The main objective of this study was to determine whether the rate of cavitation in xylem channels correlates with tree height by measuring the water tension from leaves at the top against leaves from the bottom of Acer Platanoides (Norway Maple) trees. We hypothesized that water tension would be higher at the top of trees than at the bottom. The secondary focus was to determine if varying water tension would affect the structural composition of leaves. In order to identify a relationship, we compared leaf traits including mass, thickness, and area, from leaves collected at the treetop and at the bottom of the canopy. We sampled leaves from branches of four mature Acer platanoides trees. To determine the xylem tension we measured the pressure
…show more content…
2004). Consequently, trees face limitations in tree height and leaf expansion as they grow taller. The Cohesion-Tension theory explains that trees transport water through continuous chains of water molecules in the xylem, which are pulled upward by an increase in tension at the top of each column caused by evaporation in leaves (Tyree et al. 2003). As such, trees reach a height limit in which the tension is too great for water to be pulled from the column. With increasing height, trees must allocate their energy and resources efficiently to maximize photosynthetic capability in the face of water stress, by closing its leaves’ stomata and limiting growth. The risk of cavitation, or the possibility of water columns breaking, is also factored into these biomechanical changes, as the risks increase with height and water …show more content…
The average calculated water tension in Acer platanoides increased by 0.6MPa from the bottom branches to the top branches. This correlates with the results from a study focused on Sequoia sempervirens (Redwood) trees which witnessed a decline in negative pressure from 0.93MPa at 50m to 0.48MPa at 110 m (Koch et al. 2004). Similarly, a study examining Pinus strobus (Eastern White Pine) trees found that drought stress increased with height, the xylem pressure potential at the bottom branches measuring at -1.2MPa and at the top branches, -1.8MPa (Fulton et al. 2014; Woodruff et al. 2007). These inverse measurements also follow an upward trend of water tension, demonstrating that the water tension relationship with tree height is not limited to a particular
2004). Consequently, trees face limitations in tree height and leaf expansion as they grow taller. The Cohesion-Tension theory explains that trees transport water through continuous chains of water molecules in the xylem, which are pulled upward by an increase in tension at the top of each column caused by evaporation in leaves (Tyree et al. 2003). As such, trees reach a height limit in which the tension is too great for water to be pulled from the column. With increasing height, trees must allocate their energy and resources efficiently to maximize photosynthetic capability in the face of water stress, by closing its leaves’ stomata and limiting growth. The risk of cavitation, or the possibility of water columns breaking, is also factored into these biomechanical changes, as the risks increase with height and water …show more content…
The average calculated water tension in Acer platanoides increased by 0.6MPa from the bottom branches to the top branches. This correlates with the results from a study focused on Sequoia sempervirens (Redwood) trees which witnessed a decline in negative pressure from 0.93MPa at 50m to 0.48MPa at 110 m (Koch et al. 2004). Similarly, a study examining Pinus strobus (Eastern White Pine) trees found that drought stress increased with height, the xylem pressure potential at the bottom branches measuring at -1.2MPa and at the top branches, -1.8MPa (Fulton et al. 2014; Woodruff et al. 2007). These inverse measurements also follow an upward trend of water tension, demonstrating that the water tension relationship with tree height is not limited to a particular