Abstract Detail

Ecophysiology

Lachenbruch, Barbara [1].

Where dye goes: insights into water movement and morphological legacy in conifers.

Research on plant structure and function suggests that a plant’s morphology at one moment will affect its response to the environment in the next moment.  As part of an ongoing study on the influence of wood morphology and tree architecture on die-back and mortality, I am using dyes to visualize the xylem paths engaged in water transport under different circumstances.  1) Dye ascents were undertaken indoors in a heated laboratory to learn the paths used in cut 2-m tall trees during their dormant season (January and February, similar to what occurs to Christmas trees). Trees were cut, transported to the lab, re-sawed at the base, and immediately placed in aqueous acid fuchsin for 1-20 hours.  In this time period, the dye did not reach the top of the plants.  The uppermost dye was located in the outer growth ring in most trees but in an inner ring in ¼ of the specimens of both Douglas fir (Pseudotsuga menziesii) and noble fir (Abies procera) (16 trees tested per species). I speculate that this pattern resulted from individuals experiencing different driving forces in each ring, which could potentially result from the different age cohorts of needles:  their relative distal areas and stomatal control, and the specific growth rings through which they withdrew water.  For example, experiments that pulled dye through a stem segment via an attached needle showed that in trees from different habitats, a 3-year old needle can draw water from 3-year old wood; from 3, 2, and 1-year old wood; or from only 1-year old wood.  2) The wood structure across the growth ring can be more variable in noble fir than Douglas-fir.  Nonetheless, the uppermost dye was usually in the inner earlywood (EW2) and absent from the narrow initial zone of earlywood (EW1) in both species.  Moreover, experiments in which noble fir branch segments were artificially droughted showed relatively systematic differences in the part of the growth ring that transported water at different water potentials.  After ‘droughting’ to -1 or -2 MPa, dye tended to be everywhere within the growth rings.  After droughting to – 3, -4, -5, -6, or -7 MPa, the dye was almost exclusively in the EW1 in the innermost growth ring, and EW2 in the second and third growth rings.  This research suggests we will benefit from adding spatial and temporal dimensions to studies of morphology and water transport in living (and dying) trees.  

1 - Oregon State University, Forest Ecosystems & Society, Corvallis, OR, 97331, USA

Keywords:
hydraulic architecture
water transport
conifers
morphological legacy
embolism
dye
Drought
Wood anatomy.

Presentation Type: Oral Paper:Papers for Topics
Session: 15
Location: Firs South/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 11:15 AM
Number: 15013
Abstract ID:775
Candidate for Awards:None