Crescimento vegetativo, absorção de nutrientes e trocas gasosas em mangueiras submetidas a estresse salino

• Autor(a) principal: Lucena, Cicero Cartaxo de
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4507
• topic: Mangifera indica; Salinidade; Porta-enxerto; Nutrientes; Mangifera indica; Salinity; Root stock; Nutrients; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

The present work dealt with the evaluation of the tolerance to salt stress by the characterization of the influence of salinity on vegetative growth, nutrient content and distribution, gas exchanges and photochemical efficiency of the photosytem II of four commercial cultivars of mango trees grafted on the root stock Imbú . The experiment was carried out in a randomized block factorial (4 x 4) design , with 4 salt concentrations (0; 15; 30; and 45 mmol L-1 NaCl) and 4 mango cultivars ('Haden', 'Palmer', 'Tommy Atkins', and 'Ubá', all of them grafted on the root stock Imbú ), with 5 replications and 1 plant per experimental unit. The shootings were about 18 months old and were transferred from plastic bags containing substrate (3:1 earth-sand) to vases containing 7dm³ of modified Hoagland's nutrient solution. After 30 days of acclimatization to the hydroponic system, the salt concentrations were added to the nutrient solution. The shootings were submitted to salt stress for 100 days. The solution was changed every time the electrical conductivity of the control treatment reduced 20% of the initial value. 15, 25, 45, 60, 75 and 95 days after the exposure to salt stress (DAEES), the stem length, stem diameter, plant height and leaf emission were evaluated, all of them grown after the exposure to salt stress, difference in temperature (room leaf) ºC, internal concentration of CO2 (Ci), stomatal conductance (gs), transpiratory rate (E), liquid photosynthesis (A), leaf water potential (MPa) and parameters of the chlorophyll fluorescence a (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv /Fm , PSII = [(Fm -Fs)/(Fm )], D = (1- Fv /Fm ) and ETR = ( PSII x FFF x 0,42). At the end of the experiment, at 100 DAEES, the plants were collected and and roots, stem and leaves were separated. The stem was subdivided into two parts: stem of the root stock and stem of the cultivar. Next, the average leaf area (cm2), total leaf area of the plant (cm2), toxicity index in the leaves (%) and the index of leaf abscission (%) were determined. The dry mass of the root, stem of the root stock stem of the cultivar, leaf and total were determined after drying in a greenhouse Then, the contents of N-total, P, K, Ca, Mg, Na and Cl were determined for the root, stem of the root stock, stem of the cultivar and leaves. The results achieved were submitted to the variance and regression analyses at the level of 5% of probability. The mango cultivars analyzed presented decreases in stem length and diameter, plant height, leaf emission, average leaf area and total leaf area of the plant. In all the cultivars, there was a decrease, in different degrees, in the gas exchanges, leaf water potential and photochemical efficiency of the photosystem II, which were intensified in the concentrations above 15 mmol L-1 NaCl. The cultivars presented decreases for the dry mass of roots, stem, leaf and total when submitted to concentrations above 15 mmol L- 1 NaCl. Increments were observed in the indexes of leaf toxicity and leaf abscission, although symptoms of leaf toxicity were not observed in 15 mmol L-1 NaCl. The nutrient absorption was reduced, and decreases were observed in the contents of essential elements, mainly in the roots and leaves. The highest contents of ions Na+ and Cl- were observed in the part of the stem next to the canopy of the plants and mainly in the leaves, as the NaCl concentrations increased. However, the distribution of ions Na+ and Cl- was more balanced in the plant organs (root, stem and leaf) when submitted to 15 mmol L-1 NaCl. The Tommy Atkins cultivar presented more tolerance to salt stress than the other cultivars evaluated.