorem MeSH
• kyseliny indoloctové * MeSH
• membránové transportní proteiny MeSH
• protein-serin-threoninkinasy * MeSH
• proteiny huseníčku * MeSH

Wood formation consumes around 15% of the anthropogenic CO2 emissions per year and plays a critical role in long-term sequestration of carbon on Earth. However, the exogenous factors driving wood formation onset and the underlying cellular mechanisms are still poorly understood and quantified, and this hampers an effective assessment of terrestrial forest productivity and carbon budget under global warming. Here, we used an extensive collection of unique datasets of weekly xylem tissue formation (wood formation) from 21 coniferous species across the Northern Hemisphere (latitudes 23 to 67°N) to present a quantitative demonstration that the onset of wood formation in Northern Hemisphere conifers is primarily driven by photoperiod and mean annual temperature (MAT), and only secondarily by spring forcing, winter chilling, and moisture availability. Photoperiod interacts with MAT and plays the dominant role in regulating the onset of secondary meristem growth, contrary to its as-yet-unquantified role in affecting the springtime phenology of primary meristems. The unique relationships between exogenous factors and wood formation could help to predict how forest ecosystems respond and adapt to climate warming and could provide a better understanding of the feedback occurring between vegetation and climate that is mediated by phenology. Our study quantifies the role of major environmental drivers for incorporation into state-of-the-art Earth system models (ESMs), thereby providing an improved assessment of long-term and high-resolution observations of biogeochemical cycles across terrestrial biomes.

• Klíčová slova
• Northern Hemisphere conifer, photoperiod, temperature, wood formation, xylogenesis,
• MeSH
• biologické modely MeSH
• cévnaté rostliny genetika   růst a vývoj   MeSH
• dřevo růst a vývoj   MeSH
• ekosystém MeSH
• fotoperioda MeSH
• globální oteplování MeSH
• klimatické změny MeSH
• lesy MeSH
• podnebí MeSH
• roční období MeSH
• stromy růst a vývoj   MeSH
• teplota MeSH
• xylém růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

The phenology of wood formation is a critical process to consider for predicting how trees from the temperate and boreal zones may react to climate change. Compared to leaf phenology, however, the determinism of wood phenology is still poorly known. Here, we compared for the first time three alternative ecophysiological model classes (threshold models, heat-sum models and chilling-influenced heat-sum models) and an empirical model in their ability to predict the starting date of xylem cell enlargement in spring, for four major Northern Hemisphere conifers (Larix decidua, Pinus sylvestris, Picea abies and Picea mariana). We fitted models with Bayesian inference to wood phenological data collected for 220 site-years over Europe and Canada. The chilling-influenced heat-sum model received most support for all the four studied species, predicting validation data with a 7.7-day error, which is within one day of the observed data resolution. We conclude that both chilling and forcing temperatures determine the onset of wood formation in Northern Hemisphere conifers. Importantly, the chilling-influenced heat-sum model showed virtually no spatial bias whichever the species, despite the large environmental gradients considered. This suggests that the spring onset of wood formation is far less affected by local adaptation than by environmentally driven plasticity. In a context of climate change, we therefore expect rising winter-spring temperature to exert ambivalent effects on the spring onset of wood formation, tending to hasten it through the accumulation of forcing temperature, but imposing a higher forcing temperature requirement through the lower accumulation of chilling.

• Klíčová slova
• cambium, chilling temperatures, conifers, forcing temperatures, phenological models, wood phenology,
• MeSH
• Bayesova věta MeSH
• biologické modely * MeSH
• cévnaté rostliny růst a vývoj   MeSH
• dřevo růst a vývoj   MeSH
• klimatické změny MeSH
• roční období MeSH
• teplota * MeSH
• xylém růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH
• Kanada MeSH

Cortical microtubules (MTs) play a major role in the patterning of secondary cell wall (SCW) thickenings in tracheary elements (TEs) by determining the sites of SCW deposition. The EXO70A1 subunit of the exocyst secretory vesicle tethering complex was implicated to be important for TE development via the MT interaction. We investigated the subcellular localization of several exocyst subunits in the xylem of Arabidopsis thaliana and analyzed the functional significance of exocyst-mediated trafficking in TE development. Live cell imaging of fluorescently tagged exocyst subunits in TE using confocal microscopy and protein-protein interaction assays were performed to describe the role of the exocyst and its partners in TE development. In TEs, exocyst subunits were localized to the sites of SCW deposition in an MT-dependent manner. We propose that the mechanism of exocyst targeting to MTs involves the direct interaction of exocyst subunits with the COG2 protein. We demonstrated the importance of a functional exocyst subunit EXO84b for normal TE development and showed that the deposition of SCW constituents is partially compromised, possibly as a result of the mislocalization of secondary cellulose synthase in exocyst mutants. We conclude that the exocyst complex is an important factor bridging the pattern defined by cortical MTs with localized secretion of the SCW in developing TEs.

