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Abstract Detail

Recent Topics Posters

Suissa, Jacob [1].

Advanced humidity-driven motion of fertile fronds governs the unique timing of spore dispersal in the widespread fern species Onoclea sensibilis L.

PREMISE: The sensitive fern is one of the most widespread species in eastern North America and has an atypical timing of spore dispersal among temperate ferns. This species produces modified spore-bearing leaves in the summer, which persist above ground until the following early spring, when they finally disperse spores. While botanists have observed this timing of spore dispersal in the sensitive fern for over 120 years, a clear understanding of the physiological and structural mechanisms responsible for this phenology has never been documented.
METHODS: By integrating field observations with growth chamber manipulations and scanning electron microscopy, I investigated the mechanism underlying the unique timing of spore dispersal in the sensitive fern.
RESULTS: I show that fertile leaflets open in direct response to humidity changes, exhibiting functional parallels with multicellular hygromorphic structures in seed plants. These parallels include differences in cellulose fiber orientation of the cell walls. The dynamic of this hygroscopic movement concomitant with unique abscission zones along the leaflets, leads to the specific phenology of early spring spore dispersal in the sensitive fern.
CONCLUSIONS: While hygroscopic structures are common in seed-free plants, this is the first documentation of humidity-driven movement in the fertile fronds of any fern. This mechanism of propagule dispersal occurs in multicellular structures across gymnosperms and angiosperms, such as pine cones and wheat awns. The rarity of this mechanism contemporaneous with the repeated occurrence across diverse lineages, suggests that the evolution of this trait may be infrequent but is a useful strategy for efficiently regulating the timing of propagule dispersal.

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1 - Harvard University, Department of Organismic and Evolutionary Biology, 26 Oxford St, Cambridge, Massachusetts, 02138, United States

sensitive fern
Onoclea sensibilis.

Presentation Type: Recent Topics Poster
Session: P1, Recent Topics Posters
Location: Virtual/Virtual
Date: Thursday, July 22nd, 2021
Time: 5:00 PM(EDT)
Number: P1RT008
Abstract ID:1397
Candidate for Awards:None

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