Responses of pelargonium (Pelargonium x hortorum L. H. Bailey) to long-term salinity stress induced by treatment with different NaCl doses

The aim of this research was to study the physiological and biochemical responses of pelargonium growing in saline substrate. Salt stress caused an increase of sodium and chlorine, and decrease potassium ions concentrations in pelargonium leaves depending on their level in peat substrate. About 4-16-fold increase of sodium, 4-6-fold increase of chlorine were found in leaves of plants growing in substrate treated with the lowest (452 mg dm(-3)) and highest (2992 mg dm(-3)) NaCl doses, respectively. The concentration of potassium ions decreased by 20 to 27 % in leaves of plants growing in substrate supplemented with NaCl doses from 1976 to 2992 mg dm(-3), respectively. However, lower doses of sodium chloride did not affect the content of potassium ions in pelargonium leaves. The increasing salinity of substrate after the addition of 960-2992 mg NaCl dm(-3) caused the reduction of plant fresh matter in the range of 25-65 %, plant height 10-37 %, and leaf area 15-55 %. There were no changes in relative water content (RWC) and no signs of damage in the form of necrotic spots for any of the used salt concentrations. The content of chlorophyll pigments decreased proportionally to salt concentration, but the content of carotenoids did not change. Maximum photochemical activity of PSII (F-v/F-m) was reduced only in plants growing at the highest dose of NaCl. Proline and anthocyanin levels increased in response to elevated NaCl concentration. At the highest dose of NaCl proline level increased by 30 % while the content of anthocyanins increased about 2.5-fold in relation to the control. It can be assumed that proline and anthocyanins accumulated in pelargonium leaves may be responsible for the amelioration of the adverse effects of salt stress. The results revealed that the investigated pelargonium 'Survivor Dark Red' is somewhat tolerant to salinity and it can be cultivated in substrate and soil polluted with NaCl at the level lower than 1976 mg dm(-3).