BACKGROUND AND AIMS: The onset of spring growth and vessel formation were examined within three deciduous woody plant species, Acer rubrum, Populus balsamifera ssp. trichocarpa and Quercus rubra. We were broadly interested in the lag between the onset of girth expansion and the formation of mature and hydraulically conductive vessels within the new xylem. METHODS: Dendrometers were installed on 20 trees (6-7 per species), and expansion of both bole and distal stems was monitored throughout the growing season in a common garden. For each species, four to six distal stems were harvested every other week for anatomical examination of vessel formation. Additionally, for Populus and Quercus, hydraulic conductivity measurements and active xylem staining were completed on all stem samples. KEY RESULTS: For all three species, the timing of girth expansion was similar. Expansion of distal branches occurred 12-37 d earlier than that of the bole. Vessel formation initiated several weeks prior to leaf-out, but no new earlywood vessels were mature at the time of bud break for Acer and Populus and only a few were present in Quercus. Initial stem girth expansion occurred 2 to >6 weeks before the maturation of the first current-year vessels, and there was an additional delay of up to 4 weeks before mature vessels became hydraulically functional. Hydraulic conductivity was strongly correlated with the number and diameter of stained vessels. CONCLUSIONS: Bud break and leaf expansion relied predominantly on water supplied by vessels formed during prior seasons. Early-season activity is likely affected by the function of older xylem vessels and the environmental factors that influence their structure and function. Understanding the functional lifespan of vessels and the varying contributions of new and older vessels to conductivity are critical to understanding of the phenology and vascular function of long-lived woody plants in response to changing climates.
BACKGROUND AND AIMS: The onset of spring growth and vessel formation were examined within three deciduous woody plant species, Acer rubrum, Populus balsamifera ssp. trichocarpa and Quercus rubra. We were broadly interested in the lag between the onset of girth expansion and the formation of mature and hydraulically conductive vessels within the new xylem. METHODS: Dendrometers were installed on 20 trees (6-7 per species), and expansion of both bole and distal stems was monitored throughout the growing season in a common garden. For each species, four to six distal stems were harvested every other week for anatomical examination of vessel formation. Additionally, for Populus and Quercus, hydraulic conductivity measurements and active xylem staining were completed on all stem samples. KEY RESULTS: For all three species, the timing of girth expansion was similar. Expansion of distal branches occurred 12-37 d earlier than that of the bole. Vessel formation initiated several weeks prior to leaf-out, but no new earlywood vessels were mature at the time of bud break for Acer and Populus and only a few were present in Quercus. Initial stem girth expansion occurred 2 to >6 weeks before the maturation of the first current-year vessels, and there was an additional delay of up to 4 weeks before mature vessels became hydraulically functional. Hydraulic conductivity was strongly correlated with the number and diameter of stained vessels. CONCLUSIONS: Bud break and leaf expansion relied predominantly on water supplied by vessels formed during prior seasons. Early-season activity is likely affected by the function of older xylem vessels and the environmental factors that influence their structure and function. Understanding the functional lifespan of vessels and the varying contributions of new and older vessels to conductivity are critical to understanding of the phenology and vascular function of long-lived woody plants in response to changing climates.
Authors: Lorène Julia Marchand; Inge Dox; Jožica Gričar; Peter Prislan; Jan Van den Bulcke; Patrick Fonti; Matteo Campioli Journal: Tree Physiol Date: 2021-07-05 Impact factor: 4.196
Authors: Nicolas Delpierre; Ségolène Lireux; Florian Hartig; Jesus Julio Camarero; Alissar Cheaib; Katarina Čufar; Henri Cuny; Annie Deslauriers; Patrick Fonti; Jožica Gričar; Jian-Guo Huang; Cornelia Krause; Guohua Liu; Martin de Luis; Harri Mäkinen; Edurne Martinez Del Castillo; Hubert Morin; Pekka Nöjd; Walter Oberhuber; Peter Prislan; Sergio Rossi; Seyedeh Masoumeh Saderi; Vaclav Treml; Hanus Vavrick; Cyrille B K Rathgeber Journal: Glob Chang Biol Date: 2019-01-06 Impact factor: 10.863