Crops under pressure: Conductivity, root pressure, and productivity in droughted maize and sorghum

Authors: DROBNITCH, SARAH - Colorado State University; Comas, Louise; Gleason, Sean; Young, Jason; Barton, Ryan; Trippe Iii, Richard; Travers, Veronica

Submitted to: Gordon Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/25/2018
Publication Date: 6/17/2018
Citation: Drobnitch, S.T., Comas, L.H., Gleason, S.M., Young, J.S., Barton, R.W., Trippe Iii, R.C., Travers, V.H. 2018. Crops under pressure: Conductivity, root pressure, and productivity in droughted maize and sorghum. Gordon Research Conference Proceedings. https://www.grc.org/multiscale-plant-vascular-biology-conference/2018/.

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. Data were collected on carbon assimilation rates, transpiration, diurnal stomatal conductance, maximum hydraulic conductance of shoot and root systems, root pressure, and sap flux during guttation from cut stems. Maize genotypes with the highest yield under drought in the field had the lowest photosynthesis, transpiration, and stomatal conductance under controlled drought in the greenhouse. Because both transpiration and photosynthesis declined similarly among genotypes during drought stress, instantaneous water use efficiency assessed under control drought in the greenhouse was similar among genotypes and showed no relationship with yield under drought in the field. Genotypes with the highest yield under drought in the field had the highest maximum hydraulic conductance both in the field and under controlled experiments in the greenhouse. Maximum stomatal conductance measured over the course of the day in the field was higher in genotypes with higher yield in the field. Interestingly, there was a strong positive relationship with genotypes having high sap flux from guttation after re-watering in the greenhouse and high yield under drought in the field. Immediately after stems are cut, there was no sap flux from the cut stem but after plants were re-watered and given an hour for recovery, there was substantial flux, which we suspect is a key mechanism important for repairing xylem embolisms and resuming carbon fixation. Additionally, in sorghum, it is clear that sap flux is higher in droughted plants than well-watered plants. Together these data suggest that high yielding plants may 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.