Do lags in hydraulic time constants of sap flow through maize stems correspond to the size of capacitance tissues?

Authors: Comas, Louise; Wenz, Joshua

Submitted to: International Workshop on Sap Flow
Publication Type: Abstract Only
Publication Acceptance Date: 8/7/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/A

Technical Abstract: Lags in hydraulic time constants have been routinely observed across multiple species and sap flow sensor types but their interpretation has stimulated controversy. These lags have been construed as occurrences when water uptake through root systems was insufficient and stored water from plant capacitance tissues downstream of sap flow sensors was required to supplement transpiration. We show consistent 30-minute lags in hydraulic time constants in maize sap flow compared to continuous gravimetric transpiration measurements in young plants in pots in the greenhouse. Differences in transpiration from sap flow lags during the late morning were similar to those in the afternoon such that daily estimates of plant water use from sap flow sensors matched gravimetric measurements (R2 = .89). In the field, we found larger lags in sap flow in mature plants with bigger stalks, on days with greater vapor pressure deficit (VPD) and solar radiation, on days prior to irrigation, and in deficit compared to full irrigation treatments. These patterns are consistent with an interpretation of lags in sap flow hydraulic time constants indicating the functioning of capacitance tissues during periods of high VPD and suggest capacitance tissues are crucial for maintaining daily plant transpiration rates. Being able to identify genotypes with greater hydraulic capacitance tissues and breed for this trait could provide valuable new avenues for improving crop productivity.