Root Severance at Harvest Increases Embolism and Decreases Sap Flow of Field-grown Acer rubrum L.

Abstract

<jats:p>Root severance during field harvesting alters the water status of a tree, resulting in water stress and reduced post-transplant growth. Two experiments, using <jats:italic>Acer rubrum</jats:italic> L. (red maple), determined the influence of root severance at harvest on sap flow and xylem embolism. Trees 1.5–1.8 m tall (4 years old) were utilized in the first experiment, and trees 1.2–1.5 m tall (2 years old) were utilized in the second. Sap flow sensors were installed on the 4-year-old trees prior to root severance and remained on the trees until 1 week after harvest. Within 1 day after root severance sap flow was reduced and remained lower than nontransplanted (control) trees for the remainder of the experiment. Leaf stomatal conductance (Cs) of transplanted trees 1 week after root severance was lower than that of control trees, but leaf water potentials (ψ) were similar. In the second experiment, sap flow was reduced relative to control trees within 2 h after root severance. Although Cs was reduced 4 hours after root severance, ψ was not. Embolism increased within 24 hours of root severance. These results indicate that root severance quickly induces increased levels of embolism, which is associated with reduced sap flow.</jats:p>

Performance of agarwood (Aquilaria crassna) seedling transplants improved by shade and fertiliser

“…However, a negative cycle can result when seedlings have a low tissue water status following transplanting, whereby root growth is inhibited by a lack of photosynthesis and in-turn photosynthesis is inhibited by a lack of root growth (Burdett, 1990). More extreme instances of water stress can cause cavitation and embolism within the xylem vessels (Kavanagh and Zaerr, 1997;Knight et al, 2000), a decline in stomatal conductance (Pena and Grace, 1986;Borghetti et al, 1989), leaf shed or stem dieback (Tyree and Zimmermann, 2002), or seedling mortality (Tyree and Sperry, 1988).…”