The Contribution of Carbon and Water in Modulating Wood Formation in Black Spruce Saplings

Abstract

ORCID IDs: 0000-0003-3830-0415 (J.-G.H.); 0000-0001-5248-9096 (M.B.).Nonstructural carbohydrates (NSCs) play a crucial role in xylem formation and represent, with water, the main constraint to plant growth. We assessed the relationships between xylogenesis and NSCs in order to (1) verify the variance explained by NSCs and (2) determine the influence of intrinsic (tissue supplying carbon) and extrinsic (water availability and temperature) factors. During 2 years, wood formation was monitored in saplings of black spruce (Picea mariana) subjected to a dry period of about 1 month in June and exposed to different temperature treatments in a greenhouse. In parallel, NSC concentrations were determined by extracting the sugar compounds from two tissues (cambium and inner xylem), both potentially supplying carbon for wood formation. A mixed-effect model was used to assess and quantify the potential relationships. Total xylem cells, illustrating meristematic activity, were modeled as a function of water, sucrose, and D-pinitol (conditional r 2 of 0.79). Water availability was ranked as the most important factor explaining total xylem cell production, while the contribution of carbon was lower. Cambium stopped dividing under water deficit, probably to limit the number of cells remaining in differentiation without an adequate amount of water. By contrast, carbon factors were ranked as most important in explaining the variation in living cells (conditional r 2 of 0.49), highlighting the functional needs during xylem development, followed by the tissue supplying the NSCs (cambium) and water availability. This study precisely demonstrates the role of carbon and water in structural growth expressed as meristematic activity and tissue formation.

Modelling intra- and inter-annual growth dynamics of Scots pine in the whole-tree carbon balance framework

“…12). This is also in accordance with the finding that a current year's carbon availability affects the new ring width and the number of produced tracheids (Babst et al 2014, Deslauriers et al 2016.…”

“…The sink limitation on short timescales is supported by the success in modelling the daily growth variation solely based on temperature, whereas over longer time scales growth was enhanced or restricted by actualized photosynthetic production. The assumption of complex sink-source interactions is also supported by the results reported by Sveinbjörnsson et al (2010), Guillemot et al (2015) and Deslauriers et al (2016).…”

“…Drought affects growth indirectly via reduced photosynthetic production due to reduced stomatal opening and thus reduced carbon assimilation and also non-stomatal factors such as lower carboxylation capacity (Lansberg andWaring 1997, Zhou et al 2013). Water availability has also a direct effect especially on secondary growth via turgor pressure, which drives cell enlargement ) and via cambial activity, which is decreased under drought conditions (Deslauriers et al 2016). Low levels of soil moisture also decrease or inhibit root growth (Bowen 1970, Valdés et al 2006.…”

“…However, the other factors do and will become highly important when predicting growth on other site types or simulating future climate conditions. Thus, the effect of water limitation should be added to CASSIA as a factor that imposes a direct limitation on growth sink strength even before it affects growth indirectly via photosynthesis , Deslauriers et al 2016. Nutrient effect on growth could be included in maximum daily growth (L) (Bergh et al 1999) and possibly phenology (Sigurdsson 2001).…”

Dynamics of non‐structural carbohydrates in terrestrial plants: a global synthesis

“…Isotopic techniques combined with modelling of carbon allocation (Richardson et al 2013, Hartmann et al 2015, Hartmann and Trumbore 2016, new methodologies to quantify cambial growth at short timescales (Chan et al 2016, Deslauriers et al 2016) and molecular approaches to decipher gene expression and metabolic profiling (Stitt and Zeeman 2012) offer promising avenues to measure the fluxes into and out of NSC pools and disentangle the roles of different NSC fractions and how they vary over time. We stress the need for concurrent assessment of NSC dynamics with phenology and physiology (e.g., gas exchange, water potential, turgor, and hydraulic performance) in different organs to allow for a better integration of whole-plant carbon and water economy.…”