Photosynthetic and Growth Responses of Olive to Proline and Salicylic Acid under Salinity Condition

Abstract

Salinity has a negative impact on growth and productivity of crops on agricultural lands. Since proline and salicylic acid are used by plants to cope with stress conditions, to test whether they can help olive plants to alleviate negative impacts of salt stress, an experiment was carried out by spraying proline (15 mM) and salicylic acid (0.25 mM) on the plants that subjected to two salinity levels (0 and 100 mM NaCl). Salinity caused an alteration in biomass partitioning; in such a way that shoot vegetative growth was more restricted by salinity than root vegetative growth. Root volume was increased in proline-sprayed plants while salinity caused a decline in the root volume. Salinity resulted in an increase in specific leaf area. Net photosynthesis, stomatal conductance and transpiration rate were decreased by salinity application in root medium. Peroxidase activity decreased in plants that subjected to salinity stress. However, application of proline resulted in improvement of vegetative growth in both control and salinity conditions. Increase in chlorophyll index was observed following proline application, while salinity caused a decline in chlorophyll index. In conclusion, salinity can cause deleterious effects on photosynthesis and vegetative growth of olive trees. Exogenous application of proline can help plants to cope with negative effects of salt stress on olive plants.