Morpho-Physiological Responses of Halophyte Climacoptera crassa to Salinity and Heavy Metal Stresses in In Vitro Condition

Climacoptera crassa is an annual halophyte species with great potential for use in the urban landscape. This study was performed to determine C. crassa tolerance to salinity and heavy metal stresses and to compare the plant associated mechanisms to counteract these stresses. For this purpose, the plant seedlings were exposed separately to various concentrations of NaCl (0–700 mM) or heavy metals cadmium (Cd) and lead (Pb) (0–2 mM). Our results indicated that C. crassa seedlings were able to survive at 700 mM NaCl. However, the optimum growth of seedlings was observed at 500 mM salinity. Plant in non-saline condition also displayed a normal growth. C. crassa seedlings were able to tolerate all levels of Pb, whereas their growth was inhibited at Cd concentrations exceeding 0.1 mM. The results also indicated that the increase in salinity levels in the culture medium was paralleled with the enhancement in proline, peroxide and sugar content in seedlings. A comparatively similar trend was observed when seedlings exposed to heavy metal stresses, although, the plant responses were more intense in this condition. These data suggest that osmolyte adjustment beside antioxidative enzyme activation account for the high salt tolerance of this species. Similarly, it was revealed that C. crassa uses the same mechanisms to cope with the excessive amount of heavy metals in culture medium. Therefore, it can be speculated that C. crassa benefits from its halophytic nature to tackle metal ion stresses. The present study clearly suggests that C. crassa is a highly tolerant taxon to salinity that can also survive the presence of low to moderate amount of Cd and Pb at seedling stage.