Morphological and physiological traits reveal differential salinity tolerance of two contrasting Glandularia cultivars

Abstract

In view of the current, continuous decrease of water availability, the need to explore new mitigation alternatives has given focus to salt-tolerant genotypes. The aim of this work was to study salt tolerance of two ornamental cultivars of Glandularia (Glandularia x hybrida) of contrasting vigor, Dulce Coral and Extrema Violeta, breeded at the Floriculture Institute of INTA. A greenhouse experiment was carried out with potted plants. Plants were subjected to four salt treatments 1.2, 2.4, 3.5, 4.4 dS m−1 (EC), and a control (0.03 dS m−1). Shoot dry weight of Dulce Coral was not affected by salinity. In contrast, the dry weight of Extrema Violeta decreased sharply as salinity increased. The root:shoot ratio was always higher for Extrema Violeta than Dulce Coral. The leaves of Dulce Coral accumulated less Na+ and Cl− than Extrema Violeta. Moreover, Extrema Violeta exhibited severe foliar salt damage, but Dulce Coral showed only a few, without compromising its commercial value. Besides, Dulce Coral had a higher assimilation rate than Extrema Violeta at all treatments. All these features could suggest Na+ and Cl− exclusion as salt-tolerant mechanism for Dulce Coral. Other mechanisms adopted by Dulce Coral to cope with salinity was the maintenance of a higher K+/Na+ and Ca2+/Na+ ratio in its leaves, a lower root:shoot ratio and the maintenance of photosynthesis. Therefore, Dulce Coral could be proposed as a parent for breeding programs with the objective of improving salt tolerance in Glandularia. In this exploratory study, we distinguish some of the most important physiological (K+/Na+ and Ca2+/Na+) and morphological (root:shoot ratio) traits related to salinity tolerance in Glandularia.