Respostas fisiológicas de genótipos de Eucalyptus grandis x E. urophylla à disponibilidade hídrica e adubação potássica

Abstract

o objetivo de estudar as respostas fisiológicas de cinco genótipos de eucalipto à disponibilidade hídrica e adubação potássica. As mudas foram plantadas em vasos preenchidos com sete litros de um Neossolo Quartzarênico, com baixo teor natural de potássio (0,2 mmol c .dm -3 K), e submetidas a dois regimes de irrigação (RI1 -diário e RI2 -irrigação suspensa até o aparecimento de sintomas iniciais de murcha), sem (K0) e com suprimento de potássio (K1 -200 mg.dm -3 K 2 O), em casa de vegetação. Avaliou-se a taxa fotossintética (A), condutância estomática (gs), transpiração (E), índice de conteúdo de clorofila (ICC), conteúdo relativo de água (CRA), eficiência fotoquímica (Fv/Fm), eficiência intrínseca (EUA intr ) e instantânea no uso da água (EUA inst ) e potencial hídrico foliar (Ψ f ). O experimento foi estabelecido no delineamento de blocos ao acaso, em esquema fatorial 5 x 2 x 2 (5 genótipos, 2 regimes de irrigação e 2 níveis de adubação potássica), com cinco repetições. À exceção da eficiência fotoquímica, as demais características apresentaram alterações significativas no regime RI2, com redução nos valores de A, gs e E e aumento em ICC e EUA inst . O suprimento de potássio nas plantas do RI2 proporcionou maiores valores de A, gs, E e CRA. Dos genótipos avaliados, o G1 é o mais resistente e o G2 o mais sensível à deficiência hídrica. Conclui-se que a adubação potássica pode amenizar os efeitos negativos da deficiência hídrica nos estádios iniciais de crescimento de eucalipto.Palavras-chave: Fotossíntese, estresse hídrico, metabolismo fisiológico. PHYSIOLOGICAL RESPONSES OF Eucalyptus grandis x E. urophylla GENOTYPES TO WATER AVAILABILITY AND POTASSIUM FERTILIZATION ABSTRACT: The aim of this work was to study the physiological responses of Eucalyptus genotypes seedlings to water availability and potassium fertilization. The plants were grown in pots filled with 7 L of the Quartzenic Neosoil, with low natural content potassium (0,2 mmol c .dm -3 K), and submitted to two irrigation regimes (IR1 -diary and IR2 -cessation of watering until visible wilting occurred), no (K0) and with (K1 -200 mg.dm -3 K 2 O) potassium fertilization in greenhouse condition. Photosynthetic rate (A), stomatal conductance (gs), transpiration (E), chlorophyll content index (CCI), relative water content (RWC), photochemical efficiency (Fv/Fm), intrinsic water-use-efficiency (iWUE), instantaneous water-use efficiency (WUE) and leaf water potential (Ψ f )were measured in all plants. The

Effect of soil water availability on gas exchange in young trees of Eucalyptus grandis W. Hill ex Maiden

“…grandis has physiological mechanisms, such as stomata closure, that allows it to respond to water stress. This is confirmed by stomatal conductance and transpiration data as these were lower with increasing water stress, whereas internal CO 2 (Ci) was higher with decreasing photosynthesis rates (Figure 1) (Mendes et al, 2013;Mejia de Tafur et al, 2014).…”

“…Stomatal conductance was similar in all genotypes, but the transpiration rate was lower in genotypes 19-1 and 24A-5, which means less water loss due to stomata closure, but at the expense of CO 2 fixation, which explains the lower rate of photosynthesis in the genotypes (Figure 1) (Mendes et al, 2013;Osorio & Pereira, 1994), which confirms the effect of genotype and indicating that E. grandis has in place physiological mechanisms, which have allowed to respond to water stress (Almeida et al, 2007).…”

“…nitens, andWhitehead &Beadle (2004), Mendes, de Paula, Scarpinatti &de Paula (2013), andEl-Sharkawy et al (1985), in E. deglupta and E. citriodora. Lima et al (2003), found in several Eucalyptus species (E. grandis, E. urophilla, E. camaldulensis, E. torelliana and E. phaeotrica) photosynthesis rates between 25-30 μmol CO 2 m -2 s -1 with atmospheric CO 2 concentrations of 700 ppm (± 30) in the dry season, whereas rates of photosynthesis were 10-15 μmol CO 2 m -2 s -1 at normal concentrations of 350 ppm (± 30).…”

Nutrient use efficiency in interspecific hybrids of eucalypt

“…The experiment was set up on 27 April 2010 in an area located at 21º13'55" S and 48º16'48" E, at an average altitude of 604 m, in Jaboticabal, in the State of São Paulo, Brazil, using five commercial hybrids of eucalypt, the result of crossing Eucalyptus grandis with E. urophylla and multiplied by minicutting, hereafter referred to as clones (C1, C2, C3, C4 and C5), as described by Mendes et al (2013). The experimental design was of randomised blocks, in a single-tree plot design with 35 replications, at a spacing of 3.5 x 2 m. The local climate is type Cwa, according to the Köppen classification, with an average annual precipitation of 1425 mm, temperature of 22.2 °C and relative humidity of 75%.…”

Composto de lodo de esgoto para o cultivo inicial de eucalipto

“…De modo geral, o eucalipto cresce rápido e responde a variações na fertilidade do solo (Mendes et al, 2013;Dias et al;. A adubação do eucalipto é realizada empregando-se geralmente fertilizantes minerais e, boa parte dos fertilizantes, é aplicada no momento do plantio (adubação de base), de modo a proporcionar o arranque das mudas no campo (Barros et al, 2000;Gonçalves, 2005).…”