Grapevine petioles are more sensitive to drought induced embolism than stems: evidence from in vivo MRI and microcomputed tomography observations of hydraulic vulnerability segmentation.

Abstract

The 'hydraulic vulnerability segmentation' hypothesis predicts that expendable distal organs are more susceptible to water stress-induced embolism than the main stem of the plant. In the current work, we present the first in vivo visualization of this phenomenon. In two separate experiments, using magnetic resonance imaging or synchrotron-based microcomputed tomography, grapevines (Vitis vinifera) were dehydrated while simultaneously scanning the main stems and petioles for the occurrence of emboli at different xylem pressures (Ψx ). Magnetic resonance imaging revealed that 50% of the conductive xylem area of the petioles was embolized at a Ψx of -1.54 MPa, whereas the stems did not reach similar losses until -1.9 MPa. Microcomputed tomography confirmed these findings, showing that approximately half the vessels in the petioles were embolized at a Ψx of -1.6 MPa, whereas only few were embolized in the stems. Petioles were shown to be more resistant to water stress-induced embolism than previously measured with invasive hydraulic methods. The results provide the first direct evidence for the hydraulic vulnerability segmentation hypothesis and highlight its importance in grapevine responses to severe water stress. Additionally, these data suggest that air entry through the petiole into the stem is unlikely in grapevines during drought.

Plant phenotyping relevance

MRIとマイクロCTによる生体内画像化を用いてブドウの茎・葉柄の木部塞栓を定量し、植物の水ストレス状態を評価する手法が研究の中心であるため。

Code and data availability

The article describes MRI and microCT embolism measurements and ImageJ/IDL/SigmaPlot analysis, but contains no public phenotype dataset, image repository, author code deposit, or data availability statement. The Supporting Information is only a time-lapse animation with no explicit deposit of data or analysis assets.

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