Abstract Detail

Anatomy and Morphology

Mozzi, Giacomo [1], Hultine, Kevin [2], Anfodillo, Tommaso [1], Crivellaro, Alan [3].

Axial variation of xylem conduits in giant cacti.

Giant columnar cacti store massive amounts of water in their parenchymous storage tissues in order to persist under conditions of extreme aridity. Nevertheless, the relationship between stem water storage capacity and the maximum efficiency to deliver water from the roots to stem storage tissues via xylem vessels remains largely unknown. Indeed, the relationship between the axial water flow in xylem and the lateral flow through the storage tissue may affect the xylem structure and, therefore, the plant water conduction strategies. Since the axial structure of vascular conduits has been demonstrated to be universal (i.e. in a broad spectrum of plant species xylem conduits widen basipetally at the same rate), we wanted to determine if both the vessel size and wall thickness in giant cactae follow the same general rule in spite of the buffer action of water storage tissue. To addresses these hypotheses, we are investigating anatomical variation in xylem structural traits and storage volume in the stems of giant cacti species belonging to different phylogenetic lineages that are native to both the Northern and Southern hemisphere (e.g.Pachycereus weberi, Echinopsis terschekii, Carnegiea gigantea). We collected cross-sections from 6 to 13 samples along the stem of each plant. We found that vessel lumina increased basipetally following a widening rate similar to what has been documented by the theoretical model (WBE model) and from existing surveys on a wide range of tree species. Cell wall thickness also increases basipetally, but at a lower rate than the vessels lumen area. Therefore, the ratio between vessel lumen area and cell wall thickness is not constant along the length of cactus stems. We concluded that the xylem architecture of columnar cacti in this study was not influenced by the buffering action of the surrounding storage tissue, and that axial water transport efficiency is compensated for the length of the path as in many other plant species.

1 - University of Padova, TESAF, Viale dell'Università , 16, Legnaro, Padova, 35020, Italy
2 - 1201 N Galvin Parkway, Phoenix, AZ, 85008, United States
3 - Cambridge University, Department of Geography, Downing site, Cambridge, UK

Keywords:
Cactaceae
xylem
anatomy.

Presentation Type: Poster
Session: P, Anatomy and Morphology Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PAM010
Abstract ID:824
Candidate for Awards:None