The water transport pipeline in herbs is assumed to be more vulnerable to drought than in trees due to the formation of frequent
embolisms (gas bubbles), which could be removed by the occurrence of root pressure, especially in grasses. Here, we studied
hydraulic failure in herbaceous angiosperms by measuring the pressure inducing 50% loss of hydraulic conductance (P50) in stems
of 26 species, mainly European grasses (Poaceae). Our measurements show a large range in P50 from 20.5 to 27.5 MPa, which
overlaps with 94% of the woody angiosperm species in a worldwide, published data set and which strongly correlates with an
aridity index. Moreover, the P50 values obtained were substantially more negative than the midday water potentials for five grass
species monitored throughout the entire growing season, suggesting that embolism formation and repair are not routine and
mainly occur under water deficits. These results show that both herbs and trees share the ability to withstand very negative water
potentials without considerable embolism formation in their xylem conduits during drought stress. In addition, structure-function
trade-offs in grass stems reveal that more resistant species are more lignified, which was confirmed for herbaceous and closely
related woody species of the daisy group (Asteraceae). Our findings could imply that herbs with more lignified stems will
become more abundant in future grasslands under more frequent and severe droughts, potentially resulting in lower forage
digestibility.