Wood structure and function change with maturity: Age of the vascular cambium is associated with xylem changes in current‐year growth

• Published in: Plant, cell and environment cell and environment, 2019-06, Vol.42 (6), p.1816-1831
• Main Authors: Rodriguez‐Zaccaro, F. Daniela, Valdovinos‐Ayala, Jessica, Percolla, Marta I., Venturas, Martin D., Pratt, R. Brandon, Jacobsen, Anna L.
• Format: Article
• Language: English
• Subjects: Age; Blood vessels; Branches; Cambium - anatomy & histology; Cambium - physiology; Cavitation; Cavitation resistance; development; Embolism; Hydraulic conductivity; Hydraulics; Plant species; Plant Stems; Porosity; Species; Species diffusion; Stems; Structure-function relationships; Trees - anatomy & histology; Trees - physiology; vascular cambium; vessel diameter; vessel length; vulnerability to cavitation; Water - physiology; water relations; Wood - anatomy & histology; Wood - physiology; Xylem; Xylem - anatomy & histology; Xylem - physiology
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13528

Xylem vessel structure changes as trees grow and mature. Age‐ and development‐related changes in xylem structure are likely related to changes in hydraulic function. We examined whether hydraulic function, including hydraulic conductivity and vulnerability to water‐stress‐induced xylem embolism, changed over the course of cambial development in the stems of 17 tree species. We compared current‐year growth of young (1–4 years), intermediate (2–7 years), and older (3–10 years) stems occurring in series along branches. Diffuse and ring porous species were examined, but nearly all species produced only diffuse porous xylem in the distal branches that were examined irrespective of their mature xylem porosity type. Vessel diameter and length increased with cambial age. Xylem became both more conductive and more cavitation resistant with cambial age. Ring porous species had longer and wider vessels and xylem that had higher conductivity and was more vulnerable to cavitation; however, these differences between porosity types were not present in young stem samples. Understanding plant hydraulic function and architecture requires the sampling of multiple‐aged tissues because plants may vary considerably in their xylem structural and functional traits throughout the plant body, even over relatively short distances and closely aged tissues. Vessel structure and stem hydraulic function varied with cambial age, with older stems producing tissue with larger vessels and greater hydraulic conductivity and cavitation resistance relative to younger stems. Xylem traits measured in younger distal stems are likely not indicative of mature wood traits for many species.