NOCTURNAL SAP FLOW MEASUREMENTS IN SQUASH USING THE T-MAX METHOD: TRANSPIRATION OR REHYDRATION?

We present measurements of nocturnal sap flow through the main stem of a squash plant using the T-max method.
Night-time sap flow was registered on nights with a high vapour pressure deficit and sustained winds after soil moisture-recharging rainfall.
The relative contribution of nocturnal transpiration and passive rehydration of plant tissue to the overall sap flow is difficult to separate.
Our transpiration model does not account for rehydration although our heat pulse measurements are likely to register it.
Therefore, we use this difference to speculate about the contribution of night-time sap flow and rehydration to the overall sap flow as a function of the night-time vapour pressure deficit.
We hope that improvements to our T-max measurement method or the use of another heat pulse technique to accurately register low flows will allow us to distinguish rehydration from transpiration during night-time sap flow with more confidence in the future.

VII International Workshop on Sap Flow

M. van der Velde, S.R. Green, B.E. Clothier

heat pulse, miniature probes, night time transpiration, modelling, tropical, Tonga, Cucurbita

https://doi.org/10.17660/ActaHortic.2009.846.10