<i>Eucalyptus</i> sp. seedling response to potassium fertilization and soil water.

Abstract

A considerable portion of Brazil‘s commercial eucalypt plantations is located in areas subjected to periods of water deficit and grown in soils with low natural fertility, particularly poor in potassium. Potassium is influential in controlling water relations of plants. The objective of this study was to verify the influence of potassium fertilization and soil water potential (Ψw) on the dry matter production and on water relations of eucalypt seedlings grown under greenhouse conditions. The experimental units were arranged in 4x4x2 randomized blocks factorial design, as follow: four species of Eucalyptus (Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus camaldulensis and hybrid Eucalyptus grandis x Eucalyptus urophylla), four dosages of K (0, 50, 100 and 200 mg dm-3) and two soil water potentials (-0.01MPa and -0.1 MPa). Plastic containers with 15 cm diameter and 18 cm height, with Styrofoam base, containing 3.0 dm3 of soil and two plants per container were used. Soil water potential was kept at -0.01MPa for 40 days after seeding. Afterward, the experimental units were divided into two groups: in one group the potential was kept at -0.01MPa, and in the other one, at -0.10 MPa. Soil water potential was controlled gravimetrically twice a day with water replacement until the desired potential was reestablished. A week before harvesting, the leaf water potential (Ψ), the photosynthetic rate (A), the stomatal conductance (gs) and the transpiration rate were evaluated. The last week before harvesting, the mass of the containers was recorded daily before watering to determine the consumption of water by the plants. After harvesting, total dry matter and leaf area were evaluated. The data were submitted to analysis of variance, to Tukey's tests and regression analyses. The application of K influenced A, gs and the transpiration rate. Plants deficient in K showed lower A and higher gs and transpiration rates. There were no statistical differences in A, gs and transpiration rates in plants with and without water deficit. The addition of K reduced the consumption of water per unit of leaf area and, in general, plants submitted to water deficit presented a lower consumption of water.

Calagem e adubação fosfatada para formação de mudas de araçá-boi

“…O delineamento experimental foi de blocos ao acaso, com quatro repetições, com uma planta por repetição, em esquema fatorial 5 x 5, sendo cinco doses de calcário dolomítico (0; 1,37; 2,83; 4,29 e 5,75 t ha-1 correspondentes a 0; 1,37; 2,83; 4,29 e 5,75 g muda-1), calculados para atingir os níveis de saturação por bases atual (1,26%) e estimadas (20%, 40%, 60% e 80%); e cinco doses de fósforo (0, 100, 200, 400 e 600 mg kg -1 de P), correspondentes à aplicação de 0; 0,56; 1,12; 2,2; e 3,35 g kg (Teixeira et al 2008). A adubação complementar foi feita na forma de solução aquosa na dose de 10 mL por saco, dividida em duas aplicações (quatro e sete meses após a calagem).…”

Potassium: a neglected nutrient in global change

“…This effect is related to the role K plays in enhancing photosynthetic CO2 fixation, improving the transport of photosynthates into sink organs and inhibiting the transfer of photosynthetic electrons to O2, thereby reducing ROS production (Cakmak, 2005). Many field studies have thus observed correlations between K concentrations in plants and soils and mechanisms of drought avoidance (Nandwal et al, 1998;Arquero et al, 2006;Teixeira et al, 2008;Fayyaz et al, 2013;Tomlinson et al, 2013). Many physiological and metabolomic studies in garden and potted plants (Babita et al, 2010;Cuéllar et al, 2010) and in crops (Römheld & Kirkby, 2010;Waraich et al, 2011;Wang et al, 2013), and some studies across environmental gradients under field conditions (Kadar & Foldesi, 2001), have observed a strong link between K concentrations and the resistance and adaptation of plants to drought.…”

“…Ashraf et al, 2002). Other physiological functions: Many plant functions that are not directly related to water economy have recently been associated with K, such as enzymatic activity and protein synthesis (Armengaud et al, 2004(Armengaud et al, , 2009, internal transport and allocation of amino acids and nitrates (Jarvis et al, 1990), photosynthetic activity and retranslocation of fixed C Teixeira et al, 2008), signal transduction and energy transport (Gajdanowicz et al, 2011), cellular, foliar and root expansion (Elumalai et al, 2002;Yin et al, 2011) and foliar movement (Travlos et al, 2008), among several other metabolic and physiological functions essential for plant life. Evidence, moreover, is increasing that adequate K fertilization plays an important role in defending crops not only against drought but also against many other biotic and abiotic stresses such as diseases, pests, salinity, cold, frost and waterlogging (see the recent review by Wang et al, 2013).…”

Nutritional Efficiency of Eucalyptus Clones Under Water Stress

“…The relationship between nutrient supply, water stress, and Eucalyptus plant growth was highlighted in several studies (Oliva et al, 1995;Teixeira et al, 2008;Valdés et al, 2013;Hodecker et al, 2014;Maseda and Fernández, 2016;Pita-Barbosa et al, 2016;Santos and Schumacher, 2016). However, since a reduced water supply can hamper nutrient uptake due to the interrelatedness of water and nutrient supply (Brouder and Volenec, 2008), knowledge about nutrient efficiency, as well as nutrient uptake, transport, and use in different Eucalyptus genotypes is still scarce.…”