Location: Water Management and Systems ResearchTitle: Plant hydraulic mechanisms underlie greater productivity under drought in grain crops.
Submitted to: International Workshop on Sap Flow
Publication Type: Abstract Only
Publication Acceptance Date: 6/13/2019
Publication Date: 10/7/2019
Citation: Comas, L.H., Drobnitch, S.T., Gleason, S.M. 2019. Plant hydraulic mechanisms underlie greater productivity under drought in grain crops [abstract]. International Workshop on Sap Flow. 2019 October 7-11. Hyytiälä, Finland.
Interpretive Summary: n/a
Technical Abstract: Although there has been great interest in plant mechanisms related to crop production under drought, hydraulic mechanisms have rarely been explored. In maize, we find genotypes with the highest yield under drought in the field have the highest maximum hydraulic conductance both in the field and greenhouse, and highest maximum diurnal stomatal conductance in the field. These genotypes have large diameter xylem vessels to facilitate this conductance. Interestingly, maize also loses > 50% of its conductive capacity each day, resulting from xylem embolization, even under well-watered conditions. However, high yielding genotypes under drought also have greater sap surge associated with root pressure following re-watering. Immediately after stems are cut, there is no sap surge from dry plants but after plants are re-watered and given an hour for recovery, there is substantial flow. In sorghum, maximum sap surge after re-watering was higher in droughted plants than well-watered plants, suggesting an actively-regulated mechanism. Measured root pressures in maize can exceed 100 kPa, which would allow the lifting of water to a height of c. 10m, thus effectively pressurizing the entire vascular system and the dissolution of emboli. We suggest hydraulic mechanisms may be key for maintaining positive hydraulic status of developing grain, reversing stem xylem cavitation, refilling potentially collapsed leaf xylem, and resuming carbon fixation.