The functional role of xylem parenchyma cells and aquaporins during recovery from severe water stress

Abstract

Xylem parenchyma cells [vessel associated cells (VACs)] constitute a significant fraction of the xylem in woody plants. These cells are often closely connected with xylem vessels or tracheids via simple pores (remnants of plasmodesmata fields). The close contact and biological activity of VACs during times of severe water stress and recovery from stress suggest that they are involved in the maintenance of xylem transport capacity and responsible for the restoration of vessel/tracheid functionality following embolism events. As recovery from embolism requires the transport of water across xylem parenchyma cell membranes, an understanding of stem-specific aquaporin expression patterns, localization and activity is a crucial part of any biological model dealing with embolism recovery processes in woody plants. In this review, we provide a short overview of xylem parenchyma cell biology with a special focus on aquaporins. In particular we address their distributions and activity during the development of drought stress, during the formation of embolism and the subsequent recovery from stress that may result in refilling. Complemented by the current biological model of parenchyma cell function during recovery from stress, this overview highlights recent breakthroughs on the unique ability of long-lived perennial plants to undergo cycles of embolism-recovery related to drought/rewetting or freeze/thaw events.

High‐resolution computed tomography reveals dynamics of desiccation and rehydration in fern petioles of a desiccation‐tolerant fern

“…Chlorenchyma may provide a source of osmotically active molecules (sucrose), contributing to the movement of water into the chlorenchyma and phloem early in resurrection. Rehydrated parenchyma may have a role in active xylem refilling, as suggested previously (Hacke & Sperry, ; Brodersen et al ., ; Secchi & Zwieniecki, , ; Secchi et al ., ). Furthermore, chloroplasts may provide energy in the form of ATP to facilitate active xylem refilling.…”

Wood allocation trade‐offs between fiber wall, fiber lumen, and axial parenchyma drive drought resistance in neotropical trees

“…The mechanisms behind the positive relationship between vessel bordering (paratracheal) axial parenchyma and K s are presently unclear. A role of paratracheal parenchyma cells in the refilling of embolized vessels has been suggested (Secchi, Pagliarani, & Zwieniecki, ; Tyree, Salleo, Nardini, Assunta Lo Gullo, & Mosca, ). Furthermore, paratracheal axial parenchyma cells are responsible for the loading of cations into the xylem vessels regulating the transpiration flow (de Boer & Wegner, ).…”

The Accumulation of miRNAs Differentially Modulated by Drought Stress Is Affected by Grafting in Grapevine

“…The candidate miRNA n_622 has three putative targets, including the hexose transporter HT5, which was functionally characterized in grapevine as a homolog of the Arabidopsis sugar transporter STP13 (Hayes et al, 2007(Hayes et al, , 2010. This could support an induction of sugar signaling pathways, which, in woody species, can facilitate adaptation and/or recovery in response to dehydration (Secchi et al, 2016).…”