Xylem network connectivity and embolism spread in grapevine(Vitis vinifera L.)

Area of Science:

• Plant physiology
• Xylem hydraulics
• Biophysics

Background:

• Xylem networks transport water in plants but are vulnerable to gas embolisms, which impede water flow.
• The 3D structure of xylem and intervessel connections influence embolism spread, but their functional impact remains unclear.

Purpose of the Study:

• To investigate how grapevine xylem network organization affects embolism spread and hydraulic conductivity loss.
• To model the functional implications of xylem network complexity under drought stress.

Main Methods:

• Reconstruction of grapevine (Vitis vinifera L.) xylem networks using 3D X-ray micro-computed tomography (microCT).
• Hydraulic modeling to simulate water transport and embolism spread under negative xylem sap pressure.
• Sensitivity analysis of network parameters on embolism spread and hydraulic performance.

Main Results:

• Mean pit area per intervessel connection was consistent, but short stem segments (0.5 cm) did not represent full network connectivity.
• Xylem network organization provided resistance to embolism spread beyond the pit membrane's air-seeding threshold.
• Network vulnerability was most sensitive to the initial number/location of embolized vessels and pit membrane vulnerability.

Conclusions:

• Grapevine xylem network organization increases stem resistance to embolism spread by 40% (0.66 MPa).
• The study challenges the assumption that single embolisms can rapidly spread throughout entire xylem networks.
• Xylem structure plays a crucial role in plant drought tolerance by limiting embolism propagation.