Cambios anatómicos en raíces e hipocótilos de plántulas de Prosopis ruscifolia (Fabaceae) sometidas a estrés salino

Abstract

Prosopis ruscifolia is a pioneer tree species in flooding or saline areas. The aim of this work was to assess anatomical changes in roots and hypocotyls of P. ruscifolia seedlings induced to saline stress under controlled conditions. Seeds, collected in natural forests of Western Chaco region in Argentina, were sown on paper towels moisturized with saline solutions of 100, 200 and 300 mM of NaCl, and a control group with distilled water. Four repetitions of 50 seeds per treatment were sown, located in hermetic polystyrene boxes, and included in a seeding chamber, at 27 ºC and 12 hours photoperiod. Were studied 35 seedlings from each saline concentration; these seedlings were processed 12 days after sown to obtain microscopic samples. The anatomical variables measured in roots and hypocotyls were the following: main root diameter (µm), bark thickness (µm), number of cell strata in bark, central cylinder diameter (µm), pith diameter (µm), number of cell strata in the pericycle and the tangential diameter of vessels (µm). ANOVA analysis were performed with hypocotyl and root diameters as the dependent variable, and bark thickness (µm), number of cell strata in the bark, the central cylinder diameter (µm), the pith diameter (µm), number of cell strata in the pericycle, the tangential diameter of vessels and the saline concentration as independent variables. Results showed that the root diameter decreased with increasing saline concentrations (P < 0.0001). The bark thickness decreased at 100 mM (P < 0.0001) and the number of cell strata of bark increased to 300 mM (P < 0.0002). The central cylinder diameter decreased at 100 mM saline concentration (P < 0.0001) and the number of cell strata of the pericycle and the pith diameter reduced progressively until 300 mM. The tangential diameter of vessels decreased at 300 mM. These anatomical changes suggested alterations in the expansion and cell division caused by the salinity, and could limit lateral roots formation and reserves storage. Hypocotyls did not show significant anatomical changes in response to increasing salinity, with exception of stomata position and an increase of the hypodermis thickness. These changes indicated that the water stress imposed by low osmotic potential is caused by increasing saline concentration. The seedlings of P. ruscifolia experienced anatomical changes in response to tested saline concentrations in traits related to reserve storage, the absorption and conduction of water, and lateral roots formation.

Crecimiento de plántulas de Tabebuia rosea y Gliricidia sepium en condiciones de salinidad clorhídrica

“…En leñosas como Persea gratísima Mill, Ramírez et al (2014) reportaron decrecimiento de la raíz a partir de 0.1 g L -1 de NaCl, la reducción fue severa a concentraciones > 3.0 g L -1 . En Prosopis ruscifolia Griseb, concentraciones > 300 mM de NaCl formaron raíces anormales, retorcidas y manchas pardo oscuras sobre los hipocótilos (Bravo et al, 2016). Es probable que la mayor tolerancia a sales de Gliricidia sepium, esté relacionada con el hecho de que en las etapas iniciales presenta un crecimiento rápido poco sostenido que le permite evadir de manera temporal el estrés salino (Sánchez et al, 2019b).…”

“…Por su parte Azaizeh et al (1992) observaron en plantas de pino sometidas a 3 g L -1 de NaCl, que las regiones meristemática y de alargamiento de la raíz, localizadas la primera a un milímetro de la yema radical y la segunda de tres a seis milímetros de la cof ia, fueron severamente dañadas por la sal, toda vez que el tamaño f inal de las células y la división celular, se redujeron. De acuerdo a Bravo et al (2016), en Prosopis ruscifolia, el diámetro de las raíces del cilindro central, la médula, el espesor de la hipodermis, el número de estratos celulares en la corteza y el periciclo, así como el diámetro tangencial de los vasos del polo de la xilema, decrecieron signif icativamente a concentraciones > 100 mM de NaCl. El decrecimiento de la raíz por efecto de soluciones de NaCl, también es señalado por Taleisnik y López (2011) en plantas leñosas del género Acacia y en arbustos del género Atriplex, en las que se afectó la magnitud de la expansión celular y el tamaño de la zona de elongación.…”