Location: Water Management and Systems ResearchTitle: Plant hydraulic mechanisms related to increased productivity under drought in maize and sorghum.
Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: 6/19/2019
Publication Date: 10/27/2019
Citation: Comas, L.H., Drobnitch, S., Gleason, S.M., Trippe III, R.C. 2019. Plant hydraulic mechanisms related to increased productivity under drought in maize and sorghum [abstract]. International Conference on Integrative Plant Physiology. 2019 October 27-29; Sitges, Spain.
Interpretive Summary: n/a
Technical Abstract: Many plant mechanisms respond concurrently when plants are under drought stress. Identifying key plant mechanisms driving productivity under drought, thus, has been challenging. We examined traits across six maize genotypes and six sorghum genotypes, each varying in productivity under drought. Measured traits included net CO2 assimilation rates, transpiration, diurnal stomatal conductance, maximum hydraulic conductance of shoot and root systems, root pressure, and sap surge following re-watering. In maize, genotypes with the highest yield under drought in the field had the greatest reduction in photosynthesis, transpiration, and stomatal conductance in response to drought in the greenhouse. Because both transpiration and photosynthesis were similarly reduced among genotypes under drought, instantaneous water use efficiency was similar among genotypes and showed no relationship with yield under drought in the field. Genotypes with highest yield in the field had highest maximum hydraulic conductance in the field and greenhouse, and maximum diurnal stomatal conductance measured in the field. Interestingly, there was a strong positive relationship with genotypes having high sap surge following re-watering in the greenhouse and high yield under drought in the field. Immediately after cutting stems of dry plants, there was no sap surge but after re-watering and an hour for recovery, there was substantial flow. In sorghum, maximum sap surge after re-watering is higher in droughted plants than well-watered plants, suggesting an actively-regulated mechanism. We propose this sap surge is a mechanism for maintaining positive hydraulic status of developing grain, repairing embolized xylem conduits, and resuming carbon fixation. Together these data suggest that high yielding plants may avoid seed abortion and maintain high levels of gas exchange in the morning through hydraulic recovery overnight via root pressure when there is soil moisture in the root zone but have conservative stomatal control and shutdown in the middle part of the day under dry conditions.