Effects of Chemical Priming on the Germination of the Ornamental Halophyte Lobularia maritima under NaCl Salinity

Abstract

Lobularia maritima or sweet alyssum (Brassicaceae) is an annual littoral halophyte, naturally thriving on sandy beaches. In addition to its obvious interest as a naturally salt-tolerant plant, this species is mainly cultivated as an ornamental plant in many countries. Laboratory experiments were carried out to assess the effects of salinity on seed germination and on germination recovery from the effects of saline conditions after transfer to distilled water. Seed germination responses were determined at 0, 50, 100, 200 and 300 mM NaCl. Salt (NaCl) does not affect the germination of L. maritima if applied at a moderate dose of 50 mM. For higher concentrations of NaCl, there is a decrease in the germination rate at 100 and 200 mM NaCl or even a total inhibition of germination at 300 mM. Salt lowers or inhibits germination only through osmotic effects. To improve the germination of L. maritima under high salinity, seeds were pretreated with KNO3, thiourea, proline and salicylic acid. The germination of seeds is improved by KNO3 in the presence or absence of salt, while thiourea increases the final germination without affecting the germination rate. Salicylic acid amplifies the effect of salt, while proline delays germination without stopping it completely. These findings indicate that the application of KNO3 and thiourea may be used to improve seed germination of L. maritima, which is of great interest for cultivating this plant for landscaping purposes in saline soils.