Mechanisms of salt tolerance in habanero pepper plants (Capsicum chinense Jacq.): Proline accumulation, ions dynamics and sodium root-shoot partition and compartmentation

Abstract

Despite its economic relevance, little is known about salt tolerance mechanisms in pepper plants. To address this question, we compared differences in responses to NaCl in two Capsicum chinense varieties: Rex (tolerant) and Chichen-Itza (sensitive). Under salt stress (150 mM NaCl over 7 days) roots of Rex variety accumulated 50 times more compatible solutes such as proline compared to Chichen-Itza. Mineral analysis indicated that Na+ is restricted to roots by preventing its transport to leaves. Fluorescence analysis suggested an efficient Na+ compartmentalization in vacuole-like structures and in small intracellular compartments in roots of Rex variety. At the same time, Na+ in Chichen-Itza plants was compartmentalized in the apoplast, suggesting substantial Na+ extrusion. Rex variety was found to retain more K+ in its roots under salt stress according to a mineral analysis and microelectrode ion flux estimation (MIFE). Vanadate-sensitive H+ efflux was higher in Chichen-Itza variety plants, suggesting a higher activity of the plasma membrane H+-ATPase, which fuels the extrusion of Na+, and, possibly, also the re-uptake of K+. Our results suggest a combination of stress tolerance mechanisms, in order to alleviate the salt-induced injury. Furthermore, Na+ extrusion to apoplast does not appear to be an efficient strategy for salt tolerance in pepper plants.

Physiological changes of pepper accessions in response to salinity and water stress

“…The main effect when plants start becoming stressed is the reduced water content in their tissue, and therefore the closure of leaf stomatal complexes takes place. Consequently, transpiration (Bray et al, 2000) and/or photosynthesis may decrease through reduced osmotic potential in the soil solution, which involves reduced water potential (Bojórquez-Quintal et al, 2014;Penella et al, 2014aPenella et al, , 2015Penella et al, , 2016. If salinity stress occurs, a specific ionic effect appears, mediated by the accumulation of toxic ions in cellular tissues (De Pascale et al, 2003) with imbalances between nutrients (Hasanuzzaman et al, 2013).…”

Salt priming improved salt tolerance in sweet sorghum by enhancing osmotic resistance and reducing root Na+ uptake

“…As the underlying reason, the difference of salt tolerance among plant varieties originates from the adjustment of root Na ? uptake (Bojorquez-Quintal et al 2014;Maathuis et al 2014). After the exploitation of non-invasive micro-test technique (NMT), ion flux at root interface has been paid more attention.…”

Germination and growth of ornamental pepper plants due to salinity

“…It is worth noting that the percentage of salt in the medium tested by the latter authors may have been insufficient to cause damage to the seedlings and concluded that further tests at higher concentrations should be done. Bojórquez-Quintal et al (2014) found differences between Chichen-Itza and Rex varieties belonging to the C. chinense species at different NaCl concentrations, the latter being more tolerant at the 100mM dose. However, the 150mM dose affected both cultivars, causing loss of fresh matter, foliar abscission and root darkening.…”

“…Bojórquez-Quintal et al (2014) reported that despite the economic importance of pepper, little is known about the mechanisms of tolerance to high salt concentrations.…”