title: Interplay of growth rate and xylem plasticity for optimal coordination of carbon and hydraulic economies in Fraxinus ornus trees.
abstract: Efficient leaf water supply is fundamental for assimilation processes and tree growth. Renovating the architecture of the xylem transport system requires an increasing carbon investment while growing taller, and any deficiency of carbon availability may result in increasing hydraulic constraints to water flow. Therefore, plants need to coordinate carbon assimilation and biomass allocation to guarantee an efficient and safe long-distance transport system. We tested the hypothesis that reduced branch elongation rates together with carbon-saving adjustments of xylem anatomy hydraulically compensate for the reduction in biomass allocation to xylem. We measured leaf biomass, hydraulic and anatomical properties of wood segments along the main axis of branches in 10 slow growing (SG) and 10 fast growing (FG) Fraxinus ornus L. trees. Branches of SG trees had five times slower branch elongation rate (7 vs 35 cm year-1), and produced a higher leaf biomass (P < 0.0001) and thinner xylem rings with fewer but larger vessels (P < 0.0001). On the contrary, we found no differences between SG and FG trees in terms of leaf-specific conductivity (P > 0.05) and xylem safety (Ψ50≈ -3.2 MPa). Slower elongation rate coupled with thinner annual rings and larger vessels allows the reduction of carbon costs associated with growth, while maintaining similar leaf-specific conductivity and xylem safety.
authors: Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy giai.petit@unipd.it.
authors: Giai
authors: G
authors: Petit
authors: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
authors: Tadeja
authors: T
authors: Savi
authors: Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy.
authors: Martina
authors: M
authors: Consolini
authors: Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy.
authors: Tommaso
authors: T
authors: Anfodillo
authors: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
authors: Andrea
authors: A
authors: Nardini
mesh_terms: D002244:Carbon / Q000378:metabolism; D031661:Fraxinus / Q000254:growth & development / Q000502:physiology*; D018526:Plant Transpiration; D014197:Trees / Q000254:growth & development / Q000502:physiology*; D052584:Xylem / Q000254:growth & development / Q000502:physiology*
chemical_list: D002244:Carbon
keywords: allocation; biomass; carbon balance; carbon use; efficiency; hydraulics; partitioning; safety; sapwood; widening