Foliar morphology and physiology of Sequoia sempervirens
Graduation Date
2008
Document Type
Thesis
Program
Other
Program
Thesis (M.A.)--Humboldt State University, Biology, 2008
Committee Chair Name
Stephen Sillett
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Morphology, Light, Photosynthesis, Redwood, Height, Humboldt State University -- Theses -- Biology
Abstract
This study examined changes in Sequoia sempervirens foliage along gradients of height and light availability. In tall trees (108-113 m), shoot morphology and physiology were analyzed at the base of the live crown, the mid-crown, and treetop. Both light and hydrostatic factors change along this within-tree gradient. To isolate the effect of hydrostatic factors related to height, morphological and physiological characteristics of foliage were quantified at the tops of trees ranging from 25 to 113 m tall. To isolate the effect of light, these characteristics were compared among treetop and non-treetop foliage from similar heights. Shoot mass:area ratio (SMA) increased with height and was less responsive to changes in light availability as height increased. Mass-based maximum photosynthetic rate (Amax,m) and mass-based internal CO2 conductance (gi,m) decreased with height while the light compensation point (LCP) and rate of dark mitochondrial respiration (Rm) increased along these gradients. In relation to SMA, Amax,m and gi,m decreased while Rm,a increased. Within tall trees, light and water potential both change drastically so that trends along the height gradient were generally pronounced. In contrast, among treetops from different height classes where light is relatively constant and only water potential changes with height, trends were generally less pronounced. Results suggest that at lower heights light is the primary determinant of morphology while at greater heights hydrostatic tension is the primary determinant. Increased respiration and decreased internal CO2 conductance associated with high tissue density likely reduce photosynthetic rates in the upper crowns of tall S. sempervirens trees. Further investigation of the relationships between internal CO2 conductance, aquaporins, and carbonic anhydrases is needed to determine if internal CO2 conductance is in fact limiting photosynthesis in tall trees.
Recommended Citation
Mullin, Lucy, "Foliar morphology and physiology of Sequoia sempervirens" (2008). Cal Poly Humboldt theses and projects. 1957.
https://digitalcommons.humboldt.edu/etd/1957
https://scholarworks.calstate.edu/concern/theses/00000269b