Effects of Salinity and Proline On Growth and Physiological Characteristics of Three Olive Cultivars

Crop growth and yield are functions of environmental factors. One of these factors is salt stress which can have harmful effects on plants. Olive is one of the most important Mediterranean plants and is moderately salt tolerant. Various mechanisms have been proposed to regulate plant adaptation and tolerance to salinity stress. Plants are more sensitive to salinity at early growth. This study was carried out in 2019 at Gorgan University of Agricultural Sciences and Natural Resources (altitude: 125 m above sea level, latitude: 36.83 N, and longitude: 54.48 E). In this study, the effects of NaCl (0, 50, 100, and 200 mM) induced salinity and proline foliar spray (0, 100, and 200 mg/L) on olive plantlets (including Arbequina, Arbosana, and Koroneiki cultivars) were investigated. The results showed that root and shoot fresh and dry weights, node number, internode length, shoot number, plant height, and stem diameter reduced as the salt concentration increased from 0–200 mM. On the contrary, there were increases in leaf necrosis, leaf abscission, and plant mortality. Salinity reduced the relative water content of the leaves, chlorophyll, and potassium content, and increased sodium content, electrolyte leakage, and proline content in the leaves. Application of proline ameliorated the adverse effects of salinity on sodium content, potassium content, electrolyte leakage, proline content, total chlorophyll, and chlorophyll b, leaf abscission and necrosis, shoot number, and internode length, but had no significant effect on the other characteristics. The highest toxicity was observed in Arbosana.