Embolism spread in the primary xylem of Polystichum munitum: implications for water transport during seasonal drought

• Published in: Plant, cell and environment Vol. 39; no. 2; pp. 338 - 346
• Main Authors: Brodersen, Craig R, Rico, Christopher, Guenni, Orlando, Pittermann, Jarmila
• Format: Journal Article
• Language: English
• Published: United States Blackwell Scientific Publications 01.02.2016; Wiley Subscription Services, Inc; Wiley-Blackwell
• Subjects: air temperature; air‐seeding; Biological Transport; cavitation; climate; drought; Droughts; embolism; fern; ferns and fern allies; functional status; growing season; Humidity; hydraulic conductivity; image analysis; indigenous species; micro-computed tomography; microCT; Plant Stomata - physiology; Polystichum - physiology; Polystichum munitum; seasonal variation; Seasons; Sequoia sempervirens; Soil - chemistry; soil heterogeneity; soil temperature; soil water; soil water content; stomatal conductance; Temperature; understory; Water - metabolism; water potential; woody plants; X-Ray Microtomography; xylem; Xylem - physiology; California; INE, USA, California; xylem; stomatal conductance; fern; drought; air-seeding; Polystichum munitum; microCT; embolism; cavitation
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12618

Xylem network structure and function have been characterized for many woody plants, but less is known about fern xylem, particularly in species endemic to climates where water is a limiting resource for months at a time. We characterized seasonal variability in soil moisture and frond water status in a common perennial fern in the redwood understory of a costal California, and then investigated the consequences of drought‐induced embolism on vascular function. Seasonal variability in air temperature and soil water content was minimal, and frond water potential declined slowly over the observational period. Our data show that Polystichum munitum was protected from significant drought‐induced hydraulic dysfunction during this growing season because of a combination of cavitation resistant conduits (Air‐seeding threshold (ASP) = −1.53 MPa; xylem pressure inducing 50% loss of hydraulic conductivity (P₅₀) = −3.02 MPa) and a soil with low moisture variability. High resolution micro‐computed tomography (MicroCT) imaging revealed patterns of embolism formation in vivo for the first time in ferns providing insight into the functional status of the xylem network under drought conditions. Together with stomatal conductance measurements, these data suggest that P. munitum is adapted to tolerate drier conditions than what was observed during the growing season.