No abstract

Major antioxidants were studied in three Citrus (C. reticulata, C. sinensis, and C. paradisi) under lowtemperature stress (1, −1, −3°C). Regulatory effects of exogenous proline (0, 15, 20 mM) were studied as well. The results indicated that treatment of exogenous proline reduced both hydrogen peroxide and lipid peroxidation in three Citrus species. The high-performance liquid chromatography chromatograms at −3°C showed that exogenous proline increases chlorogenic, gallic, p-coumaric, and ferulic acid from phenolic acids as well as naringin, quercetin, and rutin from flavonoids. The amount of oxalic, citric, and ascorbic acid increased with increasing proline concentration but tartaric acid decreased. Exogenous proline increased Gamma-aminobutyric acid although its content showed no significant difference between 15 and 20 mM. Both lowtemperature stress and treatment of proline induced the activity of ascorbate peroxidase (APX) and catalase. In contrast, lipoxygenase activity reduced with temperature decrease as well as increasing exogenous proline levels. Also, treatments of low temperature and proline showed that the levels of endogenous proline, catalase and APX in C. reticulata are higher compared with two other species and their amount increases with the reduction of temperature.

No abstract

No 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.