New perspectives in the biophysics and physiology of bryophytes

J. A. Raven, H. Griffiths, E. C. Smith, K. C. Vaughn

Research output: Chapter in Book/Conference paperChapterpeer-review

8 Citations (Scopus)

Abstract

The paper summarizes recent advances in the biophysics of membrane transport, and the biochemistry of CO2 fixation, in bryophytes. The fundamentals of transport of the plasmalemma and the tonoplast of bryophytes closely resemble those of their nearest relatives, i.e. charophycean algae and vascular plants. A good start has been made in relating these transport phenomena to the ecology of the organisms, and to their development (e.g. gametophyte to sporophyte solute fluxes), but further investigation is needed. A particularly interesting case is that of the 'action potentials' with a metabolic component in Anthoceros and Conocephalum which may have a role in signal transduction. An analysis of the relevant literature shows that the great majority of the bryophytes tested (mosses, liverworts, and the pyrenoid-less hornwort Megaceros) have C3 physiology (diffusive CO2 transport to RUBISCO), although two aquatic mosses (Fissidens cf. mahatonensis; Fontinalis antipyretica) show indications of the presence of a CO2-concentrating mechanism. There is no evidence of C4 or CAM photosynthesis in bryophytes. Those hornworts with pyrenoids (e.g. Anthoceros, Phaeoceros) have, on the basis of gas exchange and 13C/12C discrimination evidence, a well developed CO2 concentrating mechanism. Quantitative analysis of the conductances of CO2 in various parts of the pathway of CO2 transport (fluid diffusion boundary layer; transport within the cell to RUBISCO; carboxylation in situ using 13C/12C discrimination; measurement of boundary layer conductances, measurements of biochemical capacity of photosynthesis) shows that less than half of the limitation of photosynthesis in aquatic mosses, and less than a third of that in terrestrial bryophytes, relates to CO2 transport. In aquatic mosses in rapidly flowing water, and in some terrestrial bryophytes, there is little restriction of CO2 fixation by CO2 diffusion. However, there are several unexplained findings and both those bryophytes with C3 physiology and the minority with a C02-concentrating mechanism need further investigation.

Original languageEnglish
Title of host publicationBryology for the Twenty-first Century
PublisherCRC Press
Chapter17
Pages261-275
Number of pages15
ISBN (Electronic)9781351463041
ISBN (Print)9780901286901
Publication statusPublished - 2 Feb 2018
Externally publishedYes

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