The origin of a land flora : a theory based upon the facts of alternation / by F. O. Bower. With numerous illustrations.

Bower, F. O.

doi:10.5962/bhl.title.30676

Cited by 18 publications

(32 citation statements)

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“…Given that all rhizomorphic lycopsids (sensu 20–23 ) form a monophyletic group, and that extinct stigmarian rootlets were interpreted as modified leaves this suggested that the rootlets of all rhizomorphic lycopsids were modified leaves, including the rootlets of extant Isoetes 3 . The interpretation that the rootlets of extant Isoetes species were modified leaves was strikingly at odds with all previous descriptions of Isoetes rootlets that had always been interpreted as roots similar to the roots of other extant lycopsids 11,24–32 .…”

Section: Introductionmentioning

confidence: 66%

Gene expression data support the hypothesis that Isoetes rootlets are true roots and not modified leaves

Hetherington

Emms

Kelly

et al. 2019

Preprint

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Rhizomorphic lycopsids are the land plant group that includes the first giant trees to grow on Earth and extant species in the genus Isoetes. Two mutually exclusive hypotheses account for the evolution of terminal rooting axes called rootlets among the rhizomorphic lycopsids. One hypothesis states that rootlets are true roots, like roots in other lycopsids. The other states that rootlets are modified leaves. Here we test predictions of each hypothesis by investigating gene expression in the leaves and rootlets of Isoetes echinospora. We assembled the de-novo transcriptome of axenically cultured I. echinospora. Gene expression signatures of I. echinospora rootlets and leaves were different. Furthermore, gene expression signatures of I. echinospora rootlets were similar to gene expression signatures of true roots of Selaginella moellendorffii and Arabidopsis thaliana. RSL genes which positively regulate cell differentiation in roots were either exclusively or preferentially expressed in the I. echinospora rootlets, S. moellendorffii roots and A. thaliana roots compared to the leaves of each respective species. Taken together, gene expression data from the de-novo transcriptome of I. echinospora are consistent with the hypothesis that Isoetes rootlets are true roots and not modified leaves.

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Section: Introductionmentioning

confidence: 66%

Gene expression data support the hypothesis that Isoetes rootlets are true roots and not modified leaves

Hetherington

Emms

Kelly

et al. 2019

Preprint

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“…T h e number of leaf teeth varies in stems of different diameter and bears no constant relation to the three rows of segments proceeding from the division of the apical initial. Thus Bower (1908Bower ( , 1935 has pointed out that in this instance, as in many others taken from pteridophytes, apical segmentation does not dominate, or determine in any precise manner, the number and position of the lateral members, i.e. segmentation does not determine organogeny.…”

Section: Genesis and Histogenesismentioning

confidence: 75%

“…Thus Bower (1908Bower ( , 1935 has pointed out that in this instance, as in many others taken from pteridophytes, apical segmentation does not dominate, or determine in any precise manner, the number and position of the lateral members, i.e. T o those who entertained views of a strictly formal and rigid kind it seemed reasonable to expect that a close and obligate relationship would be found ; and they therefore tended to generalize from those instances in which, as a fact, new organs or tissues do arise in a consistent and regular manner in relation to the segmentation of the apical cell.…”

Section: Genesis and Histogenesismentioning

confidence: 99%

The Shoot Apex in Pteridophytes

Wardlaw

1945

Biological Reviews

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Summary (1) Some of the developments which have made for a fuller understanding of the shoot apex in pteridophytes are discussed, particular attention being paid to morphogenetic processes, (2) Of the several interpretations of growth and cellular arrangement at the apex which have been advanced, that of Naegeli, in which the importance of the apical cell is emphasized, appears to be most applicable to the livingpteridophytes; Sachs's geometrical‐mechanical views emphasize another aspect of organization at the shoot apex, while his comprehensive outlook on the nature of the meristematic region as a whole deserves careful attention. (3) In the pteridophytes, with some exceptions, there is no obligate relation between apical segmentation and organogenesis and histogenesis, i.e., segmentation does not determine organogeny. (4) The value of the facts of apical segmentation in phylogenetic studies is discussed. (5) The history of causal morphology is briefly outlined. If the phyletic history of plants were before us in full, the problems of causal morphology would still remain. These includethe external and internal factors which determine morphogenetic processes and specific structural organization. (6) The development of leaf primordia in ferns and in dicotyledons is compared: the data show that a knowledge of the fern leaf may be regarded as essential to any general theory of leaf development. Such a theory must include a consideration of spatial, metabolic and mechanical factors. (7) The view is developed that shoot buds in ferns occupy an interfoliar position at the time of their inception, the position which they eventually occupy on the shoot or leaf base being determined by the distribution of growth. Bud development thus requires a study of the integrated growth activities at the apex. (8) An account is given of the initial and subsequent differentiation and development of vascular tissue at the shoot apex; spatial, metabolic and mechanical factors which may be implicated are discussed. The view‐is held that the structural arrangements observed should be interpreted in terms of growth and not of adult functional activities. (9) Views based on comparative studies which relate to the fundamental nature of the shoot are of two kinds, i.e. axial and phytonic, a constructional unit being taken for granted‐in each case. It is anticipated that investigations of the growing point from the standpoint'of causality may eventually lead to new concepts regarding the shoot type of organization. An indication is given of some of the factors which may lend themselves to further investigation.

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“…One of the key innovations of land plants was the evolution of a mutlicellular diploid generation, the embryo, via mitoses interpolated between gamete fusion and meiosis (Bower, 1908). In seed plants, ferns, and mosses KNOX1 activity is associated with continued cell proliferation, including sporophyte apical meristem activity (Hay and Tsiantis, 2010, Sakakibara et al, 2008, Sano et al, 2005.…”

Section: Roles Of Mpknox1 In the Marchantia Sporophytementioning

confidence: 99%

Gamete-specific expression of TALE class HD genes activates the diploid sporophyte program inMarchantia polymorpha

Dierschke

Flores-Sondoval

Rast-Somssich

et al. 2020

Preprint

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Eukaryotic life cycles alternate between haploid and diploid phases and in phylogenetically diverse unicellular eukaryotes, expression of paralogous homeodomain genes in the two gametes directs the haploid-to-diploid transition. In the unicellular Chlorophyte alga Chlamydomonas KNOX and BELL TALE-homeodomain genes mediate the transition. Here we demonstrate that in the liverwort Marchantia polymorpha paternal (sperm) expression three of the five phylogenetically diverse BELL genes, MpBELL234, and maternal (egg) expression of MpKNOX1 mediate the haploid-to-diploid transition. Loss-of-function alleles of either result in zygotic or early embryonic arrest. In land plants both the haploid gametophyte and diploid sporophyte are complex multicellular organisms. Expression of MpKNOX1 and two other paralogs, MpBELL1 and MpKNOX2, during sporophyte development is consistent with a later role in patterning the sporophyte. These results indicate that the ancestral mechanism to activate diploid gene expression was retained in early diverging land plants and subsequently co-opted during evolution of the diploid sporophyte body.

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The origin of a land flora : a theory based upon the facts of alternation / by F. O. Bower. With numerous illustrations.

Cited by 18 publications

References 0 publications

Gene expression data support the hypothesis that Isoetes rootlets are true roots and not modified leaves

Gene expression data support the hypothesis that Isoetes rootlets are true roots and not modified leaves

The Shoot Apex in Pteridophytes

Gamete-specific expression of TALE class HD genes activates the diploid sporophyte program inMarchantia polymorpha

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