Water Released From Vessel Embolism May Temporarily Halt Further Embolism in Tropical Dipterocarp Trees.

The formation of air bubbles in the xylem, known as embolism, reduces hydraulic conductivity and can ultimately lead to catastrophic failure of a tree's water transport system. When a vessel embolises, it releases water into the surrounding xylem tissue. Yet, how this release affects plant water status and further embolism spread remains poorly studied, especially in tropical trees. We examined xylem vulnerability curves from branches of 38 trees representing five dipterocarp species growing in a Bornean tropical rainforest. While branch water potential progressively declined as branches desiccated over time, temporary increases in branch water potential were repeatedly observed across all trees. These increases predominantly took place in the water potential range where embolism occurred, indicating that the observed increases most likely resulted from water released from embolised vessels. Our findings suggest that water release from embolism may temporarily buffer water potential declines and further embolism spread during desiccation in dipterocarp trees, although the extent to which this buffering capacity is present in other tropical and temperate species should be investigated further. Our study provides novel insights into xylem water dynamics and the mechanisms by which trees may sustain hydraulic function during periods of water stress, potentially enhancing their drought resilience.