Abstract Detail

Ecophysiology

Zhang, Yongjiang [1], Rockwell, Fulton [2], Wheeler, James [2], Holbrook, N. Michele [3].

Dehydration-induced collapse of transfusion tracheids in conifer leafs and its association with leaf water transport.

Conifer leaves are often assumed to be vulnerable to cavitation based on vulnerability curves generated by the conventional rehydration technique. Declines in leaf hydraulic conductance, however, could be alternatively explained by tracheid wall collapse in some conifers. We developed a modified rehydration technique to separate the dehydration-induced declines in leaf hydraulic conductance into quickly-reversible versus irreversible parts and used a cryo-scanning electron microscope to test whether the leaf hydraulic conductance decline results from cavitation for Taxus baccata, a conifer species without resin. We also quantified the dehydration-induced structural changes in transfusion tracheids (TT) using a cryo-fluorescence microscope and related it to declines in leaf hydraulic conductance. The decline in leaf hydraulic conductance between -2 to -3 MPa detected with the conventional rehydration technique was reversible and was not related to xylem cavitation but deformation in TT in T. baccata. The irreversible decline in leaf hydraulic conductance, likely related to cavitation, did not occur until leaf water potentials were more negative than -3 MPa. Moreover the deformation in TT was quickly reversible, which potentially provides a mechanism to regulate leaf water transport. The commonness of reversible collapse in TT could be tested for other gymnosperms as they all possess this tissue.

1 - Harvard University, Department of Organismic and Evolutionary Biology, 16 Divinity Ave. , Biological Labs Room 3107, Cambridge, MA, 02138, USA
2 - Harvard University, Department of Organismic and Evolutionary Biology, 16 Divinity Ave., Cambridge, MA, 02138, USA
3 - Harvard University, Organismal And Evolutionary Biology, 16 Divinity Avenue, Cambridge, MA, 02138, USA

Keywords:
leaf hydraulics
conifers
vulnerability curves
transfusion tissue
cavitation.

Presentation Type: Oral Paper:Papers for Topics
Session: 15
Location: Firs South/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 11:45 AM
Number: 15015
Abstract ID:517
Candidate for Awards:None