Abstract Detail

Ecophysiology

Braun, Peter T. [1], Skillman, John B. [1].

To share or to save? Physiological integration and inducible CAM as possible drought tolerance mechanisms in the clonal invasive plant, Carpobrotus edulis (Ice Plant).

Carpobrotus edulis grows by the vegetative production of stolon-connected ramets to form an expansive, evergreen, mat-like, ground cover. Native to South Africa, this species is highly invasive in coastal, Mediterranean-climate, dune ecosystems around the world, including California. Clonal physiological integration, the capacity to share soil resources (e.g. soil water) among stolon-connected ramets growing in different microsites, may help explain the success of this species in these seasonally xeric habitats. Previous studies demonstrate the ability of C. edulis to switch from C3 to Crassulacean Acid Metabolism (CAM) photosynthesis, presumably improving plant water-use efficiency. Water-savings through drought inducible CAM may help explain the success of this species in these seasonally xeric habitats. We were interested in whether water savings through inducible CAM, and water sharing through physiological integration, were interactive or independent drought tolerance mechanisms in this important invasive species. Both stolon-connected and stolon-severed paired ramets were grown for six weeks in paired pots wherein one ramet in each pair was watered daily and the other ramet in each pair was continuously droughted. We measured air and leaf temperature, leaf titratable acidity (indicator of CAM), pre-dawn leaf water status, leaf photosynthesis, and whole shoot growth at regular intervals on replicated individuals from each of the four treatments throughout the experiment. Watered ramets, whether connected or severed, maintained high rates of (C3) photosynthesis and shoot growth throughout the study. Shoot growth stopped in the connected-droughted ramets but leaf-level physiology in these plants was indistinguishable from that of ramets in either of the regularly watered treatments. Severed-droughted ramets showed drought-stress symptoms at the leaf (e.g. reduced photosynthesis) and whole plant (e.g. growth cessation) levels of organization. CAM induction was not observed in any treatment. Our findings suggest that water-sharing via physiological integration is the primary drought tolerance mechanism for this invasive species. Whether or not water-saving via inducible CAM plays a role in C. edulis drought tolerance under more severe conditions remains unknown.

1 - California State University, Department Of Biology, 5500 University Parkway, San Bernardino, CA, 92407, USA

Keywords:
drought tolerance
invasive species
Crassulacean acid metabolism
clonal growth
physiological integration.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PEP008
Abstract ID:949
Candidate for Awards:None