A new high-pressure flowmeter for the estimation of hydraulic resistance in whole shoots of woody plants

Abstract

A new high-pressure flowmeter has been developed and used to estimate hydraulic resistance in whole shoots of woody plants. It is based on the perfusion of pressurized water in the plant, and the simultaneous measurement of water flow (introduced volume of water per unit of time). This device was first calibrated, and then used to estimate the hydraulic resistance of stems and leaves in 1-yr seedlings of broadleaf Quercus species (Q. rubra, Q. cerris, Q. velutina, Q. petraea, Q. frainetto, Q. pyrenaica). The measured values are reliable and similar to those reported in the literature, but taking into account that this study dealt with seedlings. We have found significant differences between species and groups of species according to their hydraulic resistance values for stems and leaves. Those species whose seedlings showed lower leaf hydraulic resistance values can rehydrate their leaves more quickly and survive in environments with certain water stress (e.g., Q. pyrenaica). The high leaf hydraulic resistance of other species indicate that they can not resist these levels of water stress (e.g, Q. rubra). This study provided new insight to the importance of leaf hydraulic resistance as an adaptative trait to face water stress. Hydraulic resistance variability must be studied in depth as an additional mechanism within a wide array of morphological and ecophysiological adaptations that provide tree species a greater drought tolerance.