title: Hydraulic integration and shrub growth form linked across continental aridity gradients.
abstract: Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.
authors.affiliation: Department of Biological Science, California State University, Fullerton, CA 92834-6850, USA. jschenk@fullerton.edu
authors.forename: H Jochen
authors.initials: HJ
authors.lastname: Schenk
authors.forename: Susana
authors.initials: S
authors.lastname: Espino
authors.forename: Christine M
authors.initials: CM
authors.lastname: Goedhart
authors.forename: Marisa
authors.initials: M
authors.lastname: Nordenstahl
authors.forename: Hugo I Martinez
authors.initials: HI
authors.lastname: Cabrera
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Jones
mesh_terms: D001696:Biomechanical Phenomena / Q000379:methods; D003889:Desert Climate; D017753:Ecosystem; D063245:Plant Development; D018521:Plant Physiological Phenomena