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

Abstract

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 deuteriumenriched artificial mist, followed by the evaluation of plant water status and δ 2 H 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 waterstressed 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.

Foliar water uptake: Processes, pathways, and integration into plant water budgets

“…fraseri , FWU was approximately 10% of the maximum transpiration fluxes. This is similar to the results from Cassana et al () using sap flow methods. These values provide first approximations of FWU at the leaf‐level relative to transpiration fluxes for canopy trees.…”

“…It should be noted that these methods would integrate water absorbed through both leaves and bark (e.g., Earles et al, ). The rates cited in several studies suggest that reverse flow rates can be 5% to 26% of maximum transpiration fluxes, which is consistent with leaf‐level data (Burgess & Dawson, ; Cassana et al, ; Eller et al, ; Li, Xiao, Zhao, Zhou, & Wang, ; Steppe et al, ). What is unclear in these studies is the extent to which negative sap flow in wood presents a 1:1 relationship with water absorbed at the leaf surface.…”

“…Interestingly, the highest fluxes were observed in three temperate conifers: A . angustifolia (Cassana, Eller, Oliveira, & Dillenburg, ), Picea rubens , and Abies fraseri (Berry & Smith, ). Berry and Smith () observed maximum transpiration fluxes of 1.5–2.0 mmol m −2 s −1 .…”

A Preliminary Experiment on the Effects of Leaf Wetting on Gas Exchange in Tomato Leaves

“…Therefore, interest in the positive effects of leaf wetting is limited for horticultural crops, despite many reports of these positive effects in natural environments (Limm et al, 2009) and a few reports in horticultural crops (Ozawa, 1988). Leaf wetting may have either positive or negative effects on horticultural crops, depending on plant water status (Cassana and Dillenburg, 2013;Cassana et al, 2016) and leaf morphology (Hanba et al, 2004). Because of the complexity of the effects of leaf wetting on plants, the application of its positive effects to horticultural crop cultivation are not currently fully understood.…”

Increased growth of Araucaria angustifolia under warm conditions is unaccompanied by increased photosynthetic performance

“…Few ecophysiological studies have been conducted with this species, focusing on its response to contrasting irradiance (Duarte and Dillenburg 2000), soil compaction, water relations (Mósena and Dillenburg 2004;Cassana and Dillenburg 2013;Cassana et al 2015), as well as comparisons between young and adult trees in the field (Franco et al 2005). Studies about the effects of increasing temperature on the physiology of A. angustifolia are important, even though this species is associated with cool and moist conditions of subtropical climate.…”