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.

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.

Sweet potato (Ipomoea batatas L.) plants were cultivated in vitro in Murashige and Skoog (MS) medium with 20 and 40 g L-1 of sucrose under two different photon flux densities (21 and 60 µmol m-2 s-1). Leaves developed in vitro mostly showed high variable to maximum fluorescence ratio (F V/F M) , indicating good development of photosynthetic apparatus. This ratio decreased during leaf aging, especially in the plants cultivated in vitro on medium with higher sucrose concentration and higher photon flux. Leaves developed ex vitro showed high F V/F M ratio during whole experiment. The effective photochemical efficiency (F V'/F M') was maximum at 15th day after emergence of leaves. Photosynthetic potential rate was higher in leaves developed in vitro than in leaves originated ex vitro

The sludge produced by rice parboiling wastewater treatment plants has substantial amounts of nutrients and organic matter, therefore requiring proper environmental disposal. One option is to use it as an alternative substrate for the production of forest species seedlings. This study aimed to assess the viability of using the sludge from rice parboiling wastewater as an alternative substrate for the production of Araucaria angustifolia (Bertol.) O. Kuntze seedlings. A. angustifolia seeds were kept in vermiculite until sprouting, then transferred to polyethylene bags filled with five different substrates (treatments): 100% sand (T1); 75% sand and 25% sludge (T2); 50% sand and 50% sludge (T3); 25% sand and 75% sludge (T4); 100% sludge (T5). Each treatment had 10 replicates (bag with one seedling). Shoot system growth, hypocotyl diameter, root system growth and biomass were evaluated at 94, 180, and 300 days of growth. Data were subjected to Analysis of Variance (ANOVA) followed by Tukey test with a significance level of 5%. Seedlings’ growth was similar on treatments containing 25%, 50%, and 75% sludge, while 100% sand and 100% sludge resulted in less growth at 300 days. In conclusion, the sludge from rice parboiling wastewater is suitable as an alternative substrate, and the ratio of 25% sand + 75% sludge could be recommended, for exploit larger amounts of the residue.

Na região Sul do Rio Grande do Sul, indústrias de beneficiamento de arroz produzem grande volume de resíduos tais como a casca de arroz e o lodo oriundo do processo de parboilização. Estes resíduos, que causam problemas ao meio ambiente, podem ser promissores para utilização como substratos na produção de mudas de florestais. Baseados neste fato, objetivou-se verificar a possibilidade de produção de mudas de cedro a partir de resíduos agroindustriais, reduzindo custos na aquisição de substratos comerciais e minimizando problemas ambientais. O delineamento experimental utilizado foi inteiramente casualizado com quatro repetições com 20 tubetes por parcela, totalizando 480 tubetes. Os tratamentos foram: T1 - 100% de substrato comercial; T2 - 100% de casca de arroz carbonizada (CAC); T3 - 100% de lodo de arroz parboilizado (LP); T4 – 50% de CAC e 50% de substrato comercial; T5 - 50% de LP e 50% de substrato comercial e T6 - 50% de LP e 50% de CAC. As variáveis analisadas foram: Percentual de emergência, Índice de velocidade de emergência, massa fresca de parte aérea e do sistema radicular, massa seca de parte aérea e do sistema radicular, altura de planta, comprimento da maior raiz e diâmetro do colo. Os resultados mostraram que lodo, misturado ao substrato comercial, reduz os custos de produção, proporcionando mudas de melhor crescimento e qualidade, podendo ser indicado para produção de mudas de cedro, constituindo-se em uma solução ambientalmente correta para destinação dos mesmos.