In situ microscopy reveals reversible cell wall swelling in kelp sieve tubes: one mechanism for turgor generation and flow control?. (20th May 2016)

• Record Type: Journal Article
• Authors: Knoblauch, Jan; Tepler Drobnitch, Sarah; Peters, Winfried S.; Knoblauch, Michael
• Is Part Of: Plant, cell and environment. Volume 39:Number 8(2016)
• Page Start: 1727
• Page End: 1736
• Publication Date: 2016-05-20
• Subjects: Nereocystis luetkeana -- Phaeophyceae -- alginate -- kelp -- Münch transport -- phloem -- sieve element -- sieve tube -- turgor; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.12736
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess sieve tubes for the symplasmic long‐distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized sieve tube structure and wound responses in fully functional, intact Bull Kelp ( Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause sieve tube occlusion as they assembled at the downstream side of sieve plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible and depended on intracellular pressure, as demonstrated by pressure‐injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because sieve tube transport is pressure‐driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps. Abstract : Kelps are unrelated to vascular plants but possess sieve tubes that resemble those in the phloem. When kelp sieve tubes are injured, their cell walls expand reversibly in dependence of intracellular pressure, reducing sieve tube volume to a fraction. This revives the forgotten concept of turgor generation by swelling cell walls; similar phenomena may have been overlooked also in other taxa including vascular plants.