Abstract Detail

Pteridology

Suissa, Jacob [1], Friedman, William [2], Agbleke, Andrews [3].

The hydraulic implications of rhizomatous growth and the homorhizic habit.

PREMISE: Rhizomatous growth characterizes numerous taxa across diverse vascular plant lineages. While abundant information exists on nutrient sharing and demography, it remains unknown how these metameric organisms move water through their body or how bauplan morphology and anatomy affect whole-plant hydraulic function. Importantly, the evolutionary implications of rhizomatous growth remain essentially unexplored in a hydraulic context. Here, we shed light on these questions by investigating the effects of rhizomatous growth and vascular construction on whole-plant hydraulic function.
METHODS: In five fern species with diverse vascular construction, we used microCT to examine basic body plan and vascular construction at nodes and internodes. This was integrated with measurements of stomatal conductance under rooted and uprooted conditions to relate vascular construction to leaf hydraulic status.
RESULTS: While individuals were moderately hydraulically integrated along their rhizomes, in most species stomatal conductance dropped almost 40% during local uprooting. Importantly, these drops in stomatal conductance are due to nodal zones of increased hydraulic resistance, also known as chokepoints. Chokepoints occur regardless of axial vascular architecture.
CONCLUSIONS: Nodal chokepoints may act as ‘safety-valves’, hydraulically localizing each phytomer and potentially decreasing embolism and pathogen spread. At the same time, these chokepoints also decrease hydraulic integration between phytomers, suggesting a functional tradeoff in the principal construction of the rhizome. Importantly, we propose that shoot-borne roots (homorhizy) and the prostrate habit of rhizomatous ferns decrease the hydraulic and structural burdens that upright plants typically incur. The absence of these demands may be one reason many rhizomatous plants lack, or have minimally developed, secondary xylem.

1 - Harvard University, 26 Oxford St., 1300 Centre St, Cambridge, MA, 02138, United States
2 - Harvard University, Arnold Arboretum, 1300 Centre St., Boston, MA, 02131, United States
3 - Harvard University, Center for Biological Imaging, 16 Divinity Ave, Cambridge, MA, 02138, USA

Keywords:
rhizome
Ferns
homorhizic
hydraulic integrations
physiology
Evolution
microCT
stomatal conductance.

Presentation Type: Oral Paper
Number: PTR1002
Abstract ID:169
Candidate for Awards:Edgar T. Wherry award