The periodic wetting of leaves enhances water relations and growth of the long‐lived conifer Araucaria angustifolia

Abstract

The importance of foliar absorption of water and atmospheric solutes in conifers was recognised in the 1970s, and the importance of fog as a water source in forest environments has been recently demonstrated. Araucaria angustifolia (Araucariaceae) is an emergent tree species that grows in montane forests of southern Brazil, where rainfall and fog are frequent events, leading to frequent wetting of the leaves. Despite anatomical evidence in favour of leaf water absorption, there is no information on the existence and physiological significance of a such process. In this study, we test the hypothesis that the use of atmospheric water by leaves takes place and is physiologically relevant for the species, by comparing growth, water relations and nutritional status between plants grown under two conditions of soil water (well-watered and water-stressed plants) and three types of leaf spraying (none, water and nutrient solution spray). Leaf spraying had a greater effect in improving plant water relations when plants were under water stress. Plant growth was more responsive to water available to the leaves than to the roots, and was equally increased by both types of leaf spraying, with no interaction with soil water status. Spraying leaves with nutrient solution increased shoot ramification and raised the concentrations of N, P, K, Zn, Cu and Fe in the roots. Our results provide strong indications that water and nutrients are indeed absorbed by leaves of A. angustifolia, and that this process might be as important as water uptake by its roots.

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

“…A previous study had already provided strong indication that leaves of A. angustifolia are capable of absorbing water (Cassana and Dillenburg 2013). The present results not only confirm this capacity, but, more importantly, demonstrate that this water subsidy can be transported through the xylem to the soil close to the roots, and improve plant water status.…”

“…The study by Mósena and Dillenburg (2004) reported the expected growth reductions in response to water withdrawal, but the main focus of their study was on the interactive effects of soil compaction and drought. Recently, Cassana and Dillenburg (2013) provided strong evidence that water and nutrients are absorbed by leaves of A. angustifolia, and that this process might be as important as water uptake by its roots. The present study reports on three experiments that aim to demonstrate the relevance of FWU to the water relations of well-watered and waterstressed plants of A. angustifolia, and to examine the possible redistribution of leaf-absorbed water down to the roots and soil.…”

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.…”

SOIL FERTILITY AFFECTS ELEMENTAL DISTRIBUTION IN NEEDLES OF THE CONIFER Araucaria angustifolia: A MICROANALYTICAL STUDY

“…Therefore, under cultivation application of these two nutrients represents a considerable cost. In studies with A. angustifolia, elemental composition analysis has been used to assess nutritional status and plant/water relationships (GARBIN;DILLENBURG 2008;CASSANA;DILLENBURG, 2013). However, use of total needle elemental concentrations can have limited use in the study of plant metabolism because tissue types within the needles may have variable composition (REGVAR et al, 2013;CARVALHO et al, 2016).…”