Abstract Detail



Ecophysiology

Holmlund, Helen [1], Pratt, Brandon [2], Jacobsen, Anna [3], Davis, Stephen [4], Pittermann, Jarmila [1].

High-resolution computed tomography reveals dynamics of desiccation and rehydration in a desiccation-tolerant fern.

Desiccation-tolerant (DT) plants can completely desiccate to less than 10% water content (-100 MPa) and subsequently recover all function upon rehydration. These remarkable plants are aptly named “resurrection plants” for their ability to recover from apparent death. Resurrection plants often thrive in dry niches, including rocky outcrops with shallow soil. For instance, Pentagramma triangularis is a DT fern native to the semi-arid chaparral ecosystem of southern California, where it survives extended seasonal drought in the desiccated, deep dormancy state. Most DT plants are small, non-vascular plants, including bryophytes and fern gametophytes. Vascular DT plants face several additional challenges over non-vascular plants such as 1) desiccating tissues without causing structural damage, 2) resurrecting distinct tissues and organs, and 3) refilling empty xylem conduits. In this study, high resolution micro-computed tomography (microCT), light microscopy, and fluorescence microscopy were used to characterize the dynamics of tissue desiccation and rehydration in stipes of intact DT ferns. Our study revealed unique functional and anatomical characteristics of the stipes, including densely packed chloroplasts within the vascular cylinder and perennially desiccated parenchyma (cortex) external to the vascular cylinder. During desiccation, xylem conduits embolized before cellular dehydration of living tissues within the vascular cylinder. During resurrection, the chlorenchyma and phloem within the vascular cylinder rehydrated prior to xylem refilling. We view these observed in vivo dynamics of desiccation and rehydration as a result of unique anatomical characteristics that include flexible, hydrophilic xylem conduits, osmotically active molecules synthesized by chloroplasts within the vascular cylinder, and an endodermal layer impregnated with hydrophobic substances that impede apoplastic leakage while facilitating the upward flow of water within the vascular cylinder.


1 - University of CA, Santa Cruz, Ecology and Evolutionary Biology, 130 McAllister Way, Santa Cruz, CA, 95060, USA
2 - California State University, Bakersfield, DEPARTMENT OF BIOLOGY, 9001 Stockdale Highway, Bakersfield, CA, 93311, United States
3 - California State University, Bakersfield, Dept Of Biology, 9001 Stockdale Hwy, 61 Sci, Bakersfield, CA, 93311, United States
4 - Pepperdine University, NATURAL SCIENCE DIV, 24255 Pacific Coast Highway, Malibu, CA, 90263, United States

Keywords:
desiccation tolerance
embolism repair
MicroCT
Pentagramma triangularis
resurrection fern
xylary chloroplasts
xylem refilling
endodermis.

Presentation Type: Oral Paper
Number: 0012
Abstract ID:544
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation


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