SOME DELETERIOUS EFFECTS OF LONG-TERM SALT STRESS ON GROWTH, NUTRITION, AND PHYSIOLOGY OF GERBERA (GERBERA JAMESONII L.) AND POTENTIAL INDICATORS OF ITS SALT TOLERANCE

Tolerance of gerbera (Gerbera jamesonii L.) to long-term sodium chloride (NaCl) salt stress was evaluated by subjecting plants to 0, 10, 20, 30 and 40 mM NaCl levels for ten weeks. Increased NaCl led to a significant decrease in leaf and stem biomass. Salt stress significantly affected sodium (Na+), potassium (K+) concentrations in leaves, stems and roots leading to sharp declines in K+/Na+ ratios. Magnesium concentrations in stems and roots also showed significant declines. Adverse effect of salt stress on chlorophyll content was also significant. Proline seemed less effective in osmotic adjustment under long-term high salt stress. Switching from vegetative to reproductive growth phase was crucial for certain physiological functions. Leaf Na+ concentration showed significant correlation with important traits. These data suggest that NaCl threshold level in irrigation water for gerbera is around 10 mM. Leaf fresh weight, chlorophyll content and leaf K+/Na+ ratio are promising indicators of salt-sensitivity of gerbera.