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.
- 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.
- 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.
- 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
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
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.
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.
- 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
