Effects of soil water availability on foliar water uptake of Araucaria angustifolia

BACKGROUND AND AIMS: Foliar water uptake has been reported for different species, including conifers living in drought-prone environments. We conducted three experiments to determine whether leaves might absorb mist water and how this affects the water relations of well-watered and water-stressed young plants of Araucaria angustifolia. METHODS: Three independent experiments were conducted using well-watered and water-stressed plants: immersion of shoot in water for the quantification of water uptake, the short-term exposure of plants to deuterium-enriched artificial mist, followed by the evaluation of plant water status and δ²H of xylem and soil water, and the use of the heat ratio method to measure the sap flow in saplings submitted to artificial mist. RESULTS: Foliar water uptake was demonstrated in both groups of plants, but only water-stressed plants showed a significant improvement of shoot water status. Isotope analyses indicated release of mist water in water-stressed plants rhizosphere’s, and measurements of sap flow pointed to flow reversals in saplings exposed to mist, after a soil drought period. CONCLUSIONS: The results confirm the capacity of A. angustifolia for absorbing water deposited in its leaves and demonstrate that leaf-absorbed water can be transported through the xylem to the soil close to the roots and improve plant water status.