چكيده لاتين :
Lime (Citrus aurantifolia L.) is one of the most sensitive citrus species to freezing stress. In this experiment, in order to study the effect of salicylic acid (SA) application on freezing tolerance, the seedlings at the 7-9 leaf stage were sprayed with SA at concentrations of 0 (control), 0.5, 1 and 2 mM twice per day during 3 days at 10°C. Then, plants were subjected to freezing temperatures -2, -4, -6 and -8 °C, for 12 hr. Changes in chlorophyll content, soluble sugars, electrolyte leakage, proline and chlorophyll fluorescence parameters were measured as indicators of freezing evaluation. The results showed that during freezing stress electrolyte leakage has increased and chlorophyll content, efficiency of photosystem II (Fv/Fm) and electron transfer rate (ETR) have considerably decreased. Between SA treatments, application of 0.5 mM concentration increased soluble sugars effectively and decreased electrolyte leakage, whereas 1 mM concentration increased Fv/Fm and ETR considerably. Application of SA had not significant effect on chlorophyll and proline content. According to the results, application of 0.5 and 1 mM concentration of salicylic acid could improve at least 2 °C the freezing tolerance of lime seedlings.
