Ryu J.   Hwang B.   Kim W.   Lee S.  

Direct visualization of embolism spreading and water refilling under tension in xylem vessels of intact plants

Reporter: Ryu J.

Vascular networks in plants are one of the natural microfluidic systems. Plants transport water under negative pressure through xylem vessel networks from the soil to their leaves without any mechanical pump. Although water under tension is exposed to the threats of cavitation and embolism resulting from drought, freezing-thawing stresses, and insect-borne damages, xylem vessels transport water in a stable manner and even repair the embolism. Despite a great deal of interests in the ingenious ability of plants, it has been difficult to experimentally investigate water transport, embolism spreading, and embolism repair in intact plants. In this study, we present the direct observations of the xylem embolism spreading and water refilling under tension using synchrotron X-ray micro-imaging technique. We induced xylem embolism artificially by mimicking the penetration of sap-feeding insects’ stylet, and investigated the fluid dynamics of embolism spreading by the sudden tension release. In addition, we quantitatively visualized water-refilling process under tension in intact plants. The radial-refilling process is slower than the speed of embolism spreading. However, interestingly, the radial influx from a neighboring xylem vessel leads to embolism repair in a much faster rate, compared to osmotic refilling. This study will be helpful for understanding the mysterious water management in xylems under tension in depth.

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