Abstract

MELONI, Diego Ariel; SILVA, Diolina Moura; LEDESMA, Ramón  and  BOLZON, Graciela Inés. Mineral nutrition and photosynthesis of Prosopis alba (Fabaceae) seedlings under saline stress. Cuadernos de Investigación UNED [online]. 2017, vol.9, n.2, pp.297-304. ISSN 1659-4266.  http://dx.doi.org/10.22458/urj.v9i2.1903.

Algarrobo blanco (Prosopis alba G.) is a species of forest significance native to the Western Chaco phytogeographic region. Despite being considered saline-tolerant, the physiological mechanisms that endow the species with such characteristics have not been dilucidated. This paper aimed to evaluate the impact of saline stress upon the mineral nutrition and photosynthesis of algarrobo blanco seedlings. The seedlings were grown hydroponically in 5 l containers using a 25% Hoagland nutritive solution with or without the supplementation of 500 mM of NaCl and kept in growth chamber. Daily samples were taken to quantify both the Na+, K+, Cl-, NO3 - concentrations and the nitrate reductase enzymatic activity; the chlorophyll a fluorescence emission was also measured. Root and leaf biomasses were determined after seven days of treatment. An entirely randomized experimental design with ten repetitions was used and the data analyzed with ANOVA and the Tukey Test. The saline stress inhibited the development of the aerial part but had no effect on the root development causing the increase of the root/aerial part ratio. Salinity made the leaf Na+ and Cl- concentrations increase and those of K+ and NO3 - decrease; however, the K+ concentrations kept high throughout the entire test. Together with a decrease in the NO3 - concentration, a lower nitrate reductase activity occurred out of the fourth day of treatment. A decrease in the values of qP and Fv/Fm and an increase in the NPQ that altogether indicates that saline stress caused photoinhibition was also observed. These results show that the species tolerates saline concentrations equivalents to sea water; the increase in the root/aerial part rate and the high leaf concentrations of K+ under saline-stress conditions may both be highlighted as its physiological adaptations to saline environments. Growth inhibition occurs because of the decrease in the nitrate reductase activity and photoinhibition.

Keywords : saline stress; nitrogen metabolism; chlorophyll a fluorescence; Prosopis alba.

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