BACKGROUND AND AIMS: Foliar water uptake (FWU) has been documented in many species and is increasingly recognized as a non-trivial factor in plant-water relations. However, it remains unknown whether FWU is a wide-spread phenomenon in Pinus species, and how it may relate to needle traits such as the form and structure of stomatal wax plugs. In this contribution, these questions were addressed by studying FWU in current-year and one-year old needles of seven Pinus species.

METHODS: We monitored FWU gravimetrically and analyzed the needle surface with cryo-scanning electron microscopy. Additionally, we considered the effect of artificial wax erosion by application of the surfactant Triton TM X-100, which is able to alter wax crystals.

KEY RESULTS: The results show for all species that 1) FWU occurred, 2) FWU is higher in old needles compared to young needles, and 3) there is substantial erosion of stomatal wax plugs in old needles. FWU was highest in P. canariensis which shows a thin stomatal wax plug. Surfactant treatment enhanced FWU.

CONCLUSIONS: The results of this study provide evidence for 1) widespread FWU in Pinus, 2) the influence of stomatal wax plugs on FWU, and 3) age-related needle surface erosion.