Check the ultrasonic resonance method. It is not invasive and not destructive. In Vitis vinifera, for example, allows for continous estimation of turgor changes. You can find references in Researchgate through the following authors: Domingo Sancho-Knapik, Tomas Gómez Ávarez, Eustaquio Gil-Pelegrín. There you can get the references or ask for them

@Eustaquio Gil Pelegrín

Thanks u very much!

NMR may be another option.