Abstract Detail


Regier, Jordyn [1], Hernandez, Mayra [2], Sicangco, Camille Kilayko [3], Davis, Stephen [4], Holmlund, Helen [4].

Substrate Type Affects the Drying Speed and Desiccation Tolerance of Fern Gametophytes.

Although most ferns require abundant water to thrive, some ferns can survive in habitats with limited water. Previous studies have examined the adaptations that allow xeric ferns to thrive in drought-prone ecosystems such as California. Coastal southern California is a Mediterranean-type ecosystem, dominated by drought-adapted chaparral shrublands. Several fern species thrive in the chaparral understory despite limited water availability. These chaparral fern species demonstrate niche segregation, with differences in their seasonal water use and tissue dehydration tolerance. However, the large fern sporophyte only represents one stage of the fern life cycle. The independent gametophyte phase must also survive water stress, including the six-month summer drought periods of the Santa Monica Mountains. Fern gametophytes of some tropical and temperature epiphytic species have been reported to be desiccation-tolerant (capable of recovery from near-complete drying). This ability to recover from desiccation is believed to be contingent on the gametophyte’s drying speed; rapid drying speeds likely impede gametophyte recovery. In tropical ferns, drying speed is associated with gametophyte morphology, with simple heart-shaped gametophytes drying out faster than complex ribbon- or strap-shaped gametophytes. However, in the chaparral ecosystem, all gametophytes apparently have the simple, heart-shaped morphology. Thus, we hypothesized that gametophyte substrate may slow the drying speed of chaparral fern gametophytes, improving their ability to recover from desiccation. In order to test whether substrate type affects fern gametophyte drying speed and level of recovery, we desiccated gametophytes on five different substrates ranging from slow to fast drying speed: filter paper, agar, non-acclimated and acclimated soil plugs, and soil plates. We measured dark-adapted chlorophyll fluorescence (Fv/Fm) as a metric of photosynthetic activity during desiccation and rehydration. We focused on two species native to the dry chaparral understory: evergreen Dryopteris arguta and summer-deciduous Adiantum jordanii.
Our results were consistent across both fern species measured. We found that the substrate type affected both the gametophytes’ drying speed and their ability to recover. Specifically, gametophytes growing on the various substrates showed differences in Fv/Fm over time during both desiccation and resurrection as shown by a repeated-measures ANOVA with Greenhouse-Geisser correction (p < 0.05). Gametophytes that were acclimated to and tested on soil experienced the slowest drying speed and the greatest recovery in Fv/Fm after three days of recovery (p< 0.05). Our results indicate that the soil substrate may slow the drying speed of the chaparral understory fern gametophytes, facilitating their desiccation tolerance. The desiccation tolerance trait may enable ferns to survive and reproduce in the water-limited chaparral understory. However, other adaptations of chaparral fern gametophytes remain elusive despite their critical position in the fern life cycle. With increasing global temperatures and longer drought periods, a better understanding of gametophyte ecology will illuminate fern species’ susceptibility to climate change.

1 - Pepperdine University, Natural Science Division, 24255 Pacific Coast Highway, Malibu, CA, 90263, USA
2 - CSU Dominguez Hills
3 - University of Florida
4 - Pepperdine University

desiccation tolerance
Chlorophyll fluorescence
resurrection plant
dryopteris arguta.

Presentation Type: Poster
Number: PPE004
Abstract ID:400
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize

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