Evolution and palaeophysiology of the vascular system and other means of long-distance transport

John A. Raven (Lead / Corresponding author)

    Research output: Contribution to journalReview articlepeer-review

    15 Citations (Scopus)


    Photolithotrophic growth on land using atmospheric CO2 inevitably involves H2O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H2O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H2O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport.

    Original languageEnglish
    Article number20160497
    Pages (from-to)1-14
    Number of pages14
    JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
    Issue number1739
    Early online date18 Dec 2017
    Publication statusPublished - 5 Feb 2018


    • Apoplasm
    • Arbuscular mycorrhizas
    • Endodermis
    • Phloem
    • Symplasm
    • Xylem
    • Biological Transport
    • Plant Vascular Bundle/physiology
    • Scotland
    • Paleontology
    • Embryophyta/physiology
    • Fossils

    ASJC Scopus subject areas

    • General Agricultural and Biological Sciences
    • General Biochemistry,Genetics and Molecular Biology


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