Botanica ActaVolume 109, Issue 5 p. 368-372 New Aspects of Bryophyte Taxonomy Provided by a Molecular Approach* M. Bopp, Corresponding Author M. Bopp Botanisches Institut der Universität Heidelberg, GermanyBotanisches Institut der Univ. Heidelberg Im Neuenheimer Feld 360 D-69120 Heidelberg GermanySearch for more papers by this authorIngrid Capesius, Corresponding Author Ingrid Capesius Botanisches Institut der Universität Heidelberg, GermanyBotanisches Institut der Univ. Heidelberg Im Neuenheimer Feld 360 D-69120 Heidelberg GermanySearch for more papers by this author M. Bopp, Corresponding Author M. Bopp Botanisches Institut der Universität Heidelberg, GermanyBotanisches Institut der Univ. Heidelberg Im Neuenheimer Feld 360 D-69120 Heidelberg GermanySearch for more papers by this authorIngrid Capesius, Corresponding Author Ingrid Capesius Botanisches Institut der Universität Heidelberg, GermanyBotanisches Institut der Univ. Heidelberg Im Neuenheimer Feld 360 D-69120 Heidelberg GermanySearch for more papers by this author First published: October 1996 https://doi.org/10.1111/j.1438-8677.1996.tb00585.xCitations: 20 † Dedicated to Prof. Dr. Dr. hc. E. Schnepf on the occasion of his retirement. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References Bopp, M. and Capesius, I. New aspects of the systematics of bryophytes. Naturwissenschaften 82 (1995), 193–194. Capesius, I. 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In the middle of the nineteenth century the pioneering research of Wilhelm Hofmeister (1824-1877, Professor in Heidelberg and TUbingen) put the ontogenesis of plants in the centre of botany in Germany. The comparison of the alternation

Mosses and liverworts are quite common throughout the world. They are found in all kinds of habitats; however, they do not play an important role in a technological respect — even with the use of hepatics for the production of rare secondary metabolites that are difficult to synthesize, (Becker and Helminger 1992) or of mosses as models to understand the regulation of plant morphogenesis (Bopp and Atzorn 1992a). Therefore, the bryophytes are infrequently objects of protoplast production or of fusion of protoplasts to acquire somatic hybrids, as is necessary when mutants or transgenic plants are used to study the effect of defined genes in bryophytes that are involved either in biosynthetic pathways or in morphogenetic steps (Ashton and Cove 1990; Bopp and Atzorn 1992b; Roski et al. 1992).

In vivo phosphorylation patterns of Funaria protonemata (wild type and auxin-deficient mutants) were analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE). In one of the mutants one soluble protein with enhanced phosphorylation could be indentified without hormone treatment in short-time experiments (45 min incubation with radioactive phosphate). Addition of 10−6 M indole-3-acetic acid (IAA) did not lead to a change in protein phosphorylation neither in the wild type nor in the two mutants when incubated for 15 min or 14 h. Abscisic acid (ABA) treatment (10−5 M) of the protonema caused various changes in protein phosphorylation detected after 14h of treatment in comparison to control protonemata, i.e. in soluble and mmicrosomal proteins. These changes could be suppressed by the addition of 10−5 M cycloheximide to the growth medium, indicating that for this phosphorylation de novo protein synthesis is necessary. Only one microsomal protein is independent of the cycloheximide treatment. Because drought stress and ABA induce the formation of new proteins, shown by the isolation of extremely heat resistant soluble proteins, it is possible that such proteins are targets for phosphorylation. However, in slowly dried protonemata changes in protein phosphorylation differ from those induced by ABA. Therefore, ABA does not alone induce the changes which are the response to drought stress in this plant system.

In higher plants the phytohormone ABA is involved in processes that are connected to water deficit, like stomatal closure or desiccation tolerance. In bryophytes, also containing ABA in their tissues, physiological functions remained uncertain for a long time. Quite recently, several papers have shown different effects of exogenously applied ABA: stomatal closure in Anthoceros, drought hardening in Funaria and production of the landform in Riccia. In all these cases the relevant conditions (water deficit) enhance the endogenous ABA level significantly. For induced desiccation tolerance, ABA serves as a mediator to induce specific proteins (dehydrins) strongly connected with this tolerance. Therefore, it can be concluded that in bryophytes ABA has the same function as in higher plants. It acts as a mediator in stress conditions.

The morphogenesis of mosses is regulated by the same plant hormones as in higher plants. A minimum amount of auxin and cytokinin is necessary, but the direction of morphogenesis from chloronema to caulonema needs an enhanced auxin content, from caulonema to buds a higher cytokinin level within the target cells. In both cases the higher level must act continuously and not only as a trigger. The third hormone, abscisic acid, is a mediator for the high desiccation tolerance of mosses.

InFunaria protonemata, preprophase bands (PPBs) of microtubules do not develop when the tip cell divides, when side branches are initiated or in intercalary regeneration divisions. We report here that PPBs do, however, develop when a tmema cell is formed. In the former cases, cell division is not coupled with an expansion of the mother cell wall at the site where the cell plate will attach. In the latter case, the mother cell wall ruptures at that site and the tmema cell elongates. This observation and the findings on presence and absence of the PPB in other cell types indicate a connection between PPB occurrence and mother cell wall expansion. They support the idea that the PPB might be involved in the local secretion of cell wall material. We extend this notion, suggesting that the microtubules of the PPB control the oriented deposition of a thin layer of cellulose microfibrils at the mother cell wall which supports the firm attachment of the cell plate when the mother cell wall expands.

In ageing protonemata of Funaria as well as in liquid cultures with low calcium medium, tmema cells (TC) develop, i.e. cells that disrupt chloronema filaments into fragments of one or a few cells. The frequence of TC is strongly enhanced and the formation accelerated in auxin-deficient mutants. In the mutants, the formation of TC is depressed by the application of 10 µM IAA, therefore TC formation is a result of auxin deficiency.TC formation starts with a highly unequal division near the proximal cross wall in intercalar chloronema cells. The TC contains only a few chloroplasts, if at all, which are soon reduced in size. The cell elongates in proximal direction, i.e. with «reversed» polarity, by expansion of a newly formed TC wall, not by tip growth. The new TC wall replaces the old lateral wall and also covers the tip of the TC, but is lacking at the cross wall toward the sister cell. The old lateral wall is locally loosened and soon ruptured. The new TC wall consists mainly of circumferentially oriented cellulose microfibrils that are deposited parallel to plasma membrane-associated microtubules. The high cellulose content and the array of microfibrils and microtubules is not observed in other protonema cells. The filament is disrupted by the disintegration of the TC, the swelling and dissolution of its wall. During TC development, extracellular vesicular membrane remnants are left that collapse to form bilayered discs.

Three-week-old protonemata of Funaria hygrometrica Hedw. cultivated in Petri dishes tolerate slow drying (24 h to complete dryness) but not rapid drying (1h to complete dryness). Slowly dried mosses show, on a dry-weight basis, a sixfold increase in abscisic-acid (ABA) contents during the drying process. Rehydrated, slowly dried protonemata have the ability to tolerate subsequent rapid drying. When ABA is added to three-week-old protonemata at a concentration of 10 μM for 16 h, tolerance to rapid drying is induced. These data indicate that the induction of drought tolerance in Funaria hygrometrica is mediated by ABA. Mosses treated with ABA loose their water as fast as controls do; therefore, ABA does not act via reduced water loss. However, induction of synthesis of new proteins by ABA may form an important part of the drought tolerance because 10 μM cycloheximide inhibits the ABA-mediated tolerance to rapid drying.