Abstract
This study evaluated the tolerance of mango cultivars 'Haden', 'Palmer', 'Tommy Atkins' and 'Uba' grafted on rootstock 'Imbú' to salt stress using chlorophyll fluorescence. Plants were grown in modified Hoagland solution containing 0, 15, 30, and 45 mmol L-1 NaCl. At 97 days the parameters of the chlorophyll fluorescence (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv'/Fm', ΦPSII = [(Fm'-Fs)/(Fm')], D = (1- Fv'/Fm') and ETR = (ΦPSII×PPF×0,84×0,5) were determined. At 100 days, the leaf emission and leaf area, toxicity and leaf abscission indexes were determined. In all cultivars evaluated, in different degree, there were decreases in photochemical efficiency of photosystem II, enhanced concentrations from 15 mmol L-1 NaCl. The decreases in the potential quantum yield of photosystem II (Fv/Fm) were 27.9, 18.7, 20.5, and 27.4%, for cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba', respectively, when grown in 45 mmol L-1 NaCl. It was found decreases in leaf emission and mean leaf area in all cultivars from 15 mmol L-1 NaCl. There were increases in leaf toxicity of 33.0, 67.5, 41.6 and 80.8% and in leaf abscission of 71.8, 29.2, 32.5, and 67.9% for the cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba' respectively, when grown in 45 mmol L-1 NaCl. Leaf toxicity and leaf abscission were not observed in 15 mmol L-1 NaCl. The decrease in Fv/Fm ratio were accompanied by decreasing in leaf emission and increased leaf toxicity index, showing, therefore, the potential of chlorophyll fluorescence in the early detection of salt stress in mango tree.
Highlights
MATERIALS AND METHODSThe mango (Mangifera indica L.) under irrigated conditions is widely cultivated in the semi-arid northeast of Brazil, where many have problems of soil salinity (AUDRY; SUASSUNA, 1995, HECK et al, 2003)
This study aimed to evaluate the effect of salt stress on the photochemical efficiency of photosystem II (PS II) from mango cultivars ‘Haden’, ‘Palmer’, ‘Tommy Atkins’ and ‘Uba’
Abscission and toxicity indexes There was a decrease in the leaf numbers, in all cultivars with increasing concentrations of NaCl (p≤0.05)
Summary
The mango (Mangifera indica L.) under irrigated conditions is widely cultivated in the semi-arid northeast of Brazil, where many have problems of soil salinity (AUDRY; SUASSUNA, 1995, HECK et al, 2003) Environmental factors such as salinity, which affect plant growth, have been investigated using measurements of quantum efficiency of photosystem II (PS II) (HAVAUX et al, 1988). The use of fluorescence parameters allow to assess the reduction in electron transport disorder diagnosed by the emission of heat in the form of infrared radiation or by fluorescence This methodology is based on the kinetics of light absorbed by antenna pigments and the excitation energy transferred to the reaction centers of photosystem I and II (KRAUSE; WEIS, 1991)
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