Abstract Detail

Desiccation tolerance in bryophytes: perspectives from early career scientists

Deane-Coe, Kirsten K. [1].

Comparative desiccation tolerance of biocrust mosses in colonial habit revealed by imaging chlorophyll fluorescence.

Biocrust mosses are an intrinsic ecological component of dryland ecosystems, where, as members of biocrust communities, they contribute to the regulation of soil stability, hydrology, and nutrient cycling. Syntrichia caninervis and S. ruralis are closely related taxa that represent the two dominant biocrust mosses in drylands of Western North America. These two mosses have overlapping distributions but typically occupy different niches, potentially owing to their relative levels of desiccation tolerance (DT). It has been suggested using several metrics of DT (damage control, damage repair, carbon balance as a function of water content) that S. caninervis displays a higher degree of DT than S. ruralis. Here I present new information on the comparative DT of the photosynthetic apparatus in S. caninervis and S. ruralis using imaging chlorophyll fluorescence techniques. Samples of S. caninervis and S. ruralis were collected from the field in UT and NM, USA, and 1-cm pucks containing 15-20 shoots each were loaded in to a 48-well plate above soil samples collected under or adjacent to the moss. Over the course of 12 weeks, samples underwent a desiccation stress treatment (three 2 mm precipitation events per week) or an unstressed treatment (one 6 mm precipitation event per week), and chlorophyll fluorescence was measured every two weeks for 12 continuous hours immediately following a precipitation event. Initially, recovery of photosynthesis following a period of desiccation, measured by maximum quantum yield of photosystem II (ΦPSII), occurred within 30 min of rehydration in both species, and ΦPSII values remained stable at 0.4±0.5 (S. caninervis) and 0.3±0.6 (S. ruralis). Over the course of the treatment period, however, recovery of photosynthesis became slower, often taking multiple hours, and maximum ΦPSII declined in both species in the stressed treatment. Declines in ΦPSII were greater in S. ruralis, which also displayed visibly chloric tissues following six weeks of treatment, even in the unstressed samples. The unstressed samples of S. caninervis, on the other hand, consistently displayed the highest photosynthetic performance over the course of the treatment period. These results present additional evidence for the high degree of DT in S. caninervis compared to S. ruralis, reveal that hydrologic stress thresholds for photosynthetic capacity may differ among dominant biocrust mosses, and identify relevant precipitation-induced declines in performance in the face of global change in dryland systems.

1 - Cornell University, School of Integrative Plant Sciences, 1132 Comstock Hall, Ithaca, NY, 14850, USA

Keywords:
Photosynthesis
Syntrichia caninervis
Syntrichia ruralis
precipitation
dryland
ΦPSII.

Presentation Type: Symposium Presentation
Session: SY11
Location: Salon 8/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 1:45 PM
Number: SY11002
Abstract ID:347
Candidate for Awards:None