CONICET | Buscador de Institutos y Recursos Humanos

tPlant morphology, anatomy, ultra-structure and metabolism are deeply affected by salt stress. Althoughsalt mixtures occur naturally in soils there are few studies considering their effect in plant salt tolerance,particularly in halophytes. The aim of the present study was to determine the effects of the salt mixtureNa2SO4+ NaCl at different concentrations on the anatomy of Prosopis strombulifera, and to compare themwith the responses observed earlier in iso-osmotic monosaline cultures. Seedlings were grown hydropon-ically in Hoagland?s solution adding salt pulses of NaCl + Na2SO4(25 mM L−1and 19 mM L−1, respectively),every 48 h until final ovalues of −1, −1.9, and −2.6 MPa. Control plants were grown under unsalted con-ditions. The salt-mixture also induced anatomical and histological alterations in roots, stems and leafletsin comparison with control plants and monosaline treated plants. These changes were noticeable fromo= −1.9 MPa. Reduction in cortical tissues in roots and stems, and reduction in the mesophyll thicknesswere observed in treated plants, as well as lower number of leaflets. The different degrees of anatom-ical modifications were dependent on the organ/tissue analyzed and could be particularly attributedto the presence of Cl−or SO42−in the culture medium. Some of them developed features intermediatebetween those observed in monosaline (NaCl or Na2SO4) treated plants, in agreement with the rever-sion of the toxic effect of SO42−anion on plant growth under iso-osmotic salt-mixture. We propose thatplant anatomical modifications are responses correlated with the chemical nature of the ions present inthe medium. When Cl−and SO42−are simultaneously present in the solution, ionic interactions occurdetermining specific responses which differ in their degree or intensity from those caused by monosalinesolutions.

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