Trees stop growing taller due to various mechanisms, including respiration, nutrient limitation, maturation, and hydraulic limitation. The hydraulic limitation hypothesis is the most promising explanation for the maximum tree height and age-related changes in height growth. As trees grow taller, the path length for water movement increases, and the xylem becomes less permeable, leading to higher water tension in the xylem. This increased tension can cause cavitation, which damages the water-conducting system. To prevent cavitation, stomata in taller trees close earlier, reducing transpiration and photosynthesis, thus limiting height growth. Hydraulic resistance increases with tree height and branch length, leading to reduced photosynthesis in older trees. This hypothesis explains variations in maximum tree height and growth rates across different environments and species. Evidence supports that hydraulic resistance limits tree growth, especially at the treetop and tips of long branches. Studies show that older trees have lower photosynthesis and stomatal conductance, consistent with hydraulic limitations. The hydraulic limitation hypothesis also explains why trees in resource-poor environments grow shorter and why different species attain different maximum heights. This hypothesis is supported by experiments showing that stomata respond to changes in hydraulic resistance and that older trees have higher hydraulic resistance. The hypothesis suggests that increased hydraulic resistance limits carbon assimilation, reducing new xylem production and slowing growth. Overall, hydraulic limitation is a key factor in determining tree height and growth patterns.Trees stop growing taller due to various mechanisms, including respiration, nutrient limitation, maturation, and hydraulic limitation. The hydraulic limitation hypothesis is the most promising explanation for the maximum tree height and age-related changes in height growth. As trees grow taller, the path length for water movement increases, and the xylem becomes less permeable, leading to higher water tension in the xylem. This increased tension can cause cavitation, which damages the water-conducting system. To prevent cavitation, stomata in taller trees close earlier, reducing transpiration and photosynthesis, thus limiting height growth. Hydraulic resistance increases with tree height and branch length, leading to reduced photosynthesis in older trees. This hypothesis explains variations in maximum tree height and growth rates across different environments and species. Evidence supports that hydraulic resistance limits tree growth, especially at the treetop and tips of long branches. Studies show that older trees have lower photosynthesis and stomatal conductance, consistent with hydraulic limitations. The hydraulic limitation hypothesis also explains why trees in resource-poor environments grow shorter and why different species attain different maximum heights. This hypothesis is supported by experiments showing that stomata respond to changes in hydraulic resistance and that older trees have higher hydraulic resistance. The hypothesis suggests that increased hydraulic resistance limits carbon assimilation, reducing new xylem production and slowing growth. Overall, hydraulic limitation is a key factor in determining tree height and growth patterns.