Morphophysiological responses and mechanisms of salt tolerance in four ornamental perennial species under tropical climate

Abstract

Salinity affects growth and quality of ornamental plants, but studies on mechanisms of salt tolerance in these plants are scarce, particularly under tropical climate conditions. Thus, the morphophysiological leaf responses of four tropical ornamental species were studied, in order to identify the mechanisms involved in the tolerance to salinity and their potentials to be irrigated with brackish water. The research was conducted in a greenhouse using a completely randomized block design, in a 10 x 4 factorial scheme, with four repetitions. The treatments consisted of ten levels of electrical conductivity of irrigation water (0.5; 1.0; 2.0; 3.0; 4.0; 5.0; 6.0; 8.0; 10.0 and 12.0 dS m-1) and four ornamental tropical species (Catharanthus roseus, Allamanda cathartica, Ixora coccinea, and Duranta erecta). At 30 and 60 days after the beginning of saline treatments (DAST), measurements of leaf gas exchange and chlorophyll index were performed. At 60 DAST, leaf area, specific leaf area, leaf area ratio, leaf succulence, Na+ and proline concentrations were measured. The physiological and morphophysiological responses of the leaves indicate that I. coccinea species has high capacity to grow under irrigation with saline water. Its higher tolerance to salinity is related to the lower concentration of Na+ in the leaves. Conversely, the sensitivity of D. erecta was associated with high Na+ and proline concentrations in leaves. The leaf concentration of proline showed to be an indicator more related to the sensitivity of ornamental plants to salt stress; however this relationship should not be generalized for all ornamental species studied.

Physiological responses of the beet crop under agricultural environment and saline stress

“…Under salinity conditions, the instantaneous carboxylation efficiency is influenced by the increase in internal CO2 concentration, due to the decrease in photosynthetic rate (Dias et al, 2018). Opposite results to the present study were found by Lacerda et al (2020) when analyzing the morphophysiological responses and salt tolerance mechanisms in four perennial ornamental species grown in a greenhouse, found a decrease in A/Ci with increasing electrical conductivity of irrigation water.…”

“…The use of irrigated agriculture becomes fundamental for a safe production (Léllis et al, 2022;Lacerda et al, 2020). This practice becomes indispensable in regions that present a high climatic variability, as is the case of the semi-arid region of Brazil; however, the vast majority of water sources available for irrigation in this region present a high content of salts (Fernandes et al, 2016;Pereira et al, 2019;Dias et al, 2020).…”

Bacilli Rhizobacteria as Biostimulants of Growth and Production of Sesame Cultivars under Water Deficit

“…For E (transpiration), a reduction was observed in both cultivars in all treatments under water deficit ( Figure 1 c). The reduction in E comes from stomatal closure since plants under water restriction or at high temperatures tend to close their stomata so as not to lose water, as highlighted in studies with sesame plants under water deficit [ 28 , 29 ]. E is a crucial factor for processes such as leaf temperature regulation.…”

Gas exchange and yellow passion fruit production under irrigation strategies using brackish water and potassium

“…In the semi-arid region of north-eastern Brazil, some of the water sources used in irrigation are considered brackish, a determining factor for soil salinization and a reduction in crop yield. An excess of salts in the irrigation water promotes stress in the plants and has a negative effect on chlorophyll biosynthesis, photochemical effi ciency and gas exchange, and consequently on production, due to the action of specifi c ions such as sodium (Na + ) and chlorine (Cl -) (NUNES et al, 2017).…”