Characterizing the effects of salt stress in Calendula officinalis L.

In this study the effects of salt stress on growth and several stress markers were investigated in the ornamental and medicinal plant Calendula officinalis. One month old plants were submitted to increasing concentrations of salt up to 150mM NaCl for a period of 30 days. Salinity affected growth in terms of stem length and fresh weight of the plants, but water content remained unchanged indicating a certain tolerance to low and mild concentrations of salt. Although Na+ and Cl− increased in parallel to applied salt treatments, the levels of K+ and Ca2+ showed no significant change, while Mg2+ levels recorded a two folds increase upon the application of the highest salt concentration. Other measured parameters showed a more significant change, notably proline that registered a nine folds increase under salt stress. In conclusion, although plants suffered from salt stress as shown by the degradation of photosynthetic pigments and increased MDA levels, they continued their vegetative growth under low concentrations of salt. The main mechanisms of response to stress in this species are based on the insurance of K+ and Ca2+ homeostasis and the accumulation of proline as a functional osmolyte.