• Klíčová slova
• conserved oligomeric Golgi (COG) complex, exocyst, microtubules, secondary cell wall, tracheary elements, xylem,
• MeSH
• Arabidopsis růst a vývoj   metabolismus   ultrastruktura   MeSH
• biologické modely MeSH
• buněčná diferenciace MeSH
• buněčná membrána metabolismus   MeSH
• buněčná stěna metabolismus   MeSH
• cévní svazky rostlin metabolismus   MeSH
• glukosyltransferasy metabolismus   MeSH
• konzervovaná sekvence MeSH
• mikrotubuly metabolismus   ultrastruktura   MeSH
• mutace genetika   MeSH
• podjednotky proteinů metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• xylém cytologie   růst a vývoj   metabolismus   ultrastruktura   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cellulose synthase MeSH Prohlížeč
• glukosyltransferasy MeSH
• podjednotky proteinů MeSH
• proteiny huseníčku MeSH

Bud outgrowth is controlled by environmental and endogenous factors. Through the use of the photosynthesis inhibitor norflurazon and of masking experiments, evidence is given here that light acts mainly as a morphogenic signal in the triggering of bud outgrowth and that initial steps in the light signaling pathway involve cytokinins (CKs). Indeed, in rose (Rosa hybrida), inhibition of bud outgrowth by darkness is suppressed solely by the application of CKs. In contrast, application of sugars has a limited effect. Exposure of plants to white light (WL) induces a rapid (after 3-6 h of WL exposure) up-regulation of CK synthesis (RhIPT3 and RhIPT5), of CK activation (RhLOG8), and of CK putative transporter RhPUP5 genes and to the repression of the CK degradation RhCKX1 gene in the node. This leads to the accumulation of CKs in the node within 6 h and in the bud at 24 h and to the triggering of bud outgrowth. Molecular analysis of genes involved in major mechanisms of bud outgrowth (strigolactone signaling [RwMAX2], metabolism and transport of auxin [RhPIN1, RhYUC1, and RhTAR1], regulation of sugar sink strength [RhVI, RhSUSY, RhSUC2, and RhSWEET10], and cell division and expansion [RhEXP and RhPCNA]) reveal that, when supplied in darkness, CKs up-regulate their expression as rapidly and as intensely as WL Additionally, up-regulation of CKs by WL promotes xylem flux toward the bud, as evidenced by Methylene Blue accumulation in the bud after CK treatment in the dark. Altogether, these results suggest that CKs are initial components of the light signaling pathway that controls the initiation of bud outgrowth.

• MeSH
• biologické modely MeSH
• časové faktory MeSH
• cytokininy metabolismus   farmakologie   MeSH
• meristém genetika   růst a vývoj   metabolismus   MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• regulace genové exprese u rostlin účinky léků   účinky záření   MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• Rosa genetika   růst a vývoj   metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• signální transdukce účinky léků   genetika   účinky záření   MeSH
• světlo * MeSH
• tma MeSH
• výhonky rostlin genetika   růst a vývoj   metabolismus   MeSH
• vývojová regulace genové exprese účinky léků   účinky záření   MeSH
• xylém genetika   růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH

The development and growth of plants, as well as their successful adaptation to a variety of environments, is highly dependent on the conduction of water, nutrients and other important molecules throughout the plant body. Xylem is a specialized vascular tissue that serves as a conduit of water and minerals and provides mechanical support for upright growth. Wood, also known as secondary xylem, constitutes the major part of mature woody stems and roots. In the past two decades, a number of key factors including hormones, signal transducers and (post)transcriptional regulators have been shown to control xylem formation. We outline the main mechanisms shown to be essential for xylem development in various plant species, with an emphasis on Arabidopsis thaliana, as well as several tree species where xylem has a long history of investigation. We also summarize the processes which have been shown to be instrumental during xylem maturation. This includes mechanisms of cell wall formation and cell death which collectively complete xylem cell fate.

• Klíčová slova
• auxin, cell wall, cytokinin, pattern formation, root development, vascular development, wood, xylem,
• MeSH
• buněčná smrt MeSH
• buněčná stěna fyziologie   MeSH
• listy rostlin fyziologie   MeSH
• xylém anatomie a histologie   cytologie   růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Despite its major economic importance and the vulnerability of Picea abies (L.) H. Karst. to climate change, how its radial growth at intra-annual resolution is influenced by weather conditions in forest stands with a high production capacity has scarcely been explored. Between 2009 and 2011, phenological variation in seasonal cambial cell production (CP) was analysed in adult P. abies trees from three contrasting sites, differing in altitude and latitude. The results indicate that the timing of cambial CP is a highly synchronic process within populations since in all cases the cambium simultaneously started and stopped producing xylem and phloem cells. Our results also demonstrate that the phenology of cambial CP is highly variable and plastic between years, depending on seasonal temperature and precipitation variation. Differences among sites, however, are only partially explained by different environmental (elevation and altitude) and climatic conditions, suggesting that local adaptation may also play a decisive role in the strategy of P. abies for adapting wood and phloem increments to function optimally under local conditions.

• Klíčová slova
• Norway spruce, cambium, growing degree days, growth/weather relation, light microscopy, radial growth,
• MeSH
• déšť MeSH
• dřevo růst a vývoj   MeSH
• floém růst a vývoj   MeSH
• fyziologická adaptace * MeSH
• kambium růst a vývoj   MeSH
• klimatické změny MeSH
• lesy MeSH
• nadmořská výška MeSH
• podnebí MeSH
• roční období * MeSH
• smrk fyziologie   MeSH
• stromy fyziologie   MeSH
• teplota MeSH
• xylém růst a vývoj   MeSH
• životní prostředí * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH