Abstract Detail



Ecophysiology

Prats, Kyra [1], Brodersen, Craig [2].

Seasonal coordination of leaf hydraulics and gas exchange in the wintergreen fern Polystichum acrostichoides.

While some perennial species avoid winter exposure through deciduous leaves, the wintergreen fern Polystichum acrostichoides has fronds that are photosynthetically active all year, despite diurnal and seasonal changes in soil moisture, air temperature, and light availability. This species can fix the majority of its total annual carbon during periods when the deciduous canopy is open. Yet, remaining photosynthetically active during this window requires the maintenance of many physiological systems during freeze-thaw cycles that can lead to gas bubble formation in the xylem that block flow and reduce photosynthesis. We aimed to determine the anatomical and physiological strategies that P. acrostichoides uses to maintain positive carbon gain, and the degree of coordination between the hydraulic and photosynthetic systems. We measured hydraulic conductivity of fronds through the year and found that the percent loss of conductivity (PLC) increased 25% after the first frost, suggesting that freeze-thaw induced embolism was occurring. Maximum photosynthetic rate recovered in spring, despite PLC remaining high. The remaining hydraulic capacity was therefore sufficient to supply the leaves with water. The onset of colder temperatures also coincided with the development of a necrotic hinge zone at the base of the stipe, which allows fronds to overwinter lying prostrate, thereby minimizing the damaging effects of snow loading and maintaining a favorable energy balance. Our conductivity data show that the hinge zone did not affect leaf hydraulics because of the flexible nature of the vascular bundles. Collectively, these strategies allow P. acrostichoides to remain competitive and abundant in northeastern forests.


1 - Yale University, School of Forestry and Environmental Studies, 195 Prospect Street, Kroon Hall, New Haven, Connecticut, 06511
2 - Yale University, School Of Forestry & Environmental Studies, 195 Prospect Street, Kroon Hall, New Haven, CT, 06511, United States

Keywords:
gas exchange
photosynthesis
hydraulic conductance
freeze-thaw embolism
ferns.

Presentation Type: Oral Paper
Number: 0009
Abstract ID:295
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation


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