Climatic and physiological regulation of the bimodal xylem formation pattern in Pinus pinaster saplings

Núria Garcia-Forner*, Joana Vieira, Cristina Nabais, Ana Carvalho, Jordi Martínez-Vilalta, Filipe Campelo

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

10 Citations (Scopus)

Abstract

Seasonality in tree cambial activity and xylem formation encompass large variation in environmental conditions. Abiotic stressors such as warming or drought also modulate plant behavior at species and individual level. Despite xylem formation susceptibility to carbon (C) and water availability, it is still unknown which are the key physiological variables that regulate xylogenesis, and to what extent plant performance contributes to further explain the number of cells in the different phases of xylem development. Xylogenesis and physiological behavior was monitored in saplings of Pinus pinaster Aiton, a bimodal growth pattern species, distributed in different irrigation regimes. Xylogenesis and plant physiological behavior were compared between treatments and the relationship between climate, physiology and the number of cells in the cambium, enlargement and cell-wall thickening phases was evaluated. Xylogenesis regulation shifted from physiological to climatic control as cell differentiation advanced to mature tracheids. The number of cells in the cambium increased with assimilation rates and decreased with the water potential gradient through the plant. Enlargement was the most susceptible phase to plant relative water content, whereas no physiological variable contributed to explain the number of cells in the wall thickening phase, which declined as temperatures increased. All treatments showed a bimodal growth pattern with a second growth period starting when primary growth was completed and after plants had experienced the highest summer hydraulic losses. Our study demonstrates the importance of including physiological responses and not only climate to fully understand xylogenesis, with special attention to the enlargement phase. This is critical when studying species with a bimodal growth pattern because the second growth peak responds to internal shifts of C allocation and may strongly depend on plant hydraulic responses and not on a fine tuning of cambial activity with soil water availability.

Original languageEnglish
Pages (from-to)2008-2018
Number of pages11
JournalTree Physiology
Volume39
Issue number12
DOIs
Publication statusPublished - 1 Dec 2019

Keywords

  • C stocks
  • C uptake
  • drought
  • water relations
  • wood phenology
  • xylogenesis

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