Tahmaseb Asemaneh

Salinity is a major abiotic stress limiting plants growth and development. As silicon (Si) has been stated to alleviate salt stress in some plant species, effects of Si on Lens culinaris Medik under salinity were investigated in this study. The effects of four levels of Si in nutrient solution (0, 0.1, 0.25, and 0.5 mM) on the plant growth and physiological parameters under salinity (0, 40, and 80 mM of NaCl) were considered in a factorial experiment. Salinity decreased dry weight, stem length, leaf area, chlorophyll and anthocyanin content, potassium (K) and protein concentration, K to sodium (Na) ratio and root Si content, while increased carotenoids content. Si, especially at 0.1 mM concentration in nutrient solution, increased root and shoot length, plant dry weight and leaf area. However, higher concentrations of Si often had a negative impact on most of the characteristics. Also, some levels of Si treatment significantly increased leaf chlorophyll, carotenoids and anthocyanin, K, Si and protein content but decreased the amount of plant Na content under salinity. In overall, it seems that, the use of low levels of Si is capable to reduce harmful effects of salinity on L. culinaris and improve plant resistance to salt stress.

This study investigated the cellular and subcellular compartmentation of Ni in the Eurasian serpentine species Alyssum murale, Alyssum bracteatum and Cleome heratensis and a non-serpentine population of A. murale (as a control) grown in hydroponic culture. Plant growth responses and Ni uptake clearly revealed the higher Ni tolerance of serpentine plants than the non-serpentine plants. Serpentine A. murale and A. bracteatum grew better at elevated (0.01 mM) Ni in the nutrient solution, supporting the view that the Ni hyperaccumulators have a higher requirement for Ni than normal plants. Low shoot Ni content of C. heratensis in response to the high Ni treatments indicated that this species employs an avoidance strategy for Ni tolerance. Energy-dispersive X-ray microanalysis showed that Ni was highly concentrated in the cell walls and cell lumen, most likely the vacuoles, of leaf epidermis of A. murale and A. bracteatum rather than in the mesophyll cells. EDX spectra from leaves of the non-serpentine A. murale suggested that Ni accumulated in both epidermal and mesophyll cells but not in the epidermal cell walls. Growth reduction and Ni toxicity in plants of the non-serpentine A. murale could be due to accumulation of Ni in the lumen of leaf mesophyll cells. Our data suggest that cellular and subcellular compartmentation are both possible mechanisms for Ni tolerance employed by the serpentine A. murale and A. bracteatum.