Abstract Detail

Xylem apoplast-symplast interactions

Pratt, R. [1], Jacobsen, Anna [2], Tobin, Michael [3].

Storage versus hydraulics: the impact of the xylem symplast on xylem function.

The xylem of plants transports water, provides structural support for leaf and reproductive displays, and stores carbohydrates. It is well established that there is a tradeoff between transport safety (resistance to cavitation) and transport efficiency. There is also a cost to greater transport safety, which is greater structural reinforcement of cells that leads to a positive association between transport safety and mechanical strength. In contrast to these first two functions, the third function of the xylem, storage, has been little studied. In the present study, we examined if increased xylem carbohydrate storage, which occurs within the living cells of the xylem (i.e. the xylem symplast), comes at the cost of reduced hydraulic efficiency or safety, which are largely controlled by non-living fibers and vessels (i.e. the xylem apoplast). We sampled resistance to cavitation due to water stress, carbohydrate storage, mechanical strength, and transport efficiency (xylem specific hydraulic conductivity) of stems and roots for 36 species of chaparral shrubs. We found that carbohydrate storage capacity was negatively associated with cavitation resistance in both stems and roots. This suggests that the increased storage of carbohydrates in the symplast comes at the cost of reduced transport safety of the apoplast. Mechanical strength of tissue was not associated with carbohydrate storage. Our findings support the existence of xylem tradeoffs that are likely driven by limited space and resources. Increased storage came at the cost of decreased transport safety. This may represent an important plant functional axis between stress resistance and avoidance. Interestingly, storage did not impact mechanical strength, perhaps because the presence of living fibers in a large number sample species allowed these cells to provide both these functions without limiting one another. Similarly, the ability to alter vessel traits such as density, diameter, and connectivity to alter conductivity while not requiring increased space allocation may uncouple tradeoffs between this trait and carbohydrate storage.

Broader Impacts:

1 - CALIFORNIA STATE UNIVERSITY BAKERSFIELD, DEPARTMENT OF BIOLOGY, 9001 Stockdale Highway, Bakersfield, CA, 93311-1099, USA
2 - California State University Bakersfield, 9001 Stockdale Hwy, 61 SCI, Bakersfield, CA, 93311, USA, 310-740-7659
3 - 3910 Tilson Lane, Houston, TX, 77080, USA

Keywords:
xylem
cavitation
carbohydrate storage.

Presentation Type: Symposium or Colloquium Presentation
Session: C3
Location: Belle-Chasse/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 8:15 AM
Number: C3002
Abstract ID:811
Candidate for Awards:None