Abstract Detail

Bryology and Lichenology

Whitaker, Katherine [1], Budke, Jessica [2].

Exploring Sporophyte Transpiration Rates in Mosses.

Moss sporophytes are physically attached to and depend on the maternal gametophyte through their entire life. During early development, the sporophyte apex is covered by the calyptra, which is a cap of gametophyte tissue that can protect the sporophyte from short-term desiccation events. Previous studies have reported that the rate of sporophyte transpiration is 1.3× higher when the calyptra is removed from the apex compared to sporophytes with calyptra present. However, these comparative studies that were undertaken in the 1950s do not report sample sizes or the laboratory conditions (i.e., temperature and relative humidity). Thus, the aim of this study is to examine the influence of the calyptra on sporophyte transpiration rates in mosses under controlled laboratory conditions. (1) We predict that sporophytes with calyptra on their apices will have a lower rate of transpiration compared to sporophytes with their calyptra removed. (2) We also predict that moss species with taller sporophytes will have higher transpiration rates compared to species with shorter sporophytes. 
We used two laboratory grown moss species for this study: Funaria hygrometrica Hedw., which has a relatively large sporophyte (12-80 mm) and calyptra (3-5 mm), and Physcomitrium pyriforme (Hedw.) Hampe, which has a smaller sporophyte (~15 mm) and calyptra (2-3 mm). Sporophytes with either the calyptra present on the apex or removed were placed in a growth chamber under controlled conditions (22°C, 55% RH, 22.8 µmol m-2 s-1) and a dye solution was used to visualize and determine the rate of water movement through the sporophyte.  
We analyzed these results using generalized linear mixed effects models to determine the main effects of treatment (calyptra present or removed) and species on the transpiration rate, while accounting for the covariates of sporophyte height and diameter as fixed effects and experiment date as a random effect. We found a significant effect of treatment; when the calyptra was removed, there were higher rates of sporophyte transpiration compared to individuals with the calyptra present. Species also had a significant effect on the transpiration rate with sporophytes of F. hygrometrica having a lower rate compared to P. pyriforme. These results provide additional evidence that supports the importance and influence of the calyptra on sporophyte transpiration in mosses. 

1 - University of Tennessee, Ecological and Evolutionary Biology , 569 Dabney Hall, Knoxville, TN, 37996, USA
2 - University Of Tennessee, Ecology And Evolutionary Biology Department, 569 Dabney Hall, Knoxville, TN, 37996, United States

transpiration rates
maternal effects

Presentation Type: Oral Paper
Session: BL1, Bryology/Lichenology AJ Sharp Session
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 11:30 AM
Number: BL1007
Abstract ID:275
Candidate for Awards:None

